Physics and Astronomy Calendar

semester, 2014


Monday, January 20th 2014

Tuesday, January 21st 2014
11:15 am:
Nuclear Physics Seminar in 435 Physics
Organizational Meeting
12:20 pm:
Speaker: Dmitry Spivak, University of Minnesota
Subject: Kondo Physics in Metallic Lateral Spin Valves
1:25 pm:
To be announced.
2:30 pm:
Biophysics Seminar in 210 Physics
Speaker: Hye Yoon Park, Albert Einstein College of Medicine, Yeshiva University,
Subject: Imaging Single Endogenous mRNA in Live Mammalian Cells and Tissues

Wednesday, January 22nd 2014
3:30 pm:
Speaker: Ilya Krivorotov, UC Irvine
Subject: Spin-orbitronics in metallic nanostructures
Refreshments served in Room 216 Physics after colloquium

Manipulation of the spin of electron by electric rather than magnetic field is at the core of spintronics. A well known example of coupling spin to electric field is spin orbit interaction (SOI), but until recently efficient spin manipulation by SOI was only possible in dielectrics and semiconductors. In this talk, I will review several recent discoveries of surprisingly strong SOI effects in metals, including SOI-induced pure spin currents and electric field control of magnetic anisotropy. I will then demonstrate how these effects can be employed for generation and tuning of collective spin excitations in metallic magnetic nanostructures that can find use in applications such as non-volatile computer memory and nanoscale microwave sources.

Faculty Host: Paul Crowell

Thursday, January 23rd 2014
11:15 am:
Space Physics Seminar in 157 Physics
There will be no seminar this week.
12:15 pm:
Speaker: Emilian Dudas (Ecole Polytechnique)
Subject: Flavour models with Dirac and fake gluinos

In supersymmetric models where gauginos may have both
Majorana and Dirac masses, we investigate constraints from
favour-changing processes on the scalar masses. One finds that the chirality-flip suppression of flavour-changing e ffects usually invoked in the pure Dirac case
holds in the mass insertion approximation only, and fails in particular for inverted hierarchy models.
We comment on the limit of large Majorana gaugino masses compared to the chiral
adjoint and Dirac masses, where the light eigenstate is the "fake" gaugino having suppressed couplings to quarks.

1:25 pm:
Condensed Matter Seminar in 210 Physics
Speaker: Ilya Krivorotov, University of Califorinia, Irvine
Subject: Tunable triplet superconductivity in spin valve/superconductor multilayers

A film of singlet s-wave superconducting material placed in direct contact with a ferromagnet develops a superconducting condensate with unusual properties. Most notably, the condensate can acquire a triplet component immune to pair breaking by exchange field and thereby can penetrate deep into the ferromagnet. In this talk, I will show how the amplitude of this triplet component can be measured and efficiently tuned by controlling the magnetic state of a pair of ferromagnetic layers (a spin valve) proximate to the superconducting film. I will also discuss applications of the magnetically tunable triplet condensate in superconducting spintronic devices such as nonvolatile memory for energy-efficient cryogenic computing.

Faculty Host: Paul Crowell
3:00 pm:
Special Biophysics Seminar in 110 Physics and Nanotechnology
Speaker: Sang-Hyuk Lee University of California, Berkeley
Subject: How SpoIIIE knows which direction to walk on DNA in vivo: insights from the super-resolution microscopy and the single-molecule counting.

Cell division is featured as one of the fundamental and important developmental processes of cell. During the cell division, successful delivery of DNA into daughter cells is essential. Depending on cell type and developmental stage, various different cellular machineries are developed and adopted to assure the complete inheritance of the genetic material. Specifically, when Bacillus subtilis goes through sporulation life cycle in a harsh environment, the division septum is positioned asymmetrically, resulting in a DNA trapped by the division septum with ~70% of the DNA on the wrong side. To pump this portion of the DNA into the correct daughter cell compartment, motor protein SpoIIIE is recruited to the site. However, how SpoIIIE robustly translocates the DNA always in the right direction remains puzzling. I employed single-molecule counting photoactivated localization microscopy in combination with novel genetic tools in order to dissect the macromolecular structure of SpoIIIE and the DNA translocation mechanism in vivo. I will describe the new finding that SpoIIIE translocates DNA through two or four channels formed by head-to-head hexamers across the division septum. This symmetric organization of SpoIIIE strongly suggests that the direction of DNA translocation is rather encoded into DNA itself through the SpoIIIE recognition sequence (SRS) that is askewly
distributed over the circular bacterial DNA.


Friday, January 24th 2014
To be announced.
Speaker: Jan Estep, Department of Art, University of Minnesota
Subject: Art, Emotion, Mind: What can brain scans tell us about being human?
Refreshments served in Room 275 Nicholson Hall at 3:15 p.m.

This talk will describe my participation in a collaborative interdisciplinary art and cognitive neuroscience project titled Thinking Portraits: Mind, Body, Language. The group used functional magnetic resonance imaging (fMRI) to explore the relationship between abstract and concrete language as processed by the brain during semantic decision tasks. As a test subject in the study, I collected hundreds of anatomical MRI images of my brain. Viewing these remarkable images got me wondering about the way brain scans convey empirical data, given the often hidden decisions and processing procedures that contribute to their production. They appear photographic and indexical, yet their actual relationship to their referent is far more complicated. They appear so informative, yet brain science is still very young. As an artist these philosophical issues naturally paralleled a set of more personal, emotional concerns about the connections between brain, body, mind, and world. Hoping to understand these connections on a more visceral, intuitive level, I began a series of drawings using the MRI images as a substrate. Working back into the brain with my hands has become a means to investigate my embodied experience and a way to question and qualify what a brain image does and does not show.

3:35 pm:
Organizational Meeting
4:40 pm:
Speaker: Jorge Vinals, University of Minnesota
Subject:  Nonlinear dynamics and pattern formation

Monday, January 27th 2014
12:15 pm:
There will be no seminar this week.

Tuesday, January 28th 2014
11:15 am:
Nuclear Physics Seminar in 435 Physics
Speaker: Wolfgang Bauer, Michigan State University
Subject: Using Kinetic Theory to Perform Hydrodynamics Calculations for Relativistic Heavy Ion Collisions and for Supernova Studies

I will show that it is possible to start from kinetic theory and successfully solve all standard hydrodynamics tests. In addition, our approach extends naturally to Reynolds and Knundsen numbers outside the hydrodynamics domain. This is vitally important for addressing realistic problems in relativistic heavy ion collisions and in supernova precursor dynamics, two problems of vastly different scale showing a surprising number of commonalities.

12:20 pm:
There will be no seminar this week.
There will be no seminar this week.
2:30 pm:
Speaker: Elias Puchner, University of California, San Francisco
Subject: Tracking organelle biogenesis and signaling in cells with quantitative super-resolution microscopy

Wednesday, January 29th 2014
3:35 pm:
Speaker: Wolfgang Bauer, Michigan State University
Subject: The Physics of the Global Energy Problem and Possible Solutions
Refreshments served in Room 216 Physics after colloquium

Humans consume approximately 16 TW of power, with almost 90% derived from burning fossil fuels. The consequences are a sharp and continued increase in atmospheric CO2, global warming, sea level rise, and ocean acidification, among others. We need to employ alternative power generation methods, all of which require careful considerations of trade-offs. I will show how physics considerations can inform our choices. In particular I will concentrate on biomass-based approaches.


Thursday, January 30th 2014
Speaker: Stou Sandalski and Terry Jones
12:15 pm:
Speaker: Tim Cohen (SLAC)
Subject: On Heavy Supersymmetry

The discovery of a 125 GeV SM-like Higgs boson along with the absence of additional new physics signals have reinvigorated studies of "simple" supersymmetry breaking sectors. One such paradigm relies on anomaly plus gravity mediation; this model favors 3 TeV wino dark matter and gluinos in the O(10 TeV) range. Given these large masses, this model is difficult to test. In this talk, we will review the status of this scenario, followed by a description of two concrete experimental probes. An existing search for line photons emanating from the center of the galaxy will be used to challenge the wino dark matter hypothesis. Estimates for the reach of a future 100 TeV proton collider will be shown. This will demonstrate the potential to probe much of the interesting parameter space using human buildable technology.

1:25 pm:
Condensed Matter Seminar in 210 Physics
Speaker: Mengkun Liu, UC-San Diego
Subject: Exploring the fundamental time and length scales of Strongly Correlated Electron Materials

ABSTRACT: In strongly correlated electron materials (CEMs), the delicate interplay between spin, charge, and lattice degrees of freedom often leads to extremely rich phase diagrams exhibiting intrinsic phase inhomogeneities. The key to studying and disentangling such complexities usually lies in characterization and control of these materials at their fundamental energy, time and length scales. Using the prototypical correlated insulator vanadium dioxide (VO2) as a case study, I will show in this talk that ultrafast and ultrasmall optical spectroscopy offers unique insights into this electronic/structural interplay with unprecedented spatial and temporal resolutions. Specifically, with scanning near-field infrared microscopy we resolved the long-lasting enigma of electronic anisotropy in VO2 and revealed three distinct stages of the insulator to metal transition (IMT) at nanoscopic length scales. Using ultrafast terahertz pump terahertz probe spectroscopy we have also unambiguously demonstrated that the IMT occurs at picosecond time scales via electric field-induced electron liberation. These results set the stage for future spectroscopic investigations to access the fundamental time and length scales of CEMs.

3:00 pm:
Biophysics Seminar in 110 PAN
Speaker: Andrea Soranno, University of Zurich
Subject: Probing the polymer properties of intrinsically disordered proteins with single-molecule spectroscopy

In contrast to stable folded proteins, intrinsically disordered proteins (IDPs) lack a well-defined three-dimensional structure, but, nevertheless, they are involved in many crucial biological functions. Given the large structural heterogeneity of IDPs, the polymeric properties are expected to play a major role for their conformational distributions and dynamics. Single-molecule spectroscopy in combination with Förster resonance energy transfer (FRET) can be used to probe intramolecular distance distributions and reconfiguration times of IDPs, which are key quantities for a detailed polymer physical analysis. These experiments have allowed us, e.g., to probe the role of electrostatics for unfolded state dimensions and to quantify the contribution of internal friction on unfolded state dynamics.
I will focus on recent results on the effects of macromolecular crowding on IDPs. We observe a compaction of the proteins not only with increasing concentration, but also with increasing size of the crowding agents. The observed behavior can be explained quantitatively if the polymeric nature of both the IDPs and the crowding molecules is taken into account. The results suggest that excluded volume interactions between overlapping biopolymers and the resulting criticality of the system can be essential contributions to the physics governing the crowded cellular milieu.


Friday, January 31st 2014
Speaker: Dr. Ka-Wah Wong, Postdoctoral Fellow
Subject: X-ray Emitting Hot Gas within Bondi Radius of the Nearby Supermassive Black Hole in NGC 3115

While some spectacular luminous quasars emit near their
Eddington limit (~0.1 L_Edd), the majority of supermassive black
holes, including Sgr A*, are emitting at a much lower rate (< 10^-8 L_Edd). It is widely believed that these low-luminosity active galactic nuclei (LLAGNs) are accreting through a hot accretion mode. Observational confirmation of hot accretion model predictions has been hindered by the challenge to resolve spatially the Bondi radii of black holes with X-ray telescopes. The closest billion solar mass black hole in NGC 3115 provides such an opportunity. I will present results from our Megasecond Chandra X-ray Visionary Project (XVP) observation of NGC 3115 to study the most detailed spatially and spectroscopically resolved structures of the X-ray-emitting gas inside the Bondi radius a black hole. In particular, I will present the measured temperature and density profiles of the hot gas from a fraction out to tens of the Bondi radius (R_B = 2.4-4.8 arcsec = 112-224 pc). I will discuss the nature of the hot gas within the Bondi radius of NGC 3115 and implications of the results.

Speaker: Hannah Landecker, Institute for Society and Genetics, University of California, Los Angeles
Subject: "The Metabolism of History: Combustion, Homeostasis, Epigenesis"
Refreshments served in Room 216 Physics at 3:15 p.m.

Since its induction into scientific terminology in the nineteenth century, metabolism has been a site of dietetic, medical, chemical and biological investigation, and a conceptual resource for political theory, philosophy, and social science. This talk mirrors ethnographic work in the contemporary life sciences and historical research to reverse the usual formulation of a history of metabolism and pursue instead the question of the metabolism of history: how the concepts of materialist animal chemistry and physiology were built into food animals, crop plants, and microbes as part of the scaling up and industrialization of biology, in the process changing the objects and problems at the heart of biochemical and biomedical research. While offering a very practical history of certain objects and narratives of metabolic science, this talk also asks: How is knowledge shaped by confronting the products – the biological manifestations - of its previous applications? And might we seek rapprochement between intellectual history and material culture in a rigorous excavation of their intercalation in the process of historical change?

3:35 pm:
To be announced.
4:40 pm:
There will be no seminar this week.

Monday, February 3rd 2014
12:15 pm:
Speaker: Toshihiro Fujii, KICP, University of Chicago
Subject: Observations of the Universe's Highest Energetic Particles

Ultra-high energy cosmic rays (UHECRs) are the most energetic particles in the universe, and their origins should be related with energetic astronomical phenomena or exotic physics.
In order to clarify origins of cosmic rays, we steadily observe UHECRs by the Pierre Auger Observatory in the southern hemisphere and the Telescope Array Experiment in the northern hemisphere. I will review elementary cosmic ray physics, detection techniques of UHECRs and observational instruments. I will present latest results focusing on three important measurements; an energy spectrum, a mass composition, and an arrival direction. Finally I will highlight our future prospects and next-generation experiments for UHECR observation.

Faculty Host: Lucy Fortson
3:30 pm:
Speaker: Cihan Kurter, University of Illinois, Urbana-Champaign
Subject: Anomalous Josephson current in superconductor/topological insulator devices

Recently, there has been intense interest in realizing excitations of Majorana fermions(MFs) in solid-state systems. Circuits of Josephson junctions (JJs) made of closely spaced conventional superconductors on 3D topological insulators have been proposed to host low energy Andreev bound states (ABSs) which can include MFs. In this talk, I will present signatures of an anomalous supercurrent carried by such topologically non-trivial ABSs in various superconducting quantum interference devices (SQUIDs) made of Nb/Bi2Se3/Nb junctions. An electrostatic top gate placed on the JJs allows strong modulation of the Josephson current and the realization of a topological phase transition in which the spatial location of the supercurrent-carrying states in the junction is changed. This transition is accompanied by qualitative changes in the SQUID oscillations, single-junction di raction patterns, and temperature dependence of the critical current.


Tuesday, February 4th 2014
11:15 am:
Nuclear Physics Seminar in 435 Physics
Speaker: Koichi Murase, The University of Tokyo
Subject: Colored noise and white noise in causal dissipative hydrodynamics for heavy-ion collisions

Event-by-event fluctuations of the heavy ion collisions are observed in experimental observables such as higher harmonic flows vn- , and recently, it is actively discussed to extract the transport coefficients of the created matter from the data with event-by-event causal hydrodynamic simulations. Thermal fluctuations arising in the dynamical evolution of the matter, namely hydrodynamic fluctuations, can have an effect on the quantitative determination of the transport coefficients. In causal dissipative hydrodynamics, the hydrodynamic fluctuation of the dissipative currents becomes colored noise. Nevertheless noises turn out to be always white in the differential form of the constitutive equations.

Speaker: Brian Batell (U. of Chicago)
Subject: Searching for Dark Matter at Neutrino Factories

I will describe a new way to search for dark matter using intense
proton beam-target-detector setups such as those used to study
neutrino oscillations. I will discuss the ongoing effort in the
MiniBooNE collaboration to carry out the first search of this kind.
This new approach is highly complementary to traditional dark matter
search strategies, and provides a new important motivation for the
experimental program at the intensity frontier.

Faculty Host: Roger Rusack
2:30 pm:
Biophysics Seminar in 210 Physics
Speaker: Xuefeng Wang, University of Illinois, Urbana-Champaign
Subject: Cellular forces measured and perturbed at the molecular level

Mammalian cells are truly remarkable signal receivers and processors. Besides chemical, electrical and sometimes optical signals, they can also sense external mechanical stimuli and accordingly direct many important functions such as cell adhesion, stem cell differentiation and embryo development. Cell membrane hosts mechano-sensitive proteins (receptors) which bind to external target molecules (ligands) and form receptor-ligand bonds with the local environment or neighboring cells. Cells apply tensions on these bonds and process mechanical feedbacks to activate downstream cellular functions (like spiders tapping on their webs to mechanically sense ensnared preys). To study these molecular tensions, I developed a technique called tension gauge tether (TGT). The ligand is immobilized to a surface through a rupturable tether which serves as a molecular gauge to restrict the receptor-ligand tension. Using a range of tethers with tunable tension tolerances, I discovered that cells apply a universal maximum tension of about 40 piconewtons (pN) to single integrin-ligand bonds during initial adhesion. I also discovered that a force less than 12 pN is required to activate Notch receptors, a group of molecules involved in intercellular communication. Aside from simply measuring the tension, TGT can provide well-defined mechanical perturbations to cellular functions and a novel avenue to study cell mechanics at the molecular level. In the future, I will develop more tether-based methods for cellular force measurements and perturbations and apply them to study mechanical–based processes such as mechanotransduction, endocytosis and cell migration.


Wednesday, February 5th 2014
3:35 pm:
Physics and Astronomy Colloquium in 150 Tate Lab of Physics
Speaker: Don Gurnett, University of Iowa
Subject: The strange rotational modulation of Saturn's magnetosphere.
Refreshments served in Room 216 Physics after colloquium

The rotation rates of the interiors of the giant outer planets cannot be obtained from visual observations of the motion of clouds because of strong zonal winds. Instead the rotation rate given in most astronomy books is based on the rotational modulation of radio emissions produced by magnetospheric charged particles. The justification is that the motions of the charged particles are controlled by magnetic fields linked to the deep interior. This method seems to work well for Jupiter, whose radio rotation period has remained constant within fractions of a second for over fifty years. However, for Saturn the radio rotation period is observed to vary by up to one percent on time scales ranging from months to years, and is sometimes different in the northern and southern hemispheres. These strange variations appear to be related to the fact that, unlike the other giant planets, Saturn’s magnetic dipole axis is aligned almost exactly parallel to its rotational axis. This unique geometry gives important insight into how the rotation of the interior of a giant gas planet is coupled to the magnetospheric plasma.


Thursday, February 6th 2014
11:15 am:
Space Physics Seminar in 157 Physics
There will be no seminar this week because the Van Vleck lecture and Colloquium will be on the topic of Space Physics. Group members are urged to attend those talks.
Speaker: Thomas Jones
12:15 pm:
Speaker: Brian Batell (U. Chicago)
Subject: Flavored Dark Matter

Minimal Flavor Violation provides a symmetry rationale for the absence
of flavor changing neutral currents in generic extensions of the
Standard Model and also offers an alternative to R-parity conservation
for the suppression of proton decay in theories with supersymmetry. I
will show that the the flavor symmetry can also guarantee the
stability of dark matter if it carries flavor quantum numbers. This
observation leads to theories of flavored dark matter. I will outline
general features of flavored dark matter models and examine in detail
a simple model of top flavored dark matter.

1:25 pm:
Condensed Matter Seminar in 210 Physics
Speaker: Vlad Pribiag, Kavli Institute of Nanoscience Delft, Delft University of Technology
Subject: Exploiting Spin-Orbit Coupling in Semiconductor Nanowires and Topological Insulators

Conventional semiconductors with strong spin-orbit coupling and topological insulators have emerged as promising platforms for spintronics and quantum information processing. In the first part of this talk, I will present experiments relying on the strong spin-orbit interaction in InSb nanowires to demonstrate all-electrical control of individual spins in quantum dots. These experiments highlight the potential of electric dipole spin resonance (EDSR) as both a means for controlling spin-based qubits and as a powerful spectroscopic tool for electrons and holes. Holes, in particular, are very attractive for quantum information processing due to the possibility of longer spin coherence and stronger spin-orbit coupling than electrons, both consequences of the p-orbital symmetry of the Bloch wavefunction. Our work demonstrates that hole-spin states can be manipulated and probed in a transport experiment, providing a path for the implementation of hole-spin based spintronic and opto-electronic devices. In the second part of the talk, I will focus on our current efforts to develop 2D topological insulators (2D TIs) into an experimental platform for Majorana zero modes. These exotic fermionic excitations are predicted to have non-Abelian statistics, making them ideal candidates for fault-tolerant quantum computation. I will discuss superconducting junctions based on InAs/GaSb double quantum wells as a first step towards Majorana experiments based on this gate-tunable 2D TI.

6:30 pm:
Van Vleck Lecture in 150 Tate Lab of Physics
Speaker: Don Gurnett, University of Iowa
Subject: The Epic Journey of Voyager 1 into Interstellar Space

After a journey of more than 36 years a spacecraft, Voyager 1, has for the first time crossed the heliopause into interstellar space. The heliopause is the long hypothesized boundary between the hot plasma envelope of the Sun (called the heliosphere) and the relatively cool interstellar plasma. The actual crossing is believed to have occurred at a heliospheric radial distance of 121 Astronomical Units in late August 2012, when a series of sharp increases in the cosmic ray intensities were observed, along with corresponding decreases in the solar energetic particle intensities. However, the plasma measurements needed to confirm the entry into the interstellar medium were not obtained until early the following April, as reported in the Sept. 27, 2013, issue of Science. For the first time we can now measure the unaltered intensity of galactic cosmic rays incident on the heliosphere, as well as other properties of the interstellar medium, such as the magnetic field. In this talk I will review some of the great achievements of the planetary phase of the Voyager mission, often called the “The Grand Tour of the Outer Planets,” and describe the long quest to reach the heliopause and cross into interstellar space.

Don Gurnett is the James A. Van Allen/Roy J. Carver Professor of Physics in the Department of Physics and Astronomy at the University of Iowa. He began his career in 1958 by working on the design of spacecraft electronics as an undergraduate engineer in James Van Allen’s cosmic ray research group shortly after Van Allen’s discovery of Earth’s radiation belts using Explorer 1, the first U.S. spacecraft. After receiving his B.S. in electrical engineering and his Ph.D. in physics at Iowa, he spent one year at Stanford University as a NASA trainee and then joined the Physics faculty at Iowa in 1965, where has been to the present time.

Over his career he led the development of instruments on more than 30 spacecraft projects, including many early Earth-orbiting spacecraft, and on several major planetary missions such as the famous Voyager 1 and 2 flights to the outer planets, the Galileo mission to Jupiter, and the Cassini mission to Saturn. His research primarily involves the study of radio emissions and waves that are generated in hot ionized gases, called plasmas, that occur in planetary magnetospheres and in the solar wind which is a hot ionized gas flowing outward from the Sun. These plasmas produce many different types of radio emissions and plasma waves that can provide crucial information on key properties of the plasma, such as the density and temperature, and even the rotation rate of the planet, as is the case for the outer planets. Over his career he has authored or co-authored over 600 scientific papers and has received numerous awards for his research and teaching. He has guided 62 graduate research projects and many of his students now hold prominent positions in space physics research.


Friday, February 7th 2014
Speaker: No Astrophysics colloquium this week
Speaker: Robert Spekkens, Perimeter Institute for Theoretical Physics, Waterloo
Subject: "On Causal Explanations of Quantum Correlations"
Refreshments served in Room 216 Physics at 3:15 p.m.

An active area of research in the fields of machine learning and statistics is the development of causal discovery algorithms, the purpose of which is to infer the causal relations that hold among a set of variables from the correlations that these exhibit. We show that any causal explanation of certain quantum correlations—those that violate a Bell inequality—must contradict a core principle of these algorithms, namely, that an observed statistical independence between variables should not be explained by fine-tuning of the causal parameters.The fine-tuning criticism applies to all of the standard attempts at causal explanations of Bell correlations,such as superluminal causal influences, superdeterminism, and retrocausation. Nonetheless, we argue that by casting quantum theory as a theory of Bayesian inference, we can generalize the notion of a causal model and salvage a causal explanation of Bell correlations without fine-tuning.
(based on http://arxiv.org/abs/1208.4119)

3:35 pm:
There will be no seminar this week.
4:40 pm:
Speaker: Carolyn Rauber, University of Minnesota Libraries
Subject: Library research

Monday, February 10th 2014
12:15 pm:
Speaker: Kevin Schawinski, ETH Zurich
Subject: The origin of supermassive black holes

Almost all galaxies harbor supermassive black holes in their centers. They can grow up to 1e10 solar masses via accretion and their growth seems intimately linked to the evolution of their host galaxies. But how did these supermassive black holes form in the first place? We know that billion solar mass black holes already exist in extremely rare systems less than a billion years after the Big Bang, challenging our understanding of black hole seed formation. What physical processes make black holes? When and where do galaxies have the right conditions for black hole formation? I will cover some exciting recent observational advances which may challenge our view of how the universe populates itself with black holes.

Faculty Host: Lucy Fortson
2:30 pm:
Speaker: Hernan Garcia, Princeton University
Subject: How, when and where in pattern formation: Spying on embryonic development one molecule at a time
Note: the biophysics seminar will be held on a different day, this week only.

An abiding mystery in the study of living matter is how a single cell develops into a multicellular organism. As this cell divides, its progeny read the program encoded on their DNA and adopt different fates becoming familiar cell types such as those found in muscle, liver and our brains. We now know that the decisions that cells make during development are not so much based on which genes to express, but rather on when, where
and how to express them. Despite advances in determining the identities of the molecules that mediate these decisions we are still incapable of predicting how simple physical parameters such as the number, position and affinity of binding sites for these molecules on the DNA determine developmental fates. Using the fruit fly, one of the classic model systems for embryonic development, I will show how a combination of quantitative experiments and statistical mechanics is providing new insights about cellular decision making during development. In particular, I will describe how the specification of macroscopic body parts in an organism is linked to the non-equilibrium molecular-scale processes inside single cells. The goal of this interdisciplinary research is to produce a predictive understanding of developmental programs which will enable the rational control of biological size, shape and function.

3:30 pm:
Speaker: Andrea Young, MIT
Subject: Topology, symmetry, and edge states in graphene heterostructures

Low-dimensional electronic systems have traditionally been obtained by electrostatically confining electrons, either in heterostructures or in intrinsically nanoscale materials such as nanowires. Recently, a new method has emerged with the recognition that gapped symmetry-protected topological (SPT) phases can host robust surface states that remain gapless as long as the relevant global symmetry remains unbroken. The nature of the charge carriers in SPT surface states is intimately tied to thesymmetry of the bulk, resulting in one-and two-dimensional electronic systems with novel properties such as the locking of spin and momentum. I will describe our recent experimental realization of such helical states on the edge of a graphene flake subjected to very large magnetic fields. In contrast to its time-reversal-symmetric cousin, thegraphene quantum spin Hall state is protected by a symmetry of planar spin rotations that emerges as electron spins in a half-filled Landau level are polarized by the applied field. The properties of the resulting helical edge states can be modulated by balancing the applied field against an intrinsic antiferromagnetic instability, which tends to spontaneously break the spin-rotation symmetry. In the resulting cantedantiferromagnetic state, we observe transport signatures of gapped edge states, which constitute a new kind of one-dimensional electronic system with a tunable bandgap and an associated spin texture.


