Physics and Astronomy Calendar

semester, 2016


Wednesday, January 6th 2016
10:00 am:
Thesis Defense in PAN 120
Speaker: Chen Hou, University of Minnesota
Subject: One-dimensional turbulence model of PRE bursts.
This is the public portion of Mr. Hou's thesis defense. His adviser is Alexander Heger.

A Type-I X-ray burst is the thermonuclear runaway that occurs on the surface of a neutron star in a binary system. Studies on these bursts are of great importance for understanding neutron stars, nuclear reactions and the equation of state of dense matter at low temperature. I will discuss a subset of X-ray bursts, photospheric radius expansion (PRE) bursts, that is powerful to lift up the photosphere of the star with the simulations based on a new 1D turbulence model, ODT. The model is different in that the turbulent motion is implemented according to a stochastic process and an eddy event is represented by a measure-preserving map. I will compare the light curve and turbulent motion development with a KEPLER model in which the traditional mixing length theory is applied.


Saturday, January 16th 2016
12:00 pm:
Speaker: Aaron Breneman, University of Minnesota
Subject: Global coherence of hiss and electron precipitation

Monday, January 18th 2016

Tuesday, January 19th 2016
12:00 pm:
Organizational Meeting
4:30 pm:
CM Journal Club in PAN 120
There will be no journal club this week.

Wednesday, January 20th 2016
10:10 am:
Subject: to be announced.
1:25 pm:
Speaker: Cui-Zu Chang, Massachusetts Institute of Technology
Subject: From Topological Insulators to Quantum Anomalous Hall Effect

The quantum anomalous Hall (QAH) effect can be considered as the quantum Hall (QH) effect without external magnetic field, which can be realized by time reversal symmetry breaking in a topologically non-trivial system. A QAH system carries spin-polarized dissipationless chiral edge transport channels without external energy input, hence may have huge impact on future electronic and spintronic device applications with ultralow-power consumption. The many decades’ quest for the experimental realization of QAH effect received a boost in 2006 with the discovery of topological insulators (TIs). In 2013, the QAH effect was observed in thin films of Cr-doped TI for the first time [1]. In 2015, a near ideal system in V-doped TI, contrary to the expectation of first principle calculations, was demonstrated to show extremely high-precision QAH quantization with more robust magnetization and higher Curie temperature [2]. In this talk, I will introduce the route to the experimental observation of the QAH effect in above-mentioned two systems [1,2], and discuss the zero magnetic field dissipationless edge mode and the origin of the dissipative channels in the high-precision QAH state [3]. Finally I will outline the prospects and the barriers of a viable QAH-based device.
References
[1] Cui-Zu Chang et al, Science 340, 167(2013).
[2] Cui-Zu Chang et al, Nature Materials 14, 473(2015).
[3] Cui-Zu Chang et al, Physics Review Letters 115, 057206 (2015).

Faculty Host: Martin Greven
3:00 pm:
Thesis Defense in 337 Amundson Hall
Speaker: Gaurav Shukla, University of Minnesota
Subject: Thermoelastic properties of iron- and aluminum-bearing bridgmanite at high pressures and temperatures
This is the public portion of Mr. Shukla's thesis defense. His adviser is Renata Wentzcovitch, CEMS
To be announced.

Thursday, January 21st 2016
10:00 am:
Thesis Defense in 334 PAN
Speaker: Semere Tadesse, University of Minnesota
Subject: "Nano-Optomechanical System based on Microwave Frequency Surface Acoustic Waves"
This is the pulbic portion of Mr. Tadesse's thesis defense. His advisor is Mo Li, ECE

Cavity optomechnics studies interaction of cavity confined photons with nanomechanical motion. Many of the studies reported so far are focused on interaction of photons with localized mechanical modes. In my doctoral research, I did experimental investigations to extend this study to propagating phonons. We used surface travelling acoustic wave as mechanical element of the optomechanical system. The system constitutes microwave frequency surface acoustic wave transducers co-intergrated with optical cavities on piezoelectric aluminum nitride film. Acousto-optic modulation with the acoustic wavelength significantly below the optical wavelength and modulation speed over 10GHz was demonstrated. The phase and modal matching conditions in this paradigm were investigated for efficient optmechanical coupling. This system was used to demonstrate optomecahnically induced transparency and absorption, which are dynamical consequences of the optomechanical coupling. Phase coherent interaction of the acoustic wave with multiple nanocavities was also explored, highlighting the scalability of the optomechanical system. In a related experiment, a photonic nanoscavity was placed inside an acoustic echo-chamber, and interaction of a phonon pulse with the photonic cavity was investigated. One limitation of our system is that the surface generated acoustic wave leaks into the supporting silicon substrate depriving the optical cavities the strain field necessary for strong optomechanical coupling. This limitation was addressed by realizing the optomechanical system on suspended aluminum nitride membrane. The membrane confines both the acoustic and optical fields and led to a strong optmechanical coupling.

Speaker: There will be no colloquium this week
Speaker: Peter Orth, University of Minnesota
Subject: Emergent critical phase in the frustrated 2D Heisenberg Windmill Antiferromagnet

In most systems that exhibit order at low temperatures, the order occurs in the elementary degrees of freedom such as spin or charge. Prominent examples are magnetic or superconducting states of matter. In contrast, emergent order describes the phenomenon where composite objects such as higher order correlation functions exhibit longer range correlations. This can appear even though the elementary objects remain short-range ordered. One specific example are frustrated magnets, where long-range discrete order in the relative orientation of spins may occur in the absence of magnetic order. This can induce other phase transitions as is the case for the nematic transition in the iron pnictides. In my talk, I will focus on algebraic "critical" correlations of an emergent Z6 clock order parameter in an isotropic Heisenberg antiferromagnet on the windmill lattice, which consists of interpenetrating honeycomb and triangular lattices. This is surprising as the interaction of the Goldstone modes present in Heisenberg systems usually causes the spin-wave stiffness to renormalize to zero on long scales. Here it occurs due to the decoupling of an emergent collective degree of freedom given by the relative phase of spins on different sublattices. We establish this result and the formation of an extended critical phase at intermediate temperatures both using an analytical renormalization group analysis based on the Ricci flow and large-scale classical Monte-Carlo simulations. Our results also reveal that both phase transitions, which bracket the critical phase, lie in the Berezinskii-Kosterlitz-Thouless universality class.


Friday, January 22nd 2016
08:00 am:
Untitled in Physics
11:15 am:
Organizational Meeting
Speaker: Yuriy Sizyuk, University of Minnesota
Subject: "Lifting mean field degeneracies in anisotropic spin systems
Speaker: No Seminar
2:30 pm:
There will be no colloquium this week.
2:30 pm:
Thesis Defense in Nicholson 155
Speaker: Dinesh Shenoy, MN Institute for Astrophysics
Subject: A Study of Hypergiant Mass Loss in the Near-To-Mid Infrared: VY CMa, IRC +10420, mu Cep and rho Cas
This is the public portion of Mr. Shenoy's thesis defense. His adviser is Terry Jones.

Stars of initial mass greater than 9 M_sun become red supergiants (RSGs), a short-lived stage during which they experience mass-loss that strongly influences their post-RSG evolution and end state. The highest luminosity RSGs, referred to here as hypergiants, experience episodic mass-loss whose mechanism remains poorly understood and motivates observations to help constrain it. This thesis studies mass loss from hypergiant stars with near-to-mid infrared imaging over a range of angular scales. The recent mass-loss history of the extreme red supergiant VY Canis Majoris and the warm hypergiant star IRC +10420 are studied at the sub-arcsecond scale with adaptive optics imaging and imaging polarimetry from 1 - 5 micron using LMIRCam on the Large Binocular Telescope (LBT) and MMT-Pol at the MMT Observatory. The nebular features of both VY CMa and IRC +10420 are found to be highly polarized from 1 - 3 micron, with optically thick scattering required to reproduce the observed surface brightness. The polarimetry of their nebula is contrasted, with VY CMa’s consistent with scattered light alone, while IRC +10420’s nebular emission is mostly thermal with a color temperature well above that for typical astrophysical dust. To probe further into hypergiants' history of mass-loss, mid-IR imaging with MMT/MIRAC and SOFIA/FORCAST is used to study VY CMa, IRC +10420 and two additional hypergiants: the RSG mu Cep and the warm hypergiant rho Cas. Average mass-loss rates are computed using DUSTY 1-D radiative transfer models. Two distinct periods are found in the mass-loss history of IRC +10420, with an order of magnitude decrease in the recent past, with the change indicating its evolution beyond the RSG stage.

Speaker: Susan Wolf, University of Minnesota Law School
Subject: Precision Medicine & the Challenge of Sharing Genomic Results
Refreshments served at 3:15 p.m.

In January 2015, President Obama announced plans to fund a nationwide Precision Medicine Initiative (PMI). A year later, plans are under way to assemble a large and diverse cohort of 1 million participants to build a prospective research resource to fuel population-wide research. The PMI aims to use a new model of research driven by highly engaged patients actively partnering in data collection and having broad access to their own results as well as the cohort’s aggregate results. However, there remain big questions about this ambitious plan for return of results. For the last decade, the research community has actively investigated and debated those questions. Among them is how to determine what results are sufficiently understood to return, whether individuals should have access to uncertain results, and whether family members should be able to obtain a loved one’s genetic results that may have implications for relatives. These questions raise pressing issues in ethics, law, biomedical science, and clinical care.

3:35 pm:
There will be no seminar this week.
Speaker: Marco Peloso, University of Minnesota
Subject: Particle production during primordial inflation

Monday, January 25th 2016
12:15 pm:
Speaker: Karl Young , University of Minnesota
Subject: Millimeter-Wave Broadband Anti-Reflection Coatings Using Laser Ablation of Sub-Wavelength Structures

The newest millimeter and sub-millimeter telescopes are using large, high index optics that need robust broadband anti-reflection coatings (ARC). One way to produce such a coating is via sub-wavelength structures (SWS). I will give a brief review of SWS ARCs produced for the millimeter and sub-millimeter, and then report on our use of laser ablation to fabricate SWS on alumina and sapphire. Transmission measurements of our SWS ARC between 70 and 140 GHz agree with simulations. The simulations indicate that our SWS ARC should have reflections below 3% between 170 and 300 GHz when applied to both sides of an alumina or sapphire lens.

Faculty Host: Shaul Hanany

Tuesday, January 26th 2016
12:00 pm:
Subject: Interesting new results from the group
4:30 pm:
CM Journal Club in PAN 120
No journal club this week.

Wednesday, January 27th 2016
10:10 am:
Biophysics Seminar in 120 PAN
Speaker: Hermann Riecke, Northwestern
Subject: Neuronal Networks in Visual and Olfactory Sensory Processing

One of the essential tasks of the brain is is to obtain survival-relevant information about the world through its various senses. I will discuss some of our computational modeling results of aspects of the visual and the olfactory system. Through detailed biophysical modeling of a certain neuron type of the retina we have revealed the origin of oscillations that emerge in the process of retinal degeneration and may hinder the success of retinal prostheses. In the olfactory system we have developed an adaptive network model for the persistent restructuring of the olfactory network, which arises from the turn-over of a whole neuronal population. The resulting network structure is controlled by higher brain areas, which determine the survival of specific, newly born neurons. Our model suggests that this allows even very early olfactory processing to be modified based on non-olfactory information, enhancing the detection and discrimination of odors in complex environments.

1:25 pm:
Speaker: Liuyan Zhao, California Institute of Technology
Subject: Revealing Hidden Orders in Spin-Orbit Coupled Correlated Materials

Recently, there has been growing interest in electronic systems that exhibit both strong spin-orbit coupling and strong electron correlations. These systems combine two central threads of modern quantum materials research: correlated electron physics that underlies phenomena such as high-Tc superconductivity, and spin-orbit physics that describes systems such as topological insulators. When these two interactions compete at the same energy scale in a material, fundamentally new quantum phenomena have been predicted to emerge. Recently, an experimental platform with this rare interaction regime has been realized for the first time in 5d transition metal oxides such as iridium oxides. In this talk, I will focus on one specific member of this family Sr2IrO4 that has received much attention due its striking similarities to the cuprate high-Tc superconductors. I will describe a new nonlinear optical spectroscopy technique that enabled us to find an unusual hidden magnetic ordered phase in the Sr2IrO4 system. I will discuss the potential relevance of this novel phase to superconductivity in both iridates and cuprates.

Faculty Host: Martin Greven
To be announced.

Thursday, January 28th 2016
Speaker: Melanie Beck and Terry Jones
3:35 pm:
Speaker: Kathy Levin, University of Chicago
Subject: Atomic Gases as a Proxy-Laboratory for Condensed (& Other) Matter
Refreshments to be served outside 101 Fraser after the colloquium.

In this talk I summarize how experiments in atomic gases can inform about condensed matter and also quark-gluon matter. The difficulties of performing these atomic physics experiments are evident. One can't insert thermometers or put current leads into trapped atom gases. But very important are their unique capabilities which provide windows into physics not otherwise accessible. We focus on 3 successful encounters between theory and experiment in atomic Fermi superfluids which take advantage of these unique windows. The ultimate motivation behind these examples is, of course, the pursuit of various holy grails in condensed matter physics (e.g.,understanding high temperature superconductors and topological trapped superfluidity).

Faculty Host: Oriol T. Valls

Friday, January 29th 2016
11:15 am:
To be announced.
There will be no seminar this week.
Speaker: Robert Caldwell (Dartmouth)
Subject: Cosmic Polarization Rotation
2:30 pm:
Speaker: Robert Gehrz, MIfA, University of Minnesota
Subject: Infrared Observations of Novae in the SOFIA Era

Classical novae may contribute to some of the isotopic anomalies that are
present in the remnants of the primitive solar system. We describe the way
infrared (IR) photometric and spectroscopic observations can quantify the
physical parameters of nova explosions and their contributions to the
Inter-Stellar Medium (ISM). Metal abundances in the ejecta can be deduced
from both IR dust emission features and forbidden line emission. We show
that some novae have produced ejecta extremely overabundant in CNO, Ne,
Mg, Al, and Si. The properties of nova dust are compared to those of
grains in pre-planetary nebulae and comet nuclei. We describe space
observations of novae from the Spitzer Space Telescope and anticipate the
impact that the new NASA Stratospheric Observatory for Infrared Astronomy
(SOFIA) will have on future infrared studies of novae.

Speaker: Margaret Carlyle, Department of History, University of Minnesota
Subject: From Paris to St. Petersburg: Portable Anatomies in Enlightenment Europe
Refreshments served at 3:15 p.m.

In 1759, the French surgeon Sauveur-François Morand (1697-1773) was in the final stage of preparing an anatomical collection for transport to the court of Elizabeth of Russia (1709–1762), where it would be dispatched to the Medical Chancery of St. Petersburg. This “Arsenal of Surgery” was four years in the making and comprised custom-made objects fashioned by anatomical modellers, as well as joiners, cutlers, goldsmiths, and sculptors. Shortly before its departure for Russia, Morand presented the collection to members of the Paris Royal Academy of Sciences accompanied by its most remarkable contributor, Mlle Biheron (1719–1795), who demonstrated on her lifesize wax woman. With the Academy’s stamp of approval for his scheme, Morand issued a Catalogue with the royal printer detailing the Arsenal’s contents and the intricacies of trafficking anatomical knowledge.

This talk situates the ultimately failed attempt to transmit the Arsenal from Paris to St. Petersburg within the broader context of Mlle Biheron’s three decades in the business of modeling anatomical waxworks. We discuss Morand’s project alongside the second attempt by philosophe Diderot (1713–1784) to bring Biheron’s wares to Russia, as well her independently arranged exhibitions in London. We see how forms of royal patronage, as well as the creative roles of medical intermediaries and experts, were a central feature of attempts to circulate scientific knowledge in the form of object lessons. It follows that the quality of what we call ‘portability’ conferred increasing prestige both to patrons and clients who participated in the circulation of anatomical hardware, while simultaneously presenting challenges beyond those experienced in more localised forms of knowledge display. By way of conclusion, we demonstrate how the patron-client exchanges characteristic of Enlightenment knowledge production and transfer were replaced by the Revolution’s nationalization of medical education.

3:35 pm:
Speaker: Peter Bohacek , Matt Vonk, University of Wisconsin, River Falls
Subject: Using Direct Measurement Video to Teach Model Making and Model Breaking

We conducted a study to determine whether Direct Measurement Video can be used effectively teach model making, and model breaking. Model making means that students are able to discern a mathematical relationship between measured quantities using data they measure from a physical system. Model breaking means that students are able to determine whether a specific event can be explained using a known model. We performed a study using 180 intro level students to determine how well Direct Measurement Video based instruction can teach these skills. We'll describe the study, and share the preliminary results.

Speaker: Ron Poling, University of Minnesota
Subject: The BESIII Experiment: Studying Charm Quarks in Beijing

Monday, February 1st 2016
12:15 pm:
Speaker: Jianming Zheng, University of Minnesota
Subject: Dark Matter and Gauge Coupling Unification in Non-supersymmetric SO(10) Grand Unified Models

In this talk I will talk about the possibility that a non-supersymmetric SO(10) unification model may provide a dark matter candidate stablized by a remnant Z_2 symmetry. In particular, we consider models with an intermediate symmetry, and discuss phenomenological constraints including proton decay, dark matter relic density and direct detection bound, and neutrino masses.

Faculty Host: Keith Olive

Tuesday, February 2nd 2016
12:00 pm:
Speaker: Yan Song, University of Minnesota
Subject: Generation of Alfvenic Quasi-Stationary Double Layers and Charge Holes and Formation of Quasi-Static and Alfvenic Discrete Auroras
12:35 pm:
Speaker: Gábor B. Halász
Subject: Hole dynamics in exactly solvable gapped and gapless spin liquids

We present a controlled microscopic study of hole dynamics in both a gapped and a gapless spin liquid. Our approach is complementary to previous phenomenological works as we introduce mobile holes into the spin liquid ground state of the exactly solvable Kitaev honeycomb model. In the gapped phase of the model, we address the single-particle properties of individual holes (such as their particle statistics and hopping properties) and the multi-particle ground state at a finite density of holes. Our main result is that the holes possess internal degrees of freedom as they can bind the fractional excitations of the spin liquid and that the resulting composite holes with different excitations bound are distinct fractional particles with fundamentally different single-particle properties and different experimental signatures in the multi-particle ground state. In the gapless phase of the model, we consider a single hole and address the possibility of a coherent quasiparticle description by investigating its spectral function. We employ a variational treatment and also study a simplified one-dimensional problem to argue that a mobile hole has a finite quasiparticle weight which vanishes in the stationary limit.

Faculty Host: Natalia Perkins
4:30 pm:
CM Journal Club in PAN 120
Speaker: Tobias Gulden
Subject: The tenfold way and periodic table of topological insulators

In this talk I will review the basic classification of topological insulators in non-interacting fermionic systems. All systems can be classified according to their behavior under the action of three discrete symmetries: time-reversal, particle-hole and sublattice symmetry. I will show how to classify a system from the behavior near a critical point. This symmetry classification relates to the presence of different topological phases, which is summarized in the periodic table of topological insulators. For this talk I will mostly follow Andreas Schnyder’s lecture slides at the Summer School in Nancy [2].

[1] S. Ryu, A. Schnyder, A. Furusaki, and A. Ludwig: “Topological insulators and superconductors: tenfold way and dimensional hierarchy”, New. J. Phys. 12, 065010 (2010)
[2] A. Schnyder: Lectures on "Topological aspects in condensed matter physics" held at the Topical School in Theoretical Physics Nancy (2014), lecture slides are on his homepage at http://www.fkf.mpg.de/556169/20_Schnyder


Wednesday, February 3rd 2016
10:10 am:
Subject: To be announced
To be announced.

Thursday, February 4th 2016
Speaker: Evan Tyler and Julius Donnert
3:35 pm:
Speaker: Eva Halkiadakis, Rutgers University
Subject: Exploring the Energy Frontier at the Large Hadron Collider
Refreshments to be served outside 101 Fraser after the colloquium.

The Large Hadron Collider (LHC) at the CERN laboratory is the world’s most powerful particle accelerator. The start of the proton collider program at the LHC brought the dawn of the exploration of a new energy frontier. The LHC has had a successful and highly productive Run 1 (2010-2012), colliding protons with a center-of-mass energy up to 8 TeV, and in 2012 the observation of a new Higgs-like boson was announced to the world by the CMS and ATLAS collaborations. The year 2015 marked the beginning of Run 2 of the LHC and we entered a new era of even higher proton collisions at 13 TeV. The LHC experiments have an extensive program of searches for physics beyond the Standard Model, exploring uncharted territory at the energy frontier. I will present the status of the LHC and the first experimental results using the latest 13 TeV data in Run 2, with a special focus on the CMS experiment.

Faculty Host: Jeremiah Mans

Friday, February 5th 2016
11:15 am:
There will be no seminar this week.
Speaker: Gordon Stecklein, University of Minnesota
Subject: Spin Transport in One to Three Layer CVD Graphene"
Speaker: Adrian Escobar (UNAM)
Subject: Instanton calculus in quantum mechanics: quartic double-well and sine-Gordon potentials.

In this talk we discuss two quantum mechanical problems, the
quartic double-well and the sine-Gordon potentials.
Feynman diagrams in the instanton background are used for the calculation
of the tunneling amplitude (the instanton density) in the three-loop
order. Unlike the two-loop contribution where all involved Feynman
integrals are rational numbers, we will show that in the three-loop case
they can contain irrational contributions as well.

2:30 pm:
Speaker: Lindsay Glesener, Physics/MIfA, U Minnesota
Subject: New instruments for the high-energy Sun

As our closest star, the Sun offers a unique opportunity to study high-energy plasma processes — magnetic reconnection, particle acceleration via a myriad of mechanisms, and bulk plasma heating and motion. With the Earth sitting in point-blank range of the Sun’s emissions (solar wind, solar energetic particles, and coronal mass ejections), understanding these processes is of practical, as well as scientific, importance. Yet several mysteries of the Sun’s high-energy behavior elude us, including problems of how the corona is heated and the remarkable efficiency of particle acceleration in solar flares. Hard X-ray emission reveals the behavior of high-energy electrons and so offers an adept tool for probing these mysteries. But imaging is tricky in this high-energy regime, and past efforts had to rely on indirect, Fourier-based imaging methods. With the advent of direct focusing optics for hard X-rays (HXRs), imaging and spectroscopy can be performed with far better sensitivity and image quality than in previous solar-dedicated HXR missions.

In this colloquium I will discuss ongoing investigations and new instrument development to probe the high-energy Sun, including pathfinder instruments on sounding rockets and CubeSats, as well as solar observations by the NuSTAR spacecraft.

Speaker: Larry Smith, Department of History, University of Saskatchewan
Subject: Reviving Thomas Beddoes: The Chemical and Medical Alternatives of the Late Enlightenment
Refreshments served at 3:15 p.m.

Thomas Beddoes asserted the oft disputed proposition that social and medical revision went hand in hand. Among 18th century republicans he was far from alone. While his pneumatic chemistry proved no panacea, Beddoes reflected a widespread group of chemists and medics who were intent on confronting orthodoxy at every opportunity through novel, chemical and electrical, therapies emerging from private laboratories. This seminar examines Beddoes’ extensive search, with his many supporters, for medical alternatives during the chemical revolution. In so doing, it reveals Beddoes as a highly-influential and much regarded, if politically divisive, figure by the early 19th century.

3:35 pm:
Speaker: Xian Wu, Kansas State University
Subject: Investigating the Effect of Hint Modalities on Conceptual Physics Tasks

Previous research has shown that visual hints can improve learners’ performance on conceptual physics tasks. In this study, we investigate the effect of multimedia hints that include visual, text, audio modalities as well as all possible combinations thereof. The participants (N = 162) enrolled in conceptual physics classes were recruited for this study. Each of them participated in an individual 50-minute interview, which contained four task sets. Each set contained one initial task, six training tasks, one near transfer task, and one far transfer task. We used a 2 (visual hint/no visual hint) × 2 (text hint/no text hint) × 2 (audio hint/no audio hint) between subject quasi-experimental design. Subjects were randomly assigned into one of the eight conditions and would be provided hints for training tasks, corresponding to the assigned condition. Six pairs of competing hypotheses were generated according to Mayer’s cognitive theory of multimedia learning. Overall, our results showed that task solving performance on the training tasks was affected by hint modality. Unlike what we predicted based on multimedia learning theory, we found that the audio hint condition performed no better than text hint condition. The most effective hint modality was a combination of the visual and text hints. Our study has implications for student cognition in computer-assisted instruction.

Speaker: Vincent Noireaux, University of Minnesota
Subject: Cell-free expression: from gene circuits to self-assembly in a test tube
Note change of room for the remainder of the semester.

Monday, February 8th 2016
12:15 pm:
Speaker: Cheng-Hsien Li - UMN
Subject: Wave-packet treatment of neutrinos and its quantum-mechanical implications

In this talk, I will briefly discuss the 3D solution of a massless Gaussian wave packet. This solution is applied to examine whether neutrino wave packets (WPs), which are emitted from different production processes in the source, overlap in space as they propagate toward the detector. In particular, we consider the overlap among those neutrinos with mean energies differing by no more than the intrinsic energy uncertainty in a WP. The degree of overlap depends on the transverse size of the initial WP and the energy-differential production rate of the source. Such overlap is estimated to be significant for solar and supernova neutrinos and is potentially significant for those from radioactive sources. A discussion on whether the exchange symmetry of neutrinos affects detection rate will be given.

Faculty Host: Yong-Zhong Qian

Tuesday, February 9th 2016
12:00 pm:
Speaker: Jasper Halekas, University of Iowa
Subject: Dynamic Mars: First Results from MAVEN
4:30 pm:
CM Journal Club in PAN 120
Speaker: Xuzhe Ying
Subject: Topological Superconductivity

I'll discuss 1-D chain with superconductivity and show the existence of different phases for p-wave superconductivity. I'll also show the existence of Majorana bound state as well as its wave function. Also one dimensional nanowire with spin-orbit will be discussed. With the presence of Zeeman field and s-wave superconductivity, this model serves as a more realistic one for topological superconductor.

Reference: Bernevig, Taylor Hughes 'topological insulators and topological superconductors'


Wednesday, February 10th 2016
10:10 am:
Biophysics Seminar in 120 PAN
Speaker: Doug Smith, UC San Diego
Subject: Studies of motor-driven viral DNA packaging with optical tweezers: Biophysics of motor function and tight DNA confinement

In many viruses DNA is packed to near-crystalline density into ~50-100 nm prohead shells. The DNA is translocated into empty proheads by an ATP-powered molecular motor via a portal nanochannel, overcoming large forces resisting DNA confinement arising from DNA bending rigidity, electrostatic self-repulsion, and entropy loss. These biomotors are among the most powerful known, generating at least 20´ higher force than the skeletal muscle myosin motor. In addition to being of biological interest, viral packaging is an experimentally accessible model for investigating effects of spatial confinement on polymer dynamics, a topic of fundamental interest in polymer physics. We use optical tweezers to measure the packaging of single DNA molecules into single viral proheads. Our recent studies of phage phi29 have shown that: (1) The confined DNA undergoes nonequilibrium (glassy) dynamics with a very long relaxation time, causing slowing and pausing of the motor and heterogeneity in the packaging rate; (2) Contrary to theoretical predictions, net attractive DNA-DNA interactions mediated by +3 or +4 ions cause frequent stalling of packaging, which we attribute to a nonequilibrium jamming transition akin to that occurring in colloidal and granular soft matter systems; (3) Motor velocity is regulated not only by load force but also by a novel allosteric mechanism wherein ATP binding and motor pausing is regulated in response to changes in packaged DNA density and conformation. In addition, we investigate the motor mechanism by studying the effect of amino acid changes in the motor proteins. Our recent findings provide evidence for an electrostatic mechanism of force generation in the phage T4 motor and a role of ATP phosphate binding loop residues in mechanochemical coupling in the phage lambda motor, supporting recent structure-based models.

Speaker: Yann Mambrini, CNRS-Université Paris XI
Subject: Dark matter models: the diary of a particle phenomenologist

Recent exclusion limits of different collaborations seem to invalidate partially the WIMP paradigm. As a consequence, plethora of phenomenological models appeared in the literature, reopening (almost) forgotten windows of masses and coupling. I will review in this talk the different ways of embed dark matter in a coherent BSM framework respecting theoretical as observational constraints, and how these new windows
re-opened from an historical perspective.

There will be no seminar this week.

Thursday, February 11th 2016
11:15 am:
Speaker: Yongtao Cui, Stanford University
Subject: Visualizing Low Dimensional Electronic States in Complex Quantum Materials

Low dimensional systems, such as atomically thin materials and material interfaces, offer a rich ground to discover new types of electronic states. Spatially resolved electrical probes provide direct access to these states on the mesoscopic scale, complementing conventional transport techniques. In this talk, I will present two comprehensive studies on 2D electronic states employing Microwave Impedance Microscopy (MIM), a scanning probe technique that senses materials’ capacitance and conductivity on the nanoscal. The first study investigates magnetic domain walls in a unique all-in-all-out magnetic insulator, Nd2Ir2O7. Through a combined study of MIM, transport, and X-ray micro-diffraction, we conclusively show that metallic states emerge at the magnetic domain walls when the all-in-all-out magnetic order forms with a concomitant metal-insulator transition occurring in the bulk. This represents a new type of interface electronic states in a both chemically and structurally homogeneous material. The second study examines the canonical “edge state” picture of the quantum Hall (QH) effect in graphene. To our surprise, we find an unconventional edge-bulk correlation in graphene devices: the QH transport plateaus occur before the bulk Landau levels are completely filled. This result has implications in both QH transport analysis as well as understanding of general edge transport behaviors in other 2D topological systems.

Speaker: Trevor Knuth and Roberta Humphreys
3:35 pm:
Speaker: Scott Dodelson, Fermilab
Subject: Myth-Busters: Dark Energy Survey and South Pole Telescope
Refreshments to be served outside 101 Fraser after the colloquium.

The standard cosmological lore is that galaxy surveys and cosmic microwave background (CMB) experiments open up a window on fundamental physics such as dark energy and dark matter. The four distinct probes enabled by surveys -- Baryon Acoustic Oscillations, Clusters, Gravitational Lensing, and Supernovae -- together with a pristine view of the early universe via the CMB allow us to determine cosmological parameters such as the equation of state of dark energy. I argue that this paradigm is breaking down, as we come to realize that the four probes are all correlated with one another and with the CMB itself. How to proceed is the subject of a raging debate, with many possible routes and assumptions. I give a few examples and recent results from the Dark Energy Survey and the South Pole Telescope

Faculty Host: Marco Peloso

Friday, February 12th 2016
11:15 am:
There will be no seminar this week.
Speaker: Terry Bretz-Sullivan, University of Minnesota
Subject: Magnetic Field Reentrant Superconductivity in Aluminum Nanowires
Speaker: Mohammad Hossein (Harvard)
Subject: Probing the Primordial Universe using Massive Fields
2:30 pm:
Speaker: Vuk Mandic, University of Minnesota
Subject: Update on Gravitational Wave Searches
Note: the change in room from yesterday, they have moved the location to accomodate a larger audience.
Faculty Host: Lawrence Rudnick
Speaker: Otávio Bueno, Department of Philosophy, University of Miami
Subject: Visual Evidence and Styles of Scientific Reasoning
Refreshments served at 3:15 p.m.

The notion of style of scientific reasoning has been used as an analytic tool for the characterization of significant features of scientific practice (in particular, by Crombie [1994] and Hacking [2002]). Styles of scientific reasoning are different from scientific theories in a given domain of inquiry: styles are broader than theories, and they are not so dependent on features of the particular domain. In this work, I provide a characterization of the concept of style of reasoning that overcomes some difficulties that have been raised against this tool (by Bolduc [2014]). I then examine the role played by visual evidence in a characteristic style of reasoning found in much of contemporary sciences, which I call instrumental style. The implications for the normative nature of styles and some limitations of visual evidence in the sciences are finally examined.

3:35 pm:
Speaker: Binod Nainabasti, Florida International University, Leon
Subject: Role of students’ participation in learning physics in an active learning environment

Students’ interactions can be an influential component of students’ success in an interactive learning environment. From a participation perspective, learning is viewed in terms of how students transform their participation. However, many of the seminal papers discussing the participationist framework are vague on specific details about what student participation really looks like on a more fine-grained scale. As part of a larger project to understand the role of student participation in learning, we have gathered data that allowed us to quantify students’ participation in three broad areas of two student-centered introductory calculus-based physics classes structured around the Investigative Science Learning Environment (ISLE) philosophy: in-class learning activities, class review sessions that happened at the beginning of every class, and the informal learning community that formed outside of class time. Using video data, classroom observations, and students’ self-reported social network data, we quantified students’ participation in these three aspects of the class throughout two semesters. We investigated the relationship between behaviors of students’ engagement in these aspects of an active learning environment and (a) their conceptual understanding (measured by FCI gain) and, (b) academic success in the courses as measured by exam scores and scores on out-of-class assignments. We also considered the following research questions: (1) does prior students’ physics knowledge of conceptual understanding bias their participation in an interactive learning environment, (2) does the overall participation pattern change over time in an Interactive Learning Environment, (3) is the benefit of participation in an interactive learning environment extended equally to both female and male students, and (4) does participation in an interactive learning environment increase the problem solving ability through teamwork? Our results revealed that different aspects of the class play distinct roles in students’ learning and pattern of students’ participation does not change significantly over time.

Speaker: Mo Li, University of Minnesota
Subject: Silicon Photonics: photon playground for novel optical physics and materials

Monday, February 15th 2016
12:15 pm:
Speaker: Kevin Sebesta, UMN
Subject: Constraints on σ8 from joint analysis of lensing and stacking galaxy clusters

In this talk I will speak about recent results of constraining the cosmological parameter, σ8, from a joint analysis of gravitational lensing and stacking clusters of galaxies. Two methods were used to get σ8, one assuming a prior on galaxy bias, and the other making no such assumption. Both methods agreed with one another and previous results for σ8 from Planck, WMAP, and just lensing.

Faculty Host: Liliya L.R. Williams
Speaker: Ruihua He, Boston College
Subject: Angle-resolved Photoemission Spectroscopy Study of Emergent Phenomena in Correlated Materials
Note: change of time for seminar.

A central theme of modern condensed matter physics is to discover and understand emergent phenomena in quantum materials. These phenomena emerge only through the collective behavior of electrons due to their mutual interactions as well as interactions with other degrees of freedom inside the materials. In this talk, I will give two examples of the emergent phenomena which I have been studying with angle-resolved photoemission spectroscopy in recent years. The first one is the negative electronic compressibility. I will present our evidence for the first experimental case of such phenomenon in a bulk material—the electron-doped iridate—and discuss the obtained insights into its microscopic origin, which heralds an uncharted territory of negative compressibility research that potentially features a whole variety of bulk quantum materials. The second example is the pseudogap phenomena. I will show how our view about the nature of these phenomena in hole-doped cuprate superconductors has evolved in the past two decades and been finally converging into one that they signal a phase of matter which is fundamentally distinct from superconductivity and characterized by multiple broken symmetries. I will discuss our results contributing to this development as well as their implications particularly regarding the broken translation symmetry aspect of the still-mysterious pseudogap phase.


Tuesday, February 16th 2016
12:00 pm:
Speaker: Aaron Breneman, University of Minnesota
Subject: Global coherence of hiss and electron precipitation
4:30 pm:
CM Journal Club in PAN 120
Speaker: Konstantin Reich
Subject: Mobility in inversion layer limited by surface roughness

For many applications, high mobility is desirable. To achieve this goal one should eliminate all sources of scattering of carriers. In the talk i will discuss the influence of the surface roughness on the carrier mobility in an inversion layer. Namely, I will derive the relationship between the mobility and the main parameters of roughness.


Wednesday, February 17th 2016
10:10 am:
Biophysics Seminar in 120 PAN
Speaker: Paul Tillberg, MIT
Subject: Expansion Microscopy-Improved Resolution Through Uniform Specimen Expansion
Note change from Journal Club to Seminar from previous announcement.

I will present Expansion Microscopy (ExM), a method in which the optical diffraction limit is circumvented by physically expanding a biological specimen prior to imaging. Expansion brings sub-diffraction limited structures into the size range viewable by a conventional diffraction-limited microscope. In ExM, proteins and visible probes are chemically anchored to an in situ-synthesized swellable polyelectrolyte gel. Proteolytic digestion is used to disrupt native tissue structures and enable uniform, 4.5-fold expansion of the material with anchored probes.

Known sub-diffraction limited structures are shown to have the expected shape and size, demonstrating that the expansion is isotropic down to the theoretically resolvable size scale of 70nm (pre-expansion). Optical scattering is dramatically reduced, allowing this resolution to be achieved throughout the depth of the specimen, limited only by objective lens working distance and the diffusion of the gel precursor. ExM is compatible with any optical microscope, and is simple to adopt into existing experimental workflows. ExM promises to be a powerful method for imaging neural circuits at sub-synaptic resolution, in addition to other types of biological specimens.

1:25 pm:
Speaker: John Nichol, Harvard University
Subject: Quantum control and sensing with electron spins in semiconductors

Confined spins in semiconductors are a versatile platform for exploring quantum information processing and condensed matter physics. Individual spins can have coherence times exceeding seconds in some cases, making them promising quantum bits, or qubits, and also highly sensitive probes of their local electric and magnetic environments. I will discuss recent work exploiting the joint spin-state of two electrons in a GaAs double quantum dot as a “singlet-triplet” qubit. We perform high-fidelity single- and two-qubit gates with this architecture. We also use the qubit as a sensor to precisely measure its magnetic environment, which results from the statistically fluctuating nuclear spins in the semiconductor crystal. Using these measurement techniques, we extend the qubit coherence time by more than two orders of magnitude through adaptive control, and we uncover the surprisingly strong effect of spin-orbit coupling on electron-nuclear dynamics in GaAs.

There will be no seminar this week.

Thursday, February 18th 2016
08:00 am:
Untitled in Physics
08:00 am:
Untitled in Physics
Speaker: Sourabh Chauhan and Larry Rudnick
3:35 pm:
Speaker: Karl Gebhardt, University of Texas, Austin
Subject: Black Holes and Dark Energy through the Eyes of Texas
Refreshments to be served outside 101 Fraser after the colloquium.

Both the central black hole and the dark matter profile play essential roles for understanding the dominant evolutionary processes in galaxies. I will overview recent observations which demonstrate significant differences compared to previous analysis, focusing on black holes at the extreme mass ranges in galaxies. I will also present expectations from future advances in each area, specifically coming from the Hobby-Eberly Telescope Dark Energy Experiment (HETDEX).

Faculty Host: Evan Skillman

Friday, February 19th 2016
11:15 am:
There will be no seminar this week.
There will be no seminar this week.
Speaker: Yuhsin Tsai (Maryland)
Subject: Exotic Signals in The Twin Higgs Model

Twin Higgs (TH) model gives a naturalness motivation to study the non-colored BSM particles, which usually have decay processes relating to the dark-hadronization and displaced signal. In this talk, I will use the exotic twin-quarks to discuss the unique collider phenomenology of the TH models. These quarks play a vital role in UV completing the TH model, and their decay products contain both SM particles and twin-hadrons, including twin-glueballs, mesons, and leptons. These twin-objects decay displacedly into SM b-quarks or leptons, and the striking signal allows the reach of twin UV-physics at the LHC and future collider. Interesting complimentarily constraints between collider and astrophysical search will also be discussed.

2:30 pm:
MIFA Colloquium in 331 Smith Hall
Speaker: Ryan Tanner, UNC
Subject: Galactic Filaments: Pathways for Cold Gas in Galactic Winds

Starburst driven superbubbles can produce large scale galactic outflows. Embedded in these outflows are optically bright filaments containing cold, dense gas. These filaments are the main source of warm and cold gas being transported into the circumgalactic medium. Motivated by Herschel and Hubble observations of cold gas in galactic filaments I model starburst driven galactic winds and include a radiative cooling prescription with cooling down to 10 K. This allows me to investigate the structure and dynamics of filaments in a galactic wind. Optically bright filaments form at the edge of merging superbubbles and if anchored to a star forming complex will persist and grow to > 500 pc in length. The warm and cold gas contained in the filaments moves much slower than the surrounding hot, diffuse galactic wind, with the coldest gas hardly moving with respect to the galaxy. Using synthetic absorption profiles I can probe different temperature regimes and measure the velocity of the cold, warm and hot gas phases. Warm and cold gas embedded in the galactic wind show asymmetric absorption profiles consistent with observations and theoretical predictions. These asymmetries can be used to infer the kinematics of the filaments and associated dense cores.

Speaker: Richard Hirsh, Department of History, Virginia Tech
Subject: Shedding New Light on Rural Electrification: The Neglected Story of Successful Efforts to Energize Farms in the 1920s and Early 1930s
Refreshments served at 3:15 p.m. Co-sponsored with the Institute for Advanced Study.

Traditional histories of rural electrification usually glorify New-Deal efforts of the 1930s to bring electricity to farmers, enabling them to enjoy modern amenities like their urban cousins. Though not disparaging the productive work pursued by the Rural Electrification Administration (REA), created in 1935, this talk challenges the standard narrative by highlighting extensive electrification efforts undertaken in the 1920s and early 1930s by utility companies, farmers, and previously unrecognized agricultural engineers. Working at land-grant colleges, such as the University of Minnesota, these academic engineers served as intermediaries between farmers and utility managers, and they helped quadruple the number of rural homesteads that obtained electricity in the years between 1924 and 1931. (Not incidentally, the first rigorous experiment to determine how to electrify farms occurred in Red Wing, Minnesota, managed by UM agricultural engineer, Earl A. Stewart.)

The talk will also include an explanation of why the traditional historiography of rural electrification has remained so prevalent and popular. It suggests that historians may have paid inadequate attention to the context of the pre-Depression era, when government rarely became involved in enterprises undertaken largely by business organizations. More significantly, perhaps, historians found the standard narrative appealing because it contains colorful characters and a good-versus-bad storyline.

3:35 pm:
Speaker: Bin Xiao, North Carolina State University
Subject: A Problem Not in Any Textbook and All the Problems in One Textbook

Physics education researchers have introduced many novel types of problems and compared them to the end-of-chapter textbook problems. As an example, a study using a specially designed problem will first be presented. When expert problem solvers were asked to solve a very complicated circuit problem in think-aloud approach and were also required to rate their self-confidence on solving the problem during their solving process, how different would their performance be comparing to solving a typical textbook problem?

On the other hand, if we focus on the textbook problems, did they change after being studied all these years? In the second study, all the problems of the Electricity and Magnetism chapters of an introductory level textbook have been solved and coded basing on the equations needed and some other problem features. The results show some characteristics of the general textbook problems and their changes in the past three decades.

Speaker: Fiona Burnell, University of Minnesota
Subject: Symmetry and topology in condensed matter physics “

Monday, February 22nd 2016
12:15 pm:
Speaker: Christopher Sheehy, KICP Fellow, University of Chicago
Subject: Measuring CMB Spectral Distortions from the Ground

COBE/FIRAS famously measured the CMB's absolute intensity spectrum to be that of a nearly perfect blackbody. There are, however, a number of physical processes in the universe that guarantee measurable deviations. Recent renewed interest in CMB spectrum measurements has mainly focused on two classes of spectral distortions, the so-called mu- and y-distortions, which can only be measured from space and are the targets of a proposed NASA satellite mission. In this talk, I will focus on a third class of spectral distortions, the recombination spectral lines, which are relatively narrow features in the CMB spectrum originating from electronic transitions of hydrogen and helium at the time of recombination. In particular, I will discuss the possibility of measuring the recombination lines from the ground without the need for absolute intensity calibration. I will highlight a small pathfinder experiment currently under construction that will determine the suitability of one proposed technique to do this, an array of elevation tipping radiometers operating at 2-4 GHz. If a measurement is possible, the influence of helium on the line positions would allow for a direct and clean measurement of Y_p.

Faculty Host: Clement Pryke
Speaker: Zhanybek Alpichshev, Massachusetts Institute of Technology
Subject: Non-equilibrium dynamics of a frustrated Mott insulator

A handy way to tell what‘s inside a black box is to give it a good shake. Similarly it is often a good idea to bring a system far from equilibrium to understand its inner workings.

This talk mainly focuses on the results of ultrafast optical spectroscopy on Na2IrO3, a frustrated Mott insulator with strong spin-orbit coupling. Our results indicate that there is a distinct change in the non-equilibrium behavior of excitations as the system becomes magnetically ordered at low temperatures. Specifically, we observe that in the disordered phase the transient response is due to both bound “Hubbard excitons” and unpaired single particles, whereas in the ordered phase the single particle contribution becomes strongly suppressed. This is an indication of an increase of binding energy of Hubbard excitons which we argue is due to unique interplay between the strong frustrated Kitaev term and the weak Heisenberg-type ordering term in the Hamiltonian. In this regime magnetic ordering gives rise to an effective attraction between charged excitations which grows with distance causing them to become trapped within the excitons in analogy with quark confinement inside hadrons.


Tuesday, February 23rd 2016
12:00 pm:
There will be no seminar this week so that the group can attend the MIFA Colloquium.
4:30 pm:
CM Journal Club in PAN 120
Speaker: Tianbai Cui
Subject: How generic scale invariance influences quantum and classical phase transitions

Landau-Ginzburg-Wilson theory is a very powerful tool to study phase transitions and critical phenomena. It takes advantage of the fact that the low energy physics is dominated by a length scale which is diverging at a critical point, namely, the correlation length of order-parameter fluctuations. So one can derive an effective theory in terms of a single order-parameter field by integrating out all the other degrees of freedom with smaller length scales. However, this theory will breakdown if there are soft (massless) modes other than order-parameter fluctuations at criticality. These extra soft modes lead to power law behaviours in various physical correlation functions even far away from the critical point. Distinct from critical scale invariance, this is called generic scale invariance (GSI). Following Ref [1], I will talk about two major mechanisms that leads to GSI. Then I will use an example to discuss how GSI influences the critical behaviour in classical systems.

[1] D. Belitz, T. R. Kirkpatrick, and T. Vojta, Rev. Mod. Phys. 77, 579 (2005).


Wednesday, February 24th 2016
10:10 am:
Subject: To be announced.
1:25 pm:
Speaker: Eduardo H. da Silva Neto, The University of British Columbia
Subject: Universal Charge Order in the Cuprate High-Tc Superconductors

In cuprate high-temperature superconductors, an antiferromagnetic Mott insulating state can be destabilized toward unconventional superconductivity by either hole or electron doping. Besides these two phases, in hole-doped cuprates a periodic distribution of the electronic density, or charge order (CO), was recently detected in the Y-based family [1], and echoed the long-known presence of stripe order in the La-based cuprates [2]. However, at that point, the universality of the CO phenomenon to the cuprates remained to be determined.

In this talk I will first discuss a novel combined scanning tunneling microscopy (STM) and resonant X ray scattering (RXS) experimental approach that established the formation of CO in the high-temperature superconductor Bi2Sr2CaCu2O8+x (Bi-2212) [3]. The CO in this system occurs with the same period as those found in Y-based or La-based cuprates and displays the analogous competition with superconductivity, therefore establishing its commonality to hole-doped cuprates. Still, the universality of charge order remained in question, with several experiments and theories pointing to hole-doping as a critical ingredient to its formation.

Here I will also present RXS measurements that demonstrated for the first time the presence of charge order in the electron-type cuprate Nd2-xCexCuO4 (NCCO) [4]. A comprehensive study of CO in NCCO as a function of doping, temperature, and magnetic fields, shows that CO does not require a pseudogap precursor state. We also find that while CO is universal to all cuprates, its interplay with superconductivity and antiferromagnetism is not. Finally, open questions in the field, as well as prospects for future experiments, will also be discussed.

[1] G. Ghiringhelli, et al. Science 337, 821 (2012).
[2] J. M. Tranquada, et al. Nature 375, 561 (1995).
[3] E. H. da Silva Neto, et al. Science 343, 393 (2014).
[4] E. H. da Silva Neto, et al. Science 347, 282 (2015).
[5] E. H. da Silva Neto, et al. in preparation (2016).

There will be no seminar this week.

Thursday, February 25th 2016
Speaker: Huaqing Mao and Liliya Williams
3:35 pm:
Speaker: John Wilkerson, University of North Carolina
Subject:  The Neutrino — Beyond the Standard Model
Refreshments to be served outside 101 Fraser after the colloquium.

Today we know that neutrinos are not the “dull”, massless particles originally encompassed in the standard model of fundamental interactions. Instead, we have discovered — as recognized by the 2015 Nobel Prize in Physics —that neutrinos oscillate as they travel through space and matter, and have tiny, yet to be understood masses. Because neutrinos are amongst the most abundant particles in the universe, these revolutionary discoveries about neutrinos have far reaching consequences for cosmology, astrophysics, and our basic understanding of fundamental interactions. Yet there remain intriguing and unanswered questions about neutrino properties: Is lepton number a conserved quantity? Are neutrinos their own anti-particle (Majorana as opposed to Dirac)? How much do neutrinos weigh? The search for a postulated rare decay process known as neutrinoless double beta decay potentially holds the key to answering these questions and to further elucidating the properties of these elusive subatomic particles.

Faculty Host: Marvin Marshak

Friday, February 26th 2016
11:15 am:
Speaker: Yao Leon Meng, University of Minnesota
Subject: Feasibility of Accelerator-Based Boron Neutron Capture Therapy (AB-BNCT)

Boron Neutron Capture Therapy is a promising option for the treatment of glioblastoma and other recurrent brain/neck/breast cancers. Although successful clinical trials have been made using nuclear reactors, BNCT application need neutron sources which are suitable to be installed in hospitals. Particle accelerators are appropriate for this purpose. I will overview the possible nuclear reactions as a neutron source 7Li(p,n)7Be, Be9(p,n)B9, D+T, etc and the corresponding target design,neutron moderation challenge. I will introduce the application of nuclear data library and Geant4 Monte Carlo code in BNCT study. The progress of new pre-clinical neutron absorbing agents based on nano medicine and other techniques will also be reviewed briefly.

Speaker: Chris Conklin, University of Minnesota
Subject: Electrokinetic flows in liquid crystals
Speaker: Tamar Friedmann (Rochester)
2:30 pm:
Speaker: Jamesina Simpson, U. of Utah
Subject: Maxwell’s Equations Modeling of Electromagnetic Wave Propagation in the Global Earth-Ionosphere Waveguide via the FDTD Method

Prof. Simpson’s research group is developing advanced full-wave Maxwell's equations models of electromagnetic wave propagation in the global Earth-ionosphere waveguide based on the finite-difference time-domain (FDTD) method. As a grid-based and time-domain method, FDTD permits simulation of arbitrary time-varying sources, as well as modeling of detailed geometries such as the Earth’s complete topography, oceans, geomagnetic field, and magnetized ionospheric plasma composition variation with position, altitude, and time of day. Previously, the global FDTD models have been applied to a variety of applications ranging from Schumann resonances to hypothesized electromagnetic precursors to earthquakes, remote-sensing of oil fields, and remote-sensing of localized ionospheric anomalies. More recently, her research group is extending the capabilities of the models and applying them to target detection within the oceans, geolocation at very low frequencies, stochastic FDTD modeling of ionospheric propagation, and space weather hazards to electric power grids.

Speaker: Marc Ereshefsky, Department of Philosophy, University of Calgary
Subject: Science and Metaphysics: Lessons from Microbiology
Refreshments served at 3:15 p.m.

The typical view of biological individuality is that such individuals have parents from one species and start life as single zygotes. However, recent work on microbial consortia challenges this view. The lesson from microbiology is not merely that we have been wrong about our favored account of individuality, but that we have been wrong to assume that there is one correct theory of individuality. Given the contingent nature of evolution we should expect a plurality of kinds of individuality. When we answer the question ‘What is a biological individual?’ with a plurality of accounts, we are more successful than we think.

3:35 pm:
Speaker: Emily Smith from Oregon State University
Subject: Why are complex numbers and functions hard in physics?

Complex numbers and functions are used in several fields of physics including electricity and magnetism, classical mechanics, and quantum mechanics. However, as my initial research showed, formal instruction on complex algebra in the undergraduate curriculum at Oregon State University tended to repeat the same simple introduction multiple times, rather than providing a more extended treatment. We have developed and implemented assessments and interviews to gauge junior physics majors' developing fluency with complex algebra in a longitudinal study. I have identified tasks which are new to most students and have further delineated skills according to those which are easy to learn and retain, those which are fundamentally easy but cause persistent difficulties, and those which are actually difficult. Results from interviews, pretests, quizzes, and exam problems have suggested changes to in-class instruction, homework problems, and other resources in both mathematics and physics contexts. I will discuss how studies of this nature might inform changes to the curriculum and the development of computer problem solving coaches.

Speaker: Jim Kakalios, University of Minnesota
Subject: Novel Transport Phenomena in Amorphous Semiconductors

Monday, February 29th 2016
12:15 pm:
Speaker: Tomotake Matsumura, Institute of Space and Astronautical Science (ISAS/JAXA)
Subject: Next generation inflationary probe using CMB polarization: LiteBIRD

LiteBIRD is a next generation satellite mission to probe the physics of inflation by measuring the cosmic microwave background polarization. The science goal of LiteBIRD is to measure the primordial B-mode with a sensitivity of sigma_r<0.001, and this enables to test the major large-single-field slow-roll inflation models. The design philosophy is to focus on measuring the inflationary B-mode at ell below 200. Currently there is a worldwide competition to hunt this inflationary B-mode signal first by ground- based, balloon-borne, and space-borne CMB experiments. A satellite platform is ideal to probe the large angular scale B-mode with high sensitivity due to no atmosphere. LiteBIRD measures from L2 for three years using a superconducting detector array. The observing frequency spans from 40 to 400 GHz and LiteBIRD scans about 50 % of sky within a day. A signal is modulated by a half-wave plate to mitigate the detector system 1/f and the differential systematics. Currently LiteBIRD is in transition to Phase-A1. In this talk, we will describe the mission concept, the overview, and the current status of LiteBIRD.

Faculty Host: Shaul Hanany

Tuesday, March 1st 2016
12:00 pm:
Speaker: Scott Thaller, University of Minnesota
Subject: Plasmapause dynamics during geomagnetic storms; a synoptic look
Speaker: Jack Hellerstedt, Monash University
Subject: Combined in situ thin film growth and characterization of topological materials
Note change of day, time and room from usual CM Seminar

"Motivated by the persistent doping problems plaguing the seminal topological "insulator" Bi_2Se_3, we have developed an apparatus capable of thin film growth combined with in situ, real time transport measurements, which has provided insight into gaining ready access to the topological regime. We have extended this success to studying the topological Dirac semimetal Na_3Bi, whose reactivity to ambient prohibits the use of conventional sample preparation techniques. Our thin film samples have low temperature mobilities in excess of 6,000 cm^2/Vs. Perpendicular magnetoresistance up to 1T shows unusually large quadratic behavior with weak anti-localization at low field. I will discuss our latest efforts to understand our results in terms of spatial charge inhomogeneity."

4:30 pm:
CM Journal Club in PAN 120
Speaker: Ruiqi Xing
Subject: Density-matrix renormalization group(DMRG) and quantum information theory

The Density-matrix renormalization group is a powerful algorithm invented by Steven White in 1992, and it is nowadays the most efficient method for one-dimensional quantum many-body systems and has achieved unprecdented precision in the description of them.

I will talk about
(1) Introduction and the theory behind DMRG,
(2) DMRG algorithms,
(3) Why is DMRG successful: Entanglement entropy and DMRG,
(4) Matrix product state and DMRG(if time permits).

References
U. Schollwöck, The density-matrix renormalization group,RMP,77,259
Density-Matrix Renormalization - A New Numerical Method in Physics, Peschel, I., Wang, X., Kaulke, M., Hallberg, K.,Springer,1999


Wednesday, March 2nd 2016
10:10 am:
Biophysics Seminar in 120 PAN
There will be no journal club due to the biophysical society meeting.
1:25 pm:
There will be no seminar this week.
Speaker: Jianming Bian, University of Minnesota
Subject: Liquid Argon Time Projection Chamber for Neutrino Physics

The observation of neutrino oscillation has revolutionized neutrino physics and opened a window towards new physics. The next goal in neutrino oscillation physics is to build multiple-kiloton neutrino detectors to decisively determine CP violation in the neutrino sector and the neutrino mass hierarchy. Due to the high performance and low cost, the Liquid Argon Time Projection Chamber (LArTPC) is an exceptionally promising technique for the next generation of neutrino experiments. Many R&D efforts for LArTPC are being carried out around
the world. This talk will give an introduction to the LArTPC technology and an overview of LArTPC neutrino experiments.


Thursday, March 3rd 2016
08:00 am:
Untitled in Physics
Speaker: Micaela Bagley and Kyle Willett
3:35 pm:
Speaker: Leo Radzihovsky, University of Colorado
Subject: Critical matter, chiral symmetry breaking and emergent Higgs mechanism
Refreshments to be served outside 101 Fraser after the colloquium.

The upshot of extensive studies of fluctuations is that their qualitative importance typically confined to isolated critical points of continuous transitions between phases of condensed matter. This conventional wisdom also predicts the number of low energy Goldstone modes based on the pattern of symmetry breaking. I will discuss condensed matter systems, that violate this standard paradigm via an emergent Higgs mechanism. Even more spectacularly, these systems exhibit “critical” ordered phases, with universal power-law properties reminiscent of continuous phase transition, but without any fine-tuning and extending throughout the ordered phase. The most interesting recent example is the twist-bend nematic liquid crystal —— a homogeneous liquid that spontaneous breaks chiral symmetry.

Faculty Host: Natalia Perkins

Friday, March 4th 2016
11:15 am:
Speaker:  Dr. Rajan Gupta, Los Alamos National Lab
Subject: Nucleon Matrix Elements: From Charges to nEDM

In this talk I will present the progress we have made in the calculation of the matrix elements of quark bilinear operators within nucleons using lattice QCD. These are needed to probe many phenomenologically interesting quantities including (i) the isovector and flavor diagonal charges g_A, g_S and g_T; (ii) the electric, magnetic and axial vector form factors; (iii) generalized parton distribution functions (GPDs); (iv) the nucleon sigma term; (v) strangeness of the nucleon and (vi) the matrix elements of novel CP violating operators and their contributions to the neutron electric dipole moment. Strategies for obtaining high statistics results using the all-mode-averaging method and for for mitigating excited-state contamination will be discussed. I will present high statistics results for the charges and quark electric dipole moments and their implications for Split SUSY. I will also describe a new method for calculating the quark chromo electric dipole moments.

Speaker: Yang Tang, University of Minnesota
Subject: Doping dependence of the antiferromagnetic response of HgBa2CuO4+d
Speaker: No Seminar
2:30 pm:
Speaker: Jake Bailey, Earth Sciences, U. of Minnesota
Subject: Geobiology and the role of bacteria in the formation of phosphatic mineral deposits

Microbial metabolisms have fundamentally changed the face of our planet, from the production of oxygen by oxygenic photosynthesis, to the formation of certain economically-important ore deposits. And yet, the origins, evolution, and chemical mechanisms of many of these geobiological processes are not well understood. My research group investigates a group of remarkable bacteria, known as sulfur-oxidizing bacteria, which appear to be involved in the formation of calcium phosphate mineral deposits. Understanding how these deposits form is important because they currently serve as the primary source of phosphorus for agriculture, making them a non-renewable resource that is being rapidly depleted. The role of bacteria in the formation of these mineral deposits also has potential implications for paleontology and astrobiology.

Speaker: Mara Mills, Department of Media, Culture & Communication, New York University
Subject: Speed Listening by Blind Readers and the History of Audio Time Compression
Refreshments served at 3:15 p.m.

Talking Books for blind readers spurred the commercialization of mainstream audiobooks after World War II, but the two formats soon diverged in terms of reading strategies. This talk will discuss the cultural imperative for aural speed reading that drove early time-stretching innovations in the magnetic tape era, allowing playback rate to be changed without affecting pitch.

3:35 pm:
Speaker: Laura McCullough, UW-Stout
Subject: The Current Status of Women in Physics
To be announced.

Women have made significant gains in representation in physics, and yet we have a long way to go. What are the factors that affect the recruitment and retention in physics? This talk will share the most current research on the barriers that women in physics face.

Speaker: Natalia Perkins, University of Minnesota
Subject: Correlated electronic systems with strong spin-orbit coupling

Monday, March 7th 2016
12:15 pm:
Speaker: Melanie Galloway - UMN
Subject: Galaxy Zoo Hubble: First results of the redshift evolution of disk fraction in the red sequence

The transition of galaxies from the blue cloud to the red sequence is commonly linked to a morphological transformation from disk to elliptical structure. However, the correlation between color and morphology is not one-to-one, as evidenced by the existence of a significant population of red disks. As this stage in a galaxy's evolution is likely to be transitory, the mechanism by which red disks are formed offers insight to the processes that trigger quenching of star formation and the galaxy's position on the star-forming sequence. I use a large sample of galaxies from the Galaxy Zoo: Hubble project, which uses crowdsourced visual classifications, to study the population of disk galaxies in the red sequence as a function of cosmic time. Preliminary results confirm that the fraction of disks in the red sequence decreases as the Universe evolves from z = 1 to z=0.3.

Faculty Host: Lucy Fortson

Tuesday, March 8th 2016
12:00 pm:
There will be no seminar this week so that the group can attend David Brain's colloquium.
4:30 pm:
CM Journal Club in PAN 120
No JC this week.

Wednesday, March 9th 2016
10:10 am:
Subject: Summary of the Biophysics Society Meeting
1:25 pm:
Speaker: Yuan Li, International Center for Quantum Materials, Peking University
Subject: Story of Electrons Told by Phonons

Intriguing phase behaviors of correlated electrons have been a subject of major research interest over the past half a century, and they are all realized in a framework in which the electrons constantly interact with their hosting crystal lattice. As a result, not only does electrons’ footprint on the lattice help us on the detection of various electronic phases, but the explicit consideration of electron-phonon interactions may be necessary in order for us to thoroughly understand the collective behavior of the electrons.

In this talk, I will present a series of studies aiming to elucidate the role of electron-phonon interactions in electron correlations, using Raman scattering as the primary tool in conjunction with complementary techniques. I will first discuss how electron-phonon interactions, primarily in the form of dynamic magnetoelastic coupling, can be utilized to elucidate the genuine phase boundary and physical origin of the electronic nematic phase in iron-based superconductors. Then I will take a detour to a conventional charge-density-wave material and show that the momentum dependence of electron-phonon interactions is crucial for a quantitative understanding of charge ordering behavior even in the simplest case. This brings up the idea whether it is possible to enhance the interactions between conduction electrons and phonons in particularly important momentum regions, if the material also possesses local-moment magnetism on the back side of the same coin from the Fermi-liquid quasiparticles. Indeed we have found that in a structurally simple spiral magnet, the interaction between phonons and local-moment magnetism gives rise to hybrid magnetoelastic excitations, or “magnetophonons”, at the dispersion intersections between phonons and magnons. How such emerging excitations might affect conduction electrons or even mediate Cooper pairing in unconventional superconductors will be discussed.

There will be no seminar this week.

Thursday, March 10th 2016
Speaker: Vihang Mehta and Michael Rutkowski
Speaker:  Carsten Honerkamp (Institute for Theoretical Solid-State Physics, RWTH Aachen University)
Note date and time of special seminar

After an introduction, in the first part of the talk, I discuss a new fermionic functional renormalization group variant for two-dimensional lattice models that combines a physically appealing truncation of the wavevector dependence of the running interactions with certain numerical advantages. This allows for an efficient parallelized evaluation in which, e.g., the convergence of the expansion can be checked. In the second part of talk, I present new results on a model for iron superconductors that show that nematic orbital ordering occurs in different forms as competitor but also concomitant ordering tendency to the more conventional antiferromagnetic ordering and spin-fluctuation-induced pairing at low energies.

Faculty Host: Andrey Chubukov
3:35 pm:
Speaker: David Brain, University Colorado at Boulder
Subject: Has the Martian Atmosphere Disappeared Over Time?
Refreshments to be served outside 101 Fraser after the colloquium.

The Martian surface has abundant evidence for the presence of stable liquid surface water over long periods of time in its history, a situation that cannot be accommodated by the present thin atmosphere. One potential inference is that Martian atmosphere was thicker long ago, and atmospheric particles have since been removed. Escape of the atmosphere to space is one possibility, but the amount of escape that has occurred over time is highly uncertain.

I will present results from the MAVEN (Mars Atmosphere and Volatile EvolutioN) spacecraft mission to evaluate the importance of atmospheric escape for the climate history of Mars. MAVEN has orbited Mars since September 2014, and is currently in its first mission extension. I will highlight results that teach us about the chain of events that lead to atmospheric escape - including the drivers of escape from the Sun and solar wind, the atmospheric particle reservoirs for escape, and the escape processes and rates. I’ll then describe how lessons from MAVEN can teach us about planetary atmospheric evolution everywhere.