Tuesday, February 11th 2014
11:15 am:
Nuclear Physics Seminar in 435 Physics
Speaker: Professor Yang Sun, Shanghai Jiao Tong University
Subject: Overview of shell model calculations for nuclear astrophysics interests

Shell-model is an essential tool for detailed understanding of exotic nuclear structure and for providing necessary input for astrophysical models and simulations. In this talk, we give an overview of traditional shell models pointing out their strengths and weakness. We have made progress in development of new types of shell models, namely, large-scale shell model based on spherical basis and the projected shell model based on deformed basis.

We present results from our recent large-scale shell model calculations for neutron-rich nuclei with a few particles or holes around 132Sn. For a considerably large model space including neutron and proton core excitations, a new effective interaction based on the extended PQQM force has been determined. The model provides a systematical description for energy levels of A~130 nuclei, both for low and high spin states, and reproduces available data of electromagnetic transitions. This theoretical development is relevant to the recent experimental programs in this mass region.

Projected shell model is another way of thinking for shell model calculations applicable to heavy, deformed nuclei. Over many years, this model has proven its power in answering various questions in nuclear structure problems. It is an important shell model method, probably the only feasible method to use, if one wants to carry out shell model study beyond the traditional RPA method for heavy systems.

Faculty Host: Yong-Zhong Qian
12:20 pm:
There will be no seminar this week.
Speaker: Alexey Finkel
Subject: Journal Club on paper: Novel Phenomenology of Parton Distributions from the Drell-Yan Process
2:30 pm:
Biophysics Seminar in 210 Physics
The Biophysics Seminar will be held on Monday this week.

Wednesday, February 12th 2014
3:35 pm:
Speaker: Diandra Leslie-Pelicky
Subject: The Science of Speed: Why Driving Fast isn't as Easy as You Think
Refreshments served in Room 216 Physics after colloquium

Is it really all that hard to drive fast? No - assuming a spherical racecar. But once you start adding in all those real-world complications we usually dismiss as 'negligible', you quickly realize that there is far more to going fast than stepping on the accelerator. Dr. Diandra Leslie-Pelecky, author of The Physics of NASCAR and the motorsports blog Building Speed, set out to learn whether understanding the science of speed would translate into being a good racecar driver. That quest took her from race shops and materials labs all the way to the twenty-four degree banking of the Texas Motor Speedway - where centripetal force suddenly became much more than numbers on a page. This talk covers the basics of driving fast and shows that racecar drivers - even if they don't use the terminology we like to throw around - really do have to understand some complicated physics. The need for advanced techniques is even more pronounced for the engineers and physicists who must apply computational fluid dynamics and advanced materials development techniques to simultaneously optimize speed and safety. The last part of the talk focuses on how popular culture (such as sports, music and art) can be used to raise interest in math and physics to a large audience and the lessons learned from working with television, blogs and satellite radio.

About the speaker:
Diandra Leslie-Pelecky earned undergraduate degrees in physics and philosophy from the University of North Texas and a Ph.D. in condensed matter physics from Michigan State University. She was a faculty member in the Department of Physics at the University of Nebraska–Lincoln from 1994 until 2008. Her research focuses on magnetic nanomaterials – particles with diameters just a few thousandths the thickness of a human hair. In addition to fundamental studies of magnetic materials, her group uses magnetic nanomaterials for medical diagnosis and treatment processes such as drug delivery, magnetic resonance imaging and chemotherapy. Her research has been supported by the National Science Foundation, the National Institutes of Health and various other federal and state funding agencies. Diandra has been involved with science education for K-12 schools, future science teachers, and the public since graduate school. She has directed projects aimed at improving science education at all levels, supported primarily by the National Science Foundation. Diandra has given numerous presentations for technical and non-technical audiences, including addresses for the public sponsored by the American Association for the Advancement of Science and the American Physical Society. Her worked has been covered in outlets as diverse as the New York Times Science Times and Sports Illustrated, as well as in professional society publications such as C&EN and the Materials Research Society Bulletin. She appears periodically on the Sirius Speedway satellite radio program to update listeners on the scientific principles that affect their favorite drivers.


Thursday, February 13th 2014
11:15 am:
Space Physics Seminar in 157 Physics
There will be no seminar this week.
Speaker: Micaela Bagley
12:15 pm:
Speaker: Sergei Dubovsky (NYU)
Subject: Fluxtube spectra from approximate integrability at low energies
1:25 pm:
Condensed Matter Seminar in 210 Physics
Speaker: Milan Allan, Laboratory for Solid State Physics, ETH Zurich
Subject: Visualizing Electronic Nematicity and Cooper Pairing in Iron‐based Superconductors

The mechanism of high-temperature superconductivity is unresolved, both in terms of how the phases evolve with doping, and in terms of the actual Cooper pairing process. In my talk, I will introduce spectroscopic-imaging STM as a tool to explore these questions, by direct imaging of the relevant quantum mechanical waves on the atomic scale. I will discuss our discovery of strong electronic nematicity in the parent state of iron-based superconductors, and the recent realization of how dopant-atom induced unidirectional impurity states and anisotropic scattering can explain the mysterious anisotropic transport characteristics in these materials. Next, I will describe our exploration of the superconducting energy gaps and electron-boson interaction in the canonical Fe-based superconductor LiFeAs. The interactions generating unconventional Cooper pairing are often conjectured to be of electronic nature. We introduced Bogoliubov quasiparticle scattering interference (QPI) techniques for determination of both the superconducting gaps in momentum space and the electron-boson coupling self-energy. We identified anisotropic gaps and strong effects in the interband direction only, pointing towards a spin-fluctuation mechanism for Cooper pairing. Finally, I will outline the new techniques for atomic-scale imaging that I propose in order to address the most pressing open questions in quantum materials.


Friday, February 14th 2014
Speaker: No colloquium this week
Speaker: Martin Summers' Colloquium has been cancelled due to severe weather in the eastern half of the country.
Refreshments WILL be served in Room 216 Physics at 3:15 p.m. as usual!
3:35 pm:
There will be no seminar this week.
4:40 pm:
Speaker: Shaul Hanany, University of Minnesota
Subject: Searching for Signatures of the Big Bang from 120,000 ft.

Monday, February 17th 2014
12:15 pm:
Speaker: Evan Skillman, University of Minnesota
Subject: The Local Cosmology from Isolated Dwarfs (LCID) Project

I will present an overview of the LCID project - a large Hubble Space Telescope program aimed at deriving detailed star formation and chemical enrichment histories for a sample of isolated Local Group dwarf galaxies. The details of the early star formation histories of isolated dwarf galaxies can shed light on the roles of the cosmic re-ionization and supernova feedback in galaxy formation and evolution. The radial gradients in the star formation histories provide insight into the structural evolution of dwarf galaxies. The variable star populations provide independent constraints on the strengths and distributions of the earliest star formation. Comparison of the star formation histories with various galaxy evolution models demonstrate that star formation is not directly coupled to mass assembly in dwarf galaxies. Comparing the results for isolated dwarfs with those obtained for the Milky Way and M31 satellites sheds new light on the effects of environmental mechanisms, which are expected to dominate for satellite galaxies.


Tuesday, February 18th 2014
11:15 am:
Nuclear Physics Seminar in 435 Physics
Speaker: Sean Bartz , University of Minnesota
Subject: Meson Spectra from a Three-Field Potential for Holographic QCD

I will show that it is possible to construct a potential for the background fields for a holographic model of QCD with accurate chiral symmetry breaking. I will describe the construction of the potential, and the calculation of the meson spectra, which match experimental data well. I will also argue that the presence of three background fields (dilaton, chiral, and glueball) is necessary to properly describe the meson spectra.

12:20 pm:
There will be no seminar this week.
12:20 pm:
Space Physics Seminar in 210 Physics
To be announced.
2:30 pm:
Biophysics Seminar in 210 Physics
There will be no seminar this week.

Wednesday, February 19th 2014
3:35 pm:
Speaker: Dan Fabrycky, University of Chicago
Subject: The Timing of Planetary Systems
Refreshments served in Room 216 Physics after colloquium

The Kepler mission represents a breakthrough in the dynamics of exoplanetary systems. The number of systems with detectably perturbed orbits jumped from two to over a hundred. We report models of the systems with high signal-to-noise transit timing variations (TTVs). Such data can uniquely determine the mass and orbital parameters of the perturbing planet. Moreover, they open the door to a qualitatively new orbital architecture: planets orbiting binary stars. For all these systems, our dynamical models help us schedule and obtaining new transit observations, both from the ground and from space observatories, lest we lose knowledge of when to look for transits. With continued monitoring, the TTVs in these systems will result in mass-radius measurements for cool exoplanets and inferences on the formation and evolution of exoplanetary systems.


Thursday, February 20th 2014
Speaker: Dinesh Shenoy and Roberta Humphreys
12:15 pm:
Speaker: Claudia Frugiuele (Fermilab)
Subject: Dirac gauginos, R symmetry and the 125 GeV Higgs

I will talk about supersymmetric extensions of the SM where the gauginos are Dirac fermions. I will discuss the main advantages of this scenario respect to the MSSM focusing in particular on R symmetric models. I will summarise the LHC phenomenology and I will then discuss how to obtain a 125 GeV Higgs in this framework.

1:25 pm:
Condensed Matter Seminar in 210 Physics
Speaker: Jake Koralek, Lawrence Berkeley National Lab
Subject: Shedding Light on Quantum Matter

Quantum materials are those in which the interactions between constituent particles are too strong to be treated semiclassically, resulting in exotic emergent properties such as high Tc superconductivity. They represent the front line in the quest to understand the organizing principles that lead to complex collective behavior, and to eventually apply these principles to do something useful.
In this talk I will discuss the application of a wide range of optical and electron spectroscopies to quantum materials. In the cuprate superconductors, for example, we have used femtosecond pulses of laser-light to excite collective modes of the charge density wave order recently discovered in these materials. In these experiments we are able to directly observe the coupling between Cooper pairs and charge density waves, which may hold the key to high Tc superconductivity. In similar experiments, we have studied the collective modes of exotic spin textures like the Skyrmion lattice in MnSi. These experiments are complimented by time-resolved x-ray scattering to directly observe the dynamics of spin, charge and orbital order. I will also discuss the use of transient four-wave mixing to manipulate spins in a spin-orbit coupled 2D electron gas. And, finally, I will discuss some of our very recent work on Iridium oxides, which possess both strong electron-electron interactions and strong spin-orbit coupling, providing an ideal playground for demonstration of exotic new ground states.


Friday, February 21st 2014
No colloquium this week
Speaker: Eric Otremba, Department of History, Macalester College
Subject: "Experimental Empire: Science, Sugar, and Plantation Slavery in the English Atlantic, 1626-1688"
Refreshments served in Room 216 Physics at 3:15 p.m.

My talk covers the spread of the English sugar industry in the seventeenth century, and how this expansion was interpreted by the self-proclaimed "experimental philosophers" of England's natural science community during this time. Following Francis Bacon's program of empiric improvement, experimental philosophers were a novel group insofar as they found ways to link the distinct concepts of scientific experiment, useful inventions, and commercial trade into a single program of progressive national development. This program included the forced-labor work camps that were Caribbean sugar plantations. While today we rarely associate Barbadian sugar estates with paradigms of technological or economic progress, these thinkers understood sugar plantations in a radically different context, allowing them to compare plantations and sugar works to other recent wonders like gunpowder and the loadstone.

3:35 pm:
Speaker:  Miranda Straub, University of Minnesota
Subject: Issue in science education- navigating and addressing the resistance to evolution

This talk will focus on the recent debate between Bill Nye and
Ken Hamm on the topic of Creationism vs. Evolution. I will address questions including is Bill Nye the best person to be engaging this debate? What are the issues that have created the 'controversy'? What are the issues in science education such as portraying nature of science, certainty, and establishing and changing scientific understanding that have exacerbated the problem? While the issue has many facets, I will keep the focus of the talk on implications for science educators.

4:40 pm:
There will be no seminar this week.

Monday, February 24th 2014
12:15 pm:
Speaker: Rick Kessler, University of Chicago
Subject:  Startup of the Dark Energy Survey

I will give a brief review of dark energy, a mysterious entity that accelerates cosmic expansion, and summarize the measured properties from its discovery to current results. Next I will discuss the main science probes, both geometric and growth of structure, to further examine dark energy properties in the Dark Energy Survey (DES). DES is a dedicated 5000 square degree survey using the Blanco 4m telescope with a new 520 Megapixel camera (at CTIO, Chile). Finally, I will describe the DES instrumentation and show highlights from our recently completed first season of the 5-year survey.

Faculty Host: Lucy Fortson

Tuesday, February 25th 2014
11:15 am:
Nuclear Physics Seminar in 435 Physics
Speaker: John Broadhurst, University of Minnesota
Subject: Nuclear physics in medicine

This talk is a review of the contribution that the understanding of nuclear processes and structure is making to current medicine. It starts with the use of nuclear spin resonance imaging (MRI), and the localization of human cell types by positron emission tomography (PET). It then continues with the progress made in the radiation treatment of cancers by invoking selective nuclear processes to maximise the destruction of unwanted cells.

12:20 pm:
Speaker: Tobias Gulden / J. J. Nelson / Chien-Te Wu
Subject: APS March Meeting practice talks
12:20 pm:
Space Physics Seminar in 210 Physics
Speaker: Lei Dai, University of Minnesota
Subject: Excitation of poloidal ULF waves through drift-resonance wave particle interactions.
2:30 pm:
Biophysics Seminar in 210 Physics
There will be no seminar this week.

Wednesday, February 26th 2014
3:35 pm:
Speaker: Maria Gini, University of Minnesota
Subject: Distributed Decision Making for Robots
Refreshments served in Room 216 Physics after colloquium

As robots are used in more practical applications outside factories, it is becoming critical to develop methods for them to make decisions in a distributed fashion, where each robot shares its knowledge, beliefs and intentions with other robots, so that the group can achieve a global objective. Centralized solutions are still common, but distributed methods have the advantage of being scalable and robust to failures and noise. Consider the problem of exploring a building with a group of robots looking for survivors after a disaster. The exploration has to be systematic, but it is unknown how much damage the building has suffered and how likely are robots to get stuck or fail. Consider also allocation of tasks among robots, when tasks are discovered dynamically, or have a cost of completion that grows with time, or have temporal constraints. In this talk we will present distributed methods that rely on local computation and on communication among robots, to achieve a balance between optimality of solution, flexibility, and robustness.

About the speaker:
Maria Gini is a Distinguished Professor of the College of Science and Engineering at the University of Minnesota. She specializes in the design of multi-robot and multi-agent systems that are capable of making intelligent decisions. Such systems range from software agents to robots that move in unstructured and unknown environments. She is a Fellow of the AAAI and a Distinguished Scientist of the ACM.

Faculty Host: Priscilla Cushman

Thursday, February 27th 2014
Speaker: Alex Lazarian, U Wisconsin-Madison
Subject: Acceleration of cosmic rays by turbulent reconnection

I shall discuss the model of turbulent reconnection that we suggested more than a decade ago and which has been proven recently with numerical simulations. I shall show how cosmic rays get accelerated in a regular first order Fermi way within this model and present numerical simulations confirming the theory.

12:15 pm:
Speaker: James Barnard (U. Melbourne)
Subject: "UV descriptions of composite Higgs models without elementary scalars"
1:25 pm:
Condensed Matter Seminar in 210 Physics
Speaker: Xiaoyu Wang / Changjiang Liu / Terry Bretz-Sullivan
Subject: APS March Meeting practice talks
To be announced.

Friday, February 28th 2014
Speaker: Dr. Elena D'Onghia, U Wisconsin-Madison
Subject: Spiral Arms and Wobbles in Galactic Disks

The precise nature of spiral structure in galaxies remains uncertain. Using high-resolution N-body simulations, I follow the motions of stars under the influence of gravity, and show first that mass concentrations with properties similar to those of giant molecular clouds or clumps of gas can induce the development of spiral arms through a process termed swing amplification. However, unlike in earlier work, I will demonstrate that the eventual response of the disk is highly non-linear, significantly modifying the formation and longevity of the resulting patterns. I will discuss how these findings affect many phenomena, from the disk heating, to radial migration. I will also show the effects of impacts of dark matter clumps on the disk as predicted by the current cosmological framework that can wobble the disk, heating it and eventually exciting ragged spiral arms. These models predict an "Arm Morphological Classification" of disk galaxies that can be immediately applied to the upcoming SDSS-IV MANGA surveys.

Speaker: Susan Craddock, Department of Gender, Women and Sexuality Studies, University of Minnesota
Subject: "Science, Patents, and Global Health: Contradictions of Tuberculosis Vaccine and Drug Development"
Refreshments served in Room 216 Physics at 3:15 p.m.

For the first time in over four decades, tuberculosis drugs are being developed again. A more effective vaccine for TB is being developed for the first time in almost a century. Why this is occurring now, both therapeutically and politically, is the main subject of this talk. Product Development Partnerships, or PDPs, constituting nonprofit organizations, academic researchers, philanthropic representatives, and pharmaceutical companies are collaborating on new treatments for several infectious diseases such as tuberculosis, considered to be "neglected" because they primarily affect low-income populations and are therefore not lucrative enough prospects for pharmaceutical industry attention. Besides the why now question, this talk will ask what happens scientifically and ethically to the research and development process when you largely untether the profit incentive from pharmaceutical production.

3:35 pm:
Speaker: Leon Hsu, University of Minnesota
Subject: Computers as problem-solving coaches for physics students

The potential of computers to help students learn by providing them with individualized guidance and feedback has long been recognized in education. In this talk, I briefly trace the history of computers in physics education, as well as the development of computers as intelligent tutors in education in general. I then discuss how these lines of development have
influenced the work of the Physics Education Research group at the University of Minnesota in creating computer coaches designed to help students develop more expert-like problem solving skills in the context of introductory physics.

4:40 pm:
Speaker: Jeremiah Mans, University of Minnesota
Subject: Particle Physics at the Energy Frontier

Monday, March 3rd 2014
Speaker: Tommy Hofer, UMN
Subject: New Results from SuperCDMS Soudan
Faculty Host: Lucy Fortson

Tuesday, March 4th 2014
11:15 am:
Nuclear Physics Seminar in 435 Physics
Speaker: Rajan Gupta, University of Minnesota
Subject: Designing energy and climate security in different regions of the world

Spectacular developments in technology and resource exploitation have provided 2-3 billion people with unprecedented lifestyles and opportunities in the twentieth century. On the energy front, this has largely been achieved using inexpensive fossil fuels-- coal, oil and natural gas. The real costs of burning fossil fuels, many of which are hidden and long-term, have been environmental. Today, all species and nature, are being stressed at unprecedented levels and face conditions that have an increasing probability of resulting in catastrophes. Providing the same opportunities to nine or ten billion people will require 2-3 times current energy resources even with business-as-usual anticipated gains in efficiency. There is little doubt that, globally, we have the resources (100 more years of fossil fuels) and the technology to use fossil-fuels ever more cleanly so that the impacts on the environment are small and localized. Unfortunately, the emissions of green house gases and their contributions to climate change mandate we transform this existing successful system.

This talk will examine energy resources in different regions of the world and address the issue of whether these resources can provide energy security for the next forty years. I will next examine how countries with enough resources (fossil, nuclear, hydroelectric) can reduce their carbon footprint in the power sector. I will then discuss the conditions needed to integrate large-scale solar and wind resources to create sustainable systems. Finally, I will identify areas which lack adequate reserves of fossil fuels and how they can address the simultaneous challenges of energy and climate security.

12:20 pm:
There will be no seminar this week, due to APS March Meeting.
12:20 pm:
Space Physics Seminar in 210 Physics
Speaker: Dr Joan Schmelz, NSF
Subject: Some Like it Hot: What Observations Can Tell Us About Solar Coronal Heating
The Space Physics Seminar will be hosted via Skype due to severe weather on the eastcoast.

The actual source of coronal heating is one of the longest standing unsolved mysteries in all of astrophysics. The million degree corona requires a permanent heating mechanism, or the gas would cool down in about an hour. Solar physicists agree that this mechanism involves the Sun’s magnetic field, but few agree on the details of how magnetic energy in translated into thermal energy. Coronal loops, their structure and sub-structure, their temperature and density details, and their evolution with time, hold the key to understanding this coronal heating mystery. A loop had always been thought of as a simple magnetic flux tube, where each position along the loop is characterized by a single temperature and density. Recent results, however, found that this simple picture could not explain the observations and a multi-thermal analysis was required. If we picture the loop as a tangle of magnetic strands instead of single flux tube, then the multi-thermal result is expected and even predicted by some classes of coronal heating models.

There will be no seminar today. See the Cosmology seminar on March 3rd.
2:30 pm:
Biophysics Seminar in 210 Physics
There will be no seminar this week.

Wednesday, March 5th 2014
3:35 pm:
Speaker: Gerrit L. Verschuur, University of Memphis
Subject: On the Relationship between Galactic HI Structure and Small-scale Structure in the Cosmic Microwave Background
Refreshments served in Room 216 Physics after colloquium

The archive of IRIS, Planck and WMAP data available at the IRSA website of IPAC allows us to look closely at the apparent associations between galactic neutral hydrogen (HI) features and small-scale structure in the CMB found in the WMAP data (previously reported in three ApJ papers). In addition, HI new observations made with the Green Bank Telescope with a resolution of 9 arcmin allow similar associations between HI structure and Planck data to be closely examined.

The talk will demonstrate the complex nature of nearby interstellar HI and its relationship to interstellar cirrus and the small-scale structure in high-frequency continuum emission (purported to be of cosmological origin). It is concluded that serious attention should be paid to the possibility that some or all of the small-scale structure found in WMAP and PLANCK data harbors the signature of a previously unrecognized source of high-frequency continuum emission arising in the Galaxy.

A little background regarding the speaker:

Dr. Verschuur is a radio astronomer who pioneered the study of the interstellar magnetic field. He has published extensively in the astronomical literature with over 90 refereed papers to his credit.He has also published 3 papers in the field of limnology. He is author or 8 books on popular astronomy and co-author and/or editor of 3 textbooks and has written over 80 magazine articles.In additon he is con-inventor on 11 patents. He conitnues to study the nature of interstellar neutral hydrogen structure and also serves as a consultant to WS Packaging of Algoma, WI, on a project involving paper tickets for slot-machines.

*Pioneered the measurement of the strength of interstellar magnetic field using the 21-cm Zeeman effect.

*Published 80+ papers regarding interstellar HI studies.

*Discoverer of the coldest known interstellar HI clouds (15 K).

*Published 8 books including “The Invisible Universe”, “Interstellar Matters” and “Hidden Attraction; The History and Mystery of Magnetism.” Co-authored or edited 3 textbooks, including “Galactic and Extra-Galactic Radio Astronomy,” as well as “Cosmic Evolution” with George field and Cyril Ponnamperuma.

Faculty Host: Kris Davidson

Thursday, March 6th 2014
Speaker: Mehdi Lame'e and Vihang Mehta
12:15 pm:
Speaker: Paolo Creminelli (ICTP)
Subject: Cosmological Consistency Relations
1:25 pm:
Condensed Matter Seminar in 210 Physics
There will be no seminar this week, due to APS March Meeting.

Friday, March 7th 2014
Speaker: Dr. Walter Brisken, NRAO
Subject: VLBI and some non-standard applications

Very Long Baseline Interferometry is a technique that coherently combines signals captured by widely separated radio telescopes for the purpose of exploring the radio sky at extremely high resolution. I will briefly describe VLBI and some of its common applications and then will describe three experiments that make use of VLBI equipment in unusual ways. First I will describe an experiment to image the scattering disk of pulsar B0834+06 using a global VLBI array. Second, I will describe the commensal V-FASTR transient search project. Finally, a novel use of a VLBI array for asteroid spin state determination will be discussed.

Speaker: E. Haven Hawley, Program in History of Science and Technology, University of Minnesota
Subject: "Mimeography: Constructing Culture through Reproduction"
Refreshments served in Room 216 Physics at 3:15 p.m.

The analysis of print artifacts provides a way to consider the role of print and technological access in the construction of Ukrainian national identity. Thousands of soldiers from the First Division of the Ukrainian National Army surrendered to British forces as the Soviet military swept westward in the closing weeks of World War II. Ukrainian prisoners produced an array of cultural print to accompany the courses, choirs and sporting clubs that they devised to uplift and unite internees. Publications wove the vision of Ukrainian independence deeply into camp culture, cementing relations between elite and illiterate soldiers. Through an archaeological method, these rare publications can be examined as evidence of the role of second-hand technologies in the construction of culture.

3:35 pm:
Speaker: Peter Bohacek, , Henry Sibley High School
Subject: Direct Measurement Videos in Physics Class

will present progress in the development of Direct Measurement Videos for physics instruction. We will highlight three aspects of the current project: our progress towards scalable, movable grids, rulers and protractors; how direct measurement videos can be used to support teaching science practices (such as the "Physics Face-off"); and the instructional support material available on our direct-measurement video project website. Of course, we’ll also show some of our newest direct measurement videos

4:40 pm:
There will be no seminar this week.

Monday, March 10th 2014
12:15 pm:
Speaker: Michel Janssen, UMN
12:20 pm:
Speaker: Dr. Julia Meyer, Grenoble
Subject: "Ac Josephson Effect in Topological Josephson Junctions"
Faculty Host: Alex Kamenev
Speaker: Gabriele Veneziano (College de France)
Subject: "Transplanckian collisions of particles, strings and branes"

I will give an overview on what we have learned so far on transplanckian-energy collisions of particles, strings, and branes, mention some open problems, and speculate on the lessons we may hope to draw in the near future from these gedanken experiments.