Faculty Host: Cynthia Cattell

Friday, March 11th 2016
11:15 am:
Speaker: Mikhail Voloshin, University of Minnesota
Subject: Heavy Exotic Mesons and Baryons

According to the original quark model template there are mesons consisting of a quark and anantiquark, and baryons made from three quarks. Strongly interacting particles that do not fit this template are called exotic. Experimental findings of recent years have uncovered existence of exotic mesons: tetraquarks, and baryons: pentaquarks, containing an additional heavy quark-antiquark pair. All such well established exotic states contain heavy quarks (c or b). I discuss some properties of such particles and the current theoretical approaches to understanding their internal dynamics.

APS March Meeting practice talks
Speaker: Yuri Bonder (ICN - UNAM)
Subject: Using effective field theory to test Lorentz invariance
2:30 pm:
Speaker: Dr. Danielle Berg, U of Wisconsin-Milwaukee
Subject: Building a Cosmological Abundance Scale

Tracing galaxy populations over cosmic time is key to understanding their evolutionary processes. The chemical abundances of local galaxies have been well studied, revealing a wealth of information about the processes which produce them, the physical conditions of the nebular gas, and their relationship to the mass and luminosity which characterizes the host galaxy. While nearby low-mass dwarfs (< 1E8 Msol) are relatively easy to study, their faintness and relatively small sizes make them difficult to observe in the distant universe. We can overcome this challenge by using strong gravitational lensing, which can amplify the flux of a source by a factor of 30 or more, to study the detailed physical properties of distant galaxies. Interestingly, the best studied objects at cosmological distances have revealed that the physics of distant low-metallicity star-forming galaxies can be very different than their local counterparts. I will present secure measurements of the physical conditions in individual sources, both near and far, providing insights into the chemical abundance ladder and helping to build a uniform cosmological abundance scale.

No Colloquium: Spring Break
3:35 pm:
There will be no seminar this week.
Speaker:  Dan Dahlberg
Noise in Mesoscale Magnetic Particles

Monday, March 14th 2016
There will be no seminar this week.

Tuesday, March 15th 2016
12:00 pm:
There will be no seminar this week, spring break.
4:30 pm:
CM Journal Club in PAN 120
No journal club, spring break

Wednesday, March 16th 2016
10:10 am:
Biophysics Seminar in 120 PAN
There will be no seminar this week, spring break.
1:25 pm:
There will be no seminar this week, spring break.

Thursday, March 17th 2016
Speaker: No Journal Club - Spring Break
Speaker: There will be no colloquium this week--SPRING BREAK

Friday, March 18th 2016
11:15 am:
There will be no seminar this week, spring break.
There will be no seminar this week, spring break.
Speaker: No Seminar (Spring Break)
2:30 pm:
Speaker: No colloquium this week - U of M closed
No Colloquium: Spring Break
3:35 pm:
There will be no seminar this week, spring break.
There will be no seminar this week, spring break.

Monday, March 21st 2016
12:15 pm:
Speaker: Christina Ignarra - SLAC
Subject: The LUX and LZ Dark Matter Experiments

The Large Underground Xenon (LUX) experiment is searching for Weakly Interacting Massive Particles (WIMPs) via direct detection. LUX studies particle interactions in 350 kg of liquid xenon using a dual-phase xenon TPC at the Sanford Underground Research Facility (SURF). We have recently improved our "run 3" limits with extensive detector calibrations and analysis improvements, and will finish our final run, run 4, within the next few months. LUX will be replaced by the LUX-ZEPLIN (LZ) detector, scaling up the WIMP search volume by a factor of 50. A combination of the larger size and other upgrades such as a liquid scintillator outer detector will significantly increase discovery potential.

Faculty Host: Shaul Hanany

Tuesday, March 22nd 2016
12:00 pm:
There will be no Space Physics Seminar this week.
4:30 pm:
CM Journal Club in PAN 120
No JC this week.

Wednesday, March 23rd 2016
10:10 am:
Subject: To be announced.
1:25 pm:
Speaker: Maxim Khodas, University of Iowa and Hebrew University, Jerusalem
Subject: Spin resonance in two-dimensional electron systems confined to narrow channels

We consider the two-dimensional electron gas confined laterally to a narrow channel. As the Zeeman splitting matches the inter-subband splitting due to the geometrical quantization, the non-local spin polarization develops a minimum as reported by Frolov et al. [Nature (London) 458, 868 (2009)]. This phenomenon termed Ballistic Spin Resonance is due to the degeneracy between the nearest oppositely polarized sub-bands lifted by spin-orbit coupling. The resonance survives the weak and short-range interaction. The latter detunes it and as a result shifts the Zeeman splitting at which the minimum in spin polarization occurs. The shift is attributed to the absence of Kohn theorem for the spin sloshing collective mode. We characterized the shift due to weak interaction quantitatively by analyzing the spin sloshing mode phenomenologically.

Speaker: Michelle Stancari, Fermilab.
Subject: The Deep Underground Neutrino Experiment: Physics program and Liquid Argon Detector Prototyping

Thursday, March 24th 2016
Speaker: Matt Gomer and Denis Wittor (Hamburg)
2:00 pm:
Thesis Defense in PAN 210
Speaker: Dominick Rocco, University of Minnesota
Subject: Muon Neutrino Disappearance in NOvA with a Deep Convolutional Neural Network Classifier
This is the public portion of Mr. Rocco's thesis defense.

The NuMI Off-axis Neutrino Experiment (NOvA) is designed to study neutrino oscillation in the NuMI beam. Neutrinos at the Main Injector (NuMI) is currently being upgraded to provide 700 kW. NOvA observes neutrino oscillation using two detectors separated by a baseline of 810 km; a 14 kt Far Detector in Ash River, MN and a func- tionally identical 0.3 kt Near Detector at Fermilab. The experiment aims to provide new measurements of ∆m232 and θ23 and has potential to determine the neutrino mass hierarchy as well as observe CP violation in the neutrino sector. Essential to these analyses is the classification of neutrino interaction events in NOvA detectors. Raw detector output from NOvA is interpretable as a pair of images which provide orthogonal views of particle interactions. A recent advance in the field of computer vision is the advent of convolutional neural networks, which have delivered top results in the latest image recognition contests. This work presents a novel approach particle physics analysis in which a convolutional neural network is used for classification of particle interactions. The approach has been demonstrated to improve the signal efficiency and purity of the event selection, and thus physics sensitivity. Early NOvA data has been analyzed (2.74×1020 POT, 14 kt equivalent) to provide new best-fit measurements of sin2(θ23) and |∆m232|.

3:35 pm:
No colloquium due to late cancellation

Friday, March 25th 2016
11:15 am:
Speaker: Projjwal Banerjee, University of Minnesota
Subject: Neutron_capture in Metal-Free and Metal-Poor Stars

We propose a new site for neutron-capture process in massive metal-free and metal-poor stars during the late stages of their evolution. We find that a wide range of neutron-capture abundance patterns can be produced. This can explain the fact that neutron-capture elements have been observed in most of the metal-poor stars even at the lowest metallicities and that the observed patterns of these elements show deviations from the solar-r process pattern.

Speaker: Mengxing Ye, University of Minnesota
Cancelled today -- Moved to April 8th
Speaker: Matthew Schwartz, (Harvard)
Subject: Tunneling in Quantum Field Theory and the Fate of the Universe

One of the most concrete implications of the discovery of the Higgs boson is that, in the absence of physics beyond the standard model, the long term fate of our universe can now be established through precision calculations. Are we in a metastable minimum of the Higgs potential or the true minimum? If we are in a metastable vacuum, what is its lifetime? To answer these questions, we need to understand tunneling in quantum field theory. As we delve into how tunneling works, we find many unusual elements: complex quantities which should be real, gauge-dependent quantities which should be physical, an hbar expansion which differs from the ordinary loop expansion, and ultraviolet degrees of freedom that don't decouple. This talk will discuss some of these elements and present some new perspectives on quantum tunneling.

2:30 pm:
Speaker: Wlodek Kluzniak, Copernicus Astronomical Center, Warsaw
Subject: High frequency luminosity variations in accreting black holes

Several black holes in our Galaxy are known to accrete matter from their stellar binary companion. Most of these sources are X-ray transients, being luminous during long "outbursts" usually lasting many months. In certain spectral states, some of these sources exhibit two very high frequencies, which are quite stable over the years. In each of the three or four sources where they appear the two frequencies are in a 3:2 ratio, and they scale inversely with the mass of the black hole. The highest known frequency of 450 Hz occurs for a six solar mass black hole. I will discuss some models of these so called high frequency quasi-periodic oscillations (QPOs), and their possible counterparts in supermassive black holes.

Speaker: Bruce Glymour, Department of Philosophy, Kansas State University
Subject: Evolutionary Biology and Inertia in Theory Change: A Preliminary Indictment of Explanatory Commitments
Refreshments served at 3:15 p.m.

Kuhn famously argued that scientific paradigms are immensely resilient to empirical evidence against their core theories. I offer a tentative and contentious diagnosis of one such case in evolutionary biology. Post-Synthesis evolutionary theory has been characterized by three nominally distinct theories of natural selection—classical population genetics and its extensions, quantitative genetics, and the halfway house occupied by models employing variants of the Price equation. Notwithstanding their important differences, all share the idea that selection is to be understood in terms of differences among types in one or another measure (generally called fitness) defined as some function or partial function of a probability density over reproductive success. Models implementing that idea immediately confront some intractable problems that limit their explanatory and predictive power. There are alternative conceptions of selection which do not face exactly those problems, and the mathematical tools requisite to them were available either before or roughly contemporaneously with the Synthesis itself. While more orthodox models generally employ the analysis of variance or co-variance in both discovery and explanatory contexts, the alternative models rely on regression and path analysis, and in so doing generate importantly different kinds of explanation and are vulnerable to a different suite of errors. In this paper I delineate (some of) the problems plaguing traditional models, and explore the idea that their continued dominance in both evolutionary population biology and philosophy biology is owed in large measure to a prior commitment to the explanatory importance of one kind of non-causal, statistical explanation.

3:35 pm:
Speaker: Miranda Pihlaja
Subject: Understanding Students’ Experience using a Citizen Science Project: Initial Results

Using science practices in science education has been the norm
for over three decades. Science education has turned from fact-learning to
activity-based learning. While students act or think like scientists, they
are missing a key part of science- the unknown. Using a citizen science
project as part of a science curriculum may be useful in giving students a
real scientist experience by having them participate in real science. This
talk outlines the methodology for a two-part study of students’ responses
to participating in a citizen science project as part of a class
assignment. I will also discuss initial results and implications

Speaker: Martin Greven, University of Minnesota
Subject:  Hidden magnetism and hidden Fermi-liquid behavior of the cuprate high-temperature superconductors

Monday, March 28th 2016
12:15 pm:
Speaker: Matthew Fritts - UMN
Subject: CDMS WIMP detectors

The CDMS collaboration searches for dark matter WIMPs using cryogenic detectors which measure both the ionization and the phonons produced by a particle interaction. I will describe two different detector technologies employed to probe a wide range of possible WIMP masses, show measurements being performed on next-generation CDMS detectors at UMN, and present plans for the SuperCDMS SNOLAB phase of the experiment.

Faculty Host: Vuk Mandic

Tuesday, March 29th 2016
12:00 pm:
There will be no seminar this week.
4:30 pm:
CM Journal Club in PAN 120
Speaker: Mengxing Ye
Subject: Coherent state path integral in quantum spin systems

I will introduce a very useful method to study quantum spin systems, namely, the coherent state path integral. One can see that the Berry phase term appears naturally in the path integral. I will take the antiferromagnetic model on a bipartite lattice as an example, and discuss the phases and phase transitions in this model.


Wednesday, March 30th 2016
10:10 am:
Biophysics Seminar in 120 PAN
Speaker: Allen Liu, University of Michigan
Subject: Mechanobiology of Membrane: from Mechanosensitive Channels to Artificial Cells

Biological membranes are involved in a large number of cellular processes including cell migration, membrane trafficking, and cell signaling. Significant amount of work have elucidated the molecular machineries that regulate dynamic membrane-based processes. In parallel, there are growing interests in recent years in trying to understand how mechanical state of the cells are utilized as a regulatory input to control cellular processes. My lab is interested in studying the mechanochemical responses of biological systems. In this talk, I will present two projects related to this theme. On the cellular level, we have reconstituted the function of a bacterial mechanosensitive channel MscL in mammalian cells. Using this system, we investigated the role of actin cytoskeleton in mediating local membrane tension that activates MscL. On the synthetic level, we are building artificial systems that can sense mechanical input and transduce a biochemical response. To this end, we are attempting to build artificial platelets that mimic the functionalities of natural platelets. I will discuss several modular platforms that we have developed that together will integrate into functional artificial cells. Together, our work will provide basic understanding of cellular mechanotransduction and potential applications of force-activated synthetic biology.

1:25 pm:
Speaker: Abhay Pasupathy, Columbia University
Subject: Electronic Nematicity in the Iron Pnictides

I will discuss scanning tunneling microscopy (STM) measurements of electronic nematicity in the iron pnictide superconductors, focusing on the compound NaFeAs. I will show that a clear signal of the electronic nematicity can be seen in the local density of states as measured by STM. Questions that can be answered from the STM measurements include (a) do magnetic or structural degrees of freedom drive nematicity (b) how can we distinguish between true long range order and a strong susceptibility using STM measurements (c) where in the phase diagram are nematic order and fluctuations observed (d) what is the energy scale associated with nematicity at different points in the phase diagram (e) what is the relationship between nematicity (either order or fluctuations) and superconductivity. I will discuss answers to all of these questions, and along the way discuss new STM techniques that we have developed for this purpose that are broadly applicable to other quantum materials.

Speaker: Lisa Whitehead, University of Houston
Subject: CAPTAIN experiment

Thursday, March 31st 2016
Speaker: Tom Jones
3:35 pm:
Speaker: Abhay Pasupathy, Columbia University
Subject: Experiments in Flatland
Refreshments to be served outside 101 Fraser after the colloquium.

In the past decade, scientists have figured out how to create and probe crystalline materials that are a single or few atomic layers in thickness. These two-dimensional (2D) materials have a host of new physical, chemical and mechanical properties. The most well-known member of this family is graphene, but in the past few years we have been able to synthesize a whole host of 2D materials including semiconductors, superconductors, magnets, charge density waves, and so on. In this talk, I will present some of my research group's experimental exploration of these materials. In particular, I will discuss the following topics (a) how one can induce spatially ordered phases in graphene (b) what happens to a crystalline superconductor when we take it to the 2D limit (c) ways in which complex phases like charge density waves can be tuned in 2D samples.

Faculty Host: Rafael Fernandes

Friday, April 1st 2016
11:15 am:
There will be no seminar this week.
12:20 pm:
Speaker: Biqiong Yu, University of Minnesota
Subject: “X-ray scattering study of Charge-Density-Wave order in Nd2-xCexCuO4 and HgBa2CuO4+d
Note: change of location for seminar, this week only.
Speaker: Kiel Howe (Fermilab)
Subject: Induced Electroweak Symmetry Breaking and the Composite (Twin) Higgs

In induced electroweak symmetry breaking models, the SM-like Higgs vev is triggered by a small hidden sector electroweak symmetry breaking tadpole. This structure decouples the physical Higgs mass from the quartic term in the Higgs potential, leading to interesting possibilities in UV completions of the Higgs sector as a composite pseudo-Nambu Goldstone boson (PNGB). This framework can allow the minimal ~v^2/f^2 tuning of some models to be evaded, and is particularly appealing in the case of the composite twin Higgs where neutral top partners cut off the leading contributions to the PNGB potential.

2:30 pm:
Speaker: Warren Skidmore
Subject: The Thirty Meter Telescope Observatory: The Next Generation Ground Based Optical/Infra-Red Observatory

After a construction status update, I will describe how the telescope design was developed to support a broad range of observing capabilities and how the observatory is being engineered. I'll discuss some of the observational capabilities that the Thirty Meter Telescope will provide and some of the areas of study that will benefit from the TMT's capabilities, specifically synergistic areas with new and future proposed astronomical facilities. Finally I will describe the avenues through which astronomers can have some input in the planning of the project and potential NSF partnership, prioritizing the development of 2nd generation instruments and directing the scientific aims for the observatory.

Speaker: Jan Golinski, Department of History, University of New Hampshire
Subject: The Experimental Self: Humphry Davy and the Making of a Man of Science
Refreshments served at 3:15 p.m.

Humphry Davy (1778-1829) was a pivotal figure in the emergence of new scientific disciplines at the beginning of the nineteenth century, but his career cannot be understood through the traditional narrative of specialization and professionalization. Davy was a protean individual who forged his social persona with remarkable creativity. He exploited his institutional location to build a charismatic reputation with a public audience. He applied new electrical instruments and powers to reconfigure the discipline of chemistry. And he engaged in a sustained and profound exploration of his own subjectivity, through testing nitrous oxide and galvanism on his own body, and through literary exercises of poetry and fiction. Social ambidexterity, interdisciplinary creativity, and sometimes grueling self-experimentation were the keynotes of this extraordinary individual’s self-made identity. I shall argue that Davy’s experiments in selfhood illuminate the historical formation of the man of science in an era when social institutions and personal subjectivity were both in flux.

3:35 pm:
Speaker:  Bijaya Aryal UMN-Rochester
Subject: "Exploring Students’ Views about an Internet-based Computer Coaching System for Physics Problem Solving"

We have implemented an Internet-based Computer Coaching System for problem solving at University of Minnesota Rochester for last several semesters. Some of the Coaches are introduced in classroom as part of group activity and the other Coaches are made optional for them to use outside classroom as a supplement in problem solving support. Recently, we interviewed students to assess students’ degree of favorability about the Coaches and usefulness and effectiveness of the Coaches. In this presentation I will describe interview results focusing on the areas of strengths and areas of weakness of the Coaches as perceived by the students. I will also discuss attributions of students’ quantitative and computer technology skills on their opinions about the Coaches and their usage pattern.

Speaker: Carolyn Bishoff, Physics, Astronomy and Earth Sciences Librarian
Subject: Workshop on data management

Monday, April 4th 2016
12:15 pm:
Speaker: Projjwall Banerjee, University of Minnesota
Subject: Synthesis of Heavy Elements in Primordial Stars

We propose a new site for the synthesis of heavy elements by neutron-capture process in primordial metal-free as well as metal-poor stars during the late stages of their evolution. We find that a wide range of neutron-capture abundance patterns can be produced. This can explain the fact that neutron-capture elements have been observed in most of the metal-poor stars even at the lowest metallicities and that the observed patterns of these elements show deviations from the solar-r process pattern.

Faculty Host: Yong-Zhong Qian

Tuesday, April 5th 2016
12:00 pm:
There will be no seminar this week.
4:30 pm:
CM Journal Club in PAN 120
Speaker: Xiaoyu Wang
Subject: Spin glass and replica symmetry breaking

Spin glass is a phenomenon where spins are randomly frozen in space, while having negligible temporal fluctuations. Spin glass occurs typically in disordered systems. In this talk, I will discuss the Sherrington-Kirkpatrick (SK) model of Ising spins, the mean field phase diagram of which can be studied using the replica method. I will explain replica symmetry breaking (RSB) as a definition of spin-glass phase, and discuss the Parisi solution in full detail. I will conclude by discussing the physical implications of the Parisi solution.

Ref: Statistical Physics of Spin Glasses and Information Processing - An Introduction, Hideyoshi Nishimori


Wednesday, April 6th 2016
10:10 am:
Biophysics Seminar in 120 PAN
There will be no seminar this week.
1:25 pm:
Speaker: Alan I. Goldman, Iowa State University and Ames Laboratory
Subject: Magnetic rare-earth-based quasicrystals

In the thirty years since the discovery of quasicrystals by Dan Shechtman there has been tremendous progress in our understanding of the structure of quasicrystals and aperiodic systems in general. Indeed, the question first asked by Per Bak soon after Shechtman’s discovery, “Where are the atoms?”, can largely be answered for at least one class of quasicrystals, the i-YbCd5.7 icosahedral phase. Progress in our understanding of the consequences of aperiodicity for physical phenomena such as the electronic, magnetic, and optical properties has lagged somewhat but we have recently seen a surge of activity and new results. On the magnetism front, the discovery of a new family of magnetic quasicrystals and their closely related crystalline approximants, has allowed for a direct comparison of the impact of aperiodicity on magnetic interactions in compounds that have similar local structures.

Examples of stable binary icosahedral quasicrystals are quite rare and, before the discovery of icosahedral quasicrystals in the i-R-Cd system (R = Gd to Tm, Y), there were no known examples that featured localized magnetic moments. Local-moment-bearing binary quasicrystals represent the compositionally simplest system for the study of magnetic interactions in aperiodic compounds and, therefore, the new R-Cd quasicrystal family will play a key role in these studies, offering non-magnetic, Y, Heisenberg-like, Gd, and non-Heisenberg (CEF split) Tb to Tm members, in addition to the structural and compositional simplicity of a binary phase. Furthermore, the existence of a corresponding set of cubic approximants, RCd6, to the icosahedral phase allows for direct comparisons between the low- temperature magnetic states of crystalline and quasicrystalline phases with fundamentally similar local structures. RCd6 may be described as a body-centered cubic packing of the same clusters of atoms as found in the newly discovered icosahedral phase. Using x-ray resonant magnetic scattering we have shown that the RCd6 approximants manifest long-range magnetic order at low temperatures, whereas the related icosahedral phase exhibits only spin-glass-like freezing at low temperatures. In order to understand the reason for the absence of long-range magnetic ordering in the quasicrystalline phase, we have recently completed a full structural refinement of the i-R-Cd system (R = Gd, Dy) series and are in the midst of both elastic and inelastic neutron scattering measurements of i-Tb-Cd. Our results, to date, will be described and discussed.

There will be no seminar this week.

Thursday, April 7th 2016
Speaker: Tony Young
3:35 pm:
Speaker: Adam Lyon, Fermilab
Subject:  The New Muon g-2 Experiment at Fermilab
Refreshments to be served outside 101 Fraser after the colloquium

The anomalous magnetic moment of the muon is a direct window to new physics and has been the subject of nuclear and particle physics experiments for the past 60 years. It drives both theory and experiment to new levels of precision and sensitivity. The latest result in this enterprise is from the 1999-2001 run of the Brookhaven E821 experiment. With 0.54 parts per million (ppm) precision, it differs from the Standard Model prediction by more than 3 sigma – enough to be extremely intriguing, but not conclusive. By moving the main apparatus, a 50 foot diameter superconducting storage ring, from Brookhaven to Fermilab, the experiment will be repeated with a more intense and cleaner beam and all new detectors. The outcome will be a factor of four improvement in precision. If the difference seen at E821 between experiment and the Standard Model persists, the discrepancy will greater than 5 sigma and possibly be greater than 7 sigma if the theoretical prediction improves as expected. Such a result would be an undeniable signal of new physics. I will present the past, present, and future aspects of Muon g-2 measurement. With first muons only a year away, I will focus on the progress at the Fermilab experiment.

Faculty Host: Dan Cronin-Hennessy

Friday, April 8th 2016
11:15 am:
Speaker: Evan O'Connor, North Carolina State University
Subject: The Death of Massive Stars

Core collapse marks the end stage of stellar evolution and the beginning of one of the most energetic events in the modern universe. The transformation of the iron core in an evolved massive star to a neutron star releases a huge amount of gravitational binding energy, the equivalent of a few tenths of a solar mass. This energy source is tapped to produce the explosion we see as a core-collapse supernova. Core-collapse supernovae are a cornerstone of astrophysics. They unbind the nucleosynthetic products of massive stars, trigger local star formation, are the birth place for both neutron stars and black holes, the site of long gamma-ray bursts, and the list goes on.

At the heart of core-collapse supernovae is the central engine that turns the initial implosion of the iron core into an explosion that eventually propagates out through the star (or fails and produces stellar mass black holes). In order to understand this engine we must perform multidimensional hydrodynamic simulations that includes state of the art hydrodynamics, neutrino transport, nuclear microphysics, and treatments of gravity, among others, that make this problem truly rich in physics. In this talk, I will give an update on the present status of understanding the core-collapse supernova central engine including showing recent multidimensional results using a new neutrino transport scheme developed in the hydrodynamics package FLASH. I will also discuss the progenitor dependence of core-collapse supernovae and how we can use observables of the central engine, namely neutrinos, to constrain the late stages of stellar evolution.

Faculty Host: Yong-Zhong Qian
Speaker: Mengxing Ye, University of Minnesota
Subject: Quantum Phase Transitions in Triangular Heisenberg Antiferromagnets in a Magnetic Field
Speaker: Yasha Shnir (LTP, JINR)
Subject: Gravitating solitons and hairy black holes

We overview the pattern of evolution of self-gravitating solitons in the Einstein gravity coupled to matter field. We consider transformation of the matric and links between the Skyrmions and monopoles in flat space-time and Bartnik-McKinnon solitons and hairy black holes. We also briefly discuss corresponding solitons in asymptotycally AdS spacetime

2:30 pm:
Speaker: No colloquium this week. Please see the listing for the SPA colloquium on April 7th
Speaker: Deborah Mayo, Department of Philosophy, Virginia Tech
Subject: How to Stop Refighting the Statistics Wars
Refreshments served at 3:15 p.m.

If a statistical methodology is to be adequate, it needs to register how “questionable research practices” (QRPs) alter a method’s error probing capacities. If little has been done to rule out flaws in taking data as evidence for a claim, then that claim has not passed a stringent or severe test. The goal of severe testing is the linchpin for (re)interpreting frequentist methods so as to avoid long-standing fallacies at the heart of today’s statistics wars. A contrasting philosophy views statistical inference in terms of posterior probabilities in hypotheses: probabilism. Presupposing probabilism, critics mistakenly argue that significance and confidence levels are misinterpreted, exaggerate evidence, or are irrelevant for inference. Recommended replacements—Bayesian updating, Bayes factors, likelihood ratios—fail to control severity.

3:35 pm:
There will be no seminar this week.
Speaker: Nancy Sims, Copyright Program Librarian
Subject: Workshop on copyrights

Monday, April 11th 2016
12:15 pm:
Speaker: Giacomo Ciani - University of Florida
Subject: LISA Pathfinder: (free)-falling like never before

The recent announcement by the LIGO scientific collaboration has spurred excitement for the first direct detection of gravitational waves. However, the physical information contained in the signal is the real prize of this endeavor: the goal of the gravitational-wave community is to use routine detections as a tool to do astronomy, astrophysics and cosmology. To achieve this, we must cover as much of the gravitational-wave frequency spectrum as possible, in the same way we do with EM astronomy. LISA, a joint ESA-NASA space-borne interferometer designed to explore the signal-rich band from 0.1 to 100 mHz, has been officially canceled in 2011 due to budget constraints at NASA; it has however left two important legacies: eLISA and LISA Pathfinder. eLISA is a concept which is the baseline design for ESA's L3 large mission, currently projected to be lunched in 2034 with a likely contribution from NASA as a junior partner. LISA Pathfinder is a space mission designed to demonstrate free-fall at the unprecedented level of 30 fm/s^2/Hz^{1/2} spurious acceleration at 1 mHz, just a factor 10 short of what is needed for eLISA and several orders of magnitude better than any other space mission flown or under development. In doing this, it tests the core technologies likely needed by any interferometric GW space mission concept. LISA Pathfinder was lunched last December from the ESA spaceport in French Guiana, and started scientific operations at the beginning of March. Although official results are not yet available, I'll describe the mission design, its goals, the main technologies it is testing and the most recent updates and expectations.

Faculty Host: Shaul Hanany

Tuesday, April 12th 2016
12:00 pm:
There will be no seminar this week.
1:30 pm:
Thesis Defense in 130 PAN
Speaker: Nicholas Raddatz, University of Minnesota
Subject: Muon Neutrino Disappearance in NOvA
This is the public portion of Mr. Raddatz's thesis defense. His adviser is Dan Cronin-Henessy
3:00 pm:
Special Condensed Matter Seminar in 130 PAN (MNC Seminar Room)
Speaker: David Toyli, University of California, Berkeley
Subject: Resonance Fluorescence from an Artificial Atom in Squeezed Vacuum

Superconducting circuits offer a compelling platform for investigating light-matter interactions inaccessible to conventional atomic systems. Aided by the low-dimensionality and low loss of such circuits, here we experimentally investigate how changing the properties of the electromagnetic vacuum modifies atomic fluorescence. We strongly couple microwave-frequency squeezed light to a superconducting artificial atom and detect the resulting fluorescence with high resolution using a near-quantum-limited parametric amplifier. We observe a dramatic dependence of the spectrum of resonance fluorescence on the relative phase of the driving and squeezed vacuum fields and observe subnatural radiative linewidths that indicate up to 3.1 dB of squeezing below the ordinary vacuum level in the artificial atom’s environment [1]. Our results both validate the canonical predictions for resonance fluorescence in squeezed vacuum and provide a circuit architecture for investigating high-precision superconducting qubit measurement with squeezed input light.

[1] D.M. Toyli, A.W Eddins, et al., arXiv:1602.03240

Faculty Host: Paul Crowell
4:30 pm:
CM Journal Club in PAN 120
Speaker: Ioannis Rousochatzakis
Subject: The exactly solvable resonating valence bond liquid of the spin-1/2 Heisenberg kagome antiferromagnet

Abstract:
I will discuss one of the earliest examples of exactly solvable spin liquids in two spatial dimensions, introduced by G. Misguich et al back in 2002 [1] for the kagome lattice. The ground state of this model (a Rokhsar-Kiverson wavefunction) is currently believed to be adiabatically connected to the actual Z2 spin liquid ground state of the nearest-neighbor spin-1/2 Heisenberg model on the kagome, that is closely realized in herbertsmithite ZnCu3(OH)6Cl3.

[1] G. Misguich, D. Serban, and V. Pasquier, PRL 89, 137202 (2002)


Wednesday, April 13th 2016
10:10 am:
Subject: To be announced.
1:25 pm:
Speaker: Daniel Agterberg, UW-Milwaukee
Subject: Spin 3/2 pairing in topological half-heusler superconductors

Two key symmetries underlie the formation of superconductivity: parity and time reversal. These symmetries lead to the usual description of superconductivity in terms of pseudo-spin 1/2 fermions. Strong spin-orbit coupling plays an essential role in defining pseudo-spin and, we show, also allows for the intriguing possibility of pseudo-spin 3/2 fermions. In this talk, after a discussion on the role of symmetry on superconducting pairs, I will contrast the physics for pseudo-spin 1/2 and pseudo-spin 3/2 pairing with an emphasis on the topological half-heusler superconductors YPtBi and LuPtBi. These materials have recently been found to exhibit gapless excitations in the superconducting state. These materials also lack parity symmetry, and the general consequences of this for both pseudo-spin 1/2 and pseudo-spin 3/2 pairing will be highlighted throughout the talk.

Faculty Host: Andrey Chubukov
There will be no seminar this week.

Thursday, April 14th 2016
Speaker: Ryan Arneson and Lindsay Glesener
Speaker: Mikhail Baranov, ITP, University of Innsbruck
Subject: Majorana fermions in noisy Kitaev wires

Majorana fermions (non-Abelian anyons) appear as edge states in the topological phase of the Kitaev wire, and are naturally immune to static disorder. I discuss the effects of a classical noise ("time-dependent disorder") on the Majorana edge correlations, and on the fidelity of braiding operations for both global and local noise in the chemical potential. While in general noise will induce heating and dephasing, it is still possible to have long-lived quantum correlations in the presence of fast noise due to motional narrowing, even when the noise drives the system rapidly between the topological and non-topological phases.

3:35 pm:
Speaker: Wendy Freedman, University of Chicago
Subject: Measurement of Cosmological Parameters
Refreshments to be served outside 101 Fraser after the colloquium.

Over the past few decades, cosmologists have for the first time identified the major constituents of the universe. Surprisingly, the universe hardly resembles what we thought only a few decades ago. The universe is filled with dark matter that is not visible and energy that permeates all of space, causing its expansion to speed up with time. Accurate distances remain central to a number of fundamental problems in astrophysics and cosmology. They are critical for measurements of the acceleration of the universe using supernovae. A more accurate measurement of the Hubble constant is critical for providing independent constraints on dark energy, the geometry, and matter density of the universe. The increased precision of cosmic microwave background fluctuations (most recently with the Planck satellite) make these direct comparisons even more critical, given the physical degeneracies amongst different cosmological parameters, and the apparent tension with the direct measurements of the Hubble constant. There has been fundamental progress over the last couple of decades in measuring extragalactic distances. The upcoming decade promises robust distances and a measurement of the Hubble constant to a few percent accuracy.