Tuesday, March 11th 2014
11:15 am:
Nuclear Physics Seminar in 435 Physics
Speaker: Clint Young, University of Minnesota
Subject: J/psi suppression and quarkonium spectral functions
12:20 pm:
Speaker: Andrew Galkiewicz, University of Minnesota
Subject: Resonance in Magnetostatically Coupled Transverse Domain Walls
12:20 pm:
Space Physics Seminar in 210 Physics
To be announced.
2:30 pm:
Biophysics Seminar in 210 Physics
There will be no seminar this week.
3:00 pm:
Speaker: Johannes Knolle, Max Planck Institute - Dresden
Subject: Dynamics of a two-dimensional quantum spin liquid: signatures of emergent Majorana fermions and fluxes
Faculty Host: Rafael Fernandes

Wednesday, March 12th 2014
3:35 pm:
Speaker: J.C. Seamus Davis, Cornell
Subject: Solving the Mystery of High Temperature Superconductivity
Refreshments served in Room 216 Physics after colloquium

We review the challenge of identifying a unified mechanism for Cooper Pairing in correlated superconductors e.g. copper-oxides, iron-arsenides and heavy-fermions. Our experimental context is atomic-scale visualization of electronic structure in each of these systems using STM. Because this technique can determine simultaneously the momentum-space (k-space) structure of the superconductivity and the real-space (r-space) structure of the proximate broken symmetry states, it provides some of the best indications of the fundamental issues in strongly correlated superconductivity research.

In copper-oxides there are two types of broken-symmetry states that can be visualized directly: the Q≠0 density waves (Science 315, 1380 (2007)) and Q=0 intra-unit-cell nematic (Nature 466, 374 (2010)). The concurrent k-space imaging using Fourier-transform STM reveals the evolution of the Fermi arcs with doping (Nature 454, 1072 (2008)). In iron-arsenides we discovered that there is also a Q=0 nematic state (Science 327, 181 (2010)), while k-space imaging revealed a fully detailed picture of the superconducting energy gaps (Science 336, 563 (2010)). And in heavy fermion superconductors, we achieved the first imaging of heavy fermions (Nature 465, 570 (2010)) and the first determination of k-space energy gap structure of any heavy fermion superconductor (Nature Physics 9, 468 (2013)).

At issue, then, is whether all these disparate observations could be related to each other within a unified mechanism of high temperature superconductivity? Motivated thus, we introduced a conceptual framework that can provide a simple unified explanation of the relationship between the antiferromagnetic electron-electron interactions, the exotic broken-symmetry phases and the correlated superconductivity -- for all of these distinct systems (PNAS 110, 17623 (2013)).

Faculty Host: Martin Greven

Thursday, March 13th 2014
Speaker: Tony Young and Amit Kashi
12:15 pm:
Speaker: TBA
1:25 pm:
Condensed Matter Seminar in 210 Physics
Speaker: J.C. Seamus Davis, Cornell
Subject: Evolution of Electronic Broken Symmetry and Fermi Surface Topology across the Cuprate Quantum Critical Point

See image below for abstract

Faculty Host: Martin Greven

Friday, March 14th 2014
Speaker: Dr. Lawrence Rudnick, MIfA
Subject: Shock and Slaw: Signs of Galaxy Cluster Formation
There will be no colloquium this week..
3:35 pm:
To be announced.
4:40 pm:
Post Doc Panel

Monday, March 17th 2014

Tuesday, March 18th 2014

Wednesday, March 19th 2014

Thursday, March 20th 2014
Speaker: No Journal Club - Spring Break
12:15 pm:
Speaker: No Seminar - Spring Break

Friday, March 21st 2014
Speaker: No colloquium

Monday, March 24th 2014
12:15 pm:
Speaker: Larry Rudnick, UMN
Subject: Cosmology with the SKA(0-1)

Tuesday, March 25th 2014
11:15 am:
Nuclear Physics Seminar in 435 Physics
Speaker: Abraham Reddy, University of Minnesota
Subject: "Two loop contributions for a QHD model with nonlocal interactions"
12:20 pm:
Speaker: Mun Chan, School of Physics and Astronomy, University of Minnesota
Subject: The cuprate phase diagram : insights from neutron scattering and electrical transport

After almost three decades of research, high-temperature superconductivity in the cuprates is as yet an unsolved but actively pursued problem. Besides the superconductivity, the pseudogap phenomenon, wherein parts of the Fermi surface is gapped at a temperature T* well above the superconducting temperature Tc, is perhaps the most enigmatic. The critical open question is whether the pseudogap is a distinct ordered state and if so, what is its relationship to the superconductivity. To shed light on this problem, I have focused my experimental efforts on HgBa2CuO4+δ (Hg1201), which is arguably one of the most desirable of the 100+ cuprates to study: it features a relatively simple crystalline structure and manifests the highest Tc of the single-layered cuprates (more than twice that of La2-xSrxCuO4 (LSCO), the most widely studied compound). I will present our recent efforts utilizing neutron scattering and electrical transport to study this model compound. Our primary result is the demonstration of a hierarchy of ordering tendencies including novel magnetism and its intimate relationship to commensurate antiferromagnetic fluctuations, charge-density-wave correlations, superconductivity, and the reconstruction of the Fermi-surface at low temperatures revealed by Shubnikov de Haas oscillations.

12:20 pm:
Space Physics Seminar in 210 Physics
Speaker: Xiangwei Tang, University of Minnesota
Subject: THEMIS observations of electrostatic ion cyclotron waves and associated ion heating near the Earth's dayside magnetopause
Speaker: Kanika Sachdev
Subject: Muon Neutrino to Electron Neutrino Oscillation Measurements with NOvA Experiment

The NuMI Off-Axis nu_e Appearance (NOvA) experiment, currently under construction, is a long-baseline neutrino oscillation experiment optimized for the measurement of nu_mu -> nu_e appearance. The experiment consists of two nearly identical liquid-scintillator tracking calorimeter detectors made of PVC, separated by 810 km and exposed to NuMI beam of muon neutrinos from Fermi National Laboratory. Goals of the experiment include measurements of theta_13, resolution of the neutrino mass hierarchy, measurement of the CP-violating angle delta_cp, and the octant of the theta_23 mixing angle.

This talk will provide an overview of the detectors, physics goals of the experiment, a look at commissioning data from the far detector and plans for the nu_mu to nu_e oscillation analysis.

Faculty Host: Yuichi Kubota

Wednesday, March 26th 2014
3:35 pm:
Speaker: Alessandra Lanzara, UC Berkeley, Materials Science Division, Lawrence Berkeley National Laboratory
Subject: Controlling superconductivity with light
Refreshments served in Room 216 Physics after colloquium

After almost twenty years from their discovery, high temperature superconductivity has defied any explanation. One of the reasons is that superconductivity in these novel materials emerges from other competing phases, manifested through the so called pseudogap-state, resulting in a delicate balance that evolves through the phase diagram with doping and temperature. Understanding how this balance takes place is certainly one of the biggest challenges of condensed matter physics today.

In this talk I will discuss some of our results in the area of photo-control in high temperature superconductors. I will discuss how superconductivity can be switched on and off through optical excitations, with focus on the complex relationship between pseudogap state and superconductivity.

The implications of these results for the next steps in our quest to understand the fundamental principles underlying the nature of the unconventional superconductivity in novel materials will be discussed.

Faculty Host: Martin Greven

Thursday, March 27th 2014
Speaker: Taryn Heilman and Liliya Williams
12:15 pm:
Speaker: John Kehayias
Subject: Charge Quantization and the Standard Model from Nonlinear Sigma Models

I will present recent work in collaboration with Tsutomu Yanagida and Simeon Hellerman (arXiv:1309.0692 and 1312.6889) on a new way to obtain charge quantization, without a GUT or monopole solution. In a CP^1 model, SU(2)_G/U(1)_H, consistency conditions for a charged field and its transformation properties over the entire group manifold lead to a charge quantization condition. By gauging the U(1)_H and identifying it with hypercharge, we find charge quantization in the SM without a monopole or GUT, purely from the structure and dynamics of the nonlinear sigma model. This is easily extended to CP^2 and general CP^k models. Phenomenologically, the CP^1 model has a fractionally charged stable Nambu-Goldstone boson (NGB), which has intriguing applications to nuclear physics and dark matter. The CP^2 model has the Higgs as the NGB, connecting to models with a flat Higgs potential at high scales. With some additional minor assumptions, anomaly freedom then leads to the matter content of a generation in the SM.

1:25 pm:
Condensed Matter Seminar in 210 Physics
Speaker: Alessandra Lanzara, UC Berkeley, Material Sciences Division, Lawrence Berkeley National Laboratory
Subject: Flipping out over topological insulators

The helical spin texture of surface electrons in topological insulator has attracted a great deal of interest in the past few years. Although this texture was predicted with the discovery of topological insulators and experimentally confirmed in in few points in the momentum space, its full experimental verification has been non trivial because of the low efficiency of spin resolved experiments.

In this talk I will present new compelling experimental findings where we discovered that photoelectrons emitted from the surface states of Bi2Se3, a typical 3D topological insulator, are nearly fully polarized, and moreover their spin orientation can be manipulated in three dimensions through selection of the light polarization. When the polarization is changed from linear to circular, photoelectrons can be tuned to
 be completely opposite to their original in-plane spin orientation, and even flipped to be out-of-plane, suggesting
 the possibility of full control by light.

These results challenge previous works in the field, which due to the lack of a comprehensive momentum dependent study of the spin texture because of the low efficiency of spin-resolved photoemission technique, made conclusions based on the incorrect assumption that electronic spin is always conserved through photoconversion. Finally, the manipulation of the highly polarized photoelectrons may mark an important step towards the longer-term goal of utilizing topological insulators for spintronics by using light control.

Faculty Host: Martin Greven

Friday, March 28th 2014
Speaker: Clifford Cheung (Caltech)
Subject: Naturalness and the Weak Gravity Conjecture

The weak gravity conjecture (WGC) asserts a powerful consistency condition on gauge theories coupled to quantum gravity: an Abelian, long-range force requires a state of charge q and mass m such that q>m/mPl. Failure of this condition implies the existence of stable black hole remnants and is in tension with no-hair theorems. In this paper, we argue that the WGC creates a non-perturbative obstruction to naturalness, which is the notion that dimensionless coefficients should take on (1) values in the absence of enhanced symmetry. As an illustration, we show that for scalar quantum electrodynamics, a natural spectrum can actually be forbidden by the WGC, which bounds a radiatively unstable quantity, m, by a radiatively stable quantity, q. More generally, the WGC can be at odds with naturalness in any theory containing charged fundamental scalars. We extend the conditions of the WGC to more complicated theories with multiple gauge symmetries and particles. Finally, we discuss implications for the hierarchy problem and construct a simple model in which the natural value of the electroweak scale - at the cutoff - is forbidden by the WGC.

Speaker: Dr. B.-G. Andersson, SOFIA Science Center
Subject: Progress-report on understanding interstellar grain alignment. Or: Why everything you learned in grad school [about this] is wrong.

The polarization caused by dust grains aligned with the magnetic field is potentially a powerful and cost-effective way to probe the magnetic field, both in terms of structure and strength. The main unknown in inverting the observed polarimetry into 3D maps of the magnetic field - particularly in dense material - is the mechanism for and variability of the grain alignment. I will give an update (to my talk at UMN 4 years ago) on the research we've been pursuing in observationally testing grain alignment theories. We have now been able to show that the classical Paramagnetic ("Davis-Greenstein") alignment mechanism is nor viable, but that, in contrast, that Radiative Alignment Torque (RAT) theory has faced and successfully met a number of specific observational challenges. An observationally well constrained theory of grain alignment will not only provide a efficient probe of the magnetic field but promises to also allow studies of grain characteristics environment, as I will also exemplify.

Speaker: Gregg Mitman, Department of Medical History and Bioethics, University of Wisconsin-Madison
Subject: "A Film Never Made: History, Science, and Memory in Liberia"
Refreshments served in Room 216 Physics at 3:15 p.m.

In 1926, Richard Pearson Strong, head of Harvard's Department of Tropical Medicine, led an eight-member scientific team to conduct a four-month long biological and medical survey of the interior region of Liberia. The expedition relied heavily on the economic, personnel, and physical infrastructures being erected by the Firestone Plantations Company to secure a viable rubber supply for the United States in Liberia. While Firestone's continued presence in Liberia is one lasting legacy of the expedition, so too is the motion picture record the expedition left behind. This talk embarks on a cinematic journey that follows the extracts of an expedition and the lives of a film never made, as the expedition footage takes on a new life in post-civil war Liberia.

3:35 pm:
Speaker: Bijaya Aryal, University of Minnesota
Subject: Problem solving and transfer of learning in an integrated instructional model

In this presentation I will discuss an instructional model used in a physics course. This model is expected to provide students with a platform for developing their scientific literacy and for building up essential scientific knowledge and skills for life-long learning relevant to their future careers and everyday life. I will highlight the integration of problem-solving activities and transfer of learning activities in the model with a goal to help improve students' skills in the respective areas. In addition, I will present my study regarding student difficulties in these areas with a goal to integrate evidence-based strategies to address them.

4:40 pm:
There will be no seminar this week.

Monday, March 31st 2014
12:15 pm:
There will be no seminar this week.

Tuesday, April 1st 2014
11:15 am:
Nuclear Physics Seminar in 435 Physics
Speaker: Rajan Gupta, Los Alamos National Laboratory
Subject: Designing energy and climate security in different regions of the world

Spectacular developments in technology and resource exploitation have provided 2-3 billion people with unprecedented lifestyles and opportunities in the twentieth century. On the energy front, this has largely been achieved using inexpensive fossil fuels-- coal, oil and natural gas. The real costs of burning fossil fuels, many of which are hidden and long-term, have been environmental. Today, all species and nature, are being stressed at unprecedented levels and face conditions that have an increasing probability of resulting in catastrophes. Providing the same opportunities to nine or ten billion people will require 2-3 times current energy resources even with business-as-usual anticipated gains in efficiency. There is little doubt that, globally, we have the resources (100 more years of fossil fuels) and the technology to use fossil-fuels ever more cleanly so that the impacts on the environment are small and localized. Unfortunately, the emissions of green house gases and their contributions to climate change mandate we transform this existing successful system. This talk will examine energy resources in different regions of the world and address the issue of whether these resources can provide energy security for the next forty years. I will next examine how countries with enough resources (fossil, nuclear, hydroelectric) can reduce their carbon footprint in the power sector. I will then discuss the conditions needed to integrate large-scale solar and wind resources to create sustainable systems. Finally, I will identify areas which lack adequate reserves of fossil fuels and how they can address the simultaneous challenges of energy and climate security.

12:20 pm:
Speaker: Joe Sobek, University of Minnesota
Subject: Tuning the Iron Selenide Superconducting Transition
12:20 pm:
Space Physics Seminar in 210 Physics
Speaker: Kris Kersten, University of Minnesota
Subject: RBSP observations and test particle simulations of whistler waves and electron acceleration in the radiation belts
2:30 pm:
Biophysics Seminar in 210 Physics
There will be no seminar this week.

Wednesday, April 2nd 2014
3:35 pm:
Speaker: Oleg Lavrentovich, Liquid Crystal Institute, Kent State University
Subject: Lyotropic chromonic liquid crystals: From viscoelasticity to topological turbulence
Refreshments served in Room 216 Physics after colloquium

Lyotropic chromonic liquid crystal ((LC)2 or simply chromonics) represent dispersions of organic molecules in water that self-organize into orientationally ordered phases thanks to non-covalent reversible aggregation [1]. Since the aggregates are bound by weak van der Waals forces, their length varies strongly with concentration, temperature, ionic content. The (LC)2 are thus very dif-ferent from a standard thermotropic LC with molecules of covalently fixed shape and from a lyo-tropic LC formed by polymers of fixed molecular weight. The presentation discusses (1) concentra-tion and temperature behavior of viscoelastic properties of chromonics [2]; (2) symmetry breaking effects during phase transitions (chiral tactoids and proliferation of topological defects) [3] and (3) chromonics as the basis of living liquid crystals [4]. The studies of living liquid crystals reveal a wealth of new intriguing dynamic out-of-equilibrium phenomena, caused by the coupling between the bacteria activity-triggered flow and long-range orientational order of the medium. Among these are: (a) non-linear trajectory of the bacteria controlled by distorted director fields; (b) local melting of (LC)2 by the rotating flagella; (c) birefringence enabled visualization of the motion of nanometer thick flagella; (d) activity-induced transition from an equilibrium state of a uniaxially aligned ne-matic to low-Reynolds-number turbulence through a periodically distorted nematic with a macro-scopic length scale that depends on the elastic moduli and activity. The work is supported by NSF grants DMR 1104850 and 1121288.

References
1. H.-S. Park et al, In: Liquid Crystals Beyond Displays (2012) John Wiley & Sons, New Jersey, Editor Q. Li, pages 449-484.
2. S. Zhou et al, Phys. Rev. Lett. (2012) 109, 037801.
3. Y.-K. Kim, S.V. Shiyanovskii, O.D. Lavrentovich, J. Phys.: Condens. Matter (2013) 25, 404202.
4. S. Zhou et al, Proc. Nat. Acad. Sci. (USA) (2014) 111, 1265.

Faculty Host: Jorge Vinals

Thursday, April 3rd 2014
Speaker: Karl Young and Larry Rudnick
12:15 pm:
Speaker: Vitaly Vanchurin (U. Minnesota-Duluth)
Subject: Hydrodynamics of Strings
1:25 pm:
Condensed Matter Seminar in 210 Physics
Speaker: Oleg Lavrentovich, Liquid Crystal Institute, Kent State University
Subject: Liquid Crystal Enabled Electrokinetics

Electrokinetic phenomena in liquid crystals (LCs) show a number of distinct features not met in the isotropic media, thanks to the long-range orientational order and ensuing anisotropy of physical properties such as ionic mobility, elasticity and viscosity [1]. The electric field causes hydrodynamic flows and transport of particles by various mechanisms: dielectric torque-triggered backflow [2], LC-enabled dielectrophoresis [2], LC-enabled electrophoresis (LCEP) [3] and LC-enabled electro-osmosis (LCEO) [4]. LCEP and LCEO are rooted in broken symmetry of the medium. Namely, a spherical particle placed in a uniform nematic, causes director distortions of the dipolar type. Because of anisotropy of ionic mobility, the director distortions break the symmetry of the field-induced ionic flows. As a result, free colloidal particles move with a velocity that is proportional to the square of the applied electric field, Fig.1. A similar effect of liquid crystal – enabled electro-osmosis occurs when the nematic flows past a spherical obstacle. Micro particle image velocimetry establishes the angular and radial dependencies of electro-osmotic flows around particles with different symmetry of director distortions. The LCEP and LC-enabled electro-osmosis are nonlinear phenomena that are complementary to the induced charge electrokinetics. The important difference is that the symmetry breaking that enables the transport is caused by the medium rather than by a particle itself. The difference allows one to transport particles that are symmetric (for example, spherical droplets of water shaped by surface tension) and particles that are only weakly polarizable (glass, polymers, etc.). By controlling the properties of the LC (such as director orientation and sign of dielectric anisotropy) and the particle, one can design various 3D trajectories and move the particles from one location to another along a curvilinear path.

The work is supported by NSF DMR 1104850 grant.

References
1. O. D. Lavrentovich, Soft Matter 2014, 10, 1264.
2. O. P. Pishnyak, S. V. Shiyanovskii, O. D. Lavrentovich, Phys. Rev. Lett. 2011, 106, 047801.
3. O. D. Lavrentovich, I. Lazo and O. P. Pishnyak, Nature 2010, 467, 947; I. Lazo, O. D. Lavrentovich, Phil. Trans. Royal Society A 2013, 371, 20120255.
4. I. Lazo, S. Shiyanovskii, O. D. Lavrentovich, Submitted, 2014.
5. T.M. Squires, M.Z. Bazant, J. Fluid Mech. 2004, 509, 217.

Faculty Host: Jorge Vinals

Friday, April 4th 2014
Speaker: Dr. Andy Skemer, U Arizona
Subject: Imaging Exoplanets with the LBT

By directly imaging extrasolar planets, we can study the compositions, atmospheric properties and interiors of gas-giant planets, and eventually, the surfaces of rocky planets. The current generation of directly imaged planets are abnormally warm, and future exoplanet studies will target cooler, "normal" planets, which emit the majority of their light in the mid-infrared (>3 microns). At these wavelengths, the Large Binocular Telescope is unique in its capabilities as a high-contrast exoplanet imager. I will describe a multi-faceted program at the LBT to study planets in the mid-infrared where we are (1) executing a large survey to search for new exoplanets, using instrumentation that is sensitive to lower-mass and smaller separation exoplanets than were visible to previous surveys, (2) studying the properties of the small number of massive, widely-separated exoplanets that are currently accessible to direct imaging, and (3) developing new optics and instrumentation to improve our ability to discover and characterize exoplanets.

3:35 pm:
Speaker: Carla Fehr, Department of Philosophy, University of Waterloo
Subject: "Ignorance, Excellence, and Diversity: Improving the Representation of Women and Minorities in Science, Technology, Engineering and Mathematics"
Refreshments served in Room 275 Nicholson Hall at 3:15 p.m.

Women and members of some minority groups are underrepresented in Science, Technology, Engineering and Mathematics (STEM). I argue that in addition to this being an ethical problem, it hurts the creativity and rigour of scientific and technological research. This talk draws on philosophical accounts of the social nature of scientific work, and on qualitative and quantitative research regarding women and minorities in the academy. I explore issues of diversity in STEM in ways that are both policy-relevant and that advance our understanding of the structures of scientific research communities.

3:35 pm:
To be announced
4:40 pm:
Speaker: Rafael Fernandes, University of Minnesota
Subject: Theory of correlated materials: from high-temperature superconductors to quantum magnets

Monday, April 7th 2014
12:15 pm:
There will be no seminar this week.

Tuesday, April 8th 2014
11:15 am:
Nuclear Physics Seminar in 435 Physics
Speaker: Cheng-Hsien Li, University of Minnesota
Subject: Wave-Particle Duality in Long Baseline Neutrino Experiments

The establishment of our understanding of neutrinos requires combined efforts of theorists and experimentalists. Theorists view neutrinos as waves in calculating physical observables, while experimentalists view them as point particles in calibrating flux and simulating event rate. An interesting question then arises whether the wave-particle duality can always be taken for granted or not. The long baseline experiments provide a scenario to test the duality.It is a quantum-mechanical phenomenon that neutrino wave packets will expand in the transverse direction when they propagate in space, while the Lorentz boost restrict neutrinos from meson decays in the forward direction. Our analysis shows that if the angular size of the wave packet exceeds the characteristic angle of meson decay, the duality in the event rate may not exist and a distortion of the energy spectrum is possible. Treating the initial size of the neutrino wave packet as a free parameter, we present the total event rate and energy spectra predicted in the near and far detectors with a simplified pion beam and geometric configurations similar to the MINOS and Nova experiments. Possible conflict between the wave and particle pictures emerges if the transverse size of the neutrino wave packet is localized to O(10 fm) in pion decay.

12:20 pm:
Speaker: Xiaowei Zhang, University of Minnesota
Subject: Development of giant saturation magnetization FeN thin film
12:20 pm:
Space Physics Seminar in 210 Physics
Speaker: Dr. John Dombeck, University of Minnesota
Subject: Statistical results of auroral electron precipitation mechanisms and Important facets of Heliophysics research proposal writing
2:30 pm:
Biophysics Seminar in 210 Physics
Speaker: Jesse McCaffrey, Biochem, Molec Biol/Biophysics, University of Minnesota
Subject: SERCA-PLB Structural Dynamics and Orientation by EPR Spectroscop

In muscle cells, contraction and relaxation are regulated by intracellular calcium, which is transported through the cell by the SR calcium ATPase (SERCA). In cardiac muscle cells, SERCA activity is inhibited by binding of phospholamban (PLB), though this inhibition is relieved by phosphorylation of PLB. The mechanism for this inhibition is unknown, so I use electron paramagnetic resonance (EPR) in conjunction with site-directed spin-labeling to study the structural dynamics of SERCA, PLB, and the SERCA-PLB complex. I will present results on SERCA and PLB homo/hetero-association, as well as orientation studies that help elucidate the SERCA-PLB interaction as affected by phosphorylation


Wednesday, April 9th 2014
3:35 pm:
Speaker: Tim Tait, UC-Irvine
Subject: Searches for Particle Dark Matter
Resfreshments will be served in Room 216 Physics after collquium

Dark Matter is all around us, a clear sign of physics beyond the Standard Model, and yet we will have not understood what it
is and how it fits into the larger picture. In this talk, I will discuss what we know about dark matter and how different kinds of searches, including searches for its collision with heavy nuclei, production at accelerators, and signs of its annihilation in our galaxy, combine together to give us information about how it (doesn't) interact with ordinary matter. The picture that will emerge is one where different searches complement each other, offering rich opportunities to understand the nature of dark matter in the near future.

Faculty Host: Priscilla Cushman

Thursday, April 10th 2014
Speaker: Kyle Neary and Melanie Galloway
12:15 pm:
Speaker: Andreas Karch (University of Washington)
Subject: Entanglement and Holography

Holography is an equivalence between an ordinary quantum field theory and a classical theory of gravity. The spacetime of the gravitational theory can be viewed as emerging out of the quantum dynamics of the dual field theory. I'll describe recent advances that suggest that entanglement plays a crucial role in encoding the emergent geometry in the field theory. These new connections may help shed light on our understanding of entanglement in strongly coupled system as well as on our understanding of the basics of holography.

1:25 pm:
Condensed Matter Seminar in 210 Physics
Speaker: Senthil Todadri, MIT
Subject: Are non-fermi liquids stable to pairing?

Quantum criticality is often implicated for both the breakdown of Fermi liquid theory and the superconductivity seen in many correlated metals. In this talk I will describe recent progress in studying these issues theoretically in two dimensional metals pushed close to the onset of nematic order which breaks crystal rotation but not translation symmetries. Controlled calculations show that superconductivity is strongly enhanced near such quantum critical points. If time permits I will describe some other contrasting examples where superconductivity is suppressed.


Friday, April 11th 2014
Speaker: Dr. R. van Weeren, CFA
Subject: Exciting Physics with Merging Galaxy Clusters

Merging galaxy clusters are excellent laboratories to study particle acceleration in dilute cosmic plasmas, to explore the nature of dark matter, and to investigate galaxy cluster growth. In a few dozen merging galaxy clusters diffuse extended radio emission has been found, implying the presence of relativistic particles and magnetic fields in the intracluster medium. A major question is how these particles are accelerated up to such extreme energies. In this talk I will present X-ray and radio observations of merging clusters, providing new clues about the acceleration mechanism and extending radio studies to higher redshifts. I will also show the latest results from the new revolutionary low-frequency telescope LOFAR, allowing observations of diffuse cluster emission with unprecedented resolution and sensitivity.

Speaker: Elaine Leong, Max Planck Institute for the History of Science
Refreshments served in Room 216 Physics at 3:15 p.m.