Faculty Host: Clement Pryke

Friday, April 15th 2016
11:15 am:
Speaker: Dr. Marlene Nahrgang, Duke University
Subject: The QCD phase transition and its signatures in heavy-ion collisions

For a complete understanding of the QCD phase diagram it is important to connect first-principle thermodynamic calculations to experimental data from heavy-ion collision experiments of the RHIC Beam Energy Scan. In particular, the potential to discover the QCD critical point experimentally is of great interest. In this talk I will review the theoretical concepts of critical fluctuations at the QCD phase transition and discuss the current status of modeling these fluctuations in the dynamical evolution of heavy-ion collisions. Within the model of nonequilibrium chiral fluid dynamics I will show how different equations of state at finite baryochemical affect the dynamical domain formation at a first-order phase transition. Special emphasis is put on observables which are sensitive to the critical point and how they are affected by the out-of-equilibrium dynamics in heavy-ion collisions.

Speaker: Tianbai Cui, University of Minnesota
Subject: Rare region effects on the Ising-nematic quantum phase transition
Speaker: Jeremy Mardon, (Stanford)
Subject: Feeling the Pulse of Dark Matter

Over a huge mass range, from ~keV down to ~10^-22 eV, bosonic dark matter candidates can be described as oscillating classical fields. Through weak couplings to the Standard Model, they can induce in a variety of feint, time-oscillating classical signals. I will discuss ways to search for this dark matter “pulse”, including precision accelerometers, and the “Dark Matter Radio” being built at Stanford.

2:30 pm:
Speaker: No colloquium this week. Please see the listing for the SPA colloquium on April 14th.
Speaker: Oren Harman, Science, Technology & Society, Bar-Ilan University
Subject: The Price of Altruism
Refreshments served at 3:15 p.m.

Survival of the fittest or survival of the nicest? Since the dawn of time man has contemplated the mystery of altruism, but it was Charles Darwin who posed the question most starkly. From the selfless ant to the stinging bee to the man laying down his life for a stranger, evolution has given rise to a most perplexing behavior. Set against the sweeping tale of 150 years of scientific attempts to explain altruism, here is the moving story of a brilliant and troubled scientist - George Price - who paid the ultimate price for wrestling with the mystery of altruism.

3:35 pm:
Speaker: Brita Nellermoe, University of St. Thomas
Subject: Teaching Physics and Self-Efficacy to Pre-Service Teachers; The Evolution of Physics 101 at UST

Over the last 4 years the Physics 101 (Physics for Elementary Teachers) course at the University of St. Thomas has undergone a major shift in dynamic, structure and course goals. Here we will discuss those changes and the integration of Writing Across the Curriculum - Writing to Learn and Unit Projects to enhance student learning and self efficacy. Gains in physics knowledge and self-efficacy will be discussed as well as areas of improvement and future plans.

Subject: Panel on non-academic jobs

Monday, April 18th 2016
12:15 pm:
Speaker: Bing Zhang - University of Nevada, Las Vegas
Subject: Gravitational wave sources, short gamma-ray bursts, and fast radio bursts

Transient astrophysics has entered the multi-wavelength/multi-messenger era. It has been long speculated that short gamma-ray bursts (GRBs) may be associated with NS-NS or NS-BH mergers, so that they are leading EM counterpart for gravitational wave (GW) sources detectable by Advanced LIGO. The claim of a possible faint short GRB signal following the first BH-BH merger GW source, GW 150914, is completely unexpected. On the other hand, fast radio bursts (FRBs), a new type of coherent radio transients, are likely extragalactic and possibly have a cosmological origin. However, their physical nature remains unknown. I discuss two possible scenarios of GW/GRB/FRB associations. The first involves a supra-massive neutron star formed after a NS-NS merger, which collapses into a BH after 100s of seconds and produces an FRB. The second involves a merger of a BH-BH system, with at least one BH charged. The pre-merger magnetospheric activities of the system would power an FRB, and possibly a short GRB if the charge is large enough. I discuss how these scenarios may account for the recent interesting observations of GW 150914 and FRB 150418.

Faculty Host: Yong-Zhong Qian

Tuesday, April 19th 2016
12:00 pm:
Speaker: Charles McEachern, University of Minnesota
Subject: PC4 Models
4:30 pm:
CM Journal Club in PAN 120
Speaker: Marc Schulz

The transverse field Ising model in one dimension is the drosophila of spin systems and their phase transitions. I'll discuss the solution presented by Pfeuty (Ann.Phys.(N.Y.) 57, 79 (1970)), also referring to the underlying works (Ann.Phys.(N.Y.) 16 , 407(1961)). The topic (including many details) may already be known to many, however, the terms, in which the mathematical approach was phrased may still be interesting.


Wednesday, April 20th 2016
10:10 am:
Biophysics Seminar in 120 PAN
Speaker: Sarah Veatch, University of Michigan
Subject: Phases and fluctuations in biological membranes

The thermodynamic properties of plasma membrane lipids play a vital role in many functions that initiate at the mammalian cell surface. Some functions are thought to occur, at least in part, because plasma membrane lipids have a tendency to separate into two distinct liquid phases. We propose that these lipid mediated functions occur because plasma membrane composition is tuned close to a miscibility critical point at physiological temperature. This hypothesis is supported by our observations of micron-sized and dynamic critical composition fluctuations in isolated plasma membranes near room temperature. In this talk, I will discuss our ongoing efforts to probe for the existence and consequences of criticality in the plasma membranes of intact cells. These recent efforts include using quantitative super-resolution fluorescence localization microscopy to monitor the organization of plasma membrane proteins in B cell lymphocytes, both in resting cells and in cells stimulated with multivalent antigen against the B cell receptor. We also have identified a range of perturbations which alter both the magnitude of fluctuations in isolated vesicles. Some of these perturbations are also well characterized general anesthetics, and I will present evidence suggesting that some aspects of anesthetic function may be attributed to lipid heterogeneity.

1:25 pm:
There will be no seminar this week.
Speaker: Shervin Nourbakhsh, University of Minnesota
Subject: Search for new physics in the di-photon decay channel at CMS

Numerous new physics models predict the existence of heavy resonances decaying into pairs of photons. In the harsh environment at the LHC, the di-photon decay channel is one of the cleanest experimental signatures. This talk presents a search for physics beyond the standard model in the di-photon final state at CMS, focusing on the recent results obtained using data collected during the 2015 run of the LHC.


Thursday, April 21st 2016
Speaker: Mehdi Lame'e
12:20 pm:
Speaker: Chris Phenicie
Subject: Engineering the Shape of Organic Semiconductor Crystals
Faculty Host: Paul Crowell
3:35 pm:
Physics and Astronomy Colloquium in 230 STSS/Bruininks Hall
There will be no colloquium this week due to the Kaufmanis lecture
Speaker: Nobel Laureate Dr. Adam Riess, Johns Hopkins University's Krieger School of Arts and Sciences
Subject: Supernovae and the Discovery of the Accelerating Universe.
For more information refer to: http://www.astro.umn.edu/seminars/kaufmanis/

Friday, April 22nd 2016
11:15 am:
Speaker: Ming Li, University of Minnesota
Subject: Achieving High Baryon Densities in the Fragmentation Region in Heavy Ion Collisions at Top RHIC Energy

Based on our previous calculations of the energy-momentum tensor of the Glasma state, we calculated the back-reaction of the Glasma on the receding nuclei. We were able to obtain the rapidity loss and the excitation energy of the nuclear fragments. Consequently, Baryon and energy densities in the fragmentation region can be estimated using a simple space-time picture of the collision. For Au-Au central collisions at top RHIC energy, we found baryon density more than ten times larger than the normal nuclear matter. Energy density also much exceeds the critical energy density for the formation of quark-gluon plasma, indicating the transition to high baryon density quark-gluon plasma in the fragmentation region.

Speaker: Mahendra DC, University of Minnesota
Subject: Characterization of spin-orbit torques in bismuth selenide films by using dc planar Hall method
Speaker: Brian Henning (Yale)
Subject: Operator Bases and Effective Field Theories

The operator basis of an effective field theory (EFT) is the set of independent operators which contribute to scattering processes. We embark on the first systematic studies of operator bases, aiming to elucidate the structure underlying what is meant by "independent operators". We show that operator bases are organized by the conformal algebra, allowing us to systematically account for redundancies associated with the use of equations of motion and integration by parts. As a means to study the operator basis, we introduce a partition function defined to count operators weighted by their field content. We provide a matrix integral formula that allows us to compute this partition function. This allows us to solve an outstanding problem in EFTs: determining the number of independent higher dimension operators in a given EFT. This solution is applied to the Standard Model EFT, where we enumerate the operator content up to dimension fifteen. The physical definition and rich structure underlying operator bases is suggestive that more physical information can be pulled from the operator basis, and we give a few speculative thoughts along these lines.

Speaker: Dr. Adam Riess, Nobel Laureate, Johns Hopkins U. and STSci
Subject: A New Measurement of the Expansion Rate of the Universe
Note change of location

The Hubble constant remains one of the most important parameters in the cosmological model, setting the size and age scales of the Universe. Present uncertainties in the cosmological model including the nature of dark energy, the properties of neutrinos and the scale of departures from flat geometry can be constrained by measurements of the Hubble constant made to higher precision
than was possible with the first generations of Hubble Telescope instruments.
A streamlined distance ladder constructed from infrared observations of Cepheids and type Ia supernovae with ruthless attention paid to systematics now provide 2.4% precision and offer the means to do much better. By steadily improving the precision and accuracy of the Hubble constant, we now see evidence for significant deviations from the standard model, referred to as LambdaCDM, and thus the exciting chance, if true, of discovering new fundamental physics such as exotic dark energy, a new relativistic particle, or a small curvature to name a few possibilities. I will review recent and expected progress.

Speaker: Erik Conway, Jet Propulsion Lab, NASA
Subject: Dreaming of Rocks from Mars: Scientific Desires and the Engineering of Mars Missions
Refreshments served at 3:15 p.m.

In 1996, NASA and the White House held a spectacular press conference, announcing the probable discovery of the remains of martian life in a rock recovered from Antarctica, known as ALH840001. While most planetary scientists have now rejected those claims, the fact that they were made at all—one year before the first landing on Mars since 1976—provides a window through which to view the process of advocating for and engineering missions to Mars. Ever since the Viking landers parked themselves safely on the Red Planet, scientists have advocated returning samples of Mars to earth for laboratory studies as a top priority. To date, many such projects have been proposed, detailed studies done, and a few sample return projects have even been approved and funded. None has made it as far as full-scale development, though, let alone Mars.

Yet scientists’ desires have mattered. The dream of sample return has affected both program planning and vehicle engineering. In this talk, I will trace the evolution of several Mars sample return efforts, showing how technologies intended for sample return campaigns wound up being used for other missions.

3:35 pm:
Speaker: Jie Yang, University of Minnesota
Subject: Progress update on C3PO Version 2.0

C3PO Version 2.0: customizable computer coaches for physics online is designed to coach students from meta cognitive level, which means coach students to think about thinking.

Subject: Group Presentations, Part 1

Monday, April 25th 2016
10:30 am:
Thesis Defense in 142 WBOB
Speaker: Ivan Gordeli, University of Minnesota
Subject: Singlet Glueballs in Klebanov-Strassler Theory
This is the public portion of Mr. Gordeli's thesis defense. His advisor is Arkady Vainshtein.
12:15 pm:
Speaker: Phil Marshal - KIPAC
Subject: Time Delay Cosmography

Strong gravitational lenses have become an important astronomical tool: they allow us to make accurate measurements of galaxy masses, they provide a magnified view of the distant universe, and they allow us to constrain cosmological parameters. In particular, the time delays in multiply-imaged quasar systems enable measurements of distance in the Universe each with around 5% precision: I will review recent measurement of time delay distance in galaxy-scale lens systems. For us to realize the potential of this cosmological probe, we need to increase the size of our lens sample, and continue to improve the accuracy of its analysis. I will discuss the potential of LSST to provide a sample of several hundred lensed quasars with well-measured time delays that would enable competitive and complementary constraints on Dark Energy, and describe our ongoing investigations of how to find lenses, infer their time delays and model their mass distributions accurately, and account for weak lensing effects from external mass structures.

Faculty Host: Lucy Fortson
1:25 pm:
Speaker: Blake Thompson
Subject: The Development of Wave Mechanics: Implications for a Metaphor of Theory Change
Faculty Host: Paul Crowell

Tuesday, April 26th 2016
12:00 pm:
Speaker: Brian Welsch, UW Green Bay
Subject: Effects of Global and Local Magnetic Structure in Flares and CMEs

Processes at work in the initiation and subsequent evolution of solar
flares and coronal mass ejections (CMEs) remain poorly understood.
Improved understanding of such processes could improve Space Weather
forecasts. Here, I will present results from three recent
observational studies of these phenomena. The first study, an
undergrad research project, focused on the relationship between the
emergence of new active regions and the occurrence of flares in
pre-existing active regions (PEARs). Comparing NOAA Solar Region
Summary reports, which record characteristics of active regions
present on the solar disk, with records from NOAA's GOES flare
catalog, we found that the emergence of new active regions is
associated with increased rates of flaring in PEARs. The second
study, also an undergrad research project, aimed to characterize the
relative importance of two factors that had previously been found to
be correlated with CME speeds: (i) the amount of magnetic flux "swept"
out by flare ribbons observed in chromospheric / transition region
spectral lines, conventionally taken to measure the amount of coronal
magnetic flux that reconnected in a flare/CME; and (ii) the rate of
decay, with height, of magnetic field strengths above CME source
regions, estimated from potential models of the coronal magnetic
field. Finally, given sufficient time, I will discuss preliminary
results from an in-progress attempt to replicate the previously
reported correlation of ribbon fluxes versus CME speeds.

2:30 pm:
Speaker: Adarsh Ravishankar
Subject: A Quantitative Analysis of the Progression of the Genetic Disorder SCA1 using Magnetic Resonance Imaging and Spectroscopy
Faculty Host: Paul Crowell
4:30 pm:
CM Journal Club in PAN 120
Speaker: Laura Classen
Subject: The functional RG and its application to critical behavior

Following [1], I will briefly sketch the derivation of the flow equation for the scale-dependent effective action, which generates the 1PI correlation functions. The chiral Ising and chiral Heisenberg universality class, relevant for phase transitions to CDW and SDW in two-dimensional Dirac materials, will serve as an example for the calculation of critical behavior in terms of the fRG[2]. Furthermore to establish a connection, the fRG approach will be compared to a more standard Wilsonian scheme close to the upper critical dimension of the system.
[1] arXiv:hep-ph/0611146
[2] Phys. Rev. B 89, 205403 (2014), arXiv:1402.6277


Wednesday, April 27th 2016
10:10 am:
Subject: To be announced.
1:25 pm:
CM Seminar is cancelled this week. See Sack Lunch on Friday.
2:00 pm:
FTPI Seminar in 142 WBOB
Speaker: Kaori Fuyuto
Subject: Aspects of CP violation in electroweak baryogenesis

We discuss the aspects of CP-violating effects on electroweak baryogensis in models where an extra Higgs doublet, a singlet and electroweak-interacting fermions are added. It is found that one CP-phase that directly relates the baryon asymmetry of the Universe (BAU) to the electric dipole moment (EDM) exists. Moreover, it is obtained that the parameter region for the successful BAU can be verified by the electron EDM in near future.

Faculty Host: Natsumi Nagata
Speaker: Maxim Titov, Saclay
Subject: Micro-Pattern Gas Detector Technologies for Physics Projects at the Energy, Intensity and Cosmic Frontiers

Improvements in detector technology often come from capitalizing on industrial progress. Advances are made with new insights; recent industrial developments in photo-lithography, microelectronics and printed circuits technique have opened the road for the production of micro-structured gaseous amplification devices: Microstrip Gas Chamber (MSGC), Gas Electron Multiplier (GEM) and Micro-mesh gaseous structure (Micromegas), followed by the thick-GEM (THGEM), resistive GEM (RETGEM), Micro-Pixel Gas Chamber (μ-PIC), and an integrated readout of gaseous detectors using solid-state pixel chips (InGrid). By using a pitch size of a few hundred micrometers, MPGD systems now offer operational stability, protection against discharges, radiation hardness, high-rate capability (> 1MHz/mm2), excellent spatial resolution (~30 mm), and a time resolution down to a few-hundred pico-second range. This talk will highlight recent MPGD technology advances and address numerous MPGD applications at the Energy, Intensity and Cosmic Frontiers.


Thursday, April 28th 2016
10:00 am:
Thesis Defense in Civil Engineering 213
Speaker: Charles McEachern, University of Minnesota
Subject: Field Line Resonance in "Tuna Half" Dimensions
This is the public portion of Mr. McEachern's thesis defense. His advisor is Bob Lysak.
Speaker: Chris Nolting and Hugh Dickinson, Iowa State
1:25 pm:
Speaker: Brendon Jones
Subject: Conductivity of Nanocrystalline Silicon Films
Faculty Host: Paul Crowell
3:35 pm:
Speaker: Maxim Pospelov, University of Victoria and Perimeter Institute
Subject: Neutrino portal
Refreshments to be served outside 101 Fraser after the colloquium.

Neutrino masses and mixing point to the existence of new physics beyond the Standard Model. The simplest realization of neutrino mass generation is related to new fermionic massive states, the right-handed neutrinos, not charged under any of the Standard Model gauge groups. The mass scale of these new states is almost arbitrary, while their couplings are most likely related to their masses via the so-called seesaw relation. In my talk, I will describe how one can search for right handed neutrinos should their masses fall within energy reach of modern colliders and beam dump experiments, such as the LHC and new planned SHiP facility. I will also discuss modifications to the SM with neutrinos carrying new gauge interactions, and show that this increases our chances to discover right handed neutrinos within the range of couplings suggested by the seesaw relation.

Faculty Host: Tony Gherghetta

Friday, April 29th 2016
11:15 am:
Speaker: Ming Li, University of Minnesota
Subject: Achieving High Baryon Densities in the Fragmentation Region in Heavy Ion Collisions at Top RHIC Energy

Based on our previous calculations of the energy-momentum tensor of the Glasma state, we calculated the back-reaction of the Glasma on the receding nuclei. We were able to obtain the rapidity loss and the excitation energy of the nuclear fragments. Consequently, Baryon and energy densities in the fragmentation region can be estimated using a simple space-time picture of the collision. For Au-Au central collisions at top RHIC energy, we found baryon density more than ten times larger than the normal nuclear matter. Energy density also much exceeds the critical energy density for the formation of quark-gluon plasma, indicating the transition to high baryon density quark-gluon plasma in the fragmentation region.

12:20 pm:
Speaker: Chun Chen, University of Minnesota
Subject: Tunable splitting of the Ground-State Degeneracy in Quasi-1D Parafermion systems
Please note change of speaker from last announcement.
Speaker: Sebastian Ellis (Michigan)
Subject: TBA
2:30 pm:
There will be no colloquium this week.
Speaker: Philip Kitcher, Department of Philosophy, Columbia University
Subject: Progress in the Sciences -- and also in the Arts
Refreshments served at 3:15 p.m.

The view that the sciences make progress, while the arts do not, is extremely common. This lecture will challenge it. I begin by distinguishing teleological progress from pragmatic progress. You make pragmatic progress not by coming closer to a goal, but by solving some of the problems of your current state. Scientific progress should be seen as pragmatic. When the point is recognized, it becomes evident that scientific progress has social dimensions. A socially embedded notion of scientific progress then allows for a parallel concept of progress applicable to the arts.

3:35 pm:
To be announced.
Subject: Group Presentations, Part 2

Monday, May 2nd 2016
12:15 pm:
Speaker: Patrick Meyers, University of Minnesota
Subject: Probing the Stochastic Gravitational-wave Background in the Advanced LIGO Era

With the first detection of a binary black hole merger (BBH), and the successful first run of the Advanced LIGO detectors, a new era of Gravitational-wave (GW) astrophysics has begun. First, I will give an overview of stochastic gravitational-wave background (SGWB) searches with LIGO. I will then address the implications of GW150914, the first direct detection of GWs, on the search for an astrophysical SGWB. I will touch briefly on ongoing searches for an SGWB using Advanced LIGO data and then I will talk about prospects and techniques for improving low-frequency sensitivity in SGWB searches moving forward.

Faculty Host: Vuk Mandic

Tuesday, May 3rd 2016
12:00 pm:
Speaker: Evan Tyler, University of Minnesota
Subject: Partitioning of Energy Flow from Reconnection
4:30 pm:
CM Journal Club in PAN 120
Speaker: Peter Orth
Subject: Universal post-quench coarsening and quantum aging at a quantum critical point

I will discuss non-equilibrium dynamics of an interacting bosonic quantum field theory following a rapid change of a parameter. Such a quench protocol was realized recently in a number of cold-atom experiments and corresponds to a fast change of parameters such as magnetic field or pressure in a solid-state system. I first introduce basic features of non-equilibrium and the non-equilibrium Keldysh notation for a parameter quench in a non-interacting system, which corresponds to rapidly changing the quadratic potential of a harmonic oscillator. Then, I will discuss the effect of quartic interactions within a large-N approach. I show that if a system is tuned to close proximity of a critical point, the non-equilibrium dynamics shows universal features characterized by a new scaling exponent.

This is based on work published in

P. Gagel, PPO, J. Schmalian, Phys. Rev. Lett. 113, 220401 (2014)
P. Gagel, PPO, J. Schmalian, Phys. Rev. B 92, 115121 (2015)


Wednesday, May 4th 2016
10:10 am:
Biophysics Seminar in 120 PAN
Speaker: Michael Guy Poirier, Ohio State University
To be announced.
1:25 pm:
Subject: There will no seminar this week.
There will be no seminar this week.

Thursday, May 5th 2016
Speaker: Karl Young and Claudia Scarlata
2:30 pm:
Speaker: Kyle Crocker, University of Minnesota
Subject: A Model of the Stochastic Gravitational-Wave Background due to Core Collapse to Black Holes
Faculty Host: Paul Crowell
3:35 pm:
Speaker: Josh Klein, University of Pennsylvania
Subject: Neutrinos, Antineutrinos, and No Neutrinos
Refreshments to be served outside 101 Fraser after the colloquium. Student Awards will be presented at the start of Colloquium.

Neutrinos have always been the black sheep of the particle physics world: they
make up nothing, they hardly ever interact with normal matter, and they are so
light that, for the most part, they can be completely ignored in any reaction
in which they do participate. But we now know that neutrinos influence an
enormous range of physics. They tell us how the Sun works, they allow us to
search for new forces of Nature, and, because they carry no electric charge,
they are the only fundamental particle of matter that can be both particle and
antiparticle. The talk will discuss new areas of physics that can be explored
with neutrinos, and focus in particular on the SNO+ experiment whose goals
include a test of whether the neutrino and antineutrino are really the same
thing.

Faculty Host: Marvin Marshak

Friday, May 6th 2016
Last day of instruction before final exams.
11:15 am:
There will be no seminar this week.
Speaker: Yilikal Ayino, University of Minnesota
Subject: Magnetotransport in NdTiO3/SrTiO3 Interface
Speaker: Chris Hill (Fermilab)
Subject: Some aspects of Axion Electrodynamics
2:30 pm:
There will be no colloquium this week.
2:30 pm:
Poster Session in PAN Lobby
Students in Phys 4052 will present their class projects.
3:35 pm:
To be announced.
4:00 pm:
Henry Erikson Lecturer in 101 Fraser Hall
Speaker: Dr. Jay Marx, Senior Advisor, LIGO Laboratory, California Institute of Technology
Subject: The Discovery of Gravitational Waves from Merging Black Holes

On February 11, 2016 headlines announced the discovery of gravitational waves from a merging pair of black holes 1.3 billion light years away, confirming the most radical prediction of Einstein’s theory of gravity. What is this all about? What are gravitational waves? Why is it so important?

This discovery was made by LIGO using instruments spanning miles and yet capable of measuring distances with an accuracy of one billionth the size of an atom, among the most precise instruments ever constructed. LIGO now involves about 1000 scientists and engineers from 80 universities in 16 countries around the world, including the University of Minnesota.

This talk will explain the excitement, what the discovery means, how it was made and why it will open a new window on the universe. The presentation will be aimed at non-scientists with many videos and photos and no equations or jargon.

There will be no seminar this week.

Thursday, May 12th 2016

8:45 AM Registration

8:55 AM Welcome and Opening Remarks
Arkady Vainshtein

9:00 AM Geometry and Dynamics of a Coupled 2D and 4D Quantum Field Theory
Ken Konishi
University of Pisa and INFN, Sezione di Pisa

9:30 AM Coulomb branch, Higgs branch, and nilpotent orbits
Amihay Hanany
Imperial College, London

10:00 AM Liberation on walls in gauge theories and quantum anti-ferromagnets
Tin Sulejmanpasic
North Carolina State University

10:30 AM COFFEE BREAK

11:00 AM Cusp anomalous dimension in QCD and its supersymmetric extensions
Gregory Korchemsky
IPhT, Saclay

11:30 AM On supergravity coupled with vector fields: a gauge theory perspective
Radu Roiban
Pennsylvania State University

12:00 PM POPE for scattering amplitudes
Andrei Belitsky
Arizona State University

12:30 PM LUNCH BREAK

2:00 PM Instanton-dyons generate both deconfinement and chiral symmetry restoration transitions
Edward Shuryak
Stony Brook University

2:30 PM Oblique confinement and metastable states in the "deformed QCD" model
Eric Zhitnitsky
University of British Columbia

3:00 PM New aspects of abelian confinement
Erich Poppitz
University of Toronto

3:30 PM COFFEE BREAK

4:00 PM Axion EFT and Dense Axion Stars
Eric Braaten
Ohio State University

4:30 PM Anomalous magnetic moment of a bound electron
Andrzej Czarnecki
University of Alberta

5:00 PM Decay of a bound muon
Robert Szafron
University of Alberta

5:30 PM Low-Energy Effective Action of the Supersymmetric CP(N-1) Model in the Large-N Limit
Pavel Bolokhov
University of Minnesota, Duluth


Friday, May 13th 2016

9:00 AM What the Standard Model may not want us to know
David Kaplan
Institute for Nuclear Theory

9:30 AM Veneziano Amplitude, Large-N QCD, and Holography
Adi Armoni
Swansea University

10:00 AM Lessons from numerical holography
Laurence Yaffe
University of Washington

10:30 AM COFFEE BREAK

11:00 AM Towards a QCD based description of non-leptonic multi-body decays
Thomas Mannel
University of Siegen

11:30 AM Aspects of the sign problem in QCD
Thomas Cohen
University of Maryland

12:00 PM A hidden symmetry of crazy QCD
Leonid Glozman
Institute for physics, University of Graz

12:30 PM LUNCH BREAK

2:00 PM QCD light-cone sum rules for B to dipion transition form factors
Alexander Khodjamirian
University of Siegen

2:30 PM Virtuality Distributions
Anatoly Radyushkin
ODU/JLab

3:00 PM Structure constant of twist-2 light-ray operators in the BFKL limit
Ian Balitsky
JLab/ODU

3:30 PM COFFEE BREAK

4:00 PM Topology and the Dirac Spectrum for One-Flavor QCD
Jacobus Verbaarschot
Stony Brook University

4:30 PM Thermal fluctuations and hydrodynamic EFT
Adam Ritz
University of Victoria

5:00 PM Thermalization of a strongly coupled system: local vs nonlocal observables
Pietro Colangelo
INFN

12:20 pm:
Speaker: David Harrison, University of Minnesota
Subject: Dimensional Crossover in Spin Glass Dynamics
Students staff and faculty are invited to join the celebration.

Saturday, May 14th 2016

9:00 AM Correlations in hadronic wave function
Alex Kovner
University of Connecticut

9:30 AM Continuous chiral symmetry breaking in a calculable regime
Aleksey Cherman
INT, University of Washington

10:00 AM Approaching conformality in lattice models
Yannick Meurice
University of Iowa

10:30 AM COFFEE BREAK

11:00 AM Quantum corrections for the generators of conformal transformations in QCD
Vladimir Braun
University of Regensburg

11:30 AM Dilaton, conformal symmetry and Weyl invariance
Alexander Monin
EPFL

12:00 PM All order linearised hydrodynamics from fluid-gravity correspondence
Michael Lublinsky
Ben-Gurion University of the Negev

12:30 PM LUNCH BREAK

2:00 PM Resurgence and Large N
Gerald Dunne
University of Connecticut

2:30 PM Toward Picard-Lefschetz Theory of Path Integrals and the Physics of Complex Saddles
Mithat Unsal
NCSU

3:00 PM Resurgence, exact WKB and quantum geometry
Gokce Basar
University of Maryland

3:30 PM COFFEE BREAK

4:00 PM Instanton-torus knot duality in SQCD
Alexander Gorsky
iitp RAS

4:30 PM String pair production in non homogeneous backgrounds
Stefano Bolognesi
Universita' di Pisa, Dipartimento di Fisica

5:00 PM Toward a Theory of the QCD String
Sergei Dubovsky
New York University


Sunday, May 15th 2016

9:00 AM Alexei Yung, University of Minnesota, FTPI

Critical string from non-Abelian vortex in four dimensions

9:30 AM Muneto Nitta, Keio University

Vortices in Neutron Superfluids

10:00 AM Keisuke Ohash, University of Pisa, INFN

Large-N CP(N-1) sigma model on a finite interval with the Dirichlet  condition

10:30 AM COFFEE BREAK

11:00 AM Edwin Ireson, Swansea University

Worldsheet-induced corrections to the holographic Veneziano amplitude

11:30 AM Sergey Monin, University of Minnesota

Non-Abelian string of a finite length

12:00 PM Peter Koroteev,Perimeter Institute for Theoretical Physics

How supersymmetry helps to understand hydrodynamics

Monday, May 23rd 2016

Wednesday, May 25th 2016
Speaker: Bekele H. Badada, University of Cincinnati
Subject: Probing Electronic Band Structure and Quantum Confined States in Single Semiconductor Nanowire Devices

I will explore electronic band structure of various group III-V semiconductor nanowires using electrical transport and photocurrent spectroscopy on photo-lithographically contacted single nanowire devices. The nanowires were grown by MOCVD technique where the growth was initiated by a 50-100 nm gold catalyst which determines the diameter of the nanowire. Typically these nanowires are 4-6 µm long. Further, I will introduce a more complex GaAs/AlGaAs core-multishell heterosturucres, quantum well tube (QWT), where a thin GaAs layer was embedded inside a thick AlGaAs shell surrounding a 50 nm diameter GaAs nanowire core. Here I will present the nature of exciton localization in single GaAs/AlGaAs QWT nanowire devices using photocurrent (PC) spectroscopy combined with simultaneous photoluminescence (PL) and photoluminescence excitation (PLE) measurements at 10 K . Excitons confined to GaAs quantum well tubes of 8 nm and 4 nm widths embedded into an AlGaAs barrier are seen to ionize at high bias levels. Spectroscopic signatures of the ground and excited states confined to the QWT seen in PL, PLE, and PC data are consistent with numerical calculations. The demonstration of good electrical contact with the QWTs enables the study of Stark effect shifts in sharp emission lines of excitons localized to quantum dot-like states within the QWT. Atomic resolution cross-sectional TEM measurements and an analysis of the quantum confined Stark effect of these dots provide insights into the nature of the exciton localization in these nanostructures.

Faculty Host: Vlad Pribiag
Speaker: Maury Goodman, Argonne National Laboratory
Subject: New measurements from Double Chooz

Friday, May 27th 2016
3:30 pm:
Thesis Defense in 142 WBOB
Speaker: Jin Chen, University of Minnesota
This is the public portion of Jin Chen's thesis defense. Chen's advisor is Arkady Vainshtein.

Monday, May 30th 2016

Wednesday, June 8th 2016
1:25 pm:
Speaker: Peter Wolfle, Karlsruhe Institute of Technology
Subject: Heavy-fermion criticality of YbRh2Si2: Is the T* line just the onset of spin-flip scattering?