Recipes, whether medicinal, alchemical, culinary or technical, occupied a central place within the transmission and circulation of practical household knowledge. The large number of manuscript recipe collections still extant in the archives is suggestive of their ubiquity within the early modern domestic sphere. Modern readers often marvel at the thousands of similar yet slightly different remedies contained in these notebooks. A glance at any pre-modern recipe collection frequently yields a handful of recipes for the same ailment or several versions of well-known recipes such as 'lucatella's balsam' or 'Dr Steven’s water'. Comparison of individual recipes reveals that the variants differ slightly with minute changes in methods, ingredients and use. A second puzzling feature of early modern recipes lies in the fact that many of these similar recipes are attributed to different authors creating what to modern eyes is a complex web of information.

This paper intends to address these two distinctive features of manuscript recipe collections through an investigation of the compilation process. Analysis of individual notebooks and of the marks left by readers and users demonstrate that pre-modern recipe collections were created through a simple three-step process. The process began with the gathering of recipes from practitioners, family, friends and printed books. The collected information was then tested for efficacy and suitability to the compiler's household. If deemed a success, the recipe was assimilated into the household's trusted trove of practical knowledge. During this process, compilers often customized the recipes to suit the requirements and needs of their families. This personalization may take the form of ingredient substitution, the use of a preferred production method or even an outright rejection of the suggested procedure. After these modifications, the recipe, now bearing the name of a different author, re-enters the recipe exchange circuit as a new recipe and as 'new' knowledge. I argue that this three-step process of recipe compilation is in itself a process of knowledge production. After all, these tidbits of practical hands-on knowledge were tried, tested by personal experience and altered (or rejected) accordingly. Tweaking, I suggest, is creating. The recovering of these processes allows us to further understand informal knowledge production within early modern households. Early modern homes, it turns out, were vibrant sites for knowledge codification.

Cosponsored by the Institute for Advanced Study

3:35 pm:
Speaker: Scot Hovan, Mahtomedi High School
Subject: Facilitating Discourse

Although the Next Generation Science Standards (NGSS) Science and Engineering Practices incorporate the role of discourse in science instruction, few teacher-training programs instruct teachers how to facilitate discourse in the classroom. This research presents a high school physics teacher’s self-study of his experiences facilitating discourse in an attempt to move students closer to those practices espoused by the NGSS.

4:40 pm:
To be announced.

Monday, April 14th 2014
12:15 pm:
Speaker: Kam Arnold, UC San Diego
Subject: Results from Polar Bear on Lensing B-modes.

Tuesday, April 15th 2014
11:15 am:
Nuclear Physics Seminar in 435 Physics
Speaker: Zhen Yuan, University of Minneota
Subject: Halo Evolution and Chemical Enrichment of Fornax Dwarf Spheroidal Galaxy

Recent observations provided detailed star formation history as well as elemental abundances in Fornax Dwarf Spheroidal Galaxy. Knowing how these small galaxies evolved is crucial to unraveling the formation and evolution of the Milky Way. I utilized the two data sample to reconstruct the halo evolution and chemical enrichment history of Fornax. I will show a consistent story from my semi analytic model and 2-D simulation results.

12:20 pm:
Speaker: Yilikal Ayino, University of Minnesota
Subject: Metal Insulator Transition in STO
12:20 pm:
Space Physics Seminar in 210 Physics
Speaker: Aaron Breneman, University of Minnesota
Subject: First experimental verification of loss cone scattering of energetic electrons by whistler mode hiss in the plasmasphere
Speaker: Matt Fritts
Subject: Seeking Neutrinoless Double-Beta Decay with CdZnTe Detectors

The observation of neutrinoless double-beta decay (0n2b) would prove the Majorana nature of neutrinos and provide a measurement of the absolute neutrino mass scale. The COBRA experiment is looking for 0n2b using CdZnTe crystals as both source and detector. I will discuss some details of coplanar grid CdZnTe detectors and report on the progress of a small-scale prototype operating in the Gran Sasso underground laboratory.

2:30 pm:
Biophysics Seminar in 210 Physics
There will be no seminar this week.

Wednesday, April 16th 2014
3:35 pm:
Speaker: Chandra Varma, UC Riverside
Subject: Higgs Bosons in Superconductors, in Cold Bosons, and Elsewhere
Refreshments served in Room 216 Physics after colloquium

Spurred by some strange experimental observations in some superconductors, the theory of a new collective mode in superconductors and how it can be experimentally found very easily under certain circumstances was provided in 1981. It was called the "Amplitude Mode" to distinguish it from the "Phase Modes" which provide Josephson effects and which in homogeneous superconductors are coupled to charge fluctuations and are at the energies of the plasmons. More generally, this mode is the amplitude mode of a particle-hole symmetric U(1) field, i.e the model treated by Higgs and others in the1960's whose generalizations have played an important role in the standard model of particle physics.

I will tell the story of the above and why such modes were missed in the theory of superconductivity for so long and the applications of the ideas about such modes for cold bosons and fermions in optical lattices and in quantum anti-ferromagnets. I will also comment, as a very interested outsider and an enthusiast, on the Higgs in particle physics being discovered at LHC from the point of view of the theory of superconductivity.

Faculty Host: Martin Greven
4:40 pm:
Senior Honors Thesis in 236A Physics
Speaker: Isaiah Gray, University of Minnesota
Subject: AC Magnetic Susceptibility in a Thin Film of Permalloy

Thursday, April 17th 2014
Speaker: Soroush Sotoudeh
12:15 pm:
Speaker: Lam Hui (Columbia University)
Subject: "Symmetries in Large Scale Structure"

We will discuss the role of symmetries in three different
areas of large scale structure: 1. how to test the equivalence principle
using black holes in centers of galaxies; 2. how to measure gravitational
redshifts using parity-violating signatures in correlation functions;
3. how spontaneously broken symmetries give us fully non-perturbative
relations between N- and N+1-point functions.

1:25 pm:
Condensed Matter Seminar in 210 Physics
Speaker: Chandra Varma, UC Riverside
Subject: Deciphering relevant Phases competing with Superconductivity in Cuprates and in Other Compounds
Faculty Host: Martin Greven

Friday, April 18th 2014
Speaker: Clem Pryke, University of Minnesota
Subject: Detection of B-mode Polarization at Degree Angular Scales
Note change of location, this week only. Refreshments served in the lobby of the Physics and Nanotechnology Building after the colloquium.

The theory of Cosmic Inflation postulates that our entire observable universe
was spawned from a minute quantum fluctuation in an incredibly brief burst of
hyper expansion. Using data from a specialized radio telescope called BICEP2
operating from the South Pole in Antarctica our collaboration recently
reported direct evidence that Inflation actually occurred. By making super
sensitive polarized maps of the after glow of the Big Bang we infer the
existence of gravitational waves launched into the fabric of space time in
that first instant of creation - the long sought "smoking gun" for inflation.

Speaker: Suzanne Moon, Department of the History of Science, University of Oklahoma
Subject: Thinking through Technology and Religion: Industrialization and Islam in New Order Indonesia
Refreshments served in Room 216 Physics at 3:15 p.m.

In the late 1980s and early 1990s, a group of Indonesian Muslim intellectuals, including engineers, doctors, and physicists, advocated that Muslims consider the significance of Indonesian technological development for Islam, and of Islam for both Indonesian and global trajectories of scientific and technological change. Arguing that the spiritual devotion of Islamic engineers and scientists, and their involvement in complex modern technologies, held the key to producing a more harmonious and socially just technoscientific order, they aimed to influence state policies, cultural assumptions, and individual technical and religious practices. By articulating moral critiques of contemporary industrial societies, they asserted a meaningful relationship between technological practices and spiritual devotion, challenged the presumptive trajectories of industrialization in Indonesia, and posited scientists and engineers as a kind of technocracy for the global community of believers.

3:35 pm:
Speaker: Yao Meng, University of Minnesota
Subject:  My TA experience in the tutoring room--what why and how
4:40 pm:
Speaker: Dan Dahlberg, University of Minnesota
Subject: Magnetic Microscopy

Monday, April 21st 2014
12:15 pm:
Speaker: Alberto Dominguez, University of California, Riverside
Subject: The measurement of the expansion rate of the Universe from gamma-ray attenuation

We discuss the detection of the cosmic gamma-ray horizon (CGRH) that is independent of any extragalactic background light (EBL) model, which allows us to measure the Hubble constant by using gamma-rays. The CGRH is a fundamental quantity in cosmology. It gives an estimate of the opacity of the Universe to very-high energy (VHE) gamma-ray photons due to photon-photon pair production with the EBL. Our CGRH detection is possible thanks to a multiwavelength catalog of blazars that includes the latest data analysis from the Fermi satellite and Cherenkov telescopes. Interestingly, the observed CGRH is compatible with the current knowledge of the EBL. We show how the detection of the CGRH allows us to measure the expansion rate of the Universe from gamma-ray attenuation. The value of the Hubble constant that we derive is compatible with present-day measurements using well established methods such as local distance ladders and cosmological probes. We also discuss an observational strategy aimed to reduce the uncertainties in the Hubble constant estimate from our novel and independent technique.

Faculty Host: Lucy Fortson
4:40 pm:
Senior Honors Thesis in 236A Physics
Speaker: Ryan Frink, University of Minnesota
Subject: Superconducting fluctuations in the high-Tc cuprate superconductor LSCO

Tuesday, April 22nd 2014
11:15 am:
Nuclear Physics Seminar in 435 Physics
Speaker: Menquan Liu, University of Minnesota
Subject: Electron Capture in Type II Supernovae and npe± System

The electron capture plays a very important role in Type II supernovae and other astrophysical situations. In this seminar, I will show how electron screening affects the electron capture for a single nucleus and the whole collapse process during evolution by using a 1-D numerical simulation code. I also will introduce a new chemical potential equilibrium formula, mu_n=mu_p+C*mu_e(C maybe 2 or some else), for a steady system composed by neutron, proton, electron and positron except our familiar formula: mu_n=mu_p+mu_e. It sounds strange but it really exists. As example, the new formula is applied to the GRB accretion disk and neutrino-driven wind from proto-neutron stars.

12:20 pm:
Speaker: Gaurav Shukla, University of Minnesota
Subject: High Temperature Elasticity of Iron and Aluminum-bearing MgSiO3 Perovskite: A First Principles Study
12:20 pm:
Space Physics Seminar in 210 Physics
There will be no seminar this week so that group members can attend Scott Thaller's thesis defense.
2:30 pm:
Biophysics Seminar in 210 Physics
There will be no seminar this week.
3:00 pm:
Thesis Defense in 435 Physics
Speaker: Scott Thaller, University of Minnesota
Subject: The storm time evolution in the night-side, high-altitude, field-aligned wave Poynting flux and its relation to low altitude downward electron kinetic energy flux at low latitudes.

Wednesday, April 23rd 2014
3:35 pm:
There will be no Colloquium this week due to the PAN Grand Opening
4:40 pm:
Thesis Defense in 236A Physics
Speaker: Noah Trebesch, University of Minnesota
Subject: A Computational Method for Investigating Bifurcations in Oscillatory Biochemical Reaction Networks

Thursday, April 24th 2014
11:00 am:
Grand Opening Open House in Physics and Nanotechnology Building
Session I of the open house runs from 11 a.m.-2 p.m., Session II runs from 4-7 p.m.
Speaker: Kyle Dolan and Claudia Scarlata
12:15 pm:
Speaker: Xingang Chen (Cambridge, DAMTP)
Subject: "Standard Clock in Primordial Density Perturbations and Cosmic Microwave Background"

Experimentally distinguishing different primordial paradigms that could lead to the Big Bang model is an outstanding challenge in modern astrophysics and cosmology. In this talk we introduce a novel type of observables that can be used as an independent and direct evidence for the inflation paradigm or other possible alternatives. These signals are induced by Standard Clocks in the primordial epoch, and are capable of directly recording the scale factor of the primordial universe as a function of time a(t), which is the defining property of different paradigms. We present an interesting candidate in the Planck data, which has all the characteristics of inflation.

Speaker: Ilana Percher / Quentin Ebner (University of Minnesota)
Subject: Using Dissipation to Tune Superconductivity in Ultra Thin Films / Observation of Microwave Induced Resistance Oscillations in 2D Hole Ge/SiGe Heterostructures
There will be no seminar this week.

Friday, April 25th 2014
Speaker: Dr. Aline Kiessling, JPL
Subject: Measuring Dark Energy to 1% Accuracy Using Cosmological Simulations

The nature of dark energy, thought to be driving the accelerating expansion of the Universe, is one of the most compelling mysteries in all of science. Determining the equation of state of dark energy to 1% accuracy is currently a leading goal for many planned cosmological surveys such as NASA’s Wide-Field Infrared Survey Telescope (WFIRST), ESA’s Euclid and the Large Synoptic Survey Telescope (LSST). Numerical simulations of structure formation are required to make predictions for these surveys and to help mitigate systematics. My SUNGLASS pipeline (Simulated UNiverses for Gravitational Lensing Analysis and Shear Surveys) is able to produce Monte Carlo suites of numerical simulations and rapidly generates mock weak lensing galaxy shear catalogues. These catalogues are being used to investigate astrophysical systematics, to generate accurate covariance matrices that account for the non-linear nature of the Universe and as an integral part of end-to-end image simulation pipelines – each element being essential to the measurement of the dark energy equation of state to 1% in future telescope missions. In this talk, I will discuss SUNGLASS and its vital role in dark energy telescope mission development and analysis.

3:35 pm:
Speaker: Richard Zach, Department of Philosophy, University of Calgary
Subject: "Carnap and Logic in the 1920s and 1930s"
Refreshments served in Room 275 Nicholson Hall at 3:15 p.m.

During the hey-day of the Vienna Circle, Rudolf Carnap pursued two technical projects in logic: the first was the general axiomatics program, in which he attempted to develop a general theory of axiomatized systems within the framework of the type theory of Principia mathematica. The second was the program of Logical Syntax. A proper understanding of the relationship of these projects, their relevance to the development of Carnap's though and the development of metamathematics, is best obtained by viewing it in the context of the broader history of logic at the time, e.g., the work of Tarski and Gödel.

3:35 pm:
Speaker: Brita L. Nellermoe, University of Minnesota and University of St. Thomas
Subject: PER Research Methods and Current Research Overview

This presentation will describe the main types of research used in PER and give current examples of each type of research. Research types include: case studies, phenomenology, and mixed methods as well as quantitative methods.

4:40 pm:
Speaker: Greg Pawloski, University of Minnesota
Subject: Ethics in Research, Part 1

Monday, April 28th 2014
12:15 pm:
Speaker: Michael Rutkowski, UMN
4:40 pm:
Senior Honors Thesis in 236A Physics
Speaker: Yang Ge, University of Minnesota
Subject: X-ray Absorption Study of Doped Holes in High-Temperature Superconductor HgBa2Cu4+δ

Tuesday, April 29th 2014
11:15 am:
Nuclear Physics Seminar in 435 Physics
Speaker: Zhu Li, University of Minnesota
Subject: Parametric study of astrophysical conditions for nucleosynthesis

The origin of trans-iron elements remains a great challenge due to the complexity resulting from the interplay between nuclear physics and astrophysics. The parametric method, which is a site-free model, allows us to study the nucleosynthesis and get a glimpse of the physics hidden behind the distribution of elemental abundances. We analysed the key factors in adiabatic expansion, which is the common zeroth order approximation for many violent astrophysical events, and will show how the nuclear physics comes into this scenario.

12:20 pm:
Speaker: Bern Youngblood, University of Minnesota
Subject: Temperature dependence of two-level noise in magnetic particles
12:20 pm:
Space Physics Seminar in 210 Physics
Speaker: Adam Hupach, University of Minnesota
Subject: To be announced.
Speaker: Roger Rusack
Subject: HGCAL - A silicon-based high granularity calorimeter for the HL-LHC

HGCAL is one of two options that CMS is considering for high-luminosity LHC era to deal with a large number of parasitic collisions which will obscure interesting physics signatures unless properly dealt with. Prof. Rusack is spearheading this effort.

2:00 pm:
Thesis Defense in 2-102 CMRR
Speaker: Jinjin Zhang, University of Minnesota
Subject: Development of frequency-modulated techniques for MRI of fast relaxing spins
This the public portion of Ms. Zhang's thesis defense.
2:30 pm:
Biophysics Seminar in 210 Physics
There will be no seminar this week.
3:35 pm:
Senior Honors Thesis in 236A Physics
Speaker: Tanner Lange, University of Minnesota
Subject: Z' Search in ATLAS eµ Events

Wednesday, April 30th 2014
3:35 pm:
Speaker: Simon Billinge, Columbia
Subject: How the cat got its stripes, and how hard it is to see them: search for fluctuating local C2 symmetry states in correlated oxides
Refreshments served in Room 216 Physics after colloquium

Broken local symmetry states may be important for understanding the properties of a wide range of systems from high temperature superconductors to traditional charge density wave (CDW) materials. But these broken symmetries can be hard to find and even harder to characterize. It too 8 years from the initial discovery of high-Tc to observe charge stripes in La2-xBaxCuO2, and an additional 17 years to see them conclusively in other cuprate systems. I will discuss why they are so hard to see, but show progress that we are making in
both detecting them and characterizing their nature, and the range of temperature and doping where they are observed. In particular, I will describe the use of the atomic pair distribution function (PDF), a bulk average probe that is, nonetheless, sensitive to the local structure. I will describe how we can use this to get information about local elecronic broken symmetry states, and how combining information from spectroscopy provides greater insight. A surprising picture emerges with locally symmetry broken states existing over fairly wide ranges of doping and temperature in a number of systems. This is interesting if fluctuating short-range ordered broken symmetry states are important for materials properties or for understanding emergent properties such as superconductivity. We demonstrate a correlation between the observation of such features in the local structure and both transport and spectroscopic signatures.

Faculty Host: Martin Greven
4:40 pm:
Senior Honors Thesis in 236A Physics
Speaker: Johannes (Kevin) Nangoi, University of Minnesota
Subject: Photo-induced Conductance Changes in Composite nc-Ge/a-Si:H Thin Films

Thursday, May 1st 2014
09:00 am:
Correlated Oxides and Oxide Interfaces workshop in Mississippi Room, Coffman Memorial Union

8:40 am
Registration

8:55 am
Welcome and opening Remarks
Martin Greven and Alex Kamenev
University of Minnesota

9:00 am
Quasiparticle thermalization and recombination in cuprate superconductors
Joseph Orenstein
University of California, Berkeley

9:30 am
Theory of nonlinear phononics for coherent light-control of solids
Antoine Georges
Collège de France

10:00 am
Searching for pairing interactions with coherent charge fluctuations spectrocopy
Jose Lorenzana
ISC-Sapienza, Rome

10:30 am
COFFEE BREAK

11:00 am
The cuprate phase diagram: new insights from neutron scattering and electrical transport
Mun Chan
University of Minnesota

11:30 am
Intrinsic Superconducting Phases in Single-layer Cuprates
Zhong-Xian Zhao
Institute of Physics, Chinese Academy of Sciences, Beijing

12:00 pm
The cuprate phase diagram from NMR
Jürgen Haase
Universitat Leipzig

12:30 pm
LUNCH BREAK

2:00 pm
Fermi Surface and Pseudogap Evolution in a Cuprate Superconductor
Jennifer Hoffman
Harvard University

2:30 pm
Fermi-surface-free Superconductivity in Bi2201
Robert Markiewicz
Northeastern University

3:00 pm
COFFEE BREAK

3:30 pm
The explicit Role of O states in high oxidation state strongly correlated oxides George Sawatzky
University of Brithish Columbia

4:00 pm
Design of correlated metals without inversion symmetry
James Rondinelli
Drexel University

4:30 pm
"Molecules" in solids and orbital-selective Peierls transition
Daniel Khomskii
Universitat zu Koln

5:00 pm
Workshop Ends for the Day

Speaker: Karlen Shahinyan and Lucy Fortson
12:15 pm:
Speaker: Andrew Spray (U. Melbourne)
Subject: New Limits on Light Hidden Sectors from Fixed-Target Experiments

New physics can be light if it is hidden, coupling very weakly to the Standard Model. In this work we investigate the discovery prospects of Abelian hidden sectors in lower-energy fixed-target and high-precision experiments. We focus on a minimal supersymmetric realization consisting of an Abelian vector multiplet, coupled to hypercharge by kinetic mixing, and a pair of chiral Higgs multiplets. This simple theory can give rise to a broad range of experimental signals, including both commonly-studied patterns of hidden vector decay as well as new and distinctive hidden sector cascades. We find limits from the production of hidden states other than the vector itself. In particular, we show that if the hidden Abelian symmetry is higgsed, and the corresponding hidden Higgs boson has visible decays, it severely restricts the ability of the hidden sector to explain the anomalous muon magnetic moment.

1:25 pm:
Condensed Matter Seminar in 210 Physics
There will be no seminar this week because of the Correlated Oxides and Oxide Interfaces workshop
5:30 pm:
Honor's Thesis in 110 PAN
Speaker: Matthew Epland, University of Minnesota
Subject: Simulation Studies of Proposed Upgrades to the ATLAS Detector Tracker

Friday, May 2nd 2014
09:00 am:

9:00 am
Search for hidden broken local symmetry states in correlated electron systems
Simon Billinge
Columbia University

9:30 am
Novel multiorbital magnetic insulators arising from the interplay of correlations and spin-orbit coupling
Nandini Trivedi
Ohio State University

10:00 am
COFFEE BREAK

10:30 am
Competing superexchange interactions in osmate double perovskites
Patrick Woodward
Ohio State University

11:00 am
Topolological 2DEG at the 111 surface of KTaO3
Marc Gabay
Université Paris-Sud

11:30 am
Topological Phases in Transition Metal Oxides
Gregory Fiete
University of Texas, Austin

12:00 pm
LUNCH BREAK

1:30 pm
Exotic magnetism produced by strong spin-orbit coupling in complex Ir oxides
Hidenori Takagi
Max Planck Institute and University of Tokyo

2:00 pm
Topological and Magnetic Phases with Strong Spin-Orbit Coupling in the Hyperhoneycomb Iridates
Yong-Baek Kim
University of Toronto

2:30 pm
Critical properties of the Kitaev-Heisenberg model
Natalia Perkins
University of Wisconsin, Madisson

3:00 pm
COFFEE BREAK AND POSTER SESSION

5:00 pm Workshop ends

09:00 am:
Thesis Defense in Physics 435
Speaker: Kyle Neary
Subject: Star Formation Histories of the Large and Small Magellanic Clouds
This is the public portion of Mr. Neary's PhD thesis defense
Speaker: Dr. Dan Wiesz, U California - Santa Cruz
Subject: The Star Formation Histories of Local Group Dwarf Galaxies

I will present new insights into the evolution of faintest known galaxies in the
universe from my recent work on uniformly measuring the star formation histories
(SFHs) of 40 Local Group dwarf galaxies based on archival Hubble Space Telescope
imaging. The galaxy sample spans a wide range in stellar mass (10^4 < M< 10^9
Msun) and includes all morphological types found in the Local Group, making it the best available sample to understand how low mass galaxies form and evolve. I will explore the apparent tensions between the SFHs of Local Group dwarfs and those modeled and observed from observations of the higher redshift universe. I will also discuss the various processes that are thought to quench low mass galaxies such as cosmic reionization and tidal stripping, and highlight the complexity associated with how low mass galaxies go from star-forming and gas-rich to quiescent and gas-poor.

Speaker: Catherine Jackson, John J. Reilly Center, University of Notre Dame
Subject: Chemist’s Labour’s Lost: A History of Organic Chemistry in Four Acts
Refreshments served in Room 216 Physics at 3:15 p.m.

Existing histories of nineteenth century chemistry speak of atoms and the theories of valence, structure and stereochemistry. These are histories of theory and application, told through great men and great moments. And they have left us without a history of one of the nineteenth century’s most powerful and productive sciences: synthetic organic chemistry. This talk presents a disciplinary history of organic synthesis built on chemical practice. By studying what chemists did in long days at the laboratory bench, we see how they came to know substance and reaction in ways that ultimately enabled them to produce specified target substances by synthesis. Chemists summarized this knowledge as theory. But if we take chemical theories to be synonymous with chemical knowledge, we too are summarizing what nineteenth century chemists knew rather than explaining how they knew it.

3:35 pm:
Speaker: Jia-Ling Lin, STEM Center, University of Minnesota
Subject:  How Do Group Discussions Foster Meaningful Learning in “Flipped Classrooms”?

“Flipping classrooms” is an emerging instructional approach that replaces traditional lectures with other learning activities during in-classroom periods. Recently, it has drawn increasing interest. Just as with any new instructional models that are intended to improve STEM education, the effectiveness of non-traditional “flipped classrooms” needs to be tested.

The current study focuses on research questions concerning how students learn. We examined impacts that the new instructional model, particularly in-classroom discussions, had on student learning. Group discussions were observed during the semester, and were audio taped towards the end. A framework based on a modified taxonomy was created to analyze students’ “utterances”. It is evident that problem-centered pedagogy engages students in collaborative dialogues during group discussions. The established discourse in group discussions functions as a heuristic teaching and learning tool that facilitates learning of content knowledge and skills in a profound way. Theoretic concepts and practices of classroom discourse development will be discussed.

4:40 pm:
There will be no seminar this week.

Saturday, May 3rd 2014
09:00 am:

9:00 am
Reconstructions in Magnetic Oxide Heterostructures
Harold Hwang
Stanford University

9:30 am
Strong Electron Correlations in Oxide Quantum Wells
Susanne Stemmer
University of California, Santa Barbara

10:00 am
Emergent Magnetic Phenomena at Complex Oxide Interfaces
Yuri Suzuki
Stanford University

10:30 am
COFFEE BREAK

11:00 am
Local Electrostatic Imaging of Striped Domain Order in LaAlO3/SrTiO3
Shahal Ilani
Weizmann Institute

11:30 am
Magnetism of oxide interface LaAlO3/SrTiO3
Lu Li
University of Michigan

12:00 pm
Chiral magnetism at oxide interfaces and 2D materials
Mohit Randeria
Ohio State University

12:30 pm
LUNCH BREAK
Lunch is on your own.
Please refer to the dining guide in the back of this booklet for options.

2:00 pm
Orbital and Spin Order in t2g Two-Dimensional Electron Gases
Allan MacDonald
University of Texas at Austin

2:30 pm
Rashba Spin-Orbit Effect at the Oxide Interfaces
Sashi Satpathy
University of Missouri

3:00 pm
MBE Growth and Study of Electronic Transport of NdTiO3/SrTiO3 Heterostructures via Stoichiometry Control
Bharat Jalan
University of Minnesota

3:30 pm
COFFEE BREAK

4:00 pm
Critical dopings and superconducting domes in bulk SrTiO3
Kamran Behnia
ESPCI, Paris

4:30 pm
Metal-insulator transition in doped STO and puzzles of LAO/STO interface
Boris Shklovskii
University of Minnesota

5:00 pm
Understanding the Conductivity and Magnetism at Interfaces of Insulating Nomagnetic Oxides: The case of SrTiO3/LaAlO3
Liping Yu
University of Colorado

5:30 pm
Workshop ends for the day


Sunday, May 4th 2014
09:00 am:

9:00 am
Dimensional Confinement and Epitaxial Strain as Knobs for Manipulating Correlated Electronic States in Complex Oxide Thin Films
Kyle Shen
Cornell University

9:30 am
Complex Magnetotransport Phenomena in Ultra-Thin Film La0.5Sr0.5CoO3-d on SrTiO3
Chris Leighton
University of Minnesota

10:00 am
COFFEE BREAK

10:30 am
Magnetism and electronic reconstruction at interfaces probed by resonant soft x-ray spectroscopies
Giacomo Ghiringhelli
Politecnico di Milano

11:00 am
Understanding Interfaces as a Route to Control the Orbital Degree of Freedom in Cuprates
John Freeland
Argonne National Laboratory

11:30 am
Electrostatic Modification of Cuprate Superconductors
Allen Goldman
University of Minnesota

12:00 pm
Closing Remarks
TBA

12:45 pm
Workshop Closing
Thank you for your participation


Monday, May 5th 2014
12:15 pm:
Speaker: Geertje Heuermann, Karlsruhe Institute of Technology
Subject: Direct Dark Matter detection with the EDELWEISS and EURECA experiment

Tuesday, May 6th 2014
11:15 am:
Nuclear Physics Seminar in 435 Physics
Speaker: Pamela Vo, University of Minnesota
Subject: Predicting the First Stars From Abundance Patterns of Ultra-Metal Poor Stars
The first generation of stars formed from pristine gas of Big Bang composition. When these stars exploded as supernovae, they provided the interstellar medium with the first metals, and the next gener

The first generation of stars formed from pristine gas of Big Bang composition. When these stars exploded as supernovae, they provided the interstellar medium with the first metals, and the next generation of stars formed from this chemically-enriched gas. Preserved within the atmospheres of these metal-poor stars is the chemical signature of the supernova(e) that polluted their birth cloud. I will discuss the process of fitting abundance patterns of low-metallicity stars to the abundance yields from supernova models of progenitor stars, in order to predict the best progenitors.

12:20 pm:
There will be no sack lunch seminar this week.
12:20 pm:
Space Physics Seminar in 210 Physics
Speaker: Charles McEachern, University of Minnesota
Subject: Modeling Pi2 Pulsations in a Dipole Field - Progress and Plans
Speaker: Marcello Mannelli, CERN
Subject: Physics at the LHC and the HL-LHC

The CERN Large Hadron Collider (LHC) will resume operations in 2015 with proton-proton collisions at an energy between 13 and 14 TeV. After an accumulation of around 300 fb^-1 of data, the LHC will be upgraded to the HL-LHC to deliver even higher luminosities. At this upgraded machine the total anticipated luminosity is 3000 fb^-1 allowing for highly sensitive measurements. In this talk I will describe the potential physics measurements and observations at the LHC and the physics motivations for the High-Luminosity LHC.

1:30 pm:
Speaker: Michael Veit, University of Minnesota
Subject: Transport Measurements in the Cuprate Superconductor HgBa2CuO4+δ
2:30 pm:
Biophysics Seminar in 210 Physics
Speaker: Filippo Caschera, University of Minnesota
Subject: Experimental strategies towards the assembly of an artificial cell

The total synthesis of an artificial cell, a complex system that does not exist in nature, represents a big challenge for the synthetic biology community. There are several reasons why scientists are trying to achieve this goal. The original motivations were mainly epistemological, in particular related to the origin of life and to understand what is life. However, with the advent of synthetic biology we started building for understanding the fundamental principles behind natural design and evolution. I am trying to design and construct an artificial cell in laboratory following a bottom-up approach. In particular, through a modular design based on the integration of three modules: container, metabolism and information. I will present different experiments describing the assembly and characterization of chemical and biological components into functional modules. Worldwide, different research groups have presented several experimental designs. However, the integration of the modules into a functional unit, i.e. an artificial cell, has failed. This is mainly due the complexity of the design where non-trivial interactions among the system’s components are preventing a priori prediction of the emerging properties. As a strategy, I am exploring different types of containers with distinctive properties that potentially could lead to artificial cell models, either based on lipid vesicles or oil droplets. In addition, I aim to apply a machine learning approach to interlock all the system components in a functional way. I aim to design and construct an evolvable artificial cell to exploit life’s principles (selfmaintenance, self-reproduction and evolvability) to promote technological innovation. Therefore to generate new drug delivery systems or produce valuable compounds for medical and industrial applications. In conclusion, lipid vesicle fusion, oil droplets dynamics (fusion and division), selforganization of prebiotic amphiphiles, in vitro metabolisms for steady-state production of ATP and finally a machine learning approach to optimize the properties of complex lipid mixtures and cell-free expression systems will be presented. In the future, I aim to design robust modules that can be efficiently integrated to synthesize an evolvable artificial cell.

4:00 pm:
Senior Honors Thesis in 236A Physics
Speaker: Christopher Nolting, University of Minnesota
Subject: Fitting DARKexp predictions to dark matter halo profiles from simulation

Wednesday, May 7th 2014
3:35 pm:
Speaker: Misha Shifman, University of Minnesota
Subject: High Energy Physics: What's happening and where are we heading
Refreshments served in Room 216 Physics after colloquium

Professor Shifman will give a broad nontechnical review of the current status of high energy physics from theorist’s perspective.

Faculty Host: Mikhail Shifman
4:40 pm:
Senior Honors Thesis in 236A Physics
Speaker: Max Veit, University of Minnesota
Subject: Stochastic Simulation of Genetic Regulatory Networks

Thursday, May 8th 2014
Speaker: Melanie Noble and Kristy McQuinn
12:15 pm:
Speaker: Emanuel Katz (Boston University)
Subject: Effective Conformal Dominance and a New Approach to Solving a Gauge Theory

I will consider the case of a CFT deformed by a relevant perturbation
resulting in a mass gap. I will argue that in such a case, operators of
high scaling-dimension can decouple exponentially quickly from low-energy
bound states. This observation motivates a new way of solving strongly
coupled theories. In particular, I will describe the method applied to 2D
QCD-like theories both at large and at small N.


Friday, May 9th 2014
12:00 pm:
Thesis Defense in 210 PAN
Speaker: Abe Reddy, University of Minnesota
Subject: Nonlocal Field Theories at Finite Temperature and Density.
This the public portion of Mr. Reddy's thesis defense.
There will be no colloquium this week.
There will be no colloquium this week.
3:35 pm:
Speaker: Carolyn Rauber, University of Minnesota Libraries
Subject: Information Literacy in Physics and Astrophysics
To be announced.

Information literacy is, according to the Association of College and Research Libraries, "a set of abilities to identify the need for information, procure the information, evaluate the information and subsequently revise the strategy for obtaining the information, to use the information and to use it in an ethical and legal manner." I'll be talking about opportunities that I have identified to develop these abilities in physics students at UMN, the challenges therein, and my approach to teaching students about critically engaging with the information systems they encounter.

4:40 pm:
Speaker: Greg Pawloski, University of Minnesota
Subject:  Ethics in Research, Part 2

Monday, May 12th 2014

Thursday, May 15th 2014
12:15 pm:
Speaker: Tony Zee (UCSB)
Subject: Galactic Neutrino Communication
2:00 pm:
Thesis Defense in 110 PAN
Speaker: Derrick Toth, University of Minnesota
Subject: Measurement of non-DDbar decays of the psi(3770) resonance at BESIII
This is the public portion of Mr. Toth's defense.

The psi(3770) resonance is the first ccbar resonance above open-charm threshold and has a much larger width than the lower mass charmonium resonances. It is expected to decay predominantly to open-charm DDbar final states, with only a couple percent branching fraction to non-DDbar final states. However, inclusive branching fraction measurements of psi(3770) -> non-DDbar vary quite a bit, in a range from zero to fifteen percent. We present a measurement of the branching
ratio of e+e- -> psi(3770) -> non-DDbar hadrons at center-of-mass energy 3.773 GeV using data taken with the BESIII detectora as well as a measurement of the DDbar production cross section at this energy.


Friday, May 16th 2014
4:30 pm:
Congratulations Graduating Seniors!

Monday, May 19th 2014
1:00 pm:
Thesis Defense in 210 Physics
Speaker: Dan Endean, University of Minnesota
Subject: The Origin of Magnetic Noise in Square Nanoscale Magnetic Dots
This the public portion of Mr. Endean's thesis defense.
Speaker: Boris Ermolaev - (Ioffe Institute)
Subject: “New Approach to QCD Factorization”

Tuesday, May 20th 2014
12:20 pm:
Speaker: Mun Chan, University of Minnesota
Subject: The cuprate phase-diagram: insights from electrical transport and neutron scattering

Friday, May 23rd 2014
09:00 am:
Thesis Defense in 435 Physics
Speaker: Jianjie Zhang, University of Minnesota
Subject: A Dark Matter Search Using the Final CDMS-II Data and 100 mm SuperCDMS Ge Detector Ionization Test
This the public portion of Mr. Zhang's thesis defenser

The data of the CDMS II final runs were reprocessed with improved charge reconstruction algorithm. The dark matter search result from a reanalysis of the data will be presented. As part of the development effort for the next generation SuperCDMS detectors, the ionization test of the 100 mm diameter germanium detectors will also be discussed.

3:00 pm:
Thesis Defense in PAN 120
Speaker: Aaron Smith, University of Minnesota
Subject: Ebert-Fastie Spectral Response Measurements and Simulation for EBEX Calibration
This is the public portion of Mr. Smith's defense.

I will be talking about simulations and measurements for an Ebert-Fastie Spectrometer and how they compare to one another. This involves use of reflective diffraction gratings and theoretical simulations of such gratings. This information is important as a calibration device for the EBEX CMB experiment.


Friday, May 30th 2014
12:00 pm:
Speaker: Hannes Hubmayr, NIST
Subject: Continuum polarimetry from the millimeter to the far-IR

Monday, June 2nd 2014
2:30 pm:
The School of Physics and Astronomy cordially invites you to a gathering to welcome our 2014 REU participants. Please stop by to say hello and enjoy some refreshments!

Wednesday, June 11th 2014
Speaker: Kevin Klapoetke
Subject: Measurements of Z Transverse Momentum Shape Using a Novel Variable at the CMS Detector

The understanding of transverse momentum of the Z boson in a proton-proton collision is important, and yet at low values, measurements of transverse momentum are not in agreement with proposed models. This talk describes a measurement of the physics behind the transverse momentum of the Z boson using a novel variable (phi-star) that increases the precision of the analysis beyond that of a conventional transverse momentum measurement.


Friday, June 13th 2014

Monday, June 16th 2014

Tuesday, June 24th 2014
1:00 pm:
Thesis Defense in 210 Tate
Speaker: Chad Geppert, University of Minnesota
Subject: Electromotive force generated by spin accumulation in ferromagnet/n-GaAs heterostructures
This the public portion of Mr. Geppert's thesis defense.

Friday, July 4th 2014

Monday, July 7th 2014
2:00 pm:
Thesis Defense in PAN 110
Speaker: Chien-Te Wu, University of Minnesota
Subject: Proximity Effects in Ferromagnet/Superconductor Layered Heterostructures with Inhomogeneous Magnetization
This is the public portion of Mr. Wu's PhD thesis defense

Wednesday, July 9th 2014
1:30 pm:
Thesis Defense in 435 Physics
Speaker: Tianran Chen, University of Minnesota
Subject: Disorder Effects on Electron Transport in Nanocrystal Assemblies and Topological Insulators.
This the public portion of Ms. Chen's PhD thesis defense.

Friday, July 11th 2014

Monday, July 14th 2014

Monday, July 21st 2014
08:00 am:
NOvA Collaboration Meeting in various locations in Tate and PAN

Tuesday, July 22nd 2014
08:00 am:
NOvA Collaboration Meeting in various locations in Tate and PAN
10:00 am:
Academic Calendar in NHH 2-101 
Speaker: Jesse McCaffrey, Biochem, Molec Biol/Biophysics, University of Minnesota
Subject: Elucidating the Structural Dynamics of SERCA-PLB Regulation by Electron Paramagnetic Resonance
This is the Public Portion of Mr. McCaffrey's thesis defense

In muscle cells, contraction and relaxation are regulated by intracellular calcium, which is transported by the SR calcium ATPase (SERCA). In cardiac muscle cells, SERCA activity is inhibited by binding of phospholamban (PLB), though this inhibition is relieved by phosphorylation of PLB during adrenaline response. The mechanisms for this inhibition and relief of inhibition are unknown, so I use electron paramagnetic resonance (EPR) in conjunction with site-directed spin-labeling to study the structural dynamics of SERCA, PLB, and the SERCA-PLB complex. I will present results on SERCA and PLB homo/hetero-association, as well as orientation studies that help elucidate the SERCA-PLB interaction as affected by phosphorylation.


Wednesday, July 23rd 2014
08:00 am:
NOvA Collaboration Meeting in various locations in Tate and PAN

Thursday, July 24th 2014
08:00 am:
NOvA Collaboration Meeting in various locations in Tate and PAN

Friday, July 25th 2014
08:00 am:
NOvA Collaboration Meeting in various locations in Tate and PAN
11:00 am:
Speaker: Andrew W. Howard, Institute for Astronomy, University of Hawaii - Manoa
Subject: Earth-sized Exoplanets

The Kepler Mission has taught us that Earth-sized planets in the Habitable Zones of Sun-like stars are common and that many Earth-sized planets have rocky compositions. Three recent results highlight these remarkable properties of Earth-sized planets. First, our team measured the mass of the planet Kepler-78b, the first Earth-sized planet with a measured mass and radius outside of the Solar System. The bulk density of 5 grams per cubic centimeter suggests a rocky composition with an insubstantial atmosphere, similar to Earth. In a separate project, we showed that high densities are common for small exoplanets. Planets smaller than about 1.5 times Earth-size are mostly rocky, while thick gas atmospheres envelop most larger planets. Finally, our team estimated that 22 percent of Sun-like stars have a planet that is 1-2 times the size of Earth orbiting in the Habitable Zone. Warm, Earth-sized planets appear to be common.


Saturday, July 26th 2014
08:00 am:
www.physics.umn.edu/events/AAPT.html?

Sunday, July 27th 2014
08:00 am:
www.physics.umn.edu/events/AAPT.html?

Monday, July 28th 2014
08:00 am:
www.physics.umn.edu/events/AAPT.html?

Tuesday, July 29th 2014
08:00 am:
www.physics.umn.edu/events/AAPT.html?

Wednesday, July 30th 2014
08:00 am:
www.physics.umn.edu/events/AAPT.html?

Wednesday, August 6th 2014
09:00 am:
Please stop by and view Powerpoint presentations by the students in the 2014 REU program, poster session ends at 2:00 p.m.

Thursday, August 7th 2014
12:00 pm:
REU Poster Session in 110 PAN
Please stop by and view posters by the students in the 2014 REU program, poster session ends at 1:30 p.m.
1:00 pm:
Speaker: Dr. Kyung-Won Suh
Subject: A catalog of AGB stars, and models for silicate carbon stars
Dr. Suh works on dust shell models for evolved stars and is a former Astronomy graduate student here at the UofM

Kyung_Won's recent research has been pushing our understanding of mass loss in evolved stars into the realm of 3D modeling. He will be in Tom Jones' office (369 Tate) during his visit


Friday, August 8th 2014

Wednesday, August 13th 2014
2:00 pm:
Thesis Defense in 435 Physics
Speaker: Mike Schecter, University of Minnesota
Subject: Dynamics of Mobile Impurities in One-Dimensional Quantum Liquids

We study the dynamics of mobile impurities in a one-dimensional quantum liquid. Due to singular scattering with low-energy excitations of the host liquid, the impurity spectral properties become strongly renormalized even at weak coupling. This leads to universal phenomena with no higher-dimensional counterparts, such as lattice-free Bloch oscillations, power-law threshold behavior in the impurity spectral function and a quantum phase transition as the impurity mass exceeds a critical value. The additional possibility of integrability in one-dimension leads to the absence of thermal viscosity at special points in parameter space. The vanishing of the phonon-mediated Casimir interaction between separate impurities can be understood on the same footing.

We explore these remarkable phenomena by developing an effective low-energy theory that identifies the proper collective coordinates of the dressed impurity, and their coupling to the low-energy excitations of the host liquid. The main appeal of our approach lies in its ability to describe a dynamic response using effective parameters which obey exact thermodynamic relations. The latter may be extracted using powerful numerical or analytical techniques available in one-dimension, yielding asymptotically exact results for the low-energy impurity dynamics.

Speaker: Joe Pastika
Subject: Search for a Heavy Right-Handed W Boson and Heavy Neutrino of the Left-Right Symmetric Standard Model

The search for direct production of a heavy right-handed WR- boson, which decays to a right-handed neutrino N(l)(l=e,mu) consistent with a left-right symmetric extension to the standard model, will be presented. The search was conducted using the full 19.7 fb - 1- of proton-proton collision data collected at a center of mass energy of \sqrt{s}=8 TeV by the Compact Muon Solenoid detector at the Large Hadron Collider. The search is conducted in a final state containing two same-flavor leptons and two jets. No significant deviation from the standard model is observed in either channel. 95% confidence level exclusion limits on the disallowed region in the plane of WR- mass versus right-handed neutrino mass are set for the electron and muon channel that extends up to 3 TeV in WR- mass and exclude most neutrino masses below the mass of the WR- . The electron and muon channel data is also combined assuming degenerate right-handed neutrino masses.


Friday, August 15th 2014
11:00 am:
"Electrostatic Screening in Nanostructures" in Room 435 Tate Laboratory 
Speaker: A. V. Chaplik, Rzhanov Institute of Semiconductor Physics, Novosibirsk, Russia
Faculty Host: Boris Shklovskii
1:30 pm:
Thesis Defense in 110 PAN
Speaker: Kyle Zilic, University of Minnesota
Subject: Calibration and Design of the E and B EXperiment (EBEX) Cryogenic Receiver
This the public portion of Mr. Zilic's thesis defense.

Thursday, August 21st 2014
2:00 pm:
Thesis Defense in 435 Physics
Speaker: Sean Bartz, University of Minnesota
Subject: Meson Spectra from a Dynamical Three-Field Model of AdS/QCD
This is the public portion of Mr. Bartz's thesis defense.

Gauge/gravity dualities are tools that allow the analytic analysis of strongly-coupled gauge theories. The Anti-de Sitter Space/Conformal Field Theory conjecture posits a duality between ten-dimensional string theory and a super Yang-Mills theory. A phenomenologically-motivated modification of this correspondence is known as AdS/QCD, a duality between strongly-coupled QCD-like theories and weakly-coupled gravitational theories in an additional dimension. Quantum chromodynamics (QCD) is not scale-invariant, so the dual theory must be modified in the conformal dimension to reflect this.

I will discuss soft-wall models of AdS/QCD, wherein the conformal symmetry is broken by a field known as a dilaton. The dynamics of the dilaton and other background fields are examined, and a potential for these fields is determined. The background fields are numerically derived from this potential and used in the calculation of meson spectra, which match well to experiment.


Friday, August 22nd 2014

Sunday, August 24th 2014
Speaker: Dr. Enrique Rodriguez, U Texas-San Antonio

Monday, September 1st 2014

Tuesday, September 2nd 2014
Speaker: Mike Veit, University of Minnesota
Subject: Transport Measurements in the Cuprate Superconductor HgBa2CuO4+δ

Wednesday, September 3rd 2014
1:25 pm:
Nuclear Physics Seminar in 435 Physics
Subject: Organizational Meeting

Friday, September 5th 2014
Subject: There will be no seminar this week.

Monday, September 8th 2014
12:15 pm:
Speaker: Tim Eifler, JPL
Subject: Constraining Cosmology and Dark Energy Models with the Dark Energy Survey

The Dark Energy Survey (DES) has recently started its second season of
Observations; so far it covers ~1800 square degrees (23.5 mag i-band).
This high quality data set will be extended to 5000 square degrees (24 mag i-band) over the next 4 years and it poses new challenges for the precise
modeling of observables of the Universe's Large-Scale Structure (LSS),
and its astrophysical and observational systematics.

The tightest constraints on cosmology from DES data will be obtained from
a joint analysis of all probes (e.g., weak lensing, galaxy clustering, and
magnification) that can be extracted from the DES data set. Such joint
analyses face several difficulties: First, the cosmological information is
highly correlated, which requires a joint likelihood including all cross
correlations between the individual probes. Second, even more problematic
are the correlations of various systematic effects originating from
astrophysics and the measurements themselves.

In this talk I will give an introduction to the DES collaboration and
ongoing and future DES projects. I will describe the CosmoLike code
framework that we have developed for a joint likelihood analysis of
multiple cosmological probes extracted from DES data. This multi-probe DES
analysis is an excellent starting point to prepare for challenges of
future cosmological data sets from LSST, Euclid, and WFIRST.


Tuesday, September 9th 2014
Speaker: Qianhui Shi, University of Minnesota
Subject: Strongly anisotropic transport in a Ge/SiGe quantum well in tilted magnetic fields
12:20 pm:
Space Physics Seminar in 210 Physics
Speaker: Scott Thaller:, University of Minnesota
Subject: The Van Allen Probes Convection Electric Field and Inner Magnetospheric Dynamics
There will be no seminar this week.
2:30 pm:
Biophysics Seminar in 210 Physics
There will be no seminar this week.

Wednesday, September 10th 2014
1:25 pm:
Nuclear Physics Seminar in 435 Physics
Speaker: Yong-Zhong Qian (UMN)
Subject: Neutrino-Induced Nucleosynthesis in He Shells of Early Supernovae

Proto-neutron stars produced by core-collapse supernovae emit neutrinos and antineutrinos of all three flavors for approximately 10 s. These neutrinos can produce neutrons through spallation of alpha particles, which dominate the composition of the He shell of the supernova. Both light nuclei such as 7Li and 9Be and heavy nuclei up to the actinides can be produced through subsequent neutron capture. I will discuss how this neutrino-induced nucleosynthesis depends on neutrino physics, neutron-capture cross sections, initial metallicity of the supernova progenitor, and supernova explosion energy. Comparison with observations of elemental abundances in metal-poor stars will be presented.

3:35 pm:
Speaker: Greg Aldering, Lawrence Berkeley Laboratory, University of California
Subject: Some Fault is in our Stars: Bias on the Road to Cosmological Concordance
Refreshments served in Room 216 Physics after colloquium

The discovery of the accelerating expansion of the Universe, driven by a mysterious ``dark energy'', was based on measurements of the relative brightnesses of stellar explosion known as Type Ia supernovae (SNe Ia). SNe Ia remain the leading tool for measuring the dark energy equation of state, w, due to their statistical power, the great distances to which they can be measured, and the complementarity of SNe Ia and cosmic microwave background (CMB) constraints. In this talk I will describe current efforts to hone SNe Ia as cosmological tools. These efforts have found new ways to improve the statistical power of SNe Ia, but have also unearthed previously unrecognized biases due to the behavior of SNe Ia. Correction for one of these biases reduces the Hubble Space Telescope (HST) measurement of the Hubble constant, bringing it significantly closer to the value inferred from Planck and WMAP CMB measurements. It also is likely that current measurements of w are affected by these biases at the level of several percent. I will close with a description of a new large HST program that will significantly increase the number of SNe Ia in the redshift range 1 < z < 2, with the goal of measuring time variation in w such as that suggested by recent Lyman-alpha forest baryon acoustic oscillation measurements.

Faculty Host: Roberta Humphreys

Thursday, September 11th 2014
Speaker: Dr. Stephen Odewahn, McDonald Observatory
Subject: Integral Field Spectroscopy with the Upgraded Hobby-Eberly Telescope
12:15 pm:
Speaker: Howard Baer
Subject: Radiatively-driven supersymmetric naturalness with implications for LHC, ILC, axion and WIMP detection
1:25 pm:
Condensed Matter Seminar in 210 Physics
Speaker: Erez Berg, Weizmann Institute of Sciences, Israel
Subject: Coherent Transmutation of Electrons into Fractionalized Anyons

Electrons have three quantized properties – charge, spin, and Fermi
statistics – that are directly responsible for a vast array of
phenomena. Here we show how these properties can be coherently and
dynamically stripped from the electron as it enters certain exotic
states of matter known as quantum spin liquids (QSL). In a QSL,
electron spins collectively form a highly entangled quantum state that
gives rise to emergent gauge forces and fractionalization of spin,
charge, and statistics. We show that certain QSLs host distinct,
topologically robust boundary types, some of which allow the electron
to coherently enter the QSL as a fractionalized quasiparticle, leaving
its spin, charge, or statistics “at the door.” We use these ideas to
propose a number of universal, “smoking-gun” experimental signatures
that would establish fractionalization in QSLs.

Faculty Host: Andrey Chubukov

Friday, September 12th 2014
Speaker: Dr. Jeff Larsen, USNA
Subject: Reflections from a Glassy Sea: The Beauty, Hazard and Utility of the Near-Earth Asteroids as Examined Through the Spacewatch Project
Speaker: Martin Summers, Department of History, African and African Diaspora Studies Program, Boston College
Subject: 'A Maze of Unintelligibility': Psychotherapy and African American Patients at Saint Elizabeths Hospital, 1900-1940
Refreshments served in Room 216 Physics at 3:15 p.m.

With its emphasis on the individualization of mental disease, dynamic psychiatry held out the promise of more efficacious treatment modalities. If psychiatrists could get beneath the surface of patients' symptoms and understand their "meanings and values," then they had a better chance of facilitating mentally ill individuals' readjustment to their social environments. This talk is an examination of the use of psychotherapy on African American patients at Saint Elizabeths Hospital, a federal mental institution in Washington, D.C., in the early twentieth century. The psychiatrists and nurses engaged with these patients in ways that both revealed a concern for their mental well-being and a deep sense of racial antipathy. African American patients were not merely objects of medical scrutiny and targets of institutional management however. They interacted with the staff in ways that challenged the medical authority to not only determine the clinical encounter, but to establish particular truth claims about black insanity as well.

Speaker: Shaul Hanany, University of Minnesota

Monday, September 15th 2014
12:15 pm:
There will be no seminar this week.