Friday, June 10th 2016
08:00 am:

Monday, June 13th 2016

8:55 am Welcome
Andrey Chubukov
University of Minnesota, FTPI

SESSION CHAIR: ANDREY CHUBUKOV

9:00 am Intertwined orders in highly correlated electronic materials: Phenomenology
Steven Kivelson
Stanford University


10:30 am COFFEE BREAK

11:00 am Quantum spin liquids and their theoretical applications I
Senthil Todadri
Massachusetts Institute of Technology

12:30 pm LUNCH BREAK

SESSION CHAIR: NATALIA PERKINS

2:00 pm Strongly correlated superconductivity: cuprates and organics I
André-Marie Tremblay
Université de Sherbrooke

3:30 pm COFFEE BREAK

4:00 pm Quantum thermalization and many-body Anderson localization I
David Huse
Princeton University

5:30 pm POSTER SESSION & WELCOME PARTY

7:00 pm End of day


Tuesday, June 14th 2016

SESSION CHAIR: RAFAEL FERNANDES

9:00 am Intertwined orders in highly correlated electronic materials: Theoretical approaches
Steven Kivelson
Stanford University

10:30 am COFFEE BREAK

11:00 am Quantum thermalization and many-body Anderson localization II
David Huse
Princeton University


12:30 pm LUNCH BREAK

SESSION CHAIR: ALEX KAMENEV

2:00 pm Strongly correlated superconductivity: cuprates and organics II
André-Marie Tremblay
Université de Sherbrooke

3:30 pm COFFEE BREAK

4:00 pm Quantum spin liquids and their theoretical applications II
Senthil Todadri
Massachusetts Institute of Technology


5:30 pm End of day


Wednesday, June 15th 2016

SESSION CHAIR: ANDREY CHUBUKOV

9:00 am ARPES of high temperature superconductors: I
Daniel Dessau
University of Colorado Boulder

10:30 am COFFEE BREAK

11:00 am Topology and Correlation in Quantum Materials with Strong Spin-Orbit Coupling I
Yong-Baek Kim
University of Toronto

12:30 pm LUNCH BREAK

SESSION CHAIR: RAFAEL FERNANDES

2:00 pm Lecture I
Cristian Batista
University of Tennessee/
Oak Ridge National Laboratory

3:30 pm COFFEE BREAK

4:00 pm Superconductivity and spin-charge order in quadratic band touching systems I
Oskar Vafek
Florida State University


5:30 pm End of day


Thursday, June 16th 2016

SESSION CHAIR: NATALIA PERKINS

9:00 am ARPES of high temperature superconductors: II
Daniel Dessau
University of Colorado Boulder

10:30 am COFFEE BREAK

11:00 am Topology and Correlation in Quantum Materials with Strong Spin-Orbit Coupling II
Yong-Baek Kim
University of Toronto

12:30 pm LUNCH BREAK

SESSION CHAIR: ANDREY CHUBUKOV

2:00 pm Lecture II
Cristian Batista
University of Tennessee/
Oak Ridge National Laboratory

3:30 pm COFFEE BREAK

4:00 pm Superconductivity and spin-charge order in quadratic band touching systems II
Oskar Vafek
Florida State University

5:30 pm End of day


Friday, June 17th 2016

SESSION CHAIR: RAFAEL FERNANDES

9:00 am Design and growth of novel materials
Paul Canfield
The Ames Laboratory

10:30 am COFFEE BREAK

11:00 am Exotic local moment magnetism
Collin Broholm
Johns Hopkins University

12:30 pm LUNCH BREAK

SESSION CHAIR: ALEX KAMENEV

2:00 pm Frusterated Magnets and Spin Liquids I
John Chalker
University of Oxford

3:30 pm POSTER SESSION & COFFEE BREAK

5:30 pm End of day


Saturday, June 18th 2016

SESSION CHAIR: NATALIA PERKINS
9:00 am Synthesis as the heart of New Materials Physics
Paul Canfield
The Ames Laboratory

10:30 am COFFEE BREAK

11:00 am Spin correlations in conducting and superconducting materials
Collin Broholm
Johns Hopkins University

12:30 pm LUNCH BREAK

SESSION CHAIR: ALEX KAMENEV

2:00 pm Frusterated Magnets and Spin Liquids II
John Chalker
University of Oxford

3:30 pm End of Summer School Program


Monday, July 4th 2016

Saturday, July 16th 2016
8:30 pm:
Universe in the Park in Afton State Park
Summer telescope observing program at local state parks. Contact: nolting@astro.umn.edu for more info.

Tuesday, July 19th 2016
2:00 pm:
Thesis Defense in PAN 120
Speaker: Tanner Prestegard, University of Minnesota
Subject: Unmodeled searches for long-lasting gravitational-wave signals with LIGO and studies of underground seismic noise for future gravitational-wave detectors.
This is the public portion of Mr. Prestegard's thesis defense.

Friday, July 22nd 2016
12:00 pm:
Thesis Defense in PAN 110
Speaker: Adam Peterson, University of Minnesota
Subject: Low energy dynamics of non-perturbative structures in high energy and condensed matter systems
This is the public portion of Mr. Peterson's thesis defense.

This dissertation presents some results on the application of low energy effective field theory vortex dynamics in condensed matter and materials systems. For the first half of the presentation we discuss the possibility of non-Abelian gapless excitations appearing on U(1)- vortices in the B phase of superfluid ^3 He. Specifically, we focus on superfluid ^3 He-like systems with an enhanced SO(3)L- rotational symmetry allowing for non-Abelian excitations to exist in the gapless spectrum of vortices. We consider a variety of vortices in the B-phase with different levels of symmetry breaking in the vortex core, and show conditions on the phenomenological parameters for certain vortices to be stable in the bulk. We then proceed to develope the low energy effective field theory of the various vortex types and consider the quantization of excitations. The process of quantization leads to interesting surprises due to non-lorentz symmetry that are not typically encountered in the analogous cases of U(1)×SU(N)- gauge models discussed in high energy theory.

The second half of this dissertation focuses on two types of vortices that appear in a particular model that is a modification of the well known Abelian-Higgs model. The specific modification includes a vector spin field in addition to the U(1)- Higgs field and gauge fields of the original model. The particular form of the lagrangian results in a cholesteric vacuum structure, with interesting consequences for the vortices in the model. We observe the effects of such a modification on the well known U(1)- vortex appearing in the original model due to the emergent spin field in the vortex core. We also consider a new type of vortex that is most closely related to a spin vortex. This vortex appears due to the topology introduced by the new spin field. The low energy effective field theory is also investigated for this type of vortex.


Friday, July 29th 2016
8:30 pm:
Universe in the Park in Tettegouche State Park
Summer telescope observing program at local state parks. Contact: nolting@astro.umn.edu for more info.

Saturday, July 30th 2016
8:30 pm:
Universe in the Park in Gooseberry Falls State park
Summer telescope observing program at local state parks. Contact: nolting@astro.umn.edu for more info.

Friday, August 5th 2016
10:00 am:
Theis Defense in 142 WBOB
Speaker: Marcos Garcia, University of Minnesota
Subject: No-scale inflation
This is the public portion of Mr. Garcia's thesis defense. HIs adviser is Keith Olive.
1:00 pm:
Thesis Defense in PAN 110
Speaker: Barry Costanzi, University of Minnesota
Subject: Emergent 1/f noise in systems of oscillating nanomagnetic dots
This is the public portion of Mr. Costanzi's thesis defense. His adviser is Dan Dahlberg.
8:30 pm:
Universe in the Park in Father Hennepin State Park
Summer telescope observing program at local state parks. Contact: nolting@astro.umn.edu for more info.

Saturday, August 6th 2016
8:30 pm:
Universe in the Park in Mille Lacs Kathio State Park
Summer telescope observing program at local state parks. Contact: nolting@astro.umn.edu for more info.

Tuesday, August 9th 2016
Speaker: Dr. Andra Stroe, European Southern Observatory
Subject: Giant cosmic tsunamis: accelerating electrons and galaxy evolution?

Galaxy cluster grow through mergers with other clusters, events which give rise to the largest cosmic shock waves. Shocks travel like giant tsunamis through the cluster galaxies as well as the electron plasma located between them. I will discuss how merger shocks accelerate ICM electrons to relativistic speeds, producing diffuse synchrotron emission extended over Mpc scales. I will also describe how these shock waves shape the evolution of galaxies within the cluster by triggering formation of new stars.


Friday, August 12th 2016
11:00 am:
Untitled in PAN 110
Speaker: Xavier Prochaska, U of California Santa Cruz
Subject: Rise of the Giant Lya Nebulae

I will describe the discovery and analysis of giant (>100kpc)
Lya nebulae in the z~2 universe, found predominantly around luminous AGN. These phenomena reveal massive (~10^11 Msun) reservoirs of cool, enriched gas with kinematics suggestive of gravitationally infalling material and galactic-scale outflows. I’ll review the recent results and describe anticipated advances with the advent of optical IFUs on 10m-class telescopes.

8:30 pm:
Universe in the Park in Lake Maria State Park
Summer telescope observing program at local state parks. Contact: nolting@astro.umn.edu for more info.

Saturday, August 13th 2016
8:30 pm:
Universe in the Park in William O'Brien State Park
Summer telescope observing program at local state parks. Contact: nolting@astro.umn.edu for more info.

Monday, August 22nd 2016

8:45 AM
Registration
West Bank Office Building, Room 142
1300 2nd Street S
Minneapolis, MN 55455

8:55 AM
Welcome and Opening Remarks
Tom Jones
University of Minnesota

9:00 AM
New Kid on the Block: Kinematic Sunyaev-Zel'dovich Effect
Daisuke Nagai
Yale University

9:25 AM
Viscosity, Conduction, Convection, and Dynamo in a Weakly Collisional Magnetized Plasma
Matthew Kunz
Princeton University

9:50 AM
New High‐order Methods using Gaussian Processes for CFD
Dongwook Lee
University of California, Santa Cruz

10:15 AM COFFEE BREAK

10:35 AM
Rest-Frame UV Spectroscopy of Hot Gas in the Centers of Cool Core Brightest Cluster Galaxies
Megan Donahue
Michigan State University

11:00 AM
Cluster kinematics in the post-Hitomi era
Sebastian Heinz
University of Wisconsin

11:25 AM
Poster abstracts
Nine Poster Abstracts (~5 min per)

12:10 PM
Discussion Session I

12:30 PM LUNCH BREAK

2:00 PM
Flow dynamics in galaxy clusters
Elke Roediger
University of Hull

2:25 PM
Simulating the ICM As Seen Through the Next Generation of X-ray Telescopes
John ZuHone
Massachusetts Institute of Technology

2:50 PM
Deep Chandra observations as probes of detailed ICM physics
Norbert Werner
Stanford University

3:15 PM COFFEE BREAK

3:35 PM
Microphysics of ICM from X-ray images: effective equation of state, turbulence, heating
Irina Zhuravleva
Stanford University

4:00 PM
Witnessing the growth of the nearest galaxy cluster
Aurora Simionescu
ISAS – Japan Aerospace Exploration Agency

4:25 PM
High-resolution micro-calorimeter X-ray spectroscopy of the core of the Perseus Cluster of galaxies
Hitomi Collaboration

4:50 PM
Discussion Session II

5:20 PM Workshop Ends for the Day


Tuesday, August 23rd 2016

9:00 AM
Insights on non-thermal phenomena in the ICM from radio observations
Annalisa Bonafede
University Hamburg

9:25 AM
Merging clusters as physics laboratories - first results from LOFAR
Marcus Brüggen
University Hamburg

9:50 AM
The challenge of turbulence in galaxy clusters: physics and particle acceleration
Gianfranco Brunetti
IRA-INAF, Bologna

10:15 AM COFFEE BREAK

10:35 AM The Role of Turbulence in Accelerating Cosmic Rays and Amplifying B-fields in the ICM
Peng Oh
University of California, Santa Barbara

11:00 AM
Cosmic Ray Propagation in High Beta Plasmas
Ellen Zweibel
University of Wisconsin, Madison

11:25 PM
Superdiffusion and Streaming and Acceleration of Cosmic rays
Alex Lazarian
University of Wisconsin, Madison

11:50 PM
Discussion Session I

12:20 PM LUNCH BREAK

2:00 PM
Is cosmic ray heating relevant in cool core clusters?
Christoph Pfrommer
Heidelberg Institute for Theoretical Studies

2:25 PM
Role of cosmic ray heating in the ICM
Mateusz Ruszkowski
University of Michigan

2:50 PM
Shock Waves in the Outskirt of Galaxy Clusters
Dongsu Ryu
Ulsan National Institute of Technology

3:15 PM COFFEE BREAK

3:35 PM
Cluster outskirts as a gateway to the physics of particle acceleration and magnetogenesis
Franco Vazza
University of Hamburg

4:00 PM
Re-acceleration Model for Radio Relics in Galaxy Clusters
Hyesung Kang
Pusan National University

4:25 PM
New Models of the Sausage Relic
Julius Donnert
University of Minnesota

4:50 PM
Discussion Session II

5:20 PM
Workshop Ends for the Day

6:00 PM

Banquet for ICM workshop participants
(Details below)

11:30 am:
Thesis Defense in 120 PAN
Speaker: Tobias Gulden
Subject: A semiclassical theory on complex manifolds with applications in statistical physics and quantum mechanics
Advisor: Alex Kamenev

Wednesday, August 24th 2016

8:45 AM
Shattering cold gas into tiny cloudlets
Mike McCourt
University of California, Santa Barbara

9:10 AM
Metal Mixing in the Presence of a Magnetic Field
Evan Scannapieco
Arizona State University

9:35 AM TBA
Martin Pessah
Niels Bohr Institute

10:00 AM COFFEE BREAK

10:20 AM
Jet-Lobe Morphology Under the Cluster Weather: Inferences on ICM Dynamics and Jet Composition
Hui Li
Los Alamos National Laboratory

10:45 AM
Properties of the ICM of Galaxy Cluster from hydrodynamical simulations with AGN feedback
Elena Rasia
University of Michigan

11:10 PM
How AGN Jets Heat the Intracluster Medium – Insights from Simulations
Karen Yang
University of Maryland

11:35 PM
Discussion Session I

12:05 PM LUNCH BREAK

1:35 PM
Heating in Simulated Galaxy Clusters with Momentum-driven AGN Feedback
Yuan Li
Columbia University

2:00 PM
Thermal Instability in Low Entropy Gas Lifted behind Buoyantly-Rising X-ray Bubbles
Brian McNamara
University of Waterloo

2:25 PM
Nonlinear thermal instability in the radio mode feedback cycle
Paul Nulsen
Center for Astrophysics, Harvard-Smithsonian

2:50 PM COFFEE BREAK

3:10 PM
Triggering and delivery methods for AGN feedback
Brian O’Shea
Michigan State University

3:35 PM
The Black-Hole Feedback Valve
Mark Voit
Michigan State University

4:00 PM
Simulations of AGN jet feedback in galaxy clusters: heating and cooling cycles
Prateek Sharma
Indian Institute of Science, Bangalore

4:25 PM
Discussion Session II

5:00 PM Workshop Closing
Thank you for your participation!

Speaker: Yong Wu - U.C. Riverside
Subject: Quantum Transport in Strained Graphene, Graphene Heterostructures & Few-Layer Graphene

Recently, strain engineering of graphene’s electronic properties has attracted significant attention [1]. I will report transport studies in graphene sheets with linearly-shaped strain regions created by nm-scale wide folds. We find that these strain regions act as quantum wires and waveguides. We attribute this to strain-induced pseudomagnetic fields acting as confining barriers. I will also discuss transport studies on coupled massive and massless electron systems, realized using twisted monolayer graphene/natural bilayer graphene stacks. Due to the interlayer screening, we observe a nonlinear monolayer gate capacitance. Moreover, in a perpendicular magnetic field, we observe a distinct pattern of gate-tunable Landau level crossings that enable the mass and Fermi velocity in the layers to be determined. We find different values than those of isolated layers, indicating that the interlayer interactions renormalize the band structure parameters. Additionally, novel physics in graphene under different external conditions, for example under one-dimensional (1D) periodic potentials [2] and aligned to boron nitride (BN) substrates, will also be reported. Our recent studies on natural few-layer graphene, including quantum Hall effect, Landau level transitions and new Dirac points [3] in ABA-stacked trilayer graphene will also be introduced.

References:
[1] Nikolai N. Klimov, Suyong Jung, Shuze Zhu, Teng Li, C. Alan Wright, Santiago D. Solares, David B. Newell, Nikolai B. Zhitenev, and Joseph A. Stroscio. Electromechanical properties of graphene drumheads. Science, 336(6088):1557–1561, 2012.

[2] Cheol-Hwan Park, Young-Woo Son, Li Yang, Marvin L. Cohen, and Steven G. Louie. Electron beam supercollimation in graphene superlattices. Nano letters, 8(9):2920–2924, 2008.

[3] Maksym Serbyn and Dmitry A. Abanin. New dirac points and multiple Landau level crossings in biased trilayer graphene. Physical Review B,
87(11):115422, 2013.


Thursday, August 25th 2016
09:00 am:
CSE at the Minnesota State Fair in Minnesota State Fairgrounds
10:00 am:
Physics Force Public Show-STEM Day in Carousel Stage, Minnesota State Fair
2:00 pm:
Physics Force Public Show-STEM Day in Carousel Stage, Minnesota State Fair

Friday, August 26th 2016
1:00 pm:
Thesis Defense in PAN 120
Speaker: Terry Bretz-Sullivan, University of Minnesota
Subject: Transport in ionic liquid gated and superconducting nanostructures
This is the public portion of Mr. Bretz-Sullivan's thesis defense. His advisor is Allen Goldman.

Friday, September 2nd 2016
10:00 am:
Physics Force Public Show in University of Minnesota Stage, MN State Fair
11:00 am:
Physics Force Public Show in University of Minnesota Stage, MN State Fair

Saturday, September 3rd 2016
10:00 am:
Physics Force Public Show in University of Minnesota Stage, Minnesota State Fair
11:00 am:
Physics Force Public Show in University of Minnesota Stage, Minnesota State Fair

Monday, September 5th 2016

Wednesday, September 7th 2016
10:00 am:
Speaker: David Goldhaber-Gordon (Stanford)
Subject: Emergent symmetries in quantum impurities built from quantum dots

We are all familiar with spontaneously broken symmetry: the north pole of a magnetic needle will be at one end or the other, not a superposition of the two. Conversely, can a system possess at low energies a symmetry that the bare Hamiltonian does not? I'll discuss a case where such a symmetry emerges in measurements of a nanopatterned system of electrons: a double quantum dot (Ref. 1).

Then I will tell how a similar system with no obvious symmetry can be tuned using voltage on nanoelectrodes to a quantum critical point with an exact theoretical description even at finite temperature (Ref. 2). The excitations of nearby mobile electrons at the critical point are collective and look nothing like individual electrons: this is a non-Fermi liquid. Tuning across the critical point, the crossover from one phase to the other through the quantum critical region turns out to have surprising universal properties (Ref. 3).

I hope that this approach to many-body systems and quantum phase transitions -- engineering and building an artificial realization of a well-defined Hamiltonian, then probing its properties experimentally -- will drive theoretical and computational efforts, and ultimately will help us understand the richness of electronic materials such as heavy fermion metals.

1. A. J. Keller, S. Amasha, I. Weymann, C. P. Moca, I. G. Rau, J. A. Katine, Hadas Shtrikman, G. Zaránd and D. Goldhaber-Gordon, "Emergent SU(4) Kondo physics in a spin-charge-entangled double quantum dot" Nature Physics 10, 145 (2014).
2. R. M. Potok, I. G. Rau, H. Shtrikman, Y. Oreg, and D. Goldhaber-Gordon, "Observation of the two-channel Kondo effect" , Nature 446, 167-171 (2007).
3. A. J. Keller, L. Peeters, C. P. Moca, I. Weymann, D. Mahalu, V. Umansky, G. Zaránd & D. Goldhaber-Gordon, "Universal Fermi liquid crossover and quantum criticality in a mesoscopic system," Nature 526, 237–240 ( 2015).

Faculty Host: Vlad Pribiag
2:30 pm:
Condensed Matter Seminar in Physics 110 PAN
Speaker: Max Metlitski, Perimeter Institute
Subject: Composite fermion liquid: from 2DEG to topological insulator surface

It is strongly believed that the quantum Hall fluid at filling factor \nu = ½ realizes the composite fermion liquid - an exotic phase of matter with emergent excitations - composite fermions - forming a Fermi-surface. The original theory of this state proposed by Halperin, Lee and Read (HLR) in 1993 is well supported by experiments. However, one aspect of HLR theory has continued to puzzle theorists for the past 20 years: an apparent lack of particle-hole symmetry expected to emerge in the lowest Landau level. Recently, D. Son has conjectured a surprising resolution of this puzzle, proposing that the composite fermion is a Dirac fermion. I will give a derivation of this conjecture by making a connection between the physics of a half-filled Landau level and the surface of a 3d topological insulator (TI). The derivation will proceed via a dual theory of the single Dirac cone on the TI surface, given by quantum electrodynamics (QED3) with a single dual Dirac fermion coupled to a fluctuating gauge field. Finally, I will present smoking-gun numerical evidence for the Dirac nature of the composite fermion coming from DMRG simulations of quantum Hall fluid at \nu = ½.

Faculty Host: Andrey Chubukov
To be announced.
4:30 pm:
CM Journal Club in PAN 110
Subject: General meeting

Thursday, September 8th 2016
11:00 am:
Biophysics Seminar in 110 PAN
To be announced.
Speaker: No Journal Club this week
12:20 pm:
Space Physics Seminar in 115 Ford Hall 
Organizational Meeting
3:35 pm:
There will be no colloquium this week.

Friday, September 9th 2016
10:10 am:
Subject: Organizational Meeting
12:20 pm:
Speaker: Ziran Wang
Subject: GMR enhancement and oscillation in Fe/Ag/Fe/InAs/Ag(100)
There will be no seminar this week.
There is no colloquium this week.
Speaker: Dr. Michel Janssen, Physics/History of Science and Technology
Subject: "Common Origin Ideas"
Refreshments served at 3:15 p.m.

In 2002, I introduced COI (Common Origin Inference) as a subspecies of IBE (Inference to the Best Explanation). I hoped to avoid problems with the 'E' by noting that the kind of explanation involved in COI (tracing striking coincidences to a common origin) should pass muster on any philosophically satisfactory account of explanation. Following Peter Lipton, I hoped to steer clear of the problem with the 'B' by taking IBE simply to be a slogan for any kind of inference guided by explanatory considerations. I stood firm on the 'I', arguing that the use of COI in various episodes from the history of science shows that, pace Bas van Fraassen, explanations can have epistemic value (i.e., can themselves be a reason to believe in the explanation).

I have changed my mind on this last count, at least when it comes to the use of COI and IBE in science. On closer examination, COI served not so much as an engine for transferring truth values from premises to conclusions (as inferences would) but as an engine for generating pursuit-worthy ideas. In general, evidence for such ideas must be generated in other ways.

In view of this, I want to redefine the 'I' in COI from 'Inference' to 'Idea'. This may be the best defense against the main charge Wes Salmon brought against IBE in a debate with Lipton published in 2001: Why should likeliness track loveliness? Why should a lovely explanation be more likely than an ugly one? Surrendering the I in COI and IBE, one can retreat to the position that pursuit-worthiness tracks loveliness, a line that is much easier to hold.

3:35 pm:
To be announced.
To be announced.

Monday, September 12th 2016
12:15 pm:
Speaker: Yong-Zhong Qian (University of Minnesota)
Subject: Did a Low-Mass Supernova Trigger the Formation of the Solar System? Clues from Stable Isotopes and 10Be
Please note change of venue for the seminar.

About 4.6 billion years ago, some event disturbed a cloud of gas and dust, triggering the gravitational collapse that led to the formation of the solar system. A core-collapse supernova, whose shock wave is capable of compressing such a cloud, is an obvious candidate for the initiating event. This hypothesis can be tested because supernovae also produce telltale patterns of short-lived radionuclides, which would be preserved today as isotopic anomalies. Previous studies of the forensic evidence have been inconclusive, finding a pattern of isotopes differing from that produced in conventional supernova models. Here we argue that these difficulties either do not arise or are mitigated if the initiating supernova was a special type, low in mass and explosion energy. Key to our conclusion is the demonstration that short-lived 10Be can be readily synthesized in such supernovae by neutrino interactions, while anomalies in stable isotopes are suppressed.


Tuesday, September 13th 2016
12:20 pm:
Space Physics Seminar in 110 Ford Hall 
There will be no seminar this week.

Wednesday, September 14th 2016
2:30 pm:
Condensed Matter Seminar in Physics 110 PAN
Speaker: Michael Hermele, University of Colorado at Boulder
Subject:  Topological phases protected by point group symmetry

Symmetry protected topological (SPT) phases are generalizations of topological band insulators; they are quantum phases of matter with a bulk energy gap and characteristic edge or surface properties. Over the past few years, exciting progress has been made in the theory of SPT phases with strong interactions, and, separately, SPT phases with crystalline symmetry. The intersection of these two directions — strongly interacting crystalline SPT phases — has potential experimental relevance but remains rather poorly understood. In this talk, I will present a general framework to classify and characterize SPT phases protected by crystalline point group symmetry. The basic insight is that all such SPT phases can be reduced to lower-dimensional topological phases with internal symmetry. This leads to a physically transparent approach that is generally applicable to bosonic or fermionic systems in any spatial dimension, without regard to the strength of interactions. I will illustrate the key ideas via discussion of a few interesting examples.

Faculty Host: Fiona Burnell
There will be no seminar this week.

Thursday, September 15th 2016
11:00 am:
Biophysics Seminar in 110 PAN
There will be no seminar this week.
Speaker: Terry J. Jones
3:35 pm:
Speaker: Vuk Mandic
Subject: First Direct Detections of Gravitational Waves
Refreshments to be served outside Keller 3-210 after the colloquium.

During their first observation run the Advanced LIGO gravitational-wave detectors recorded signatures of mergers of binary black hole systems. These events mark the beginning of gravitational-wave astrophysics, enabling a new approach to studying various astrophysical phenomena. I will describe the LIGO detectors and the events they recorded, and I will discuss the implications of these observations as well as our expectations for future observations.


Friday, September 16th 2016
Speaker: Michael Sammon, University of Minnesota
Subject: Electron Accumulation Layer in the Extreme Quantum Limit
Speaker: Jared Kaplan (John Hopkins)
Subject: Information Loss in AdS_3 / CFT_2

We discuss information loss from black hole physics in
AdS_3, focusing on two sharp signatures infecting CFT_2 correlators at
large central charge c: 'forbidden singularities' arising from
Euclidean-time periodicity due to the effective Hawking temperature,
and late-time exponential decay in the Lorentzian region. We study an
infinite class of examples where forbidden singularities can be
resolved by non-perturbative effects at finite c, and we show that the
resolution has certain universal features that also apply in the
general case. Analytically continuing to the Lorentzian regime, we
find that the non-perturbative effects that resolve forbidden
singularities qualitatively change the behavior of correlators at
times t ∼ S_{BH}, the black hole entropy. This may resolve the
exponential decay of correlators at late times in black hole
backgrounds. By Borel resumming the 1/c expansion of exact examples,
we explicitly identify 'information-restoring' effects from heavy
states that should correspond to classical solutions in AdS_3. Our
results suggest a line of inquiry towards a more precise formulation
of the gravitational path integral in AdS_3.

Speaker: Daniel Weisz, U.C. Berkeley
Subject: A PHAT New Measurement of the High-Mass Stellar IMF

The initial mass function (IMF) for stars above ~1 Msun is essential to testing and validating theories of star formation, constraining chemical enrichment models, the frequency of core-collapse supernovae, and interpreting the stellar populations of galaxies across cosmic time. Yet, despite more than 60 years of research, observational constraints on the high-mass IMF remain remarkably uncertain. Widely used high-mass IMFs (e.g., Kroupa) have associated uncertainties approaching an order-of-magnitude, making it virtually impossible to determine if the high-mass IMF varies with respect to environment (e.g., metallicity or star formation intensity) or is “Universal". In this talk, I will present the most precise measurement of the high-mass IMF to date. Using ~100 young, resolved star clusters in M31 imaged as part of the Panchromatic Hubble Andromeda Treasury (PHAT) survey, we find the high-mass IMF slope to be Gamma=1.45+/-0.03. Compared to the canonical Kroupa IMF (Gamma=1.3+/-0.7), the high-mass IMF in M31 is 0.15 dex steeper (i.e., fewer massive stars) and represents a factor of ~20 improvement in precision. There are no significant trends between the cluster IMF slopes and their ages, masses, and sizes, indicating that the IMF is remarkably “Universal” in this sample of ~100 clusters. I will illustrate some of the broader implications of a steeper IMF slope (e.g., on star formation rate indicators, core-collapse supernovae rates) and will conclude by discussing the prospects for precision IMF measurements in other environments.

Speaker: Eileen Reeves, Princeton University
Subject: "Drawing on Galileo: Art, Astronomy, and Appropriation"
Refreshments served at 3:15 p.m.

This lecture involves a quarrel between Galileo Galilei, newly established as early modern Europe’s premier astronomer, and an aristocratic student at a Jesuit college. At stake here is the staying power of this particular struggle, which first emerged around 1613 and then resurfaced nearly twenty years later in Galileo’s celebrated discussion of the imperceptibility of common motion. Though this conflict began with elaborate displays of indifference, it soon depended upon comic manipulation of the opponent’s arguments, a fable concerning a shipboard artist, and an extraordinary series of odd, distracting woodcuts.

3:35 pm:
To be announced.
There will be no seminar this week.

Monday, September 19th 2016
08:00 am:
Untitled in Physics
Speaker: Cornelia Lang, U. Iowa
Subject: The Central Molecular Zone of the Galaxy: Dense Molecular Clouds, Massive Stars and Magnetic Fields

In addition to harboring a supermassive black hole at its very core, the Galactic Center is one of the most physically extreme environments in the Galaxy. Dense and massive molecular clouds are abundant in this region, yet star formation is not as active as one might expect. In addition, radio observations have revealed a population of synchrotron-emitting filaments that provide insight on the magnetic field strength and configuration in this unique region of the Galaxy. Physical interactions may be occurring at the interfaces of dense molecular clouds and the interstellar magnetic filaments. I will review recent observational results of several unusual molecular clouds and the population of magnetized filaments that stand out in radio continuum images of the Galactic center and discuss the implications for better understanding the astrophysics of this region.

12:15 pm:
Speaker: Irshad Mohammed, Fermi National Accelerator Laboratory
Subject: Towards precision cosmology with large scale structures: the halo model and perturbative approaches

The theoretical modeling of the statistical observables of the large-scale structures of the Universe, like galaxy clustering, weak lensing etc., is necessary in order to derive any constraints on the cosmological parameters. One of the most important ingredients of the theoretical model is the two-point correlation function, or its Fourier transform the matter power spectrum. I will discuss the precision in its calculations based on a modified halo model, and the systematic effects due to the baryonic processes. Further, I will also discuss the covariance matrix of the matter power spectrum and its estimators based on the halo model and the perturbation theory. We find the agreement with the simulations is at a 10% level up to k ∼ 1 h/Mpc. We show that all the connected components are dominated by the large-scale modes (k < 0.1h/Mpc), regardless of the value of the wavevectors of the covariance matrix. Finally, I will provide a prescription for how to evaluate the covariance matrix from small box simulations without the need to simulate large volumes.

Faculty Host: Liliya L.R. Williams

Tuesday, September 20th 2016
09:30 am:
Speaker: Dr. Andreas Keiling, Space Science Lab, UCB
Subject: Art & Aurora
Note change of time and location from previous announcement. The seminar will be in this location at this time for the remainder of the semester.

Wednesday, September 21st 2016
2:30 pm:
Condensed Matter Seminar in Physics 110 PAN
Speaker: Ivan Schuller, UCSD
Subject: Unique Science of Strongly Correlated Oxides

Recently, strongly-correlated transition metal oxides, that exhibit first order metal-insulator transitions, have received renewed attention because they can be controlled and manipulated at the nanoscale to develop unique properties. Although the existence of these materials has been known for some time, the physical origin of many of these phenomena remains a very controversial issue. In addition, hybrid heterostructures allow the engineering of new material properties by creative uses of proximity effects. When two dissimilar materials are in close physical proximity the properties of each one may be radically modified or occasionally a completely new material emerges. By properly designing hybrid ferromagnet/oxides new magnetic properties arise unlike any known magnetic materials. I will describe the static and dynamical properties of strongly correlated nanostructured oxides, which exhibit metal-insulator transitions. These materials when reduced to the nanoscale exhibit interesting properties such as avalanches, unique response to disorder and critical slowing down in their fast time dependence. In a series of recent studies, we have investigated the magnetic properties of different hybrids of ferromagnets (Ni, Co and Fe) and oxides, which undergo metal-insulator and structural phase transitions. Both the static as well as dynamical properties of the ferromagnets are drastically affected. Static properties such as the coercivity, anisotropy and magnetization and dynamical properties are clearly modified by the proximity effect and give raise to interesting perhaps useful properties. The oxide work supported by the US-AFOSR and the magnetism aspects by the US-DOE. Work done in collaboration with many young researchers who will be individually credited.