Tuesday, September 16th 2014
Speaker: Samuel Ducatman, University of Minnesota
Subject: Magnetic order of FeTe Compounds
12:20 pm:
Space Physics Seminar in 210 Physics
To be announced.
To be announced.
2:30 pm:
Biophysics Seminar in 210 Physics
Speaker: Marc Riedel, University of Minnesota
Subject: Towards a Computer Engineering Discipline based on DNA

Just as electronic systems implement computation in terms of voltage (energy per unit charge), molecular systems compute in terms of chemical concentrations (molecules per unit volume). In this talk, we present novel constructs for logical and arithmetic functions such as addition, multiplication, exponentiation, and logarithms with molecular reactions. Building on these results, we present a general methodology for implementing synchronous sequential computation. A four-phase clock signal is generated through robust, sustained chemical oscillations. Memory elements are implemented by transferring concentrations between molecular types in alternating phases of the clock. We illustrate the methodology with the design of filters for digital signal processing. All of our designs are mapped to DNA-strand displacement reactions (as proposed by Soloveichik, PNAS 2010). We validate these through ODE simulations of the mass-action kinetics of the DNA reactions. Although conceptual for the time being, this research has potential applications in fields such as drug delivery, biochemical sensing, and metabolic engineering.

7:00 pm:
Misel Public Lecture in McNamara Alumni Center
Speaker: Andrei Linde, Stanford University
Subject: Universe or Multiverse?

Cosmological observations show that the universe is very uniform on the largest scales accessible to our telescopes, and the same laws of physics operate in all of its parts that we can see now. The best theoretical explanation of the uniformity of our world was provided by the theory of inflation, which was proposed about 30 years ago. Rather paradoxically, this theory also predicts that on a very large scale, much greater than what we can see now, the world may look totally different. Instead of being a single spherically symmetric balloon, our universe may look like a "multiverse", a collection of many different exponentially large balloons ("universes") with different laws of physics operating in each of them. In the beginning, this picture looked more like a piece of science fiction rather than a scientific theory. However, recent developments in inflationary cosmology, particle physics, and string theory provide strong evidence supporting the new cosmological paradigm. It changes our standard view of the origin and global structure of the universe and on our own place in the world.

Faculty Host: Keith Olive

Wednesday, September 17th 2014
10:30 am:
Thesis Defense in PAN 110
Speaker: Jeff Klein
Subject: Design, Implementation, and Calibration of Half-Wave Plate Polarimetry for the E and B Experiment
This is the public portion of Mr. Klein's thesis defense.

The E and B Experiment (EBEX) is a balloon-borne telescope designed to measure the polarization of the Cosmic Microwave Background (CMB) and dust foregrounds at 10' scales and three frequency bands of 150 GHz, 250 GHz, and 410 GHz in order to detect or constrain B-mode polarization. Results may provide evidence to support the theory of cosmological inflation, or constrain specific models.

EBEX's polarization measurement capability is implemented via continuously-rotating Half-Wave Plate (HWP) polarimetry. We discuss the design and implementation of the polarimetry hardware for the E and B Experiment (EBEX). In order to achieve low-temperature rotation of our 15 cm, 635 g achromatic HWP stack, we implement a unique application of a Superconducting Magnetic Bearing (SMB), building off an earlier prototype. We discuss design constraints, detail our implementation, and present results of tests of power dissipation, rotation speed stability, dynamic stability, and operational lifetime. We find power dissipation of 15 mW in our LDB configuration, and achieve successful operation of the system in both a 2009 test flight and a 2012 Long Duration (LDB) flight.

We design and carry out calibration tests to verify our ability to measure polarized signals. We develop a data analysis pipeline to extract polarization measurements from the chopped polarized signals we use in calibration; we verify and optimize the performance of this pipeline with a simulation. We find that a thorough understanding of the time constants of EBEX's bolometric sensors is essential to measure polarization. We develop methods to measure and remove the effects of these time constants. Tests of polarization rotation across our bands verify predictions of rotation due to our achromatic HWP 5-stack. Polarized beam scans allow us to set an absolute calibration for EBEX with a standard deviation of 1.5 degrees.

1:25 pm:
Nuclear Physics Seminar in 435 Physics
Speaker: Clint Young, University of Minnesota
Subject: Hydrodynamical fluctuations of the universe

The density, pressure, and flow velocities of any static fluid have fluctuations determined by statistical mechanics. An expanding, cooling, viscous fluid will have in its fluctuations the remnants of the large thermal noise from earlier times. This is not only true in heavy ion collisions but also in the early universe. In this talk, I will review earlier work on thermal fluctuations in FRW backgrounds, and outline how changes in phase and second-order hydrodynamical corrections can affect the shape and size of cosmological perturbations driven by thermal noise.

Speaker: Andrei Linde, Stanford University
Subject: Inflation and cosmological attractors
Refreshments served in Room 216 Physics after colloquium

Observational data from WMAP and Planck 2013 provided strong support to the theory of the cosmological inflation. They also stimulated a search for new inflationary models. One of the most puzzling results was that two completely different inflationary theories, the Starobinsky model and the Higgs inflation model, give nearly identical observational predictions, which provide a perfect fit to the Planck results. Recent investigations revealed the existence of several broad classes of inflationary models which make similar predictions. We called them "the cosmological attractors". Further studies have shown that the predictions of these models may have more than one attractor points. I will describe these theories and their advanced versions based on the models with conformal and superconformal symmetries.


Thursday, September 18th 2014
Speaker: Soroush Sotoudeh and Terry Jones
12:15 pm:
Speaker: Haruki Watanabe (U. California, Berkeley)
Subject: Nambu-Goldstone bosons in nonrelativistic systems

Spontaneous symmetry breaking is a very universal phenomenon seen in both relativistic and nonrelativistic systems. When it occurs in nonrelativistic situations, such as magnets and cold spinor BECs, there is a variety in the spectrum of gapless excitations even when the symmetry breaking patterns are the same as Lorentz invariant cases. We develop an effective Lagrangian to understand the number and the dispersion of Goldstone bosons in general. The effective Lagrangian is also useful to understand the dynamics of topological defects and skyrmions. We will also talk about interactions between Goldstone bosons and nonrelativistic fermions (electrons in solids with a Fermi surface), which sometimes result in the breakdown of the Fermi-liquid description and overdamping of Goldstone bosons.

1:25 pm:
Condensed Matter Seminar in 210 Physics
Speaker: Wei Pan, Sandia National Labs
Subject: Old issues in the quantum Hall effect revisited

In this talk, I will revisit a few old issues in the quantum Hall effect in high quality two-dimensional electron systems (2DES). I will first present our experimental results to quantitatively examine the theoretical model of spin splitting collapse in the quantum Hall regime [by Fogler and Shklovskii, Phys. Rev. B 52, 17366 (1995)] at fixed magnetic fields as a function of electron density in a high quality heterojunction insulated-gate field effect transistor. In the second part, I will talk about the quantum criticality of quantum Hall (QH) plateau to plateau transitions in alloy disordered two-dimensional electron systems. In one short-range random alloy disorder dominated sample, a perfect temperature (T) scaling, (dRxy/dB)|Bc  T-, was observed through two full decades of T from 1.2K down to 12 mK. This manifests unequivocally that in an Anderson disordered 2DES the scaling behavior indeed prevails. Moreover, our temperature and size dependent data allow direct determination of both the localization critical exponent,  = 2.38, and the dynamical exponent, z = 1. If time permits, I will also talk about the resistivity law observed ~ 30 years ago. Our recent work in ultra-high mobility 2DES has brought new insight on this problem.

Faculty Host: Michael Zudov

Friday, September 19th 2014
Speaker: No colloquium
Subject: See Misel lecture Sept 16th and SPA colloquium Sept. 17th
Speaker: Karen Detlefsen, Department of Philosophy, University of Pennsylvania
Subject: Generation, Individuation, and Teleology: Malebranche's and Leibniz's Divergent Theories of Pre-formation
Refreshments served in Room 275 Nicholson Hall at 3:15 p.m.

When some early modern natural philosophers rejected Scholastic substantial forms in favor of a parsimonious, and often explanatorily powerful, mechanistic philosophy, one natural phenomenon they had particular difficulty accommodating was the generation of new living beings. In this talk, I look at how Malebranche and Leibniz deal with this difficulty, and the different ways they draw upon teleology to help them provide theories of generation that can preserve the new mechanism. In the process, I underscore the complexity of theories of teleology in the 17th century.

Sponsored by Minnesota Center for Philosophy of Science.

Speaker: Andrey Chubukov, University of Minnesota
Subject: Superconductivity -- what is super about it

Monday, September 22nd 2014
12:15 pm:
Speaker: Zhen Yuan, U Minnesota
Subject: Chemical Evolution Model of Fornax Dwarf Spheroidal Galaxy

Dwarf Spheroidals (dSphs) represent the building blocks of large galaxies according to the hierarchical structure of cold dark matter halos. Recent observation gives us the detailed star formation histories(SFH) of several nearby dSphs. Based on that, we reconstructed the gas dynamics as well as the chemical evolution history of Fornax dSph. Our empirical model considers the inhomogeneous mixing of Supernovae enrichment, which is the key to explain the scatter of alpha elements in these systems, such as [Mg/Fe], [Ca/Fe] and [Si/Fe] etc .

1:35 pm:
CM Journal Club in 210 Tate
Speaker: Marc Schulz, University of Minnesota
Subject: Effective Quantum Dimer Models

The long-standing problem of the nature of the ground-state in the anti-ferromagnetic spin-1/2 Heisenberg model on the Kagome lattice has triggered manifold efforts.The results of different approaches do not coincide and thus display a playground of further analysis, focusing on different derivations of effective low-energy models. In my presentation, I'll discuss the approach to derive effective quantum dimer models [1], whose extensive numerical studies have predicted the ground state to be a valence bond solid [2] in contradiction to recent variational results of the density-matrix renormalization group [3]. If time allows, I'll discuss a recent non-perturbative derivation of an effective quantum dimer model going beyond the first presented approach, which eventually predicts a topological spin liquid as ground state [4].

[1] Schwandt, M. et al., PRB 81, 214413 (2010)
[2] Poilblanc, D. et al. PRB 81, 180402(R) (2010)
[3] Depenbrock, S. et al., PRL 109, 067201 (2012)
[4] Rousochatzakis, I. et al., PRB 90, 100406(R) (2014)


Tuesday, September 23rd 2014
Speaker: Changjiang Liu, University of Minnesota
Subject: Sensitive detection of electron spins in FM/n-GaAs heterostructures using ferromagnetic resonance
12:20 pm:
Space Physics Seminar in 210 Physics
There will be no seminar this week.
Speaker: Chunhui Chen, Iowa State
Subject: Production of high transverse momentum vector bosons reconstructed as single jets at ATLAS and its application to search for new particle at LHC

Highly boosted hadronically decaying particles have been widely used as a unique signature to search for new particle at LHC. In this talk, we present a measurement of the cross-section for high transverse momentum W and Z bosons produced in pp collisions and decaying to all-hadronic final states by the ATLAS experiment. The measurement is performed by reconstructing boosted W or Z bosons in single jets. The reconstructed jet mass is used to identify the W and Z bosons, and a jet substructure method based on energy cluster information in the jet center-of-mass frame is used to suppress the large multi-jet background. In this talk, we will also discuss potential applications of the jet substructure in the jet rest frame in searches for new particle at LHC.

Faculty Host: Yuichi Kubota
2:30 pm:
Biophysics Seminar in 210 Physics
There will be no seminar this week.

Wednesday, September 24th 2014
1:25 pm:
Nuclear Physics Seminar in 435 Physics
There will be no seminar this week.
3:35 pm:
Speaker: Paul Chaikin, New York University
Subject: Some small steps toward Artificial Life
Refreshments served in Room 216 Physics after colloquium

The properties we often associate with living things are motility, metabolism, self-replication and evolution. According to the Nobel Laureate Richard Feynman: “What I can’t create, I don’t understand”. We thought we’d give it a shot - understanding life - and in the process we’ve made two different systems, one that exhibits both autonomous motility and metabolism and another which is the first artificial system that can replicate arbitrarily designed motifs. The first system, artificial swimmers, provides insight into many natural phenomena such as a flocking of birds and schooling of fish. The second system needs no external intervention other than cycling temperature and light, mimicking daily cycles on earth. In fact the system replicates when put outside on a rooftop. The system exponentially grows and through 24 doubling cycles has produced offspring multiplying the initial seed more than 7million times. It provides a new way of producing many, many copies of nanoscale devices and may give insights into the origin of conventional life on earth. We have initiated an elementary form of evolution and shown selection of one species over another.

Faculty Host: E. Dan Dahlberg

Thursday, September 25th 2014
Speaker: Melanie Beck and Tom Jones
12:15 pm:
Speaker: Mariangela Lisanti (Princeton University)
Subject: Bringing Dark Matter into Focus

Although dark matter comprises the vast majority of the matter in the universe, its properties remain elusive. Direct detection experiments are a promising avenue for discovering and characterizing the dark sector. These experiments seek to identify dark matter particles as they scatter off nuclei in underground detectors. The standard picture since the 1980s is that the scattering rate modulates annually due to the Earth's orbit around the Sun. We have recently discovered a new modulation effect: Unbound dark-matter particles are focused by the Sun's gravitational potential, affecting their phase-space density in the lab frame. This 'gravitational focusing' results in a significant overall shift in the phase of the annual modulation and provides a powerful new tool for characterizing the properties of the dark matter particle.

1:25 pm:
Condensed Matter Seminar in 210 Physics
Speaker: Paul Chaikin, NYU
Subject: Classical Wigner Crystals on flat and curved surfaces, topological defects, `pleats‘ particle fractionalization and grainboundary dynamics.

Charged colloidal particles present a controllable system for study a host of condensed matter/many body problems such as crystallization. 2D crystals are invariably hexagonal. Hexagons perfectly tile a flat plane but a soccer ball requires exactly 12 pentagons dispersed among the hexagons on its curved surface. Pentagons and hexagons are positive and negative topological charges, disclinations, sources for positive and negative curvature. But we have discovered that “Pleats”, grain boundaries which vanish on the surface (and play a similar role to fabric pleats) can provide a finer control of curvature.
We experimentally investigate the generation of topological charge as flat surfaces are curved. For positive curvature, domes and barrels, there is one pentagon added for every 1/12 of a sphere. Negative curvature is different! For capillary bridges forming catenoids, pleats relieve the stress before heptagons appear on the surface. Pleats are important for controlling curvature from crystals on surfaces, to the shape of the spiked crown of the Chrysler building.
Adding a particle to a flat surface produces an interstitial - usually an innocuous point defect. On a curved surface interstitials are remarkable, forming pairs or triplets of dislocations which can fission dividing the added particles into fractions which migrate to disclinations.
We have also used “Topological Tweezers” to create grains and study the dynmaics of dislocations in gran boundaries.

Faculty Host: E. Dan Dahlberg

Friday, September 26th 2014
1:30 pm:
Speaker: Manas Kulkarni, The City University of New York, NYC College of Technology, USA.
Subject: Aspects of non-equilibrium many-body phenomena in quantum matter and light.

Non-equilibrium systems have been of tremendous interest both in physics
and engineering. Recent experimental breakthroughs in atomic, condensed
matter physics and optics have given birth to new paradigms for studying
out-of-equilibrium quantum systems. Understanding such phenomena require
an inter-disciplinary approach uniting ideas from these diverse fields.

For an isolated Bose gas, I will present a deep connection between the
Gross-Pitaevskii equation and Kardar-Parisi-Zhang universality class of
stochastic dynamics [1]. In a different scenario, an ensemble of atoms
placed in a leaky optical cavity and pumped with a laser constitutes an
exotic light-matter open quantum system. I will describe the
non-equilibrium aspects close to an interesting phase transition in such
driven-dissipative systems [2]. I will also propose protocols to prepare
light-mediated entangled states [3] of matter by optimally designing the
laser and cavity in other hybrid light-matter systems. Our work shows
that far-from-equilibrium many-body physics is a rich field where theory
and experiments across several disciplines thrive together.

[1] M. KULKARNI, A. Lamacraft, Phys. Rev. A 88, 021603, Rapid
Communication, M. KULKARNI, D. A. Huse, H. Spohn (2014) , M. KULKARNI,
J. Stat. Phys (invited article, 2014)

[2] M.KULKARNI, B. Oztop and H. E. Tureci, Phys. Rev. Lett, 111,
220408, M.KULKARNI, K. G. Makris and H. E. Tureci (2014)

[3] C. D. Aron, M. Kulkarni, H. E. Tureci, arXiv:1403.6474 (2014)

Faculty Host: Alex Kamenev
Speaker: Dr. Marc Seigar, UMD
Subject: New Approaches for Determining the Dark Matter Content in Spiral Galaxies

Our standard cosmological model, LCDM (Lambda Cold Dark Matter),
reproduces the large scale structure of the Universe extremely well. However, on smaller, galaxy-sized scales, there are several issues. One of these is the so-called cusp-core problems, where LCDM predicts cuspy central density profiles on for dark matter halos of all mass scales. However, observational studies show that dwarf galaxies have lower than predicted densities and tend to have constant density cores. Another problem with LCDM is the Tully-Fisher zeropoint problem, which refers to the fact that standard models cannot reproduce the observed relation between galaxy luminosity and circular velocity (the Tully-Fisher relation) without over-producing the number density of galaxies at fixed luminosity. In this presentation, I will describe new methods we are pursuing to determine dark matter density profiles in galaxies, with a
view to coming to a solution to the above issues.

Speaker: Alistair Sponsel, Department of History, Vanderbilt University
Subject: Writing the Origin with Burned Fingers: Darwin's Penance for the 'Sin of Speculation'
Refreshments served in Room 216 Physics at 3:15 p.m.

Charles Darwin was notoriously slow to publish his theory of evolution by natural selection. His reticent approach to publishing on species is generally attributed to his supposed fear of advocating the potentially controversial doctrine of transmutation. I argue, by contrast, that Darwin's caution was the result of a specific scientific embarrassment in his past. What concerned him most about the prospect of publishing a theory of evolution was not the topic, evolution, but the general act of publishing a theoretical book. The one other time he had tried to do so, as a young man using his theory of coral reef formation to offer an ambitious account of the history of the earth and its inhabitants, the public criticism of his "speculations" drove him nearly to despair and made him unable to deliver the book he had promised. It was this experience which shaped Darwin's authorial priorities for his next grand theory: evolution by natural selection. He stopped thinking of his private speculations on species as an exhilarating distraction from the challenge of writing a geological book and began to plot a conservative course designed to insulate him (and eventually his species theory itself) from charges of rash speculation. I thus show that Darwin's well-known authorial decisions on the way to publishing On the Origin of Species were made as attempts to avoid repeating, and ideally to compensate for, the missteps he believed he had made as a young author. In turn I argue that our understanding of scientific authorship has been distorted by the assumption that it must have been the topic, rather than the mode of presentation, that determined how risky it felt to be the prospective author of a theory.

Speaker: Fiona Burnell
Subject: Symmetry and topology in condensed matter physics

Monday, September 29th 2014
12:15 pm:
There will be no seminar this week.
1:00 pm:
CM Journal Club in 210 Tate
Speaker:  Jian Kang, University of Minnesota
Subject: Quantum Phase Transitions of Metals in 2+1 Dimensions

The discovery of high Tc cuprates has sparked intense interest in the interplay between fermions and bosons in two spatial dimension. This talk will introduce the recent progress on the spin-fermion model with large N approximation. I will show that the Hertz theory fails when the system is close to the quantium critial point by simple scaling argument. More emphasis will be put on the introduction of field theoretic renormalziation group analysis at quantum critical point. The theory will be shown to be ill defined at the citical point by calculating the anomalous dimension. Furthermore, the expansion in 1/N fails for the problem at the higher order of loop diagrams. During the talk, I will focus on the QPT for spin density wave (SDW) with nonzero Q. [1] M. A. Metlitski and S. Schdev, PRB 82, 075127 and 075128.


Tuesday, September 30th 2014
Speaker: Tobias Gulden, University of Minnesota
Subject: Instanton calculus without equations of motion: semiclassics from monodromies of a Riemann surface
12:20 pm:
Space Physics Seminar in 210 Physics
There will be no seminar this week.
To be announced.
2:30 pm:
Biophysics Seminar in 210 Physics
Speaker: Casim Sarker, Department of Biomedical Engineering, University of Minnesota
Subject: Synthetic signaling systems for biological discovery and design

Cells utilize a plethora of signal transduction pathways to shape their responses to various environmental cues and much work has been done to dissect signaling networks in this native context in order to better understand how they contribute to cellular decision making. However, it can be difficult to study the inherent properties of a specific signaling module of interest due to the multitude of confounding interactions between the module and its native environment. To obviate these challenges, we have used computational and synthetic biology approaches to construct, analyze, and perturb signaling modules ex vivo. In this talk, I will highlight findings from our work on three such systems: information processing in a kinase cascade, ribosomal initiation of protein translation, and multi-feedback control of receptor signaling. In all three cases, we identify novel modes of regulation that underscore the inherent flexibility of these signaling modules and elucidate biological design rules that govern the operation of these systems in native and/or synthetic contexts. About the speaker: Casim Sarkar received his B.S. in Chemical Engineering from the University of Texas at Austin (1997) and his Ph.D. in Chemical Engineering from the Massachusetts Institute of Technology (2002). After a postdoctoral fellowship in the Department of Biochemistry at the University of Zurich (2002-2005), Dr. Sarkar was an assistant professor in the Department of Bioengineering at the University of Pennsylvania (2006-2013). He is currently an associate professor in the Department of Biomedical Engineering at the University of Minnesota. His research interests lie in the area of molecular cell engineering, both for fundamental biological discovery and for translational design. Applications include understanding signal processing in cell decision-making, constructing synthetic circuits for rational cell engineering, and engineering biomolecules for various biomedical and biotechnological applications. Dr. Sarkar’s honors include a Fannie & John Hertz Foundation Graduate Fellowship, an NIH NRSA Postdoctoral Fellowship, and an NSF CAREER Award.


Wednesday, October 1st 2014
1:25 pm:
Nuclear Physics Seminar in 435 Physics
Speaker: Projjwal Banerjee, U Minnesota
Subject: Beryllium Synthesis in the Early Galaxy

Beryllium is thought to be produced exclusively by the interaction of Galactic Cosmic Rays with the Inter Stellar Medium. We present two new neutrino-induced mechanisms for the synthesis of Beryllium in Core Collapse Supernovae. The first mechanism occurs in the He shell of progenitors of 11-15 solar masses with initial metallicity [Z]<~ -3 via neutron capture process. The second mechanism occurs in the compact low mass progenitors of ~8-10 solar masses where the fast expansion of the shocked He layer results in Be production. We discuss the sensitivity of the mechanisms on supernova neutrino spectra, neutrino mass hierarchy, and the explosion energy. We find that the resulting Be yields can account for Be in the early Galaxy.

3:35 pm:
Speaker: Chris Leighton, University of Minnesota
Subject: Complex Oxides: From Minerals, to Electronic Heterogeneity, to Oxide Electronics
Refreshments served in Room 216 Physics after colloquium

Complex oxides are simply the solids (typically crystalline) formed by bonding
multiple metal cations with oxygen. These materials have been known for many years, make up a large class of naturally occurring minerals, and have emerged over the last two decades or so as one of the most important platforms for the discovery of new phenomena in condensed matter physics. High temperature superconductivity and colossal magnetoresistance (up to a 1012- change in electrical resistivity in an applied magnetic field) provide the highest profile examples, but these materials also support ferroelectricity, multiferroicity (coexistence of two or more ferroic order parameters), oxygen conduction, etc. In this talk I will focus on just one class of complex oxides, the perovskites, named after the mineral prototype CaTiO3- . Focusing on electronic and magnetic behavior I will review the basic physics and chemistry of these materials, emphasizing in particular their instability towards nanoscale electronic heterogeneity (otherwise termed electronic or magnetic phase separation). In the final part of the colloquium I will review recent work from my group attempting to understand “dead layers” in these materials, where the desirable magnetic and electronic properties are heavily suppressed at surfaces and interfaces. The results point to controlled crystallization of oxygen defects as a new means to tune the behavior of oxide interfaces, potentially important in oxide electronic devices.

Faculty Host: Rafael Fernandes

Thursday, October 2nd 2014
Speaker: Tessa Vernstrom, U British Columbia
12:15 pm:
Speaker: Zachary Thomas (U. Minnesota)
Subject: Photon Lines From Decaying Goldstini Dark Matter
1:25 pm:
Condensed Matter Seminar in 210 Physics
Speaker: Alex Kamenev, University of Minnesota
Subject: "Quantum phase transitions in topological Anderson insulators and superconductors"

I'll talk about quantum criticality in the quasi one-dimensional topological Anderson insulators and superconductors. It turns out that the systems may be fully described in terms of two parameters representing localization and topological properties, respectively. Surfaces of half-integer valued topological parameter define phase boundaries between distinct topological sectors. Upon increasing system size, the two parameters exhibit flow similar to the celebrated two parameter flow describing the quantum Hall transitions. However, unlike the quantum Hall system, an exact analytical description of the entire phase diagram can be given. We check the quantitative validity of our theory by comparison to numerical transfer matrix computations.

Faculty Host: Boris Shklovskii

Friday, October 3rd 2014
Speaker: Peter Koroteev (Perimeter Institute)
Subject: Dualities in Five Dimensional Gauge Theories with Defects

We study various protected quantities in five dimensional gauge theories on \mathbb{R}^4\times S^1 with eight supercharges in the presence of defects. Surface defects can be described by a certain three dimensional quiver gauge theory on \mathbb{R}^2\times S^1, whose twisted chiral ring we extensively study by various methods including classical parameter spaces of supersymmetric vacua and exact partition functions. Three dimensional mirror symmetry and integrability of the dual spin chain play important roles in our analysis. For a coupled 5d/3d system we find a convenient description using monodromy defects along the two-plane which is orthogonal to the 3d defect. We compute the corresponding 5d ramified instanton partition function and show that it solves a system of difference equations of a certain elliptic integrable many-body system. We analyze various limiting cases of our construction and identify them with many previously known integrable models.

Speaker: Dr. Nino Pangia, STSci
Subject: Star Formation as Seen by Low Mass Stars

We have undertaken a systematic study of pre-main-sequence (PMS) stars spanning
a wide range of masses (0.5 - 4 Msun), metallicities (0.1 - 1 Zsun) and ages
(0.5 - 30 Myr). We have used the Hubble Space Telescope to identify and
characterise a large sample of PMS objects in several star forming regions in
the Magellanic Clouds, namely 30 Dor, the SN1987A field and NGC1850 in the LMC
and NGC 346 and NGC 602 in the SMC, and have compared them to PMS stars in
similar regions in the Milky Way, such as NGC 3603 and Trumpler 14.

Thanks to a novel method that we have developed to combine broad-band (V,I)
photometry with narrow-band Halpha imaging, we have determined the physical
parameters (temperature, luminosity, age, mass and mass accretion rate) of more
than 3000 bona-fide PMS stars still undergoing active mass accretion. This is
presently the largest and most homogeneous sample of PMS objects with known
physical properties, and includes not only very young objects but also PMS
stars older than 10-20 Myr that are approaching the main sequence.

I will present the current results of our project, including the fact that the
mass accretion rates are systematically higher in the Magellanic Clouds than in
the Milky Way for stars of the same mass and age, scaling roughly with the
inverse of the cube root of the metallicity. These results are bound to have
important implications for, and constraints on our understanding of the star
formation process in the Universe.

Speaker: Author: Roy Cook, Department of Philosophy, University of Minnesota. Readers: Stephen Donaho, Department of Philosophy, Normandale Community College and Roy Sorensen, Department of Philosophy, Washin
Subject: Author Meets Readers:
Refreshments served in Room 275 Nicholson Hall at 3:15 p.m.

The Yablo paradox, which consists of an infinite sequence of sentences, each of which says that all sentences following it in the list are false, seems to provide us with an example of semantic paradox containing no circularity. In The Yablo Paradox Roy T Cook examines this puzzle in detail, paying particular attention to:
(1) The characterization problem: Determining which patterns of sentential reference—circular or not—generate paradoxes.
(2) The circularity question: Determining whether, and in what sense, the Yablo paradox is non-circular.
(3) The generalizability question: Determining whether the infinitely descending pattern found in the Yablo paradox can be used to construct non-circular variants of other familiar paradoxes.

Sponsored by the Minnesota Center for Philosophy of Science.

Speaker: Paul Crowell, University of Minnesota
Subject: Spin Transport in Semiconductors

Monday, October 6th 2014
12:15 pm:
Speaker: Kyle Willett, University of Minnesota
Subject: Clustering of active galactic nuclei and the blazar population

Both observations and simulations of the matter distribution in the Universe reveal extensive large scale structure, characterized by clusters, filaments, and voids that are traced out by galaxies. Measurements of the large-scale clustering amplitudes provide limits on the relationship between the mass of the dark matter halo and the galaxies within. Small-scale clustering (at Mpc separations) probes the physics of galaxy interaction and evolution. For galaxies that contain accreting black holes, clustering measurements of the active galactic nuclei (AGN) constrain the relationship between the black hole mass and various methods of triggering its activity. I will present results from a recent workshop on AGN clustering, including measurements of the luminosity dependence and shifts based on different AGN selection methods. Finally, I will show our results on the small-scale clustering of blazars, showing that clustering does not distinguish between the flat-spectrum radio quasar and BL Lac populations.

1:00 pm:
CM Journal Club in 210 Tate
There will be no seminar this week.

Tuesday, October 7th 2014
There will be no sack lunch seminar this week.
12:20 pm:
Space Physics Seminar in 210 Physics
To be announced.
There will be no seminar this week.
2:30 pm:
Biophysics Seminar in 210 Physics
There will be no seminar this week.

Wednesday, October 8th 2014
1:25 pm:
Nuclear Physics Seminar in 435 Physics
Speaker: Joe Kapusta, University of Minnesota
Subject: Critical Thinking Points

I will summarize recent theoretical work by my collaborators and
me which is relevant to the experimental search for a critical point in
the QCD phase diagram at RHIC. This is a slightly expanded version of a
presentation at the workshop "Beam Energy Scan II - 2014" held at LBNL
September 27-29.

3:35 pm:
Speaker: Dan Cronin-Henessey
Subject:  The Neutrino: Nature’s Most Unusual Fermion
Refreshments served in Room 216 Physics after colloquium

The Standard Model of particle physics is arguably the most successful theory ever and yet we still do not have a proper theory of flavor. Flavor oscillations of neutrinos can provide crucial information concerning mass, mixing and matter/anti-matter asymmetry. I will review several of the most active areas of particle physics that exploit the neutrinos unique properties in order to advance our knowledge of fundamental laws. I will focus on neutrino oscillation experiments and specifically on the most recent experiment, NOvA.

Faculty Host: Priscilla Cushman

Thursday, October 9th 2014
Speaker: Micaela Bagley and Liliya Williams
12:15 pm:
Speaker: Thomas D. Cohen (Univ. of Maryland, College Park)
Subject: Tetraquarks at large Nc
1:25 pm:
Condensed Matter Seminar in 210 Physics
Speaker: Brian Skinner, Argonne NL
Subject: Problems in Human Motion Planning

Problems in Human Motion Planning

Moving through a densely-populated environment can be surprisingly hard, owing to the problem of congestion. Learning to deal with congestion in crowds and in networks is a long-standing and urgently-studied problem, one that can be equally well described at the level of dense, correlated matter or at the level of game-theoretical decision making. In this talk I describe two related problems associated with motion planning in congested environments. In the first part I consider a description of pedestrian crowds as densely-packed repulsive particles, and I address the question: what is the form of the pedestrian-pedestrian interaction law? In the second part of the talk I examine a simple model of a traffic network and study how inefficiency in the traffic flow arises from "selfish" decision-making. Analysis of the model reveals a surprising connection between Nash equilibria from game theory and percolative phase transitions from statistical physics.

Faculty Host: Boris Shklovskii

Friday, October 10th 2014
Speaker: Dr. Stephan Courteau, Queen's University
Subject: Puzzles in the Structure of Disk Galaxies

Galaxies can be described in terms of their structure, dynamics and stellar populations. Some very robust correlations between various galaxy structural properties, such as total luminosity, maximum circular velocity, and size show rather small scatter, hinting at well-regulated galaxy formation processes. A major challenge to understanding these scaling relations, and ultimately galaxy formation and evolution, is the elusive interplay between visible and dark matter. I will discuss the latest derivations of galaxy scaling relations and their link with modern cosmological models.

Speaker: Karen Rader, Department of History, Virginia Commonwealth University
Subject: Life on Display: The Exhibits Revolution in U.S. Science and Natural History Museums
Refreshments served in Room 216 Physics at 3:15 p.m.

Once defined primarily by their collections, by the end of the twentieth century, American natural history and science museums had become institutions defined largely by their displays. This talk will use life science exhibits to illustrate how and why this transformation occurred. Efforts to modernize displays shaped and were themselves shaped by new institutional roles and identities for museums in twentieth-century science education and in American culture.

Drawing on the speaker's co-authored book of the same name, the talk will reflect on the controversies that accompanied exhibition building, chronicling how and why curators, designers, and educators worked with and against one another to build displays intended to communicate new ideas about topics like evolution, animal behavior, and radiation to various American publics. Scientists were extraordinarily invested in the success of museums' displays and saw display as an integral element of their own public outreach work and research agendas. In turn, rapidly professionalizing exhibit designers were periodic participants in the research process, supplementing and sometimes prompting research projects through the displays they built.

Speaker: Priscilla Cushman
Subject: Searching for Dark Matter Underground

Monday, October 13th 2014
12:15 pm:
Speaker: Tania Regimbau, Observatoire de la Cote d'Azur
Subject: Cosmology with the Einstein GW Telescope

The first generation of gravitational-wave (GW) detectors such as LIGO or Virgo (2002-2013) were able to reach their design sensitivities, demonstrating the feasibility of the experiment.
With the second generation, Advanced LIGO and Advanced Virgo we are entering the era of the first GW detections. With a sensitivity about 10 times better than that of initial LIGO/Virgo, we expect the detection
of a few or a few tens of compact binary coalescences a year. With the third generation european antenna Einstein Telescope (ET) planned to be operational in 2025, GW astronomy will definitely take a step further, with the possibility
of detecting a large number of sources from a large range of processes, and providing a new tool to study fundamental physics, astrophysics and cosmology.
In this talk I will introduce the Einstein Telescope design concept and present its science goal, focussing more specifically on cosmology studies.

1:00 pm:
CM Journal Club in 210 Tate
Speaker: Brent Perreault
Subject: Quantum Quench at the X-ray Edge

A quantum quench occurs when we take a system in an eigenstate of H_0 and instantly change the Hamiltonian, then allowing it to evolve in time. In the X-ray Edge problem [1] we remove a deep electron from one molecule in the lattice on a system in its ground state. I will review this classic problem, its solution - pioneered by Nozieres et al. [2] - and its relation to dynamics in Kitaev spin liquids [3].
[1] Mahan, Phys Rev 163, 612 (1967)
[2] Nozieres & Dominicis, Phys Rev 178, 1097 (1969)
[3] Knolle et al. PRL 112, 207203 (2014)


Tuesday, October 14th 2014
To be announced.
12:20 pm:
Space Physics Seminar in 210 Physics
Speaker: John Dombeck, University of Minnesota
Subject: Auroral electron precipitation statistical results from FAST data and comparison with DMSP
There will be no seminar this week.
2:30 pm:
Biophysics Seminar in 210 Physics
There will be no seminar this week.

Wednesday, October 15th 2014
1:25 pm:
Nuclear Physics Seminar in 435 Physics
There will be no seminar this week.
3:35 pm:
Speaker: Clem Pryke
Subject: Detection of B-mode polarization at 150GHz and degree angular scales by BICEP2
Refreshments served in Room 216 Physics after colloquium

The theory of Cosmic Inflation postulates that our entire observable universe
was spawned from a minute quantum fluctuation in an incredibly brief burst of
hyper expansion. Inflation makes several predictions which appear to match
features of the actual Universe in which we find ourselves, and, in addition,
predicts that a background of gravitational waves will exist which may produce
a specific observable feature in the polarization pattern of the Cosmic
Microwave Background - the long sought B-mode polarization. Using data from a
specialized radio telescope called BICEP2 operating from the South Pole in
Antarctica our collaboration recently reported a high significance detection
of a B-modes at 150GHz and few degree angular scales. However new data from
the Planck space mission suggests that the detected B-mode may be due to an
unexpectedly high level of polarized emission from dust grains in our own
galaxy. I will describe the experiment and results, and the evolving situation
as regards dust.

Faculty Host: Shaul Hanany

Thursday, October 16th 2014
Speaker: Brian O'Neill
12:15 pm:
Speaker: Lauren Pearce (U. Minnesota)
Subject: Strongly Interacting SUSY: Theoretical Motivation and Phenomenology
1:25 pm:
Condensed Matter Seminar in 210 Physics
Speaker: Guichuan Yu, University of Minnesota
Subject:  Probing complex oxides with synchrotron X-rays
Faculty Host: Martin Greven

Friday, October 17th 2014
Speaker: Dr. Ed Guinan, Villanova University
Subject: The Secret Lives of Cepheids: Surprising New Insights into Atmospheric x-uv Heating, Pulsation and Evolution of Classical Cepheids
Speaker: Marcus Feldman, Department of Biological Sciences, Stanford University
Subject: Next Generation Theory of Cultural Evolution
Refreshments served in Room 275 Nicholson Hall at 3:15 p.m.

The human cultural niche can influence both biological and cultural evolution. The effects of changes in some norms and values may have unexpected consequences for other norms and values. One example will be shown. The role of culturally determined marriage preferences on cultural niche construction also has entirely unexpected effects. Rarely modeled effects of learning styles on the stochastic dynamics of cultural traits in small populations will be explored using agent-based simulation techniques.

Sponsored by the Minnesota Center for Philosophy of Science.

Speaker: Michael Zudov, University of Minnesota

Monday, October 20th 2014
12:15 pm:
Speaker: Andrew Miller, University of Minnesota
Subject: Gravitino Dark Matter: Problems and Prospects
1:00 pm:
CM Journal Club in 210 Tate
Speaker: Tobias Gulden
Subject: Topological invariants in interacting one-dimensional fermionic systems

Topological phases are mainly studied in the absence of interactions, but more recent results show their presence in interacting system. The Peierls-Hubbard model consists of interacting fermions in 1 dimension, and is an extension to the Su-Schrieffer-Heeger model. I will review the basic properties of the SSH model before adding the interaction term. Then I show how the topological phase can be determined from the Green's function. In the end there will be a brief discussion of effects from an additional ferromagnetic interaction, which is supported by numerical data. [1] S. Manmana, A. Essin, R. Noack and V. Gurarie: PRB 86, 205119 (2012).


Tuesday, October 21st 2014
Speaker: Zvie Razieli, University of Minnesota
Subject: Composite Silicon Thin Films for Particle Detectors and Solar Cells
12:20 pm:
Space Physics Seminar in 210 Physics
Speaker: Sheng Tian, University of Minnesota
Subject: A survey of the cusp ion outflow’s kinetic energy flux measured by Polar and FAST during conjunction events
Speaker: Matthew Malek, Imperial College London
Subject: Searching for Leptonic CP Violation with T2K and Hyper-Kamiokande

The observation of leptonic CP violation would offer an explanation for the large matter-antimatter asymmetry in our universe. Early hints can be seen in the tension between results from T2K and the reactor neutrino experiments. The logical next step is construction of a next-generation neutrino experiment, such as Hyper-Kamiokande, that is optimised for the discovery of CP violation in the lepton sector. In this talk, the latest results from the T2K experiment are reviewed, including the first observation of neutrino appearance through oscillation. An overview of the Hyper-Kamiokande experiment will also be presented, focusing on expected sensitivity and the current R&D status.

Faculty Host: Satish Desai
2:30 pm:
Biophysics Seminar in 210 Physics
Speaker: Ben Hackel, University of Minnesota
Subject: Engineering Synthetic Ligands for Molecular Imaging

Non-invasive in vivo imaging at the molecular and cellular scale has transformative clinical potential for the detection, characterization, and monitoring of disease. Molecular imaging necessitates command of molecular recognition, molecular biology of the target, biological transport at the tissue and cellular levels, and detection technology. While the seminar will briefly touch on improved understanding and technological advancement in each of these elements, the focus will be on engineering synthetic binding ligands as molecular targeting agents. In particular, I'll discuss our algorithm to efficiently evaluate naturally occurring protein domains for their potential evolutionary capacity and the resultant development of a small (45 amino acid) scaffold capable of efficient evolution of novel, high affinity binding functions.

7:00 pm:
Café Scientifique in Bryant Lake Bowl
Speaker: Michel Janssen, University of Minnesota
Subject: Café Scientifique: Einstein: The Old Sage Versus Young Turk

Drawing on his work for the Einstein Papers Project and his collaborations with scholars at the Max Planck Institute for History of Science in Berlin, Michel Janssen will explain, in layperson's terms, the scientific methodology behind the spectacular successes of the young Einstein (special and general relativity and early contributions to quantum theory). He will then show how some of Einstein's personal experiences during World War I played a key role in making the older Einstein adopt a very different methodology, one no longer driven by empirical data but by mathematical elegance. This Café Scientifique promises to be an entertaining mix of history, philosophy, and physics.

Michel Janssen has long been interested in making the results of his research on the history and philosophy of modern physics accessible to a broader audience. A professor in the History of Science, Technology, and Medicine program at the University of Minnesota, Janssen has been offering a popular seminar called Einstein for Everyone. He is also one of the editors of The Cambridge Companion to Einstein, which likewise aims at a broad audience.

Cost of tickets is $5-12.


Wednesday, October 22nd 2014
3:35 pm:
Speaker: Michael Zudov, University of Minnesota
Subject: Magnetotransport in two-dimensional systems
Refreshments served in Room 216 Physics after colloquium

High-mobility 2D electron systems realized in GaAs/AlGaAs quantum wells exhibit a rich variety of fascinating phenomena which emerge when the system is subject to magnetic fields and low temperatures, as well as microwave and/or dc electric fields. In the first part of my talk I will give an overview of the progress in this field over the past decade, focusing on our efforts over the last few years, and discuss some open issues. In the second part, I will present our recent results on magnetotransport in a 2D hole gas hosted in Ge/SiGe quantum wells, including first observations of fractional quantum Hall states and non-eqilibrium phenomena, as well as a new anisotropic phase which emerges in tilted magnetic fields.

Faculty Host: Priscilla Cushman

Thursday, October 23rd 2014
Speaker: Taryn Heilman
12:15 pm:
Speaker: David Morrissey (TRIUMF)
Subject: Light Hidden Sectors and Low-Energy Searches

New physics can be light if it is hidden, coupling very weakly to the Standard Model. In this talk I will describe searches for new light (sub-GeV) particles using lower-energy precision experiments. I will also discuss realizations of such sectors involving supersymmetry or strong interactions where the characteristic energy scale of the new hidden states is obtained naturally.

1:25 pm:
Condensed Matter Seminar in 210 Physics
Speaker: Shalom Michaeli, Department of Radiology, UMN
Subject:  Probing Biological Systems Using Frequency Swept Pulses: MRI Contrasts in High Rotating Frames "
Faculty Host: Boris Shklovskii

Friday, October 24th 2014
Speaker: Dr. Enrique Rodriguez,l U Texas-San Antonio
Subject: Revealing the Core of Active Galactic Nuclei Through Infrared Polarimetry

Magnetohydrodynamical theories consider the torus of Active Galactic
Nuclei (AGN) to be part of an outflow wind moving away from the central
engine. In this framework, the torus is a particular region of the
outflowing wind, where dusty and optically thick clouds are formed. The
outflows are strongly related to the accretion rate and magnetic field
strength, which play an important role in the creation, morphology and
evolution of the torus. Through high-angular (~0.1''-0.6") infrared (IR,
1-13 um) polarimetric observations, this talk presents (1) the role of
the magnetic fields in the torus of AGN, and (2) the polarized
synchrotron core of Cygnus A.

Although several models have been made to account for the outflowing
dusty winds from the central engine, the magnetic field strength at the
position of the torus remains poorly characterized. Through near-IR
polarimetry using MMTPol at the 6.5-m MMT, the magnetic field strengths,
accretion and outflow rates within the clumpy torus of NGC 1068 were
estimated. These results provide information about the torus evolution
within the AGN unified scheme. For the archetypical radio-loud AGN,
Cygnus A, mid-IR imaging polarimetry using CanariCam (7.5-13 um) on the
10.4-m Gran Telescopio CANARIAS revealed a highly polarized, 11+/-3% at
8.7 um, unresolved core. Polarimetric modeling suggests that the MIR
polarization arises from a synchrotron component from the pc-scale jet
in the core of Cygnus A. This result represents the most compelling MIR
polarization detection of synchrotron radiation from the pc-scale jet in
Cygnus A.

Speaker: Symposium on Vesalius
Subject: Visualizing the Body: The Convergence of Art, cadaver, & Medical Knowlege
Refreshments served in Room 555 Diehl Hall at 3:00 p.m.

Symposium program:
1:00-2:00 Michael McVaugh, University of North Carolina
"A Medieval Surgeon's Anatomy"

2:00-3:00 Jole Shackelford, Surgery Department, University of Minnesota
"Andreas Vesalius as Surgeon: Revisiting the authorship of Chirurgia Magna (1568)"

Coffee Break 3:00-3:30

3:30-4:30 Susan Lawrence, Department of History, The Ohio State University
"Working Words: Dissection, Surgery and Clinical Medicine in Eighteenth-Century London"

4:30-5:30 Myriam Nafte, Department of Anthropology, McMaster University
"Institutional Bodies: Identity, Narrative and the Undisposed Dead"

Co-sponsored by the Consortium for the Study of the Premodern World,
the Program for the History of Medicine, and the Wangensteen Historical Library

Speaker: Vlad Pribiag, University of Minnesota
Subject: Quantum spin transport and Majorana modes in topological insulators and semiconductor nanowires

Monday, October 27th 2014
12:15 pm:
There will be no seminar this week because of the MIFA public lecture on Thursday.
1:00 pm:
CM Journal Club in 210 Tate
There will be no seminar this week.

Tuesday, October 28th 2014
Speaker:  Abdul Malmi-Kakkada, University of Minnesota
Subject: Dislocation Mobility and Anomalous Shear Modulus in Quantum Crystals
12:20 pm:
Space Physics Seminar in 210 Physics
Speaker: Evan L. Tyler, University of Minnesota
Subject:  "The discrepancy between single and multi-spacecraft techniques in measurements of solar wind discontinuities"
There will be no seminar this week.
2:30 pm:
Biophysics Seminar in 210 Physics
There will be no seminar this week.
3:00 pm:
Thesis Defense in Physics 435
Speaker: Jacob Simones
Subject: An Analysis of Star Formation in M31 Using Resolved Stars and Ultraviolet Flux
This is the public portion of Mr. Simones PhD thesis defense

Wednesday, October 29th 2014
1:25 pm:
Nuclear Physics Seminar in 435 Physics
Speaker: Matt Kistler (Kavli Institute for Particle Astrophysics and Cosmology, Stanford)
Subject: Implications of the first high-energy astrophysical neutrino events in IceCube

Neutrinos have the potential to tell us much about some of the most extreme environments in the Universe; however, colossal detectors are required to overcome the weak neutrino interactions. The IceCube experiment recently announced the exciting first detection of high-energy neutrinos with plausible extraterrestrial origins. I will discuss from a theoretical perspective what this new flux has already told us about the inner workings of the sources of extragalactic cosmic rays. Additionally, I will touch upon connections with a variety of other observations in the Milky Way and beyond along with how these can be strengthened in coming years.

Faculty Host: Yong-Zhong Qian
3:35 pm:
Speaker: Jeroen van Dongen, University of Amsterdam
Subject: Communicating the Heisenberg relations: Niels Bohr and the forgotten Einstein-Rupp Experiments
Refreshments served in Room 216 Physics after colloquium

In 1926, Albert Einstein collaborated with Emil Rupp on a set of experiments that were to probe the wave versus particle nature of light. The experiments have now been forgotten, even though their history is quite surprising: after it was established that Rupp had committed fraud, they have been eradicated from the collective memory of the physics community. Niels Bohr is one of the physicists who was closely following the development of these experiments, and proposed his own interpretation of them to Einstein using Heisenberg's new relations; yet, he would not mention them in his later recollections of discussions with Einstein. In this talk, I will discuss the Einstein-Rupp experiments, their role in the discussions between Bohr and Einstein, and finally offer an analysis of the collective amnesia.

This talk is part of Rogerfest, a celebration of Roger Stuewer's 80th birthday.

Faculty Host: Michel Janssen

Thursday, October 30th 2014
11:20 am:
Thesis Defense in PaN 110
Speaker: Kevin Christie, University of Minnesota
Subject: Non-equilibrium spin accumulation in Co_2 Fe_x Mn_(1-x) Si/GaAs heterostructures
This is the public portion of Mr. Christie's thesis defense.
Speaker: Mehdi Lemee'
12:15 pm:
Speaker: Liam Fitzpatrick (Stanford U.)
Subject: The Conformal Bootstrap Near the Light-cone
1:25 pm:
Condensed Matter Seminar in 210 Physics
Speaker: Thomas Vojta, Missouri University of Science and Technology
Subject: Quantum phase transitions and disorder: Griffiths singularities, infinite randomness, and smearing

Phase transitions are fascinating phenomena in nature with consequences
ranging from the large scale structure of the universe to exotic quantum phases
at low temperatures. Many realistic systems contain impurities, defects and
other forms of quenched disorder. This talk explores the consequences of such
randomness on the properties of phase transitions.
At zero-temperature quantum phase transitions, randomness can have
particularly peculiar and strong effects. Often, rare strong disorder fluctuations and the rare spatial regions that support them dominate the physics close to the transition. They give rise to strong singularities in the free energy, the so-called quantum-Griffiths singularities. In some systems such as metallic magnets, the effects of are fluctuations can be even stronger, leading to a destruction of the phase transition by smearing. These general results are illustrated using experiments in transition metal alloys and heavy fermion systems.

Faculty Host: Rafael Fernandes
7:00 pm:
The Inaugural MIfA Public Lecture in Bell Museum Auditorium
Speaker: Dr. Clem Pryke, Professor, U of Minnesota
Subject: Viewing the Birth of the Universe from the Bottom of the World

Friday, October 31st 2014
Speaker: Liam Fitzpatrick (Stanford U.)
Subject: Wilsonian and Large N approaches to Quantum Critical Metals
Speaker: Ivan Linscott, Stanford
Subject: The Radioscience Experiment (REX), on the New Horizons Mission to Pluto
Speaker: Jeroen van Dongen, History of Science, University of Amsterdam/Utrecht University
Subject: A Virtuous Theorist’s Theoretical Virtues: Einstein on Physics versus Mathematics and Experience versus Unification
Refreshments served in Room 216 Physics at 3:15 p.m.

Special colloquium in honor of the 80th birthday of Roger H. Stuewer, founder and former director of the Program in History of Science and Technology

When Albert Einstein formulated the general theory of relativity, he combined a physical and mathematical approach, as Renn and others have shown. He retained and explicitly referred to these categories in his later work on unified field theory as well, but emphasized their usefulness differently, just as his later recollections of how he found general relativity gradually changed. These altered recollections were not only the consequence of his new, highly mathematical unification program, but also served as an advertisement for that program: Einstein enlisted idealizations of himself as justification for his highly controversial work.

Cosponsored by the School of Physics and Astronomy.

Speaker: Rafael Fernandes, University of Minnesota
Subject: Theory of correlated materials: from high-temperature superconductors to quantum magnets

Monday, November 3rd 2014
12:15 pm:
Speaker: Kristy McQuinn, University of Minnesota
Subject: Are We Correctly Measuring the Star Formation in Galaxies?

Integrating our knowledge of star formation traced by observations at different wavelengths is essential for correctly interpreting star formation activity and galaxy evolution in a variety of systems and environments. In this talk, I will compare extinction corrected integrated ultraviolet (UV) emission from resolved galaxies with star formation histories (SFHs) derived from resolved stellar populations and color-magnitude diagram (CMD) fitting techniques in 19 nearby starburst and post-starburst dwarf galaxies. The datasets are from the panchromatic STARBurst IRregular Dwarf Survey (STARBIRDS) and include deep legacy GALEX UV imaging, HST optical imaging, and Spitzer MIPS imaging. For the majority of the sample, the integrated far ultraviolet (FUV) fluxes predicted from the CMD based SFHs generally agree with the measured integrated FUV fluxes from GALEX images after correcting for extinction based on the mid-infrared emission in the MIPS images. The agreement between predictions from three different models and observations indicates that (1) the UV attenuation has been adequately corrected using the infrared flux from the MIPS images, (2) the star formation rates (SFRs) are not heavily affected by stochastic effects, and (3) stellar evolution models are correctly modeling the optical to UV fluxes at recent times. Despite being able to model the fluxes correctly, there is a systematic deviation between the SFRs based on integrated FUV luminosities and existing scaling relations, and the SFRs based on the resolved stellar populations. This offset is not driven by different star formation timescales, variations in SFHs, nor UV attenuation. While stochastic changes in the SFRs on short timescales (t<20 Myr) are a contributing factor to the dispersion in the measurements, temporal sampling of the SFHs is not the dominant driver of the discrepancy. This first comparison between CMD-based SFHs and an integrated FUV emission SFR indicator suggest that the FUV-SFR scaling relation calibrated to higher-SFR galaxies does not accurately reproduce the star formation activity in dwarf galaxies. We present an empirical calibration of the FUV SFR relation for dwarf galaxies which is ~2 times larger than previous relations and provide a guide for applying FUV-SFR scaling relations in studies of unresolved, high-redshift galaxies.

1:00 pm:
CM Journal Club in 210 Tate
Speaker: Michael Schuett
Subject: Quantum Phase Transitions of Metals in 2+1 Dimensions Part II

This talk will be a continuation of the presentation given by Jian Kang. The system of interest is the Spin-Fermion (SF) model which is believed to be relevant for the understanding of the high Tc superconductivity observed in the cuprates. I will start my presentation by reminding you on the derivation of the failing of the large N approach, previously shown by Jian following Ref. [1]. I will then, following Ref. [2], motivate modifications to the original SF model, which will allow for an effective low energy field theory describing the QPT. If time allows i will briefly explain the arising d-wave superconductivity and the QDW-state that is predicted by the theory. [1] M. A. Metlitski and S. Schdev, PRB 82 075128. [2] K.B. Efetov, H. Meier and C. Pepin, Nature Phys. 9 442 (2013).

Speaker: Alexander Gorsky
Subject: Baryons as Dyonic Instantons

Tuesday, November 4th 2014
12:20 pm:
Speaker: Markus Mueller, ICTP Trieste
Subject: Many-body localization without quenched disorder
NOTE: Change of location for this week only.

We explore the possibility and conditions under which translationally invariant quantum many body systems undergo a genuine glass transition, at which ergodicity and translational invariance break down spontaneously. In such circumstances quantum memory can arise, since large scale equilibration is prevented. In contrast to analogous classical systems, where the existence of such ideal glass transition remains a controversial question, a genuine phase transition is predicted in the quantum regime. This ideal quantum glass transition can be regarded as a many body localization transition due to self-generated disorder.

Faculty Host: Boris Shklovskii
12:20 pm:
Space Physics Seminar in 210 Physics
To be announced.
There will be no seminar this week.
2:30 pm:
Biophysics Seminar in 210 Physics
There will be no seminar this week.

Wednesday, November 5th 2014
1:25 pm:
Nuclear Physics Seminar in 435 Physics
Speaker: Zhu Li, University of Minnesota
Subject: Exploration of Nucleosynthesis in Low Mass Supernovae

In the low mass supernovae (~8 times solar masses), the shocked ejecta from the protoneutron star undergoing extremely high temperature and density enhances the production of heavy elements (A>56). We find that even in environments with equal number of protons and neutrons, some proton-rich nuclei could be synthesized in significant amounts compared to the solar abundance. When the neutrino interactions on light nuclei are taken into consideration, the protons and neutrons from the spallation reactions were observed to further improve the yields of heavy nuclei.

3:35 pm:
Speaker: Ben Bederson, NYU & Susan Seestrom, Texas A&M
Subject: Hans Courant's 90th Birthday Symposium:Highlights of the Physics Challenges during the Manhattan Project
Refreshments served in Room 216 Physics after colloquium

Ben Bederson will be speaking on “Recollections of a Los Alamos Soldier-Scientist.”

Susan Seestrom will discuss some of the key physics and materials challenges that had to be solved in the development of the atomic bomb. The approach to these challenges during the Manhattan Project was Edisonian in nature because of the intense time pressures involved, but was based on a foundation of basic research in physics during the first decades of the 19th century. I will discuss how that approach impacted the course of the Manhattan project and the subsequent development of the cold war nuclear arsenal, as well as the ability of the nuclear weapons laboratories to cope with the cessation of nuclear testing. Finally, I will talk about some of the tools that have been developed to meet the challenges of the present day national security mission of Los Alamos and the importance of basic research in nuclear science along the way.

Faculty Host: Marvin Marshak

Thursday, November 6th 2014
Speaker: Tony Young and Michael Rutkowski
12:15 pm:
Speaker: P. Daniel Meerburg (Princeton U.)
Subject: Beyond slow-roll

We live in exiting times for cosmologists. There is a plethora of cosmological experiments that allow us to reconstruct the earliest moments in the Universe and test our ideas on how the Universe came into existence. Current data appear to favor an inflationary model that produces adiabatic, scale free, Gaussian fluctuations with an amplitude of 10^-5 in units of mK. WIthin the realm of cosmological models, it appears that such conditions are easily accomplished if we have a single light field slowly rolling down its potential. In this talk, I will investigate the possibility to what extend our current observations would allow for a deviation from slow-roll: several class of models predicts that the fluctuation spectra will contain superimposed features on top of their slow-roll solution. I will discuss these models and explain a novel way of extract these features from the data, both in the power spectrum as well as in the bispectrum. I will give the latest constraints from current cosmological surveys. In light of the possible detection of primordial gravitational waves, I will show that there exists evidence (3 sigma) that the data prefer a long wavelength feature driven by axion monodromy, a model that naturally predicts large tensor modes. From this I will derive a constraint on the axion decay constant. I will conclude with a discussion on how observations of higher order statistics and large scale structure could further constrain these models.

1:25 pm:
Condensed Matter Seminar in 210 Physics
Speaker: Bharat Jalan, CEMS department, UMN
Subject: Stoichiometry Control of Emergent Phenomena at Complex Oxide Interfaces

Complex oxides with ABO3 perovskite structure have been of scientific nterests for a long time due to their ability to display a wide-range of phenomena. Recent advances in thin film growth approaches have enabled the growth of this material class in thin film and heterostructure forms with structural quality, which has now become similar to that of the conventional semiconductors. However the grand challenge in the field is to obtain these materials with the high level of stoichiometric and defect control. In this talk, we will present our group’s effort to address these challenges and to utilize stoichiometry defects as a new degree of freedom to control material’s physical phenomena using the hybrid molecular beam epitaxy (MBE) approach with the focus to understand and control novel electronic and magnetic ground states in defect-managed oxide thin films and heterostructures.

Faculty Host: Boris Shklovskii

Friday, November 7th 2014
Speaker: Florian Niedermann (Munich U.)
Subject: The Universe as a Cosmic String

We are investigating modifications of general relativity that are operative at the largest observable scales. In this context, we are investigating the model of brane induced gravity in 6D, a higher dimensional generalization of the DGP model. As opposed to different claims in the literature, we have proven the quantum stability of the theory on a linear level. In particular, we have shown that the Hamiltonian of the linear theory is bounded from below. This result opened a new window of opportunity for consistent modified Friedmann cosmologies. In our recent work it is shown that a brane with FRW symmetries necessarily acts as a source of cylindrically symmetric gravitational waves, so called Einstein-Rosen waves. Their existence essentially distinguishes this model from its codimension-one counterpart and necessitates to solve the non-linear system of bulk and brane-matching equations. A numerical analysis is performed and two qualitatively different and dynamically separated classes of cosmologies are derived: degravitating solutions for which the Hubble parameter settles to zero despite the presence of a non-vanishing energy density on the brane and super-accelerating solutions for which Hubble grows unbounded. The parameter space of both the stable and unstable regime is derived and observational consequences are discussed: It is argued that the degravitating regime does not allow for a phenomenologically viable cosmology. On the other hand, the super-accelerating solutions are potentially viable, however, their unstable behavior questions their physical relevance.

There is no MIFA Colloquium this week.
There is no HSTM Colloquium this week.
Speaker: John Broadhurst, University of Minnesota
Subject: "An application of physics to clinical medicine."

Monday, November 10th 2014
12:15 pm:
Speaker: Yann Mambrini, University of Minnesota
Subject: Dark Matter Status in 2014

2014 was a year full of data in High Energy Physics, especially in DM searches. We will review in this seminar the different results which appeared this year and their interpretations as dark matter signals, or astrophysical background alternatives.

1:00 pm:
CM Journal Club in 210 Tate
There will be no seminar this week.

Tuesday, November 11th 2014
Speaker: Yahor Savich, University of Minnesota
Subject:  Density of states for a single Abrikosov vortex in disordered media.
12:20 pm:
Space Physics Seminar in 210 Physics
Speaker: Dai Lei, University of Minnesota
Subject: RBSP observations of Poloidal ULF Waves
Speaker: Jim Napolitano
Subject: Latest Results from the Daya Bay Reactor Neutrino Experiment

The Daya Bay experiment was designed for precision measurement of the neutrino mixing angle θ13- . Our first results were released in March 2012, but since then we have taken much more data with a full complement of eight “identical” antineutrino detectors. Four detectors are relatively close to the primary reactor cores, and four are at a distance that optimizes sensitivity to θ13- . I will present our most precise result to date, along with an auxiliary measurement using np capture, as well as new results on sterile neutrinos. We will also discuss our measurements of the primary reactor neutrino spectrum, including some unexpected observations.

Faculty Host: Dan Cronin-Hennessy
2:30 pm:
Biophysics Seminar in 210 Physics
There will be no seminar this week.

Wednesday, November 12th 2014
1:25 pm:
Nuclear Physics Seminar in 435 Physics
Speaker: Menquan Liu, University of Minnesota
Subject: Supernova Shock Propagation in the Interstellar Medium

Supernovae play an important role in the galactic evolution. In this talk, I will introduce the propagation process of the supernova shock after a successful explosion based on a 1D hydrodynamic simulation. The results include the energies, radius, mass and luminosity of the supernova remnant and the profile of velocity, density and temperature. The difference due to the supernova explosion energies and the metallicity of interstellar medium are analyzed. I will also discuss their effect on the galactic evolution.

3:35 pm:
Speaker: Hari Manoharan, Stanford University
Subject: Emergent Topological Phases in Quantum Materials Assembled Atom-by-Atom
Refreshments served in Room 216 Physics after colloquium

The observation of massless Dirac fermions in monolayer graphene has propelled a new area of science and technology seeking to harness charge carriers that behave relativistically within solid-state materials. Using low-temperature scanning tunneling microscopy and spectroscopy, we show the emergence of Dirac fermions in a fully tunable condensed-matter system—molecular graphene—assembled via atomic manipulation of a conventional two-dimensional electron system in a surface state. We embed, image, and tune the symmetries underlying the two-dimensional Dirac equation into these electrons by sculpting the surface potential with manipulated molecules. By distorting the effective electron hopping parameters into a Kekulé pattern, we find that these natively massless Dirac particles can be endowed with a tunable mass engendered by the associated scalar gauge field, in analogy to the Higgs field. With altered symmetry and texturing of the assembled lattices, the Dirac fermions can be dressed with gauge electric or magnetic fields such that the carriers believe they are in real fields and condense into the corresponding ground state, as confirmed by tunneling spectroscopy. Using these techniques we ultimately fabricate a quantum Hall state without breaking time-reversal symmetry, in which electrons quantize in a gauge magnetic field ramped to 60 Tesla with zero applied laboratory field. We show that these and other chiral states now possible to realize have direct analogues in topological insulators, and can be used to guide or confine charge in nontrivial ways [1,2].

[1] K. K. Gomes, W. Mar, W. Ko, F. Guinea, H. C. Manoharan, “Designer Dirac Fermions and Topological Phases in Molecular Graphene,” Nature 483, 306–310 (2012).

[2] M. Polini, F. Guinea, M. Lewenstein, H. C. Manoharan, V. Pellegrini, “Artificial Honeycomb Lattices for Electrons, Atoms, and Photons,” Nature Nanotechnology 8, 625–633 (2013).

Faculty Host: Rafael Fernandes

Thursday, November 13th 2014
Speaker: Dinesh Shenoy and Kyle Willett
12:15 pm:
Speaker: Emilian Dudas (Ecole Polytechnique, Paris)
Subject: Aspects of Inflation in Supergravity
1:25 pm:
Condensed Matter Seminar in 210 Physics
Speaker: Hari Manoharan, Stanford University
Subject: Energy Gap Texturing in Complex Two-Dimensional Electronic Systems

In this talk I will show some of our recent work involving spatial patterning of energy band gaps from the nanoscale down to atomic dimensions. Within various two-dimensional materials, these methods can be used to control charge and spins, funnel excitons, and create new lower-dimensional topologically confined states. I’ll present some examples from strain-textured monolayer dichalcogenides, valley-polarized boundary states in molecular graphene, and spin-polarized surface states emerging from a bulk band insulator.

Faculty Host: Rafael Fernandes

Friday, November 14th 2014
08:00 am:
Untitled in Physics
Speaker: Kevin Schawinski, ETH Zurich
Subject:  The complex ends of galaxy lives: star formation, black hole feedback and the fate of gas reservoirs

Massive galaxies are broadly split into those forming stars on the main sequence, and those which are quiescent. The physical processes by which galaxies quench their star formation remain poorly understood. I analyze the properties of galaxies and track their evolutionary trajectories as they migrate from the blue cloud of star forming galaxies to the red sequence of quiescent galaxies via the `green valley'. I show that there must be two fundamentally star formation quenching pathways associated with early- and late-type galaxies which are intricately linked to how hydrogen gas reservoirs are destroyed or shut off. In the quenching of late-type galaxies, environment (or halo mass) is a key parameter, while for early-types, an internal mechanism such as black hole feedback is more likely. I will present recent HI observations supporting this picture.

3:30 pm:
History of Science, Technology, and Medicine Colloquium in 211 Andersen Library, WEST BANK
Speaker: CBI Open House: Book Event

3:30 – 5:30 p.m. Open House at CBI, 211 Andersen Library, West Bank

Open House to celebrate publication of two books:

Digital State: The Story of Minnesota’s Computing Industry
Thomas Misa
Charles Babbage Institute
University of Minnesota

Computer: A History of the Information Machine, 3rd ed
Jeffrey Yost
Charles Babbage Institute
University of Minnesota

Speaker: Marvin Marshak, University of Minnesota
Subject: Hunting Asymmetry in the Universe

Monday, November 17th 2014
12:15 pm:
Speaker: Kevin Sebesta, University of Minnesota
Subject: "Gravitational Lensing Cluster Mass Reconstruction in the Hubble Frontier Fields
1:00 pm:
CM Journal Club in 210 Tate
Speaker: Ruiqi Xing
Subject: Friedel Oscillation and Kohn-Luttinger effect

Kohn-Luttinger effect is one of the most appealing and elegant effects in condensed matter physics. The idea is simple and still widely used in the study of superconductivity. In 1965, Kohn and Luttinger(KL)[1] proposed a new pairing mechanism of superconductivity. They pointed out that in 3D weakly interacting fermion systems, even in the case of purely repulsive interactions, superconductivity will occur at sufficiently low temperature, if no other orders emerge first. Following [2] and [3], I will first review Friedel oscillations to give you an oversimplified idea about the Kohn-Luttinger(KL) mechanism, and then formulate the criterion of the appearance of superconductivity, and finally show the KL effect.
[1]W. Kohn and J. M. Luttinger,Phys. Rev. Lett. 15, 524(1965)
[2]J. M. Luttinger,Phys. Rev. 150, 202[1966]
[3]Saurabh Maiti,Andrey V. Chubukov,arXiv:1305.4609


Tuesday, November 18th 2014
Speaker: Andrew Galkiewicz, University of Minnesota
Subject: Domain wall dynamics in the thermally activated regime
12:20 pm:
Space Physics Seminar in 210 Physics
Speaker: Xiangwei Tang, University of Minnesota
Subject: First simultaneous observations of lower-hybrid, whistler-mode, electrostatic solitary, and electron cyclotron waves
Speaker: Alberto Belloni
Subject: Looking toward 2025: preparing the CMS hadronic calorimeter for the High-Luminosity LHC runs

The CMS detector, installed on the Large Hadron Collider (LHC) at CERN, has collected proton-proton collision data at a center-of-mass energy of 8TeV in the 2011-2012 period, and it is ready for the 13TeV run starting in 2015. However, the LHC is planned to provide collisions at higher and higher rates, and possibly center-of-mass energy, for the next twenty years. Will the ageing CMS detector be able to cope with the increased level of radiation? Not surprisingly, the answer is no, without a significant overhaul. I will focus on the upgrade of the CMS hadronic endcap calorimeter, and present a summary of the studies that are being performed to identify a radiation-tolerant material that could withstand the hostile environment in which it will operate. In particular, I will discuss the usage of plastic and liquid scintillators, and techniques to increase their radiation tolerance. Finally, I will present an alternative way to looking at final states with electro-weak bosons (in particular, WW final states) that can be used to infer limits on new physics scenarios.

Faculty Host: Jeremiah Mans
2:30 pm:
Biophysics Seminar in 210 Physics
There will be no seminar this week.

Wednesday, November 19th 2014
1:25 pm:
Nuclear Physics Seminar in 435 Physics
Speaker:  Zhen Yuan, University of Minnesota
Subject: Chemical Evolution Model of Fornax Dwarf Spheroidal Galaxy

In this talk I will focus on the constrains and predictions of my chemical evolution model for Fornax dwarf spheroidal galaxy (dSph), following the first talk I gave in cosmology seminar this September. With all new observational data of nearby dwarf galaxies and numerical tools of galaxy formation, we are nonetheless still at the first stage to understand chemical evolution of these small systems. Observations strongly indicate that chemical enrichment in dSphs remains inhomogeneous until the end of their star formation despite their small size. Using supernova nucleosynthesis yields as
input, I simulated stochastic and inhomogeneous mixing of newly-synthesized elements by supernovae and compare the results with the observed metallicity distributions and scatter in abundances of individual elements of e.g., Mg, Si, Ca, Ti, and Fe. The extension to r-process elements, especially Eu will be also discussed.This approach not only can test supernova nucleosynthesis models, but also provides insights into mixing of supernova ejecta with the interstellar medium (ISM). I found that this mixing depends on large-scale gas flows, the clumpy structure of the ISM, and the differences between environments of core-collapse and Type Ia supernovae.

3:35 pm:
Speaker: Albrecht Karle
Subject: The hunt for high energy neutrinos with IceCube - more evidence for their astrophysical origin
Refreshments served in Room 216 Physics after colloquium

The spectrum of cosmic rays includes the most energetic particles ever observed. The mechanism of their acceleration and their sources are, however, still mostly unknown. Observing astrophysical neutrinos can help solve this problem. Because neutrinos are produced in hadronic interactions and are neither absorbed nor deflected, they will point directly back to their source. The IceCube neutrino detector at the South Pole uses more than a billion tons of natural ice as a target for neutrino detection.I will discuss the searches for neutrinos at energies from 10^12 eV to beyond 10^15 eV with IceCube, which have provided the first evidence for a flux of neutrinos of trophysical. The data are consistent with an extragalactic neutrino flux, but there may be other contributions. This includes the detection of events with energies above 10^15 eV -- the highest energy leptons ever observed. I will review the recent findings obtained with IceCube as well as strategies underway that may help to shed more light on the origin of highest energy particles in the Universe.


Thursday, November 20th 2014
Speaker: Karl Young and Amit Kashi
12:15 pm:
Speaker: Asimina Arvanitaki (Perimeter Institute)
Subject: The Highs and Lows of the QCD Axion

The QCD axion was proposed over thirty years ago and has been searched for ever since. I will talk about two experiments that cover different parts of the QCD axion parameter space. The first is based on precision magnetometry and searches for axion mediated monopole-dipole and dipole-dipole interactions. This method is sensitive to axions in the traditional window from 10^9 to 10^11 GeV in f_a and is complementary to cavity searches, such as ADMX, and astrophysical bounds. The second experiment is Advanced LIGO which probes axion decay constants above the GUT scale through the effect of black hole superradiance.

1:25 pm:
Condensed Matter Seminar in 210 Physics
Speaker: A. P. Levanyuk, Department of Physics, University of Washington, Seattle
Subject: Phase Transitions and Domain Structures in Thin Ferroelectric Films and Multilayers

Recent advances in technology made available thin ferroelectric films and ferroelectric-paraelectric multilayers of very high quality. At the same time our understanding of properties of these systems is far from being complete. This is evidenced, in particular, by difficulties in interpretation of various anomalies observed at ferroelectric phase transitions in these systems. Experimentally, they are different from the phase transition anomalies in high quality bulk systems but the reasons of the differences are debatable. The aim of the talk is to discuss some specific features of ferroelectric phase transitions in thin films and multilayers which are visible now but, to a considerable extent, are not fully taken into account by the existing theory. The discussion is limited to answering the question about character of the ferroelectric state forming just after the transition. Three possibilities are considered: single-domain, multi-domain, two-phase. First, thin films with electrodes and on a substrate will be discussed. Incomplete screening of the depolarizing field in the electrodes and difference in properties of the surface layer and the bulk implies formation of domains at the phase transition for realistic parameters of the system. Clamping by the substrate may lead also to formation of two-phase state. This phenomenon is practically unexplored for thin films on substrates. Second, ferroelectric-paraelectric multilayers will be discussed which prove to be much more challenging for theoretical study than the thin films. This is because of lack of periodicity in the polarization distribution despite of periodicity of the structure.

Faculty Host: Boris Shklovskii

Friday, November 21st 2014
Speaker: Steve Kawaler, Iowa State
Subject: The Kepler Mission's Other Legacy: Space-based Asteroseismology

By awakening us to the amazing abundance of other planetary systems, the
Kepler mission has been a landmark in advancing our understanding of the
Universe. The basis for these discoveries is accurate photometry, with high
duty cycle, of over 100,000 stars. Thousands of planetary candidates emerged through detection of rare transit events. The data corresponding to transit events, though, is far less than 0.1% of the total amount of data obtained. The remaining >99.9% of the data is an exquisite record of the time-domain behavior of an enormous variety of stars. These photometric time series enable us to probe the interiors of stars by revealing their normal modes of oscillation - a technique known as asteroseismology. In this talk I'll discuss the remarkable strides that asteroseismology has been able to make using the remarkable archive of Kepler photometry.

Speaker: Tarja Knuuttila, Department of Philosophy, University of South Carolina
Subject: Modeling, Representing and Experimenting in the Study of Genetic Circuits
Refreshments served in Room 216 Physics at 3:15 p.m.

In philosophical discussion models have traditionally been understood as representations. However, there is a growing body of literature that focuses on the features which modeling and experimentation share with each other. I will discuss the relationship between modeling, representation and experimentation through the case of mathematical and synthetic modeling within synthetic biology. Synthetic models are engineered genetic circuits that are built from genetic material and implemented in a natural cell environment. Typically, mathematical models have been used as their "blueprints". As concrete engineered things synthetic models can be considered as experimental objects that share the characteristics of both models and experiments. I will discuss how the triangulation of mathematical and synthetic modeling has led to new insights that would have been difficult to generate by either modeling or experimentation alone.

Sponsored by the Center for Philosophy of Science

Speaker: Vincent Noireaux, University of Minnesota
Subject: Synthesis of a minimal cell: from gene circuits to self-assembly.

Monday, November 24th 2014
12:15 pm:
Speaker: Annalisa Pillepich, Center for Astrophysics
Subject: New insights on the Stellar Haloes and the Assembly of Galaxies with Eris and the Illustris Simulations

Can we theoretically predict the imprint of different accretion, merger and star formation histories on the stellar components of galaxies, across a wide range of galaxy masses and types? Can we reliably reconstruct the assembly of our Galaxy from the distribution and properties of the stellar mass across its halo, in light of the upcoming, exquisitely detailed stellar maps of the Milky Way e.g. with Rave and Gaia?
To these aims, I use state-of-the-art numerical simulations of individual galaxies (the Eris Simulation) and large cosmological volumes (the Illustris Simulation) to gain insight on the build up of galaxies, with particular focus on their lowest surface brightness components - the stellar haloes - and on Milky-Way-like objects.
For example, in the first work of a series based on ~5’000 Illustris galaxies spanning a variety of morphologies and halo masses (3×10^11 < Mvir < 10^14 Msun), we show that the solely logarithmic slope of the 3D stellar halo density profile encodes a plethora of quantitative information. We find a strong trend between stellar halo slope and total halo mass, where more massive objects have shallower stellar haloes than the less massive ones. At fixed halo mass, disk-like, blue, young, and more massive galaxies are surrounded by significantly steeper stellar haloes than elliptical, red, older, and less massive galaxies. Finally, DM haloes which formed more recently, or which accreted larger fractions of stellar mass from infalling satellites, exhibit shallower stellar haloes than their older analogs with similar masses. Our findings, combined with the most recent measurements of the strikingly different stellar power-law indexes for M31 and the Milky Way, appear to favor a massive M31, and a Milky Way characterized by a much quieter accretion history over the past 10 Gyrs than its companion.

1:00 pm:
CM Journal Club in 210 Tate
Speaker: Jiashen Cai
Subject: Fermi liquid and non-Fermi liquid

Much of the conventional condensed matter physics is based on a picture of quasiparticles. A phenomenological theory of using quasiparticles to describe interacting fermions developed by Landau was successful for many years. But recent years, more and more metals can not be explained by Landau's theory. In this talk, I will first review Landau's Fermi liquid theory and discuss the diagrammatic derivation of the theory. After that, I will use RG to give another interpretation of Fermi liquid theory. In the end, I will briefly discuss about non-Fermi liquid which can not be described by the quasiparticle picture. [1]Shankar, R. "Renormalization-group approach to interacting fermions." Reviews of Modern Physics 66.1 (1994): 129.


Tuesday, November 25th 2014
Speaker: Han Fu, University of Minnesota
Subject: Anomalously large capacitance in a carbon nanotube device
12:20 pm:
Space Physics Seminar in 210 Physics
To be announced.
There will be no seminar this week.
2:30 pm:
Biophysics Seminar in 210 Physics
There will be no seminar this week.

Wednesday, November 26th 2014
1:25 pm:
Nuclear Physics Seminar in 435 Physics
To be announced.
3:35 pm:
There will be no colloquium this week

Thursday, November 27th 2014
There will be no journal club this week-University closed for Thanksgiving
12:15 pm:
There will be no seminar this week-University Closed for Thanksgiving
1:25 pm:
Condensed Matter Seminar in 210 Physics
There will be no seminar this week-University Closed for Thanksgiving

Friday, November 28th 2014
There will be no colloquium this week-University Closed for Thanksgiving
There will be no seminar this week-University Closed for Thanksgiving

Monday, December 1st 2014
12:15 pm:
There will be no seminar this week.
1:00 pm:
CM Journal Club in 210 Tate
Speaker: Xiaoyu Wang
Subject: Pair Density Wave in Cuprate Superconductors and Case Study of Two-leg Hubbard-Heisenberg Model

The mysterious pseudogap phase in cuprate superconductors is characterized by many types of fluctuating orders, such as SDW and CDW