Faculty Host: E. Dan Dahlberg
There will be no seminar this week.

Thursday, September 22nd 2016
11:00 am:
Biophysics Seminar in 120 PAN
Speaker: Prof. David Piston, Washington University School of Medicine
Subject: Imaging the Molecular Mechanisms of Pancreatic Hormone Secretion
Note change of room from previous announcement.

The release of insulin from pancreatic β-cells plays a central role in maintaining normal blood glucose levels. Regulated trans-membrane gradients of calcium and potassium ion channels signal to increase or decrease insulin release. This is exemplified with the stimulation of dopamine, a neurotransmitter, which reduces intracellular calcium oscillations by activation of the dopamine receptor D3 (DRD3) and therefore inhibits secretion of insulin (Ustione & Piston, Mol. Endocrinol. 26, 1928 (2012)). We seek to better understand the physiological and cellular functions of dopamine signaling as it could potentially lead to a novel treatment of diabetes. DRD3 is a G protein-coupled receptor that we propose might interact with cellular ion channels through the Gβγ complex. Towards understanding which channels and pathways are involved, we have turned to quantitative imaging assays, the first of which is based on Förster resonance energy transfer (FRET), a technique widely used to study biomolecular dynamics and protein interactions in live cells. Limitations due to brightness differences, donor:acceptor stoichiometry, and cross-talk between the donor and acceptor can lead to misleading or even meaningless results. To help alleviate these problems with cellular FRET measurements, we have developed a new approach for absolute and high precision measurements of FRET efficiency is based upon the use of an optical switching acceptor. By employing a defined train of optical perturbations to control the on and off states of the acceptor, it is possible to modulate the fluorescence intensity of the donor, and this can be analyzed using a lock-in detection approach. Secondly, we have leveraged two-color Fluorescence Fluctuation Spectroscopy (FFS), which can be used to directly measure diffusion and binding rates of proteins within the cell. Using FFS to measure protein binding and diffusion allows quantification at the molecular level of protein interactions. In addition, protein molecular concentration can also be determined. Quantifying the molecular interactions within the proposed dopaminergic feedback pathway illuminates the signaling pathway, and thus provides essential information for developing a therapeutic treatment of non-insulin dependent diabetes.

Speaker: Mehdi Lame'e and Tom Jones
3:35 pm:
Speaker: Lucy Fortson
Subject: Blazar Observations with VERITAS: expanding the cosmic gamma-ray horizon
Refreshments to be served outside Keller 3-210 after the colloquium.

Blazars are Active Galactic Nuclei (AGNs) that launch collimated jets of relativistic particles towards the Earth. They emit radiation that spans the entire observable electromagnetic spectrum from radio to gamma-ray energies and which varies in intensity over a wide range of timescales, from minutes to years. For the past decade, the VERITAS gamma-ray observatory has been recording very-high-energy (VHE ≥ 100 GeV) photons, yielding a catalog of over 175 VHE gamma-ray sources of which almost 40% are blazars. Pair production interactions between VHE and lower-energy photons strongly attenuate the flux of gamma-rays as they propagate to Earth through a cosmological photon field known as the extragalactic background light (EBL). This is expected to impose a gamma-ray horizon at redshifts well below unity, beyond which VHE gamma-ray sources are rendered undetectable to the current generation of instruments. I will describe recent results from the VERITAS blazar observing program including the exciting and unexpected detection of a particularly high redshift (z~1) blazar. I will then describe efforts to use blazar gamma-ray spectra to constrain the EBL and as a probe for the presence of Ultra-High Energy Cosmic Ray emission from blazars.


Friday, September 23rd 2016
10:10 am:
The Nuclear seminar has been cancelled for this week.
Speaker: Peter Martin, University of Minnesota
Subject: Investigating Soft Condensed Matter Systems Using Electron Paramagnetic Resonance Spectroscopy
Speaker: Chi-Ming Chang (Berkeley)
Subject: Five Dimensional Superconformal Field Theories

This talk consists of two parts. In the first part, we discuss indices of 5d superconformal field theories (SCFTs) with emphasis on indices of 1d operators. We construct an index for BPS operators supported on a ray in 5d SCFTs with exceptional global symmetries. We compute the E_n representations (for n=2,\dots,7) of operators of low spin, thus verifying that while the expression for the index is only SO(2n-2)\timesU(1) invariant, the index itself exhibits the full E_n symmetry (at least up to the order we expanded). The ray operators we studied in 5d can be viewed as generalizations of operators constructed in a Yang-Mills theory with fundamental matter by attaching an open Wilson line to a quark. For n\le 7, in contrast to local operators, they carry nontrivial charge under the \mathbb{Z}_{9-n}\subset E_n center of the global symmetry. In the second part, we discuss an on going project of bootstrapping 5d SCFTs. We consider the four point function of the 1/2 BPS operators. We discuss the crossing symmetry and the superconformal blocks of the four point function. We present some preliminary results on the bounds of the operator dimensions and OPE coefficients obtained from analyzing the crossing equation numerically.

Speaker: See the listing for the SPA colloquium on Sept. 22nd - Lucy Fortson
Speaker: Robyn Bluhm, Michigan State University
Subject: "How to Think About Mechanisms in Medicine"
Refreshments served at 3:15 p.m.

In this talk, I argue that the best way to think about knowledge of mechanisms in medical research and practice is to consider the relationship between knowledge of physiological mechanisms and knowledge gained from epidemiological methods, particularly clinical trials. The dominant view, rooted in evidence-based medicine, is that only clinical trials can establish treatment effectiveness, but not all such trials are equally useful. I draw on work by James Tabery and C. Kenneth Waters to show how knowledge of physiological mechanisms can improve the design and interpretation of clinical trials.

Speaker: Chris Leighton, University of Minnesota
Subject: To be announced.

Monday, September 26th 2016
12:15 pm:
There will be no seminar this week.

Tuesday, September 27th 2016
09:30 am:
Speaker: Scott Thaller, University of Minnesota
Subject: A review of plasma thrusters
3:00 pm:
Thesis Defense in Vincent Hall 364
Speaker: Jared Turkewitz, University of Minnesota
Subject: Measurement of the associated production of a Z boson with a J/psi meson with the CMS experiment at a center-of-mass energy of 8 TeV
This is the public portion of Mr. Turkewitz's thesis defense.

The associated production of a Z boson and a J/ψ meson provides information about the production mechanisms of quarkonium. A measurement of the associated production of a Z boson, which decays to leptons, and a J/ψ meson, which decays to muons, relative to the inclusive production of a Z boson, which decays to leptons, is presented. The measurement was made using the full 19.7 fb−1 of proton-proton collision data collected at a center-of-mass energy of √s = 8 TeV by the Compact Muon Solenoid detector at the Large Hadron Collider.


Wednesday, September 28th 2016
2:30 pm:
Condensed Matter Seminar in Physics 110 PAN
Speaker: Arun Bansil, Northeastern University, Boston
Subject: Miracle of topological phases of quantum matter: From Schrödinger to Einstein

The revolution started by the discovery of topological insulators a few years ago has turned out to be the proverbial tip of the much larger iceberg of exotic phases of quantum matter driven by spin-orbit coupling effects. Consideration of electronic states protected by time-reversal, crystalline and particle-hole symmetries has led to the prediction of many novel materials, which can support Weyl, Dirac and Majorana fermions, and to new types of insulators such as topological crystalline insulators and topological Kondo insulators, as well as quantum spin Hall insulators with large band gaps capable of surviving room temperature thermal excitations. [1] I will discuss our recent theoretical work aimed at predicting topological materials and identify cases where robust experimental evidence has been obtained toward their successful materials realization. [2-10] I will also comment on potential of topological materials as next generation platforms for manipulating spin and charge transport and other applications.

[1] Bansil, Lin and Das, Reviews of Modern Physics 88, 021004 (2016).
[2] Chang et al, Science Advances 2, e1600295 (2016).
[3] Huang et al., Proc. National Academy of Sciences 113, 1180 (2016).
[4] Zheng et al., ACS Nano 10, 1378 (2016).
[5] Xu et al., Science 349, 613 (2015).
[6] Zeljkovic et al., Nature Materials 14, 318 (2015).
[7] He et al., Nature Materials 14, 577 (2015).
[8] Xu et al., Nature Physics 11, 748 (2015).
[9] Crisostomo et al., Nano Letters 15, 6568 (2015).
[10] Xu et al., Science Advances 1, e1501092 (2015).

Faculty Host: Martin Greven
There will be no seminar this week.
4:30 pm:
CM Journal Club in PAN 110
Speaker: Mengxing Ye
Subject: Kosterlitz-Thouless transition

Berezinskii-Kosterlitz-Thouless transition describes the phase transition from the quasi long range ordered phase to disordered phase of certain 2d classical systems. The physics picture of the BKT transition as a transition the bounded vortex-antivortex pair becomes unpaired will be presented first. I will show how the original theory can be mapped to interacting vortices (=2d coulomb gas) through a mathematically rigorous duality transformation. Through the RG analysis, we will understand the nature of the phase transition in terms of the interacting vortices.


Thursday, September 29th 2016
11:15 am:
Biophysics Seminar in 120 PAN
Speaker: Prof. Marc Riedel University of Minnesota, Department of Electrical and Computer Engineering
Subject: T Computing with Crappy Clocks (C^3): A New Paradigm for Molecular Computing
Please note change of time from previous announcement. The seminar will be held at 11:15 for the remainder of the semester.

Clock distribution networks are a significant source of power consumption and a major design bottleneck for digital circuits, particularly with increasing variability. Completely asynchronous design methodologies have been studied for decades, but these have never gained widespread acceptance. We have proposed an alternative: splitting digital circuitry into small blocks and synchronizing these locally with independent, cheap clocks (generated with simple inverter rings). This is feasible if one adopts a stochastic representation for signal values. Logical computation is performed on randomized bit streams, with signal values encoded in the statistics of the streams. This talk will discuss extensions and applications of these ideas to molecular computing. DNA-based computation via strand displacement is the target experimental chassis.

Bio:

Marc Riedel is Associate Professor of Electrical and Computer Engineering at the University of Minnesota. From 2006 to 2011 he was Assistant Professor. He is also a member of the Graduate Faculty in Biomedical Informatics and Computational Biology. From 2004 to 2005, he was a lecturer in Computation and Neural Systems at Caltech. He has held positions at Marconi Canada, CAE Electronics, Toshiba, and Fujitsu Research Labs. He received his Ph.D. and his M.Sc. in Electrical Engineering at Caltech and his B.Eng. in Electrical Engineering with a Minor in Mathematics at McGill University. His Ph.D. dissertation titled "Cyclic Combinational Circuits" received the Charles H. Wilts Prize for the best doctoral research in Electrical Engineering at Caltech. His paper "The Synthesis of Cyclic Combinational Circuits" received the Best Paper Award at the Design Automation Conference. He is a recipient of the NSF CAREER Award.

Speaker: Qi Wen
3:35 pm:
Speaker: Greg Pawloski
Subject: Looking at the weird building blocks of the universe with the NOvA detectors
Refreshments to be served outside Keller 3-210 after the colloquium.

Neutrinos are the odd balls of the elementary particle menagerie that
forms the building blocks of the universe. Because of their odd
properties they can potentially be involved in interesting processes
that are responsible for our universe not annihilating itself. There
is currently great interest in the particle physics community to study
the properties of these particles. However, because of their odd
nature, their detection is challenging and extraordinary detectors are
needed to study them. In this talk, we will look at the role of the
NOvA detectors (the world’s largest plastic structures) in studying
the properties of neutrinos by shooting a beam of neutrinos through
the Earth from Illinois to northern Minnesota.


Friday, September 30th 2016
10:10 am:
The Nuclear seminar has been cancelled again this week.
Speaker: James Delles, University of Minnesota
Subject: Transport Properties of Exchange Biased Mesoscale Wires
Speaker: Louis Yang (UCLA)
Subject: Leptogenesis via the Relaxation of Higgs and other Scalar Fields

During inflation, a scalar field with a shallow potential such as the Higgs field can develop a large vacuum expectation value (VEV) through quantum fluctuation. The relaxation of the scalar field from this large value to the minimum of its potential after inflation can lead to several interesting consequences in the Universe. In this talk, I will explore a possibility that the baryon number asymmetry of the Universe is generated via the Higgs field relaxation during reheating. I will also show that the same leptogenesis mechanism can be applied to other scalar fields explaining the matter-antimatter asymmetry of the Universe.

Speaker: Caryl Gronwall, Penn State University
Subject: HETDEX and Star-Forming Galaxies of the z ~ 2 Universe

Next spring, the Hobby Eberly Telescope Dark Energy Experiment will begin obtaining redshifts for roughly a million Ly-alpha emitting galaxies (LAEs) between 1.9 < z < 3.5. While the main purpose of the project is to study the evolution of Dark Energy, the project will provide an incredible data base for studies of galaxy evolution. In preparation for this, we have been investigating the physical and chemical properties of emission-line galaxies in the z ~ 2 universe, using LAEs discovered from the ground and samples of [O III]-emitting objects identified from space. We show that LAEs are not “low mass, dust-poor galaxies caught in the act of formation”, but instead span the entire range of stellar masses, from at least 7.5 < log M/Msun < 10.5. We then use our galaxy samples to explore issues such as the (non)-Fundamental Metallicity Relation, the systematics of star-formation rate indicators, the behavior of dust attenuation laws versus stellar mass, and the question of what makes an LAE and LAE.

Speaker: James Fleming, Colby College
Subject: "Inventing Atmospheric Science: Gordian Knots and the Quest for Prevision"
Refreshments served at 3:15 p.m.

Atmospheric researchers have long attempted to untie the Gordian Knot of meteorology—that intractable and intertwined tangle of observational imprecision, theoretical uncertainties, and non-linear influences—that, if unraveled, would provide perfect prevision of the weather for ten days, of seasonal conditions for next year, and of climatic conditions for a decade, a century, a millennium, or longer. This presentation, based on Inventing Atmospheric Science (The M.I.T. Press, 2016), examines the work of three interconnected generations of scientists and the influence of three families of transformative technologies in the first six decades of the twentieth century, from the dawn of applied fluid dynamics to the emergence, by 1960, of the interdisciplinary atmospheric sciences.

Speaker: Ken Heller, University of Minnesota
Subject: To be announced.

Monday, October 3rd 2016
12:15 pm:
Speaker: Yong-Zhong Qian (University of Minnesota)
Subject: Neutrinos in the Cosmos: A Nobel Perspective

Neutrino experiments have been rewarded by the Nobel Prize in Physics four times, including the one for 2015. I will give an overview of how these experiments help us understand neutrinos, their production and interaction, and their flavor oscillations. The quantum mechanics of neutrino oscillations in both vacuum and matter will be discussed in analogy to precession of magnetic moments in magnetic fields. The important roles of neutrinos in a wide range of astrophysical phenomena will be described. I will conclude with a list of remaining puzzles about neutrinos.


Tuesday, October 4th 2016
09:30 am:
Speaker: Trevor Knuth and Julie Vievering, University of Minnesota
Subject: EXACT: The Experiment for X-ray Characterization and Timing CubeSat

Wednesday, October 5th 2016
2:30 pm:
Condensed Matter Seminar in Physics 110 PAN
Speaker: Srinivas Raghu, Stanford University
Subject: Composite fermions and the 2D field-tuned superconductor-insulator transition

In several two-dimensional films that exhibit a magnetic field-tuned superconductor to insulator transition (SIT), stable metallic phases have been observed. An influential theory of the SIT involves disorderd bosons (Cooper pairs and vortices) in a magnetic field. Building on this `dirty boson' description of the SIT, we suggest that the observed metallic behavior near the SIT is analogous to the composite Fermi liquid observed about half-filled Landau levels of the two-dimensional electron gas. The composite fermions here represent composites of vortices and Cooper pairs. We describe several experimental consequences stemming from these fermionized vortices.

Faculty Host: Rafael Fernandes
There will be no seminar this week.
4:30 pm:
CM Journal Club in PAN 110
Speaker: Xiaoyu Wang
Subject: Sachdev-Ye-Kitaev Model

Thursday, October 6th 2016
11:15 am:
Speaker: Prof. Kris Dahl, Carnegie Mellon University, Dept. of Chemical Engineering and BioMedical Engineering
Subject: To be announced.
Speaker: Karl Young
3:35 pm:
Speaker: Tommaso Treu, UCLA
Subject: The other 95%: insights from strong gravitational lensing
Refreshments to be served outside Keller 3-210 after the colloquium.

In the standard cosmological model ninetyfive percent of the energy content of the universe consists of dark energy and dark matter. Even though their abundance seems well determined, very little is known about their fundamental nature. I will describe how we can learn about the physics of the dark sector by studying in detail its gravitational effect on the trajectories of photons as they travel across the universe, a phenomenon known as strong gravitational lensing. In the first part of the talk, I will use strong gravitational lenses with a time variable background source to measure the expansion rate of the universe (Hubble constant) to 3.8% precision. This result is completely independent of the local distance ladder and the cosmic microwave background, and thus provides a new opportunity to understand whether the tension between the two arises from systematic uncertainties or may be indicative of new physics. In the second part of the talk I will describe how strong lensing can be used to detect the presence of dark subhalos independent of their stellar content. This measurement tests a fundamental prediction of the cold dark matter model, i.e. that galaxies should be surrounded by large numbers of dark satellite subhalos. Proof that such satellites do not exist would force a revision of the model in favor of more exotic alternatives like warm dark matter. I will conclude by discussing the exciting future of strong lensing as a tool for cosmology, in light of the huge numbers of strong lenses that are on the verge of being discovered in the current generation of wide field astronomical surveys.

Faculty Host: M. Claudia Scarlata

Friday, October 7th 2016
10:10 am:
Speaker: Christopher Plumberg, University of Minnesota
Subject: Event-by-event fluctuations and their consequence for Hanbury Brown-Twiss interferometry

The relativistic heavy-ion program is dedicated to systematically probing the properties of the atomic nucleus and the theory of quantum chromodynamics at extremely high temperatures and energy densities. Numerous observables have been developed and studied over the past several decades, allowing one to extract valuable information about heavy-ion collisions and their evolution, including total multiplicity, anisotropic flows, mean pT, interferometric radii, and so on. Many of these observables have been studied on an event-by-event basis, allowing them, along with their event-by-event probability distributions, to be used for constraining the role of event-by-event fluctuations in the evolution of heavy-ion collisions.
In this talk, I will discuss the possibility of treating the Hanbury Brown-Twiss radii as event-by-event observables, and consider the ways in which their event-by-event probability distributions might be related to interesting theoretical quantities, such as transport coefficients in the quark-gluon plasma, or used to constrain viable models of the initial state in heavy-ion collisions. I will also briefly discuss some recent efforts to extend these results to explore the effects of hydrodynamic fluctuations in heavy-ion collisions.

Speaker: Tim Peterson, University of Minnesota
Subject: Spin Hall effects in ultrathin heavy metal/ferromagnet bilayers
Speaker: Kurt Hinterbichler (Case Western Reserve)
Subject: Massive and Partially Massless Gravity

I will review recent developments in the non-linear theory of massive gravitons, or spin-2 fields. On de Sitter space, there exists a special value for the mass of a graviton for which the linear theory propagates 4 rather than 5 degrees of freedom. If a fully non-linear version of the theory exists and can be coupled to known matter, it would have interesting properties and could solve the cosmological constant problem. I will describe evidence for and obstructions to the existence of such a theory, and recent developments.

Speaker: Brad Peterson, Professor Emeritus, Ohio State University and Distinguished Visiting Astronomy, Space Telescope Sci. Institute
Subject: Exploring the Inner Structure of Active Galactic Nuclei by Reverberation
Prof. Petrson was recently awarded an Outstanding Achievement Award from the University

The innermost structure of active galactic nuclei (AGNs) consists of an accretion disk surrounding a supermassive black hole and, on somewhat larger scales, rapidly moving diffuse gas. The ultraviolet through near IR spectrum of AGNs is dominated by thermal continuum emission from the accretion disk and broad emission lines and absorption features from the diffuse gas. The continuum flux from the accretion disk varies with time, and the emission lines also change in brightness, or “reverberate,” in response to these variations, with a delay due to the light-travel time across the line-emitting region. Measurement of the emission-line time delay yields the size of the line-emitting region and by combining this with the emission-line Doppler width, the central black hole mass can be inferred. I will discuss results from recent “reverberation mapping” experiments, including a 179-orbit HST Cycle 21 program, that have been designed to explore the dynamics of the emission-line gas and are yielding a wealth of new and quite surprising information about AGN structure.

Speaker: Prisca Cushman, University of Minnesota
Subject: Dark Matter Searches with SuperCDMS

Saturday, October 8th 2016
12:00 pm:
SPA Fall Picnic in Boom Island Park Shelter

All SPA faculty, staff, postdocs, students, and their families are welcome to attend! We ask that everyone who comes either bring a dish to share or contribute $5 towards the cost of the event. Monetary contributions can be dropped off with a GradPhi officer or in any of the physics offices (with Jenny in 250 PAN, Amanda in Williamson, Angie in McNamara, Meghan in WBOB).

Please RSVP if you plan on coming to help us get everything organized.

If you're planning on bringing a side dish or dessert to share, please let us know what you will be bringing on the form.


Monday, October 10th 2016
12:15 pm:
Speaker: Keith Olive (University of Minnesota)
Subject: Dark Matter in Grand Unified Theories

The notion of the grand unification of gauge interactions has been with us for over 40 years. Supersymmetry is often regarded as the savior of grand unified theories as the additional particle degrees of freedom in theory help in the unification of the gauge couplings. In addition, supersymmetry provides us with a compelling candidate for dark matter. However, supersymmetry to date, has not been discovered at the LHC. The implications of recent LHC results for supersymmetric dark matter will be discussed as well as alternatives in non-supersymmetric grand unified theories.


Tuesday, October 11th 2016
09:30 am:
There will be no seminar this week.

Wednesday, October 12th 2016
2:30 pm:
Condensed Matter Seminar in Physics 110 PAN
Speaker: Guichuan Yu, UMN
Subject: Spatial and Orbital Distribution of Doped Holes in Cuprate High-Temperature Superconductors
Faculty Host: Martin Greven
There will be no seminar this week.
4:30 pm:
CM Journal Club in PAN 110
No journal club this week.

Thursday, October 13th 2016
11:15 am:
Speaker: Yan Chen, School of Physics and Astronomy, University of Minnesota
Subject: Receptor-mediated selective autophagy degrades the endoplasmic reticulum and the nucleus.”
Speaker: Evan Tyler and Liliya Williams
3:15 pm:
Group Photo in Civil Engineering Building Courtyard
Refreshments will be served in PAN Lobby prior to group photo. Come get a cookie and then have your picture taken with the group.
3:35 pm:
Speaker: Rafael Fernandes
Subject: High-temperature superconductivity near a quantum critical point
Refreshments to be served outside Keller 3-210 after the colloquium.

The elucidation of high-temperature superconductivity remains a fundamental challenge in quantum many-body physics, with potential implications for the development of unique technological applications. In contrast to conventional superconductors, the attractive interaction between the electrons mediated by the lattice cannot explain the formation of this quantum state of matter. Experimentally, however, high-temperature superconductivity is often observed in the vicinities of a putative zero-temperature phase transition, also known as a quantum critical point. In this talk, I will present new theoretical results for the superconducting instability of a very general model in which electrons interact by exchanging fluctuations associated with a magnetic quantum critical point. By combining numerical and analytical approaches, I will discuss the microscopic mechanisms that promote the emergence of a high-temperature superconducting state, and examine which of the many system’s parameters may be tuned to help achieving even higher transition temperatures.

7:00 pm:
Speaker: Dr. Vuk Mandic, School of Physics & Astronomy, MN Institute for Astrophysics

Advanced LIGO gravitational-wave detectors recently recorded the first signals coming from mergers of binary black hole systems, marking the beginning of gravitational-wave astronomy and astrophysics. For the first time we are able to observe and study the universe with gravitational waves, and to learn about objects never observed before. Dr. Mandic will describe the LIGO detectors and the events they recorded, and he will discuss the implications of these observations as well as expectations for future observations.


Friday, October 14th 2016
10:10 am:
There will be no seminar this week.
Speaker: Ruiqi Xing, University of Minnesota
Subject: Renormalization group analysis of competing instabilities in the four-pocket model for iron-based superconductors

In iron-based superconductors, superconductivity, magnetism and nematic orders are all observed. To understand the phase diagram and the interplay between different orders in iron-based superconductors, we use parquet renormalization group, an unbiased approach, to study the full four-pocket, 3-orbital low-energy model.

Starting from all symmetry-allowed interactions, we derive and analyze the RG flow of the couplings and susceptibilities. We obtain the hierarchy of competing instabilities and obtain, as limiting cases, the behavior, which was previously found in approximate models [A.V. Chubukov, M. Khodas and R.M. Fernandes, arxiv:1602.05503]. For parameters relevant to FeSe, we found that upon lowering the temperature, nematic order is the leading instability, followed by superconductivity, while the magnetic order doesn't appear. We found that the nematic order parameter has three components, and found particular relation between the components, consistent with ARPES experiment[A. Fedorov et al, arxiv:1606.03022].

Speaker: Lena Funcke (Max Planck Institute for Physics and Ludwig Maximilian University of Munich)
Subject: Rethinking the Origin of Small Neutrino Masses

The observed small neutrino masses are one of the greatest mysteries in current theoretical particle physics. Many possible origins have been proposed so far, such as the see-saw mechanism, radiative corrections, or large extra dimensions. While all these models have been connected in some way to the Higgs condensate, we propose a substantially different mechanism based on nonperturbative gravity: assuming that gravity contains a topological theta-term analogous to the famous theta-term of QCD, we show that a neutrino condensate emerges and effectively generates the small neutrino masses. This neutrino mass generation mechanism implies numerous phenomenological consequences, such as the invalidity of the cosmological neutrino mass bound, enhanced neutrino-neutrino interactions, and neutrino decays.

Speaker: Dr. Andreas Faisst, IPAC, Caltech
Subject: Insights into the high-redshift Universe using Spitzer and Local Galaxies

How do the first galaxies form? What is their connection to reionization? With today’s large samples of galaxies at z > 5, this is one of the burning question in modern astrophysics. Current spectrographs are not able to probe the spectral properties of the very first galaxies until the advent JWST. However, by combining deep Spitzer data with detailed studies of local galaxies we can probe the formation of the first galaxies in depth and provide the optimal samples for follow-up with JWST as well as other upcoming facilities. My talk will focus on what we learn pre-JWST about the properties and formation of
the first galaxies.

Speaker: Günter Wagner, Yale University
Subject: "The Conceptual Weight of Homology"
Refreshments served at 3:15 p.m.

The homology concept, i.e. the idea that different species can have the same or corresponding body parts, is fundamental to biology but has, as many basic concepts in biology, a rather varied history. Opinions range from accepting homology as a fundament of all of biology to complete dismissal as a pure illusion. I will give a brief outline of how we arrived at this state of affairs and then make an argument for a “reformed” homology concept that is not only capture the essence of the classical theories of homology but also is able to connect to a mechanistic understanding of developmental biology. The key idea is that homology requires developmental and genetic individuality and that many of the difficulties of current applications of homology result from ignoring this problem. I will finish with the argument that evolutionary biology needs, besides population thinking (Mayr) and tree thinking (O’Hara) a third form of intellectual framework that could be called “homology thinking” (Ereshefsky 2012).

Speaker: Jochen Mueller, University of Minnesota
Subject: To be announced.

Monday, October 17th 2016
12:15 pm:
Speaker: Noah Alexander Kurinsky (Stanford University)
Subject: Searching for MeV Dark Matter at SuperCDMS SNOLAB and Beyond
Faculty Host: Priscilla Cushman

Tuesday, October 18th 2016
09:30 am:
Speaker: Xiaochen Shen, HAO, National Center for Atmosphere Research, Boulder
Subject: Effects of solar wind positive and negative dynamic pressure impulses on magnetospheric Pc5 ULF wave characteristics

Wednesday, October 19th 2016
2:30 pm:
Condensed Matter Seminar in Physics 110 PAN
Speaker: Raymond Ashoori, MIT
Subject: Studying Tunneling into Insulators: Observation of a Long-Range Ordered Wigner-Crystal in a Two-Dimensional Electronic System

In a system of free electrons, both the Coulomb repulsion and quantum kinetic energies diminish as the electron density is decreased. Since the kinetic energy diminishes faster than the Coulomb energy, it becomes energetically favorable for electrons to localize into a crystal known as a “Wigner Crystal". In the case of 2D systems, applying a quantizing magnetic field favors crystal formation by further freezing out the kinetic energy into Landau levels. Theory predicts that a Wigner crystal of quasiparticles in a Landau level exists near integer quantum Hall states as an insulating phase with an expected transition temperature in the range of a few hundred millikelvin or below. As the state in insulating, it is very difficult to probe it. Using a refined pulsed tunneling method, capable of probing insulating phases, we are able to measure tunneling current directly into the electronic crystal. I will present high-resolution tunneling measurements that reveal very sharp structure arising from the vibrational spectrum of the spatially ordered electronic structure. This observation conclusively demonstrates the existence of a Wigner Crystal with long correlation length and opens the door to using tunneling to probe and detect a wide variety of ordered electronic phases. Finally, I will also show results from a related tunneling method that we have developed that permits quantitative determination of spectral function of the 2D electron system as a function of both energy and momentum.

Faculty Host: Vlad Pribiag
To be announced.
4:30 pm:
CM Journal Club in PAN 110
Speaker: Alberto Alvarado
Subject: Renormalization-group approach to interacting fermions

I will review the basic concepts of the Renormalization Group following the review paper by Shankar. Specifically, I will define what is renormalization, the concept of a fixed point, and show a sample calculation for a complex scalar field in 4 dimensions. The goal is to build the conceptual understanding needed for more complicated systems.

References: R. Shankar, Renormalization-group approach to interacting fermions. Rev. Mod. Phys. 66, 129 (1994).

7:00 pm:
Eleventh Annual Misel Lecture in McNamara Alumni Center
Speaker: John Preskill, California Institute of Technology
Subject: Quantum Computing and the Entanglement Frontier

The quantum laws governing atoms and other tiny objects seem to defy common sense, and information encoded in quantum systems has weird properties that baffle our feeble human minds. John Preskill will explain why he loves quantum entanglement, the elusive feature making quantum information fundamentally different from information in the macroscopic world. By exploiting quantum entanglement, quantum computers should be able to solve otherwise intractable problems, with far-reaching applications to cryptology, materials, and fundamental physical science. Preskill is less weird than a quantum computer, and easier to understand.


Thursday, October 20th 2016
08:00 am:
Untitled in Physics
11:15 am:
Biophysics Seminar in 120 PAN
Speaker: Prof. David Grunwald, University of Massachusetts Medical School
Subject: New imaging modalities and analysis approaches for life sciences

Historically, major advances in biology have rapidly followed major advances in microscopy, often driven by biologists' desires to visualize ever and ever smaller objects. Microscopy overcoming the diffraction limit and reaching single molecule sensitivity has revolutionized biochemical and biomedical research both in vitro and in vivo. Current day bioimaging techniques that allow for high xyz location precision do not allow for high time resolution and are extremely challenging in live cell applications; similarly, imaging modalities capable of high time resolution (milliseconds) are limited to monitoring a single xyz-plane. Thus, using current state of the art technology, it is impossible to track the complete 3D movement of intracellular macromolecules in real time.

Remarkably, high end imaging is not a standard tool in biomedical research like, for instance PCR or deep sequencing. A main cause for this might well be the degree of expert knowledge needed to analyze the images, which can present vexing issues in image analysis like limited signal, unspecific background, empirically set thresholds, image filtering and false-positive-detection limiting overall detection efficiency.
I present advances in real time simultaneous imaging for multiple parameters in the space and color domain and a new concept for quantitative analysis of original image data rather than of image derived meta-data.

Speaker: Melanie Beck and John Phillips
Speaker: John Preskill, California Institute of Technology
Subject: Quantum Information and Spacetime
Refreshments to be served outside Keller 3-210 after the colloquium.

Aside from enabling revolutionary future technologies, quantum information science is providing powerful new tools for attacking deep problems in fundamental physical science. In particular, the recent convergence of quantum information and quantum gravity is sparking exciting progress on some old and very hard questions.


Friday, October 21st 2016
10:10 am:
Speaker: Sean Bartz, Macalester University
Subject: Chiral phase transition and meson melting in a soft-wall model of AdS/QCD

The AdS/CFT correspondence describes many features of non-perturbative QCD. A phenomenological approach called AdS/QCD uses a dilaton field to break conformal symmetry. This describes the linear confinement of hadronic spectra at zero temperature. Using an AdS-black hole metric allows for the study of the behavior of hadrons interacting with a hot, dense medium like the quark-gluon plasma.

We present an improved AdS/QCD model for meson spectra and chiral dynamics at finite temperature and baryon chemical potential. We find a second-order chiral phase transition in the chiral limit, with a critical temperature of 155 MeV, consistent with lattice calculations, and critical baryon chemical potential of 566 MeV. For physical quark mass the transition is a rapid crossover, with a pseudo-transition temperature and density of 151 MeV and 559 MeV, respectively. Using a pure AdS-Schwarzschild metric, the light meson bound states are found to melt before the chiral phase transition occurs. This behavior may be modified with appropriate parameterization of the metric.

Speaker: Xuzhe Ying, University of Minnesota
Subject: 'Robustness and tunneling Property of Majorana in hybrid semiconductor-superconductor structure

Semiconductor nanowire with spin-orbit coupling and superconductivity from proximity effect is usually used as a model for topological superconductor. I will first talk about the topological phase transition for free electrons as well as interacting electrons. Then I'll discuss Majorana related tunneling problem and show a signature of Majorana.

Speaker: Bartosz Fornal (UCSD)
Subject: Is there a sign of new physics in beryllium transitions?

A 6.8 sigma anomaly in the invariant mass distribution of e+e- pairs produced via internal pair creation in 8Be nuclear transitions has been reported recently by Krasznahorkay et al. in Phys. Rev. Lett. 116 (2016) 042501. The data can be explained by a 17 MeV vector gauge boson X produced in the transition of an excited beryllium state to the ground state, 8Be* -> 8Be X, followed by the decay X -> e+e-. We find that the gauge boson X can be associated with a new protophobic fifth force (i.e. with a coupling to protons suppressed compared to its coupling to neutrons) with a characteristic range of 10 fm and milli-charged couplings to first generation quarks and electrons. We show that such a protophobic gauge boson is consistent with all available experimental constraints and we discuss several ways to embed this new particle into an anomaly-free extension of the Standard Model. One of the most appealing theories of this type is a model with gauged baryon number, in which the new gauge boson kinetically mixes with the photon, and provides a portal to the dark matter sector.

Speaker: Nathan Smith, U of Arizona, Steward Observatory
Subject: Blast waves in circumstellar gas, and implications for the pre-supernova evolution of massive stars

The interaction between a supernova blast wave and dense circumstellar material (CSM) provides a unique way to investigate the very latest-phases in the pre-core collapse evolution of massive stars, because mass shed by the star in the preceding decade is illuminated and shock heated. Recent studies of such supernovae have shown that these late phases of stellar evolution must, in some cases, be punctuated by violent instabilities that precede the supernova by a few years to decades. The cause of these and the types of stars which fall subject to the instability remains as an open question, but depending on the explosion energy and the mass distribution of CSM, the conversion of kinetic energy into light can produce some of the most luminous supernovae in the universe. Because of high efficiency, this process can also produce moderately luminous transients even from non-terminal eruptions or low-energy explosions. Because many of these non-terminal eruptions can repeat, because low-energy explosions can come from relatively low-mass stars, and because some of the resulting supernovae are extraordinarily luminous, CSM interaction may figure prominently in the vast array of unusual transients now being discovered by transient searches (and by LSST in the future). The talk will explore the diversity of different transients that may result from CSM interaction, including a discussion of several individual observed examples that illustrate extremes in parameter space. I'll end with a very famous and very peculiar astronomical object, where a simple model of CSM interaction may help resolve some long-standing mysteries and paradoxes that have seen little progress in the last 30 years.

Speaker: “The Dancing Bees: Karl von Frisch and the Discovery of the Honeybee Language”
Subject: Tania Munz, Linda Hall Library of Science, Engineering, & Technology
Refreshments served at 3:15 p.m.

In 1973, the Austrian-born experimental physiologist, Karl von Frisch, received a share of the Nobel Prize for Physiology or Medicine for his discovery of the honeybee dance language. Von Frisch argued that bees communicate the distance and direction of food sources via their dance-like movements. Language had long been considered the exclusive domain of humans, and the discovery of symbolic communication in insects was considered a sensation and made von Frisch one of the best-known scientists of the post-war period. Less well known today is that von Frisch performed much of this work during WWII with funding from the Nazi Ministry of Food and Agriculture – this after the German government had declared him one-quarter Jewish and threatened to oust him from his position in Munich. Then, as now, the bees were dying and food had become critically important to the German war effort. This talk – based on Munz’s recent book by the same title – explores the relationship between science and politics during WWII and how the bees transitioned over the course of the 20th century from model political animals to premier communicators at the hands of von Frisch.

Speaker: Ken Heller, University of Minnesota
Subject: To be announced.

Monday, October 24th 2016
12:45 pm:
There will be no seminar this week.

Tuesday, October 25th 2016
09:30 am:
Subject: Informal group discussion of potential solar/magnetosphere collaborations
4:30 pm:
There will be no seminar this week.

Wednesday, October 26th 2016
12:00 pm:

Please bring a baked goods plate--or--bag to donate for sale on October 26th, as well as buy a plate from the selection. Donations are also appreciated.

More information about the SPA Community Fund Drive can be found on the website

2:30 pm:
Speaker: Amir Yacoby - Harvard
Subject: Imaging Magnetic Textures and Spin Chemical Potential of Magnetic Insulators Using NV centers in Diamond

Conventional electronic transport methods have been tremendously powerful in exploring systems with low lying charge excitations. In recent years there is growing interest in similar transport properties but of the spin degree of freedom, however, an analogous set of tools for spin transport currently does not exist. A grand challenge is therefore to develop spin analogues to voltage and current sources and meters which will allow us to explore both stationary and transient spin transport phenomena in a broad range of quantum materials. In this talk I will report on some of our efforts to develop such measurement capabilities using NV centers in diamond. Specifically I will report on recent measurements we have performed that explore magnetic textures in thin magnetic films and the spin chemical potential in magnetic insulators.

Faculty Host: Vlad Pribiag
To be announced.
4:30 pm:
CM Journal Club in PAN 110
To be announced.

Thursday, October 27th 2016
11:15 am:
Biophysics Seminar in 120 PAN
Speaker: Lauren Jelenchick, University of Minnesota Medical School,
Subject: Centromere Mechanical Maturation: A New Theory for Regulation of Mechanical Signaling during Mitotic Progression
Note: change of speaker and program from last announcement.
Speaker: Trevor Knuth and Cornelia Lang, University of Iowa.
Subject: (Lang) The Big Impact of Big Ideas Courses at U Iowa – Creating and Teaching

In this talk I will describe the "Big Ideas" courses that have
recently been successfully piloted at the University of Iowa. These are undergraduate courses aimed at first year students. These courses fulfill a variety of the general education requirements and each are centered around one theme or current issue. The course "Origins of Life in the Universe" is the first Big Ideas course developed and is taught by 5 faculty across 4 departments. The course centers around Big Questions such as "What is the origin of the universe?", "What is the origin of the Solar System?" "What is the
origin of humanity?" All faculty contribute to the curriculum, which is developed together and features inquiry-guided activities taught in active-learning classrooms. Students report a high level of engagement with the course, strong satisfaction and an appreciation for the role science plays in society. The model for "Origins of Life in the Universe" has been used by the other "Big Ideas" courses and the hope is to expand the program to serve 1/4
of incoming students at the University of Iowa.

3:35 pm:
Speaker: Amir Yacoby, Harvard University
Subject: A New Spin on Superconductivity
Refreshments to be served outside Keller 3-210 after the colloquium.

Nearly a hundred years after its discovery, superconductivity remains one of the most intriguing phases of matter. In 1957 Bardeen, Cooper and Schrieffer (BCS) presented their theory of superconductivity describing this state in terms of pairs of electrons arranged in a spatially isotropic wave function with no net momentum and a spin singlet configuration. Immediately thereafter, a search began to find materials with unconventional superconductivity where pairing deviates from conventional BCS theory. One particular class of unconventional superconductors involves pairs arranged in triplet rather than singlet configurations. Such superconductors may enable dissipationless transport of spin and may also give rise to elementary excitations that do not obey the conventional Fermi or Bose statistics but rather have non-Abelian statistics where the exchange of two particles transforms the state of the system into a new quantum mechanical state. In this talk I will describe some of our recent experiments that explore the proximity effect between a conventional superconductor and a semiconductor with strong spin-orbit interaction. Using supercurrent interference, we show that we can tune the induced superconductivity continuously from conventional to unconventional that is from singlet to triplet. Our results open up new possibilities for exploring unconventional superconductivity as well as new ways for detecting unconventional pairing in known materials.

Faculty Host: Vlad Pribiag

Friday, October 28th 2016
08:00 am:
Untitled in Physics
10:10 am:
Speaker: Yong-Zhong Qian, University of Minnesota
Subject: Effects of eV-Scale Sterile Neutrinos on Supernova Explosion and Nucleosynthesis

We show that for the active-sterile flavor mixing parameters suggested by the reactor neutrino anomaly, substantial conversion between neutrinos (antineutrinos) of the electron and sterile flavors occurs in regions with electron fraction close to 1/3 near the core of an 8.8 solar mass supernova. Compared to the case without such conversion, the neutron-richness of the ejected material is enhanced to allow production of elements from Sr, Y, and Zr up to Cd in broad agreement with observations of the metal-poor star HD 122563. Active-sterile flavor conversion also strongly suppresses neutrino heating at times when it is important for the revival of the supernova shock. Our results suggest that simulations of supernova explosion and nucleosynthesis may be used to constrain active-sterile mixing parameters in combination with neutrino experiments and cosmological considerations.

Speaker: Ezra Day-Roberts, University of Minnesota
Subject: Counting Zero Energy States in the Penrose Lattice
Speaker: Peter Koroteev (Perimeter)
Subject: Revisiting mirror symmetry in three dimensions

Three dimensional gauge theories with eight and four supercharges are known to enjoy three-dimensional mirror symmetry — a duality which can be thought of a supersymmetric generalization of particle-vortex duality. In the supersymmetric world theory it interchanges Coulomb and Higgs branches of the two dual theories. Originally 3d mirror symmetry was proposed for certain type of N=2 quiver gauge theories. We shall provide a generalization to a larger class of models which includes more complicated quiver and theories with Chern-Simons terms.

Speaker: Dr. Cornelia Lang, U. Iowa
Subject: The Central Molecular Zone of the Galaxy: Dense Molecular Clouds, Massive Stars and Magnetic Fields

In addition to harboring a supermassive black hole at its very core, the Galactic Center is one of the most physically extreme environments in the Galaxy. Dense and massive molecular clouds are abundant in this region, yet star formation is not as active as one might expect. In addition, radio observations have revealed a population of synchrotron-emitting filaments that provide insight on the magnetic field strength and configuration in this unique region of the Galaxy. Physical interactions may be occurring at the interfaces of dense molecular clouds and the interstellar magnetic filaments. I will review recent observational results of several unusual molecular clouds and the population of magnetized filaments that stand out in radio continuum images of the Galactic center and discuss the implications for better understanding the astrophysics of this region.

Speaker: Nick Wilding, Georgia State University
Subject: "Forging the Moon; Or, How to Spot a Fake Galileo"
Refreshments served at 3:15 p.m.

The integrity of the historical record is a prime concern for any historian. It follows that the art of detecting forgeries is crucial to our craft. Early modern print materials have generally been held above suspicion as a technologically impossible, or at least unprofitable, subject for forgery. But the emergence in 2005 of a spectacular copy of Galileo’s cosmos-changing Sidereus Nuncius, furnished with an autograph inscription and hand drawn lunar illustrations, forced a reconsideration of this assumption. By reconstructing the recent history of the analysis of this single and singular object, Nick Wilding shows how, when viewed from different perspectives, within shifting contexts, and alongside a choice of control copies, a seemingly rigorous and secure authentication can gradually lose its certainty and eventually become proof of forgery.

Speaker: Cindy Cattell, University of Minnesota
Subject: To be announced.

Monday, October 31st 2016
12:15 pm:
Speaker: Hannah Rogers (University of Minnesota)
Subject: Multi-Dimensional Effective Field Theory Analysis for Direct Detection of Dark Matter

A new systematic analysis technique was developed using the Effective Field Theory (EFT) approach for direct dark matter detection and folding in energy-dependent information, when possible, about the detected events, experimental efficiencies, and backgrounds. The Bayesian inference tool, MultiNest, efficiently calculates highly-dimensional likelihoods over WIMP mass and multiple EFT coupling coefficients. The resulting likelihoods can then be used to set limits on these parameters and choose models (EFT operators) that best fit the direct detection data. Expanding the parameter space beyond the standard spin-independent isoscalar cross-section and WIMP mass reduces tensions between previously published experiments. Combining these experiments into a single likelihood leads to stronger limits than when each experiment is considered on its own. Simulations using two non-standard operators (operators 3 and 8) are used to test the proposed analysis technique in up to five dimensions and demonstrate the importance of using multiple likelihood projections when determining the limits on WIMP mass and EFT coupling coefficients.


Tuesday, November 1st 2016
09:30 am:
Speaker: Sheng Tian, University of Minnesota
Subject: Van Allen Probe Observation of the Large Poynting Flux in the Plasma Sheet Boundary Layer
4:30 pm:
Speaker: Bharat Jalan, Chemical Engineering and Material Science
Subject: Synthesis, disorder and electron transport at the SrTiO3/NdTiO3 heterojunction

Wednesday, November 2nd 2016
2:30 pm:
Condensed Matter Seminar in Physics 110 PAN
Speaker: Sasha Chernyshev, UC Irvine
Subject: Quantum order-by-disorder and excitations in kagome-lattice magnets

I will discuss quantum order-by-disorder effect and will present an evidence that the non-linear terms in the anisotropic kagome-lattice antiferromagnets can yield a rare example of the ground state that is different from the one favored by thermal fluctuations. The corresponding order selection will be shown to be generated by the topologically non-trivial tunneling processes, yielding a new energy scale in the system.
I will also discuss the effect of the non-linear terms in the spectra of the kagome-lattice systems and will provide an analysis of the spectral properties of realistic kagome-lattice antiferromagnets such as Fe-jarosite, for which a remarkable wipe-out effect for a significant portion of the spectrum should exist due to a resonant-like decay processes involving two flat modes.
Recent result concerning the spectrum of the kagome-lattice ferromagnets will also be presented.

Faculty Host: Andrey Chubukov
There will be no seminar this week.
4:30 pm:
CM Journal Club in PAN 110
Speaker: Ruiqi Xing
Subject: Fermi liquid and Luttinger liquid

Following Xiaoyu's talk on Fermi liquid and Non-Fermi liquid and Alberto's talk on renormalization group, I will talk about:
0. Introduction of phenomenological Landau Fermi liquid and review of RG for interacting fermions
1. Tomonaga-Luttinger liquid as a fixed point of RG flow for general 1d interacting fermions; spin-charge separation in the Luttinger model.
2. Why Fermi liquid is extremely robust-Landau Fermi liquid as a fixed point of RG flow for 2d and 3d interacting fermions.
3. Kohn-Luttinger effect and BCS in the language of RG(briefly).


Thursday, November 3rd 2016
11:15 am:
Speaker: Amanda Hayward, University of Minnesota, Dept. of Biochemistry, Molecular Biology and Biophysics
Subject: To be announced.
11:30 am:
Time to apply for a major? Consider Physics!

Over a FREE Pizza Lunch there will be former physics majors talking about their current jobs and the array of careers you can pursue with a physics degree. There will also be lab tours and a panel of current Physics majors to answer questions.

Daytime Session
11:30 a.m. - 2:20 p.m., 110 Physics & Nanotech Bldg (PAN)

Can’t make it during the day?
There will be additional lab tours at 6:00 p.m. leaving from the PAN lobby.

Speaker: Traci Johnson, U Michigan
3:35 pm:
Speaker: Vincent Noireaux
Subject: DNA programmed dynamical systems outside cells: from gene circuits to self-assembly
Refreshments to be served outside Keller 3-210 after the colloquium.

The analysis and characterization of complex dynamical interactions involved in gene regulation is a major theme in post-genomic research. Researchers from many different backgrounds have developed novel approaches to dissect gene network and to determine their basic principles.

In this talk I will present a unique cell-free platform that my lab has developed to construct complex information-based dynamical systems by executing gene circuits in vitro. The original goal was to prototype and to understand elementary regulatory gene networks in test tube reactions. Recently, we showed that our experimental platform is capable of recapitulating larger biochemical systems such as the complete synthesis of viruses that we use as a model of information to self-assembly process. Finally, I will show how we can execute gene circuits in synthetic liposomes to emulate biological functions in a synthetic cell analog.


Friday, November 4th 2016
10:10 am:
Speaker: Joe Kapusta, University of Minnesota
Subject: Including Noise in Relativistic Hydrodynamics
Speaker: Gordon Stecklein, University of Minnesota
Subject: Spin transport in graphene
Speaker: Maulik Parikh (ASU)
Subject: The First and Second Laws of Gravity

A compelling idea in quantum gravity is that gravity is not in fact a fundamental force. Rather, in this view, gravity (and perhaps spacetime itself) is regarded as emerging from the coarse-graining of some as-yet-unidentified microscopic degrees of freedom. I will show that the first and second laws of thermodynamics, applied to the underlying degrees of freedom, give rise precisely to Einstein's equations and the null energy condition, respectively.

Speaker: Attila Kovacs, MIfA, U. Minnesota
Subject: Frontier science in the submillimeter and far-infrared

I will present some recent, on-going, and upcoming efforts that push the boundaries of submillimeter and far-infrared astrophysics. The submillimeter and FIR wavelengths can probe where no other wavelengths can, and sample the distant Universe uniformly, largely unaffected by dimming. They can also provide insights into optically obscured environments of star-formation locally, in the Galaxy. I will discuss recent results from 2-mm deep fields, and resolved SZ cluster morphologies; ongoing efforts at spectroscopic redshift searches using a novel technology; future mm-wave surveys; and probing star-formation locally, in the Galaxy, via FIR polarimetry with SOFIA/HAWC+ and spectroscopy with SOFIA/HIRMES.

Subject: No HSTM/MCPS Colloquium this Week
Speaker: Dan Cronin-Hennessy, University of Minnesota
Subject: The Mu2e Experiment

Monday, November 7th 2016
12:15 pm:
Speaker: Cheng-Hsien Li (University of Minnesota)
Subject: Neutrinos from SN1987A in Light of Recent Simulations

It has been nearly three decades since the first and the only detection of neutrinos from stellar collapse. Earlier analyses on the SN1987A neutrino events observed in the Kamiokande-II detector and the Irvine-Michigan-Brookhaven detector were based on parametric neutrino emission models due to the lack of sophisticated simulation techniques. We re-examine this historical event with the state-of-the-art 1D hydrodynamic simulation results from Mirizzi et al.(2016), which includes a mixing-length treatment of proto-neutron star convection. We use an exhaustive enumeration method to perform a simple goodness-of-fit test of the simulated neutrino emission profiles against the SN1987A data. Despite the limited statistics of SN1987A data, we point out the incompatibility between the last three Kamiokande-II events, if they are associated with the core collapse of SN1987A, and the rapid cooling of the proto-neutron star prescribed by the convection treatment. The implications will be briefly discussed.


Tuesday, November 8th 2016
09:30 am:
Speaker: Aaron Breneman, University of Minnesota
Subject: Evidence for Direct one-one correspondence of chorus wave packets and microbursts: Van Allen Probe EFW and FIREBIRD 2
4:30 pm:
Speaker: Rafael Fernandes, School of Physics and Astronomy
Subject: Nematic fluctuations near the Mott insulating phase of cuprate superconductors

Wednesday, November 9th 2016
2:30 pm:
Condensed Matter Seminar in Physics 110 PAN
Speaker: Ioannis Rousochatzakis, University of Minnesota
Subject:  Classical spin liquid instability driven by off-diagonal exchange in strong spin-orbit magnets

I will show that Mott insulators with strong spin-orbit coupling and bond-dependent interactions host yet another strongly correlated regime, besides the well-known Kitaev quantum spin liquid [1]. This regime is governed by a classical spin liquid instability and unconventional spin-spin correlations along closed or open strings. The key predictions are common for all available 2D and 3D tri-coordinated materials with bond-directional anisotropy, and provide a consistent interpretation of the suppression of the x-ray magnetic circular dichroism signal reported recently [2] in β-Li2IrO3 under pressure.

[1] I. Rousochatzakis and N. B. Perkins, arXiv:1610.08463v1
https://arxiv.org/abs/1610.08463
[2] T. Takayama et al., Phys. Rev. Lett. 114, 077202 (2015).
http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.114.077202

Faculty Host: Natalia Perkins
To be announced.
4:30 pm:
CM Journal Club in PAN 110
Speaker: Avraham Klein
Subject: Regular and Irregular Motion

I will cover M.V. Berry's classic paper:
Regular and Irregular Motion, AIP Conf. Proc. 46, 16 (1978).
I will try to cover as much of the first 90 pages :) as possible.
The subject is classical Hamiltonian chaos, the KAM theorem (which we will not prove), and some beautiful implications for solar system dynamics.


Thursday, November 10th 2016
10:00 am:
Thesis Defense in PAN 130
Speaker: Changjiang Liu, University of Minnesota
Subject: Dynamic Detection of Spin Accumulation by Ferromagnetic Resonance
This is the public portion of Mr. Liu's thesis defense.
11:15 am:
Biophysics Seminar in 120 PAN
Speaker: Dr. Ruth Sommese University of Minnesota, Dept. of Genetics, Cell Biology & Development
Subject: Dissecting the regulation of collective myosin motility using DNA nanotechnology

While much is known about individual motor function, collective motility of molecular motors remains poorly understood. In the cell, myosin ensembles work together to drive numerous processes, from large-scale movement and force generation in muscle to dynamic cargo sorting to and from the cell membrane. Our lab is now developing tools to explore the regulation of myosin ensembles using DNA nanotechnology, which allows us to precisely control the biophysical properties of the motor-cargo interface. Complementing experimental approaches with computational modeling, highlights how the biophysical and structural properties of the acto-myosin interaction have been tuned to enhance collective motor behavior. Finally, we provide a novel method to pattern native protein complexes on DNA scaffolds using a GFP nanobody linkage. Overall, these approaches address an essential missing link in our understanding of collective motor function while also providing novel insight into the functional regulation of unconventional myosins.

Speaker: Stou Sandalski and Evan Skillman
3:35 pm:
Speaker: Michel Devoret, Yale University
Subject: Fighting Decoherence with Dissipation
Refreshments to be served outside Keller 3-210 after the colloquium.

State superposition and entanglement are basic quantum phenomena that are usually observed in systems sufficiently decoupled from a lossy environment. Somewhat paradoxically, a specially engineered interaction with the environment can become a resource for the generation and protection of quantum states. Moreover, this notion can be generalized to a manifold of quantum states that consists of all coherent superpositions of several stable, dissipative steady states. In particular, it has now become practically feasible to confine the state of an harmonic oscillator to the quantum manifold spanned by two coherent states of opposite phases. In a recent experiment, we have observed a superposition of two such coherent states, also known as a Schrodinger cat state, spontaneously squeeze out of vacuum, before decaying into a classical mixture. The dynamical protection of logical qubits built from Schrodinger cat states is based on an engineered driven-dissipative process in which photon pairs are exchanged rather than single photons. The recently-developed class of experiments in which quantum information is encoded and manipulated using cat states opens a new avenue in quantum information processing with superconducting circuits.

Faculty Host: Vlad Pribiag

Friday, November 11th 2016
08:00 am:
Untitled in Physics
10:10 am:
Speaker: Zewei Xiong, University of Minnesota
Subject: Oscillations of Solar High-Energy Neutrinos
Speaker: Zack Robinson, University of Minnesota
Subject: Controlling Conductivity in Zinc Oxide Nanocrystals with Intense Pulsed Light
Speaker: Bogdan A Dobrescu (FNAL)
Subject: Vectorlike fermions and new gauge bosons

A fourth generation of chiral quarks and leptons is tightly constrained by LHC data. However, new fermions may exist if their mass is not generated by the Higgs field. Such "vectorlike quarks” are searched at the LHC under the assumption that they decay into a quark and a boson. I will show that other, more exotic decays of the vectorlike quarks may be the dominant ones. Furthermore, new gauge bosons may undergo cascade decays via vectorlike fermions, leading to novel collider signatures.

Speaker: John Phillips, MIfA, U. Minnesota
Subject: The Evolution of Systems of Satellite Galaxies in Local Group-like Environments.

The Local Group is fertile ground for study of many astrophysical topics, yet still much is unknown about how it came to be as we see it today. This talk will motivate the need to study the Local Group in context of similar sparse groups in the local Universe, and will discuss some recent findings concerning the effects that membership in structures like the Local Group have on galactic evolution.

Speaker: Margaret Morrison, University of Toronto
Subject: "Scientific Modelling and the Nature of Speculation"
Refreshments served at 3:15 p.m.

The multiverse is often thought to be speculative account of how one might solve problems in fundamental physics. Yet this kind of speculation seems different from the unrealistic assumptions instrinsic to scientific modelling more generally, e.g. infinite populations of genes in population genetics. This latter kind of modelling can be further distinguished from the construction of fictional or toy models. I discuss these different modelling practices and the nature of speculation associated with each, showing why the “models as fictions” view not only fails to capture the subtleties in modelling strategies but undermines the larger goals of modelling as a scientific activity.

Speaker: Bob Lysak, University of Minnesota
Subject: Alfven Waves and the Aurora

Monday, November 14th 2016
12:15 pm:
Speaker: Andrew Matas (University of Minnesota)
Subject: Aspects of Massive Gravity

General Relativity can be described as a theory of a massless spin-2 particle (the graviton), whose interactions are local and Lorentz-invariant. It is a fundamental and long-standing question as to whether the graviton may acquire a small mass. Additionally, a small graviton mass can potentially explain cosmic acceleration in a way that avoids a technically unnatural cosmological constant. In this talk, I will describe recent progress in constructing a healthy, non-linear theory of massive gravity. I will also describe observational tests from solar system and from binary pulsar observations.


Tuesday, November 15th 2016
09:30 am:
Speaker: Cynthia Cattell, University of Minnesota
Subject: Response of the magnetosphere to a small interplanetary shock compression: Van Allen Probes, Magnetospheric MultiScale, GOES, and THEMIS
4:30 pm:
Speaker: Laxman Thoutam, Chemical Engineering and Material Science
Subject: Magnetoresistance Anisotropy and Transport Properties of WTe2

Wednesday, November 16th 2016
2:30 pm:
Condensed Matter Seminar in Physics 110 PAN
Speaker: Emanuel Gull, University of Michigan
Subject: Numerical experiment on the Hubbard model

The Hubbard model is one of the fundamental models of correlated electron physics. In two dimensions it exhibits various superconducting, Mott insulating, magnetically ordered, pseudogapped, and metallic phases. On a square lattice and for repulsive interactions comparable to the bandwidth, the model is believed to capture much of the low-energy physics of the cuprate high-temperature superconductors, while in three dimensions it can be realized experimentally in ultracold atomic gases. In this talk I will show results from `numerical experiment’ on this model and compare them to experimentally obtained response functions and theoretical calculations, illustrating how simulations can be used to further our understanding of correlated electron systems.

Faculty Host: Rafael Fernandes
Speaker: Minerba Betancourt, Fermilab
Subject: Nuclear Dependence of Quasi-Elastic Scattering at MINERvA

MINERvA is a neutrino scattering experiment to make precision measurements of cross sections and investigate nuclear effects. A precise understanding of neutrino interactions is crucial for the neutrino oscillation program. Cross sections measurements of Quasi-Elastic events on multiple nuclei (carbon, iron and lead) will be presented.

4:30 pm:
CM Journal Club in PAN 110
No journal club this week.

Thursday, November 17th 2016
11:15 am:
Biophysics Seminar in 120 PAN
Speaker: Razvan Chereji, National Institute of Child Health and Human Development
Subject: The Universality of Nucleosome Organization: From Yeast to Human

It is estimated that a human body contains about 100 trillion meters of DNA, enough to circle the Earth's Equator 2.5 million times. DNA is remarkably tightly packed inside the cell nucleus; nevertheless, transcription factors must quickly find and access the regulatory regions along the genome, should the need arise. Nucleosomes -- 147 basepairs of DNA wrapped around a histone octamer in about 2 turns -- are the basic units of DNA packaging. The precise positions of nucleosomes along the genome play an essential role in gene regulation, dictating which genes can be regulated by transcription factors. I study the nucleosome positions in various organisms (yeast, fly, mouse and human) and I build biophysical models that explain their organization. I will show that nucleosomes have a universal organization at the gene promoters, which is shared by multiple organisms, and that statistical mechanics can predict this common organization. I will show that DNA sequence alone has a limited effect in organizing the chromatin, and I will discuss the other mechanisms that have a major role in nucleosome positioning.

Speaker: Brooke Simmons
Subject: To be announced.
3:35 pm:
Speaker: Fai Mak, Penn State University
Subject: Superconductivity in single-layer van der Waals’ metals
Refreshments to be served outside Keller 3-210 after the colloquium.

The discovery of graphene has stimulated not only the field of carbon nanoelectronics, but also studies of novel electronic phenomena in a wide range of atomically thin van der Waals’ materials. In this talk, I will discuss our recent effort in the isolation of a single layer of niobium diselenide (NbSe2), a new non-centrosymmetric superconductor. As a result of the crystal symmetry and the strong spin-orbit interactions, the electron spin in single-layer NbSe2 becomes Ising-like (i.e. spins locked to the out-of-plane direction), giving rise to unique magnetic properties in the superconducting state. I will present measurements of the material’s upper critical field, which significantly exceeds the conventional Pauli paramagnetic limit, supporting the Ising pairing mechanism. I will also discuss our measurements of the superconducting gap by tunneling experiments that further provide evidence for finite spin susceptibility arisen from spin-triplet pairing correlations. Our studies pave the way for the search for topological superconductivity in two-dimensional materials.

Faculty Host: Boris Shklovskii

Friday, November 18th 2016
10:10 am:
Speaker: Cheng-Hsien Li, University of Minnesota
Subject: Neutrinos from SN1987A in light of recent simulation.

It has been nearly three decades since the first and the only detection of neutrinos from stellar collapse. I will begin with a discussion of supernova neutrino emission and then examine the historical SN1987A event with the state-of-the-art 1D hydrodynamic simulation results from Mirizzi et al.(2016). A simple goodness-of-fit test is presented to demonstrate the incompatibility between the last three Kamiokande-II events, if they are associated with the core collapse of SN1987A, and the rapid cooling of the proto-neutron star prescribed by the convection treatment in the simulation. The implications will be briefly discussed.

Speaker: Chris Conklin, University of Minnesota
Subject: Nonlinear Electrophoresis of Particles in Liquid Crystals
Speaker: Yue Zhang (Northwestern)
Subject: Search For Dark Matter In Terms of Dark Bound States

Understanding the nature of dark matter is an open question of central importance to particle physics and cosmology. In this talk, I discuss a model where the dark matter is a fermion charged under a dark U(1) gauge symmetry and its interactions are mediated by a massive dark photon. I will summarize the current status in the search for such a dark sector. The main focus of this talk is on the non-perturbative effects in particular dark matter bound states, which could have strong impact on the interpretation of existing experimental results and leads to new channels for the future search.

2:15 pm:
Condensed Matter Seminar in Physics PAN 110
Speaker: Fai Mak, Penn State Department of Physics
Subject: Berry curvature effects and valley-dependent physics in transition metal dichalcogenide semiconductors
Faculty Host: Boris Shklovskii
Speaker: Marc Huertas-Company, University of Diderot, Paris
Subject: Quenching and bulge growth in massive galaxies

The life of a galaxy is a balance between processes that trigger star formation by accelerating gas cooling and others which tend to prevent stars to form by expelling or heating gas. Over the past years, the picture is emerging that, during most of its life, a galaxy seems to live a rather quiet life, gradually growing in stellar mass through the formation of new stars which are formed at a rate remarkably proportional to its stellar mass, This is interpreted as an indirect evidence that fuel in the form of cold gas is somehow continuously being fed into the galaxies to sustain star formation. Two major events, eventually related, can break this apparent equilibrium. An episode of high star formation activity (e.g starburst) can be triggered. Or, suddenly something might happen that prevents the galaxy to continue forming new stars. Quenching is probably the most important event that a galaxy experiences during its life and a fundamental mechanism that helps understanding most of the properties of our surrounding Universe. There are a variety of different mechanisms entertained for the quenching process, e.g. feedback, interactions, halo driven shock heating, morphological quenching etc. Which one is dominantly driving galaxy evolution (if there is) or under which circumstances one or another process is triggered is still a mystery.

In my talk I will focus on the relation between structure and quenching in massive galaxies. By using advanced machine intelligence techniques, I will analyze the relation between quenching and bulge growth in massive galaxies from z~3. I will in fact show evidences of two distinct channels for the growth of bulges in the massive end of the present day Hubble sequence (Huertas-Company+15ab). I will also discuss challenges and solutions to estimate galaxy morphologies in future big-data surveys like EUCLID.

Speaker: Christopher Graney, Jefferson Community and Technical College
Subject: "The Telescope Against Copernicus -- Marius, Galileo, Riccioli, and the Problem of Telescopic Observations of Stars in the Early 17th Century"
Refreshments served at 3:15 p.m.

In his 1614 Mundus Jovialis, Simon Marius reported that telescopic observations revealed all the more prominent stars to appear as definite disks. This, said Marius, indicated the hypothesis of Tycho Brahe (in which the planets circled the sun while the sun circled the Earth) to be the correct one. Marius seems to be the first to cite telescopic observations of stars against the Copernican system. I will discuss what Marius saw, and why his telescopic observations of stars were indeed a problem for Copernicans. I will use as illustration the work of Galileo, who kept quiet about his observations, and also the work of Giovanni Battista Riccioli, who took pains to not only use telescopic star observations argue against the Copernican hypothesis, but who also provided a detailed description of how to make such observations, so that any observer could see for himself the problems with that hypothesis.

Speaker: Dave Thomas, University of Minnesota
Subject: To be announced.

Saturday, November 19th 2016
08:00 am:
Untitled in Physics

Monday, November 21st 2016
12:15 pm:
Speaker: Marco Peloso (University of Minnesota)
Subject: Relations between 2- and 3-point correlation functions, and the effect of long wavelength modes on CMB and on Large Scale Structure power spectra

I will review consistency relations between the squeezed bispectrum (three point correlation function of one long-wavelength and two short-wavelength modes) and the power spectrum of the CMB and LSS. These are powerful relations, that are exact at all orders in perturbation theory, based on symmetries, that allow us to probe primordial non-gaussianity, isocurvature modes during inflation, and fundamental principles as Galilean Invariance, and the weak Equivalence Principle.


Tuesday, November 22nd 2016
09:30 am:
Speaker: P. Subramania Athiray,
Subject: New views of the Moon in X-rays - Indian scenario

Lunar missions over the last decade have revealed the complexity of the lunar crust and the near surface environment of the Moon. Space based remote sensing measurements provide vital clues to understand the global evolution of the Moon by mapping the distribution of elements and minerals on the lunar surface in
multi-wavelengths. The surface chemistry of the Moon can be well explored in
X-rays using the X-ray Fluorescence (XRF) technique. Observational evidences help to test models of lunar evolution from the formation to the chemical
diversity of the Moon. Indian lunar space missions (Chandrayaan-1, 2) have
their modest contributions to th is field and ambitious plans for the future. The X-ray spectrometer (C1XS) on-board Chandrayaan-1 was designed to map the
global abundances of rock-forming elements (Mg, Al, Si, Ca, Ti and Fe) over
the lunar surface. C1XS observations revealed the evidence of enhanced Na abundances for the first time, from differentparts of the Moon. In this talk I
will present an overview of C1XS instrument, its observations and highlight the
results. Further, I will also show how the lessons learned from C1XS are transformed into the design and development of the upcoming X-ray instrument: CLASS for the second Indian Moon mission Chandrayaan-2.

4:30 pm:
There will be no seminar this week.

Wednesday, November 23rd 2016
08:00 am:
Untitled in Physics
2:30 pm:
There will be no seminar this week.
There will be no seminar this week.
4:30 pm:
CM Journal Club in PAN 110
Speaker: Han Fu
Subject: Electron transport in SrTiO3 (STO) accumulation layers

My talk is focused on the electron transport in SrTiO3 (STO) accumulation layers which can be induced on the interface between STO and other polar dielectrics. The nonlinear dielectric response of STO here makes the distribution of electron concentration special: it has a slowly decaying long tail of electrons. When the scattering is dominated by the surface, the tail electrons have a much higher mobility compared to those close to the interface and it turns out that they dominate the total conductivity though their concentration is small. I will explain in detail how this happens together with the divergence of other quantities and compare with experimental data.


Thursday, November 24th 2016
Speaker: No Journal Club - Thanksgiving holiday
Speaker: There will be no colloquium this week due to Thanksgiving

Friday, November 25th 2016
There will be no seminar this week.
Speaker: No seminar- University closed for Thanksgiving break
Speaker: No Colloquium - UofM closed for Thanksgiving holiday
Subject: No HSTM/MCPS Colloquium for Thanksgiving Break
Refreshments served at 3:15 p.m.

Monday, November 28th 2016
12:15 pm:
There will be no seminar this week.
12:30 pm:
Speaker: Mikhail Skvortsov Skolkovo, Institute of Science and Technology and Landau Institute for Theoretical Physics
Subject: Superconductivity suppression in disordered films: Role of ballistic scales

We consider superconductivity suppression in homogeneously disordered thin films. Anderson’s theorem stating that the critical temperature is insensitive to the degree of disorder is violated in the vicinity of the Anderson localization transition. For strongly disordered films, the interplay between disorder and interaction effectively suppresses the BCS coupling constant, thereby reducing the critical temperature. For strictly 2D films, superconductivity suppression is coming from large scales (similar to the 2D localization), and summation of the leading logarithms can be performed with the help of Finkelstein’s renormalization group. For thicker and sufficiently dirty films, there exists an additional effect originating from small scales (similar to the 3D localization). We calculate the corresponding contribution to the shift of the critical temperature and discuss its importance in the context of experimental situation.

Faculty Host: Alex Kamenev

Tuesday, November 29th 2016
09:30 am:
Speaker: John Wygant and Viacheslav Pilipenko, (Augsburg College)
Subject: The MPEX satellite mission and Informal discussion on Sudden Impulse and SSC signatures in ground magnetometers
4:30 pm:
Speaker: Andrey Chubukov, School of Physics and Astronomy
Subject: Phase diagram of high-Tc cuprates

Wednesday, November 30th 2016
Speaker: Konstantin Reich, Physics at UMN
Subject: Exciton transfer in array of epitaxially connected nanocrystals

Recently, epitaxially connected at facets semiconductor
nanocrystals have been introduced to fascilitate the electron transport
between nanocrystals. To fully deploy their potential a better understanding
of the exciton transfer between connected NCs is needed. We go beyond the two
well-known transfer mechanisms suggested by Forster and Dexter and propose a
third mechanism of exciton tandem tunneling. The tandem tunnelling occurs
through the intermediate state in which electron and hole are in different
NCs. The corresponding rate for exciton hops between epitaxially connected
at small facets NCs is larger than the Dexter rate and can be comparable with
the Forster one.

Faculty Host: Boris Shklovskii
4:30 pm:
CM Journal Club in PAN 110
Speaker: Tianbai Cui
Subject: One dimensional Luttinger liquid and bosonization

I will first introduce the Luttinger model, solve it using a bosonic description and obtain the spin-charge separation. Then, I will use the Luttinger model as a case study of the field theoretical bosonization. And finally, I will discuss why we can rewrite a fermionic theory in terms of boson degrees of freedom by introducing a constructive approach of bosonization.

References:
1. Altand and Simons, Condensed matter field theory
2. Fradkin, Field theories of condensed matter physics
3. Jan von Delft and Herbert Schoeller, Bosonization for beginners - refermionization for experts


Thursday, December 1st 2016
11:15 am:
Biophysics Seminar in 120 PAN
Speaker: Kevin Dorfman University of Minnesota, Dept. of Chemical Engineering and Material Science
Subject: The Physics of Genome Mapping in Nanochannels

Genome mapping by nanochannel confinement is an emerging method for obtaining large-scale genomic information at the single molecule level. In this method, large pieces of contiguous genomic DNA, hundreds of kilobase pairs in length, are labeled with a sequence-specific fluorescent probe while the backbone is labeled with a second color. Upon injection into a nanochannel, the labeled molecule stretches due to confinement and the locations of the probes (the “barcode”) are read by fluorescence microscopy.

Engineering DNA barcoding requires understanding two key properties: (i) the fluctuations of the DNA extension, which sets the lower bound for the error in reading the distance between barcodes; and (ii) the friction of the confined DNA, which set the minimum time scale for making uncorrelated measurements. While these quantities are well understood in the case of strong and weak confinement, nanochannel mapping takes place in moderate confinement, where the channel width is commensurate with the length scale for bending the DNA. This is a challenging regime for polymer physics, since there is no separation of length scales, and fluid mechanics, since there is no solution for the Green’s function of the Stokes equation in channel confinement. I will present our experimental and theoretical progress towards understanding the thermodynamics and hydrodynamics of this technologically relevant regime of confined polymers.

Speaker: Sourabh Chauhan and Larry Rudnick
3:35 pm:
Speaker: David Kohlstedt
Subject: From Reaction-driven to Stress-driven Melt Segregation – Formation of High-permeability Paths through Earth’s Mantle
Refreshments to be served outside Keller 3-210 after the colloquium.

Separation of small amounts of melt from residual solid and migration of that melt from deep beneath a mid-ocean ridge to its eruption at Earth’s surface require a transition from porous to channelized flow in order to preserve chemical and radiogenic disequilibrium. Chemically isolated, high-permeability melt conduits in Earth’s mantle develop as a consequence of instabilities in the deformable and dissolvable porous media. Models for the formation of such flow instabilities include stress-driven and reaction-driven melt channelization.

Melt rising from depth through mantle rocks, which are composed primarily of the minerals olivine and pyroxene, becomes under saturated in pyroxene with respect to the surrounding upper mantle. Thus, pyroxene preferentially dissolves into the melt as it migrates toward the surface. Tabular rocks rich in olivine and depleted in pyroxene found in peridotite massifs serve as channels for rapid melt extraction from partially molten regions of the mantle. Formation of such dunite channels involves dissolution-precipitation reactions between mantle rock and percolating reactive melt. Dunite channels also coincide with shear zones, indicating that deformation together with reaction plays an important role during melt channelization.

My talk focuses on results from laboratory investigations of the formation and evolution of melt-enriched channels in mantle rocks. The first part examines the formation of stress-driven, melt-enriched channels predicted by theory, while the second part considers the development of reaction infiltration instabilities in mantle rocks. These channelization processes significantly increase permeability and, hence, the flux of melt through the partially molten rocks.


Friday, December 2nd 2016
08:00 am:
Untitled in Physics
10:10 am:
Speaker: Ming Li, University of Minnesota
Subject: Revisiting the (quasi)particle spectrum in the Glasma
Speaker: Justin Watts, University of Minnesota
Subject: Spin Kondo Effect and Interdiffusion in Co/Cu Non-Local Spin Valves
Speaker: Satyanarayan Mukhopadhyay (PITT PACC)
Subject: Quark-gluon jet discrimination and its applications at the LHC

The discrimination of quark- and gluon-initiated jets is a topic being actively explored by the ATLAS and CMS collaborations, with potential applications to physics searches at the LHC. In this talk, I shall give a brief overview of observables sensitive to quark and gluon jet sub-structure, the current understanding and challenges in predicting them using Monte Carlo tools, and how some of those challenges can be overcome using data-driven templates being derived by the LHC experiments. I shall then illustrate the potential impact of quark-gluon tagging in physics searches, taking the example of gluino pair production at the LHC.

Speaker: Ming Sun, U. Alabama, Huntsville
Subject: Study Baryon Physics with Galaxy Groups and Clusters

Galaxy groups and clusters are the least massive systems where the bulk of baryons are accounted for and also the most massive systems that are gravitationally bound. Baryons locked into stars and baryons remaining diffuse provide orthogonal constraints on cosmic structure formation, which makes groups and clusters ideal systems to study baryon physics. In this talk, I will summarize new results on two projects on baryon physics in galaxy groups and clusters. The first one will focus on X-ray scaling relations of local galaxy groups. I will also discuss our recent results on stacking and its application on cluster cosmology. In the second part, I will focus on ram pressure stripping of cluster galaxies. The last decade has witnessed a burst of new discoveries about ram pressure stripping emerging from multi-wavelength, multi-scale observations. Stripped tails have emerged as another kind of ideal targets in clusters to study multi-phase media, along with cool cores. New results on optical, CO and X-rays will be discussed.

Speaker: Marcel Weber, University of Geneva
Subject: "On the Metaphysics of Biological Functions"
Refreshments served at 3:15 p.m.

This talk tries to clarify some ontological issues concerning biological functions. The guiding question is to what extent functions can be viewed as being mind-independent relations. I examine some standard arguments according to which functions are interest-dependent and show that these arguments simply fail to take into account the relational nature of functions (according to the most common analyses). However, there are other concerns that arise once we ask what kind of relation functional dependency relations are (e.g., the relation between the heart’s capacity to pump blood and the whole organism’s fitness). I argue that much like in causal relations, the truth-makers for functional statements are variegated. I examine various contenders that can play the role of a functional dependency relation, including causality, supervenience, metaphysical grounding, mechanistic constitution and mereology. I argue that each one of these (except supervenience) can be used to characterize a functional dependency relation in some set of cases, but that there is no unified account to be given for the truth-makers of functional relations.

Speaker: Roger Rusack, University of Minnesota
Subject: Physics Research at the Highest Energies

Monday, December 5th 2016
12:15 pm:
Speaker: Larry Rudnick (University of Minnesota)
Subject: Observational Tracers of Diffuse Baryon Dynamics in Clusters of Galaxies

Clusters of galaxies form at the intersection of the enormous filamentary structures of the cosmic web, and evolve through the continued infall of material along those filaments, with occasional major mergers between clusters. Or so the numerical simulations to be discussed next week by Tom Jones, tell us. The history of that evolution should be embedded in the current dynamical state of the intracluster medium (ICM), but our best tools, the thermal X-ray emission from the hot plasma, are often blind to these structures. I will discuss some of the indicators of ICM dynamics that are available using synchroton emission, what we have learned so far, and some prospects for the future.

12:15 pm:
Speaker: Larry Rudnick (University of Minnesota)

Tuesday, December 6th 2016
09:30 am:
Practice talks for AGI
4:30 pm:
Speaker: Martin Greven, School of Physics and Astronomy
Subject: New insight into the phase diagram of the cuprates

Wednesday, December 7th 2016
2:30 pm:
Speaker: Saurabh Maiti, University of Florida
Subject: Chiral-spin modes in a 2D Fermi-Liquid with spin-orbit coupling

Chiral-spin modes in a 2D Fermi-Liquid with spin-orbit coupling(SOC) are oscillations of magnetization in zero magnetic field resulting from a many-body effect. To study them, we develop a scheme to incorporate many-body effects in SOC systems. As a result, we discover a number of interesting features associated with SOC (of Rashba and Dresselahaus type). Since collective modes usually dominate the response to any probe they couple to, it is necessary to correctly formulate a theory that can express these modes in terms of the material parameters. I will show how our scheme does precisely this and highlight some unique features introduced by SOC, namely, a linear-in-q dispersion of a massive collective mode in an externally applied in-plane magnetic field, and a characteristic anisotropy of the mass with rotation of the in-plane field. Our interpretation is consistent with several observed features in a series of Raman experiments in CdMnTe quantum well (which were earlier interpreted as an indication of a strong renormalization of SOC by electron-electron interaction). We also offer predictions for other observables with/without the externally applied field.

Faculty Host: Andrey Chubukov
There will be no seminar this week.

Thursday, December 8th 2016
11:15 am:
Biophysics Seminar in 120 PAN
Speaker: Prof. Wendy Gordon, University of Minnesota, Dept. of Biochemistry, Molecular Biology, and Biophysics
Subject: To be announced.
Speaker: Chris Nolting and Micaela Bagley
3:35 pm:
Speaker: David Poland, Yale University
Subject: Critical Phenomena and the Conformal Bootstrap
Refreshments to be served outside Keller 3-210 after the colloquium.

From critical phenomena to quantum gravity, conformal field theories describe the universal scale-invariant structures that lie at the heart of theoretical physics. The conformal bootstrap is the powerful idea, dating back to the 70’s, that one can use fundamental consistency conditions to constrain, solve, and map out the space of conformal field theories. In this talk I will explain how one can use the conformal bootstrap to perform rigorous and precise calculations in strongly-interacting theories without reference to a microscopic Lagrangian, summarizing recent progress at learning about the 3D Ising and O(N) vector models, which are the universal structures describing phase transitions in fluids, magnets, superconductors, and numerous other systems in nature.

Faculty Host: Tony Gherghetta

Friday, December 9th 2016
10:10 am:
Speaker: Yao Leon Meng, University of Minnesota
Subject: Applications of proton-nucleus reactions at the MeV scale for brain cancer therapy and space exploration
Speaker: Yilikal Ayino, University of Minnesota
Subject: Ferromagnetism in NdTiO3/SrTiO3 Interface
Speaker: David Poland (Yale U.)
Subject: Mysteries at the Bootstrap Frontier

In this informal talk I will summarize various projects at the frontier of the conformal bootstrap, including studying 4-point functions of fermions, stress-energy tensors, and chiral multiplets in superconformal theories. The resulting bootstrap constraints both make contact with known theories and also reveal mysterious features that may give the first pieces of evidence for new previously unknown conformal field theories.

There will be no colloquium this week.
Speaker: Marta Hanson, Johns Hopkins University
Subject: "Material Things and Technologies of the Body in the Golden Mirror, 1742"
Refreshments served at 3:15 p.m.

In the last month of 1739, the Qianlong Emperor (r. 1736-1795) ordered the compilation of a treatise on medicine “to rectify medical knowledge” throughout the empire. By the end of 1742, eighty participants chosen from several offices within the palace bureaucracy in Beijing completed the Golden Mirror of the Orthodox Lineage of Medicine (Yizong jinjian 醫宗金鑑). In addition to integrating literati trends in evidential scholarship from the Jiangnan region into the imperial medicine of the Manchu court, the Golden Mirror also coalesced publishing trends that made medicine more accessible to a wider audience through rhymes, annotations, illustrations, and instructions to use both material things and one’s own body therapeutically. The reader could learn about not only a range of medical tools - acupuncture needles, moxabustion sticks, devices for smallpox inoculation, braces for securing broken bones – but also multiple ways to use the body-as-technology through self-cultivation, ritual, and corporeal mnemonics to improve the accuracy of pulse reading, the efficacy of drug treatments, and the predicability of disorders. Hand mnemonics, for instance, were a form of embodied medical technology that enabled the reader to memorize multiple temporal orders of the cosmos and relate them to the pulse readings and conditions of individual sufferers. In addition to mastering how to read the patient’s body accurately according to the four examinations (sizhen 四診) and how to use the various material tools of the medical trade, the ideal physician was expected to master his own body. This paper provides examples of how the three corporeal distinctions of 1) the patient’s body, 2) the physician’s body-as-technology, and 3) the physician’s hand-as-medical technology give us better purchase on the connection between the body and “material culture in health and medicine” meant for the norms of medical practice established in the Golden Mirror of the imperial Qing court in mid-eighteenth-century China.

Speaker: Vlad Pribiag, University of Minnesota
Subject: Quantum transport in low-dimensional materials

Monday, December 12th 2016
08:30 am:
Thesis Defense in Appleby Hall, Room 319
Speaker: Mark Pepin, University of Minnesota
Subject:  Low-Mass Dark Matter Search Results for the Cryogenic Dark Matter Search
This is the public portion of Mr. Pepin's thesis defense. His advisor is Priscilla Cushman.

An ever-increasing amount of evidence suggests that approximately one quarter of the energy in the universe is composed of some non-luminous, and hitherto unknown, "dark matter." Lower-mass dark matter has become more prominent in the past few years. The Cryogenic Dark Matter Search (CDMS) detectors can be operated in an alternative, higher-biased mode, to decrease their energy thresholds and correspondingly increase their sensitivity to low-mass WIMPs. This is the CDMS low ionization threshold experiment (CDMSlite), which has pushed the frontier at lower masses. This dissertation describes the second run of CDMSlite at Soudan: its hardware, operations, analysis, and results. The results include new WIMP mass-cross section upper limits on the spin-independent and spin-dependent WIMP-nucleon interactions. Thanks to the low background and threshold, these limits are the most sensitive in the world below WIMP masses of ~4 GeV/c^2. This also demonstrates the great promise and utility of the high-voltage operating mode in the future SuperCDMS SNOLAB experiment.

12:15 pm:
Speaker: Tom Jones (University of Minnesota)
Subject: The Dynamics of Galaxy Cluster Formation as Revealed by Cluster Baryons

Galaxy clusters are the most massive bound systems in the universe and the last stage of hierarchical structure formation. They occupy intersections of cosmic filaments, where they come together through accretion from the filaments and incredibly violent mergers with other clusters. While dark matter accounts for about 85% of cluster total mass, ~ 90% of the remaining, baryonic matter is in the form of diffuse, keV temperature plasma, known as the "intracluster medium" or ICM. Being dissipative on "small" scales, ICM plasma captures important characteristics of cluster formation dynamics that are otherwise obscure. At the lowest order, an ICM is virialized and relaxes to a hydrostatic equilibrium with the cluster's gravitational potential. But the cluster formation process is unsteady, non-symmetric and subject to frequent external gravitational distortion, so, at the next level ICMs are expected to be crossed with transonic winds, gravity waves, concentrated, infalling streams, weak to moderate strength shocks and turbulence, all of whose distributions should reveal much about the cluster history and its environment. The links between these patterns and cluster formation are especially strong outside of the central cores of the clusters, where thermal emissions are weak, but where non-thermal processes can be strong enough to provide discriminating signatures of ICM dynamics. I will review these issues, including some current puzzles, focusing on our local simulation and modeling efforts, past, current and planned.


Tuesday, December 13th 2016
09:30 am:
There will be no seminar this week.

Hayden McCormick, "Experimental Analysis of Oscillating Guitar Strings using High Speed Photography."

Prashant Dhakal & Jack Goodsell, "The Effect of Lateral Retention Forces of Water on a Plexiglass Surface."

Vandon Duong, "Quantitative Characterization of RF Coils Designed for Human Ultrahigh Field MRI"

Alex Luna & Garrett Marxen, "The Effect of Static Magnetic Field on the Viscosity of Ferrofluid"

Dawson Kimyon, "Pulsed NMR Spectroscopy"

Jake Royal, "Development of a Variable Spectral- Width Wavelength Tunable Laser Using a Superluminescent Diode."

4:30 pm:
Speaker: Chris Leighton, Chemical Engineering and Material Science
Subject: Engineering interface magnetism and transport via defect ordering in complex oxide heterostructures

Wednesday, December 14th 2016
Speaker: Avraham Klein, Physics at UMN
Subject: Vortex core deformation in weakly coupled superfluids, and the Abrikosov lattice instability

Quantum vortices in weakly coupled superfluids have a large healing length, so that many particles reside within the vortex core. They are characterized by topologically protected singular points, which in principal should keep their core structure rigid. I will describe how, in practice, the point singularity of a vortex deforms into a line singularity, in proportion with the Magnus force experienced by the vortex. The vortex structure is described by weak solutions of the Gross-Pitaevskii equation, similar to shock waves in hydrodynamics. I will discuss how the core deformation significantly affects many aspects of vortex dynamics. A striking example I will describe is the instability of the Abrikosov vortex lattice in the weak-coupling limit. All vortex singularities in the lattice spontaneously deform into finite cuts, which then order into superstructures.

Faculty Host: Andrey Chubukov
There will be no seminar this week.
4:30 pm:
CM Journal Club in PAN 110
Speaker: Alberto Alvarado
Subject: Time-reversal symmetry breaking superconductivity in the coexistence phase with magnetism of Fe-pnictides

I argue that superconductivity in the coexistence region with spin-density-wave (SDW) order in weakly doped Fe pnictides differs qualitatively from the ordinary s+− state outside the coexistence region as it develops an additional gap component which is a mixture of intrapocket singlet (s++) and interpocket spin-triplet pairings (the t state). The coupling constant for the t channel is proportional to the SDW order and involves interactions that do not contribute to superconductivity outside of the SDW region. I argue that the s+− and t-type superconducting orders coexist at low temperatures, and the relative phase between the two is, in general, different from 0 or π, manifesting explicitly the breaking of the time-reversal symmetry promoted by long-range SDW order.

Reference: A. Hinojosa, R. M. Fernandes, and A. V. Chubukov. Phys. Rev. Lett. 113, 167001 (2014).


Thursday, December 15th 2016
11:15 am:
Speaker:  Prof. GW Gant Luxton, University of Minnesota, Dept. of Biochemistry, Molecular Biology and Biophysics
Subject: To be announced.
2:00 pm:
Thesis Defense in PAN 110
Speaker: Brent Perreault, University of Minnesota
Subject: Identifying a Kitaev spin liquid
This is the public portion of Mr. Perreault's thesis defense. His advisor is Fiona Burnell.

The search for quantum spin liquid physics has been long and storied, but RuCl3 and the iridates A2IrO3 have opened up the possibility of realizing a new family of "Kitaev" quantum spin liquids. The Kitaev honeycomb model is a highly anisotropic quadratic spin model that has an exact QSL ground state. We study the Kitaev model on a variety of 3D lattices with the goal of identifying characteristic signatures of its QSL phase. We use the exact solution to demonstrate several features of the Kitaev QSL both quantitative and qualitative. These include broad Raman spectra characteristic of the fractionalized excitations and rich momentum-dependent RIXS spectra. We discuss how these measurements can probe novel features of these QSL's. For example, topological surface modes accessible to Brillouin scattering, and Landau level peaks in Raman spectra on carefully strained honeycomb fakes. In addition, the technical underpinnings of these calculations are reviewed in detail. Specifically, the theoretical predictions are completed with considerations of the e ects of perturbations, finite temperature studies, and careful analysis of the experimental excitations.

3:35 pm:
There is no colloquium this week.
Speaker: Yuxuan Wang, University of Illinois at Urbana-Champaign
Subject: Topological superconductivity at the onset of an inversion breaking order

We analyze the superconducting instabilities in the vicinity of the quantum-critical point of an inversion symmetry breaking order. We first show that the fluctuations of the inversion symmetry breaking order lead to two degenerate superconducting (SC) instabilities, one in the s-wave channel, and the other in a time-reversal invariant odd-parity pairing channel (the simplest case being the same as the of 3He-B phase). Remarkably, we find that unlike many well-known examples, the selection of the pairing symmetry of the condensate is independent of the momentum-space structure of the collective mode that mediates the pairing interaction. We found that this degeneracy is a result of the existence of a conserved fermionic helicity, χ, and the two degenerate channels correspond to even and odd combinations of SC order parameters with χ = ±1. As a result, the system has an enlarged symmetry U(1) × U(1), with each U(1) corresponding to one value of the helicity χ. We discuss how the enlarged symmetry can be lifted by small perturbations, such as the Coulomb interaction or Fermi surface splitting in the presence of broken inversion symmetry, and we show that the resulting superconducting state can be topological or trivial depending on parameters. We present a global phase diagram of the superconducting states and discuss possible experimental implications.

Faculty Host: Andrey Chubukov

Friday, December 16th 2016
10:10 am:
There will be no seminar this week.
11:15 am:
Thesis Defense in Akerman Hall 313
Speaker: Alberto Hinojosa Alvarado, University of Minnesota
Subject: Time-reversal symmetry breaking superconductivity in the coexistence phase with magnetism in Fe pnictides
This the public portion of Mr. Alvarado's thesis defense. His advisor is Andrey Chubukov.

I argue that superconductivity in the coexistence region with spin-density-wave (SDW) order in weakly doped Fe pnictides differs qualitatively from the ordinary s+− state outside the coexistence region as it develops an additional gap component which is a mixture of intrapocket singlet (s++) and interpocket spin-triplet pairings (the t state). The coupling constant for the t channel is proportional to the SDW order and involves interactions that do not contribute to superconductivity outside of the SDW region. I argue that the s+− and t-type superconducting orders coexist at low temperatures, and the relative phase between the two is, in general, different from 0 or π, manifesting explicitly the breaking of the time-reversal symmetry promoted by long-range SDW order.

There will be no seminar this week.
Speaker: Ian Lewis (University of Kansas)
Subject: New Physics in Double Higgs Production

With the discovery of a Higgs boson, the Standard Model of Particle Physics is complete. However, there is still much to learn about the Standard Model and we may yet expect new physics. This talk will discuss the various ways in which new physics can appear in measurements of processes involving Higgs bosons. There will be a particular focus on double Higgs production. Measurement of this process is important for determining the shape of the scalar potential and the mechanism of electroweak symmetry breaking in the Standard Model. I will give an overview of new physics that can appear in this channel, including resonant production in a simple extension of the Standard Model.

2:00 pm:
Thesis Defense in Room 162 Amundson Hall
Speaker: Yanjun Yang, University of Minnesota
Subject: An Attempt to Synthesize Mn-doped Pyrite Thin Films
This is the public portion of Mr. Yang's Masters Thesis Defense. His advisors are Prof. Chris Leighton, Prof. Eray S. Aydil

Solar energy is a good choice to meet the energy and environmental challenges nowadays. Researchers have been searching for materials to make a solar absorber which can be widely applied in inexpensive photovoltaic devices. Pyrite FeS2 has long been recognized as a potential candidate for its theoretical high efficiency, low cost, earth-abundance and non-toxicity. However, the performance of pyrite based solar cells has been limited for some unknown reasons since the mid-1980s. The poorly understood doping mechanisms might be a reason for this low efficiency. Identifying unknown dopants, however, remains a big challenge, as does controlled n and p doping. In this work, we explore an approach to study doping by intentionally introducing Mn into pyrite thin films, which we may produce a p-type pyrite thin film. We focus on p-type films because unintentionally doped films were recently shown to be n-type, likely due to S vacancies. Development of a p dopant would therefore enable p-n junctions, a key step in creating a pyrite based solar absorber. In this work, we synthesized and studied the chemical, structural and electronic transport properties of Mn-doped pyrite thin films via ex situ sulfidation.

There is no colloquium this week.
There is no colloquium this week.
There will be no seminar this week.

Monday, December 19th 2016
08:00 am:

Tuesday, December 20th 2016
08:00 am:

Wednesday, December 21st 2016
08:00 am:

Thursday, December 22nd 2016
08:00 am:

Friday, December 23rd 2016

Monday, December 26th 2016

Thursday, December 29th 2016
2:00 pm:
Thesis Defense in M10 library, Mesonic Memorial Building
Speaker: Pamela Sooriyan, University of Minnesota
Subject: Dose enhancement in bone due to the 16O(γ,n)15O reaction
This is the public portion of Ms. Sooriyan's thesis defense. Her thesis advisor is John Broadhurst.

External beam radiation therapy is the most common option in the treatment of malignant tumors. It mainly uses Bremsstrahlung photons produced when highly accelerated electrons are incident on a target of high atomic number, gamma rays produced by radionuclides, and electrons beams. In the mega-voltage range of photon beams, the dose absorbed by the tumor is primarily by the incident photons losing their energy to the tissues of the tumor by Compton scattering and pair production. Enhancing photonuclear disintegrations offers the possibility of increasing the dose to the tumor (for the same delivered dose) by introducing secondary charged particles in the irradiated region.
The dose delivered by secondary charged particles from the 16O(γ,n)15O reaction in bone was measured in an attempt to explore the feasibility of local dose enhancement due to photo nuclear disintegrations.

For an externally delivered dose of 13 Gray, the additional dose due to positrons was measured to be 0.18 mGray in bone and 0.025 mGray in tissue, using a photon beam that had about 1.3% of photons of energy needed to initiate the 16O(γ,n)15O reaction.

The weekly calendar is also available via subscription to the physics-announce mailing list, and by RSS feed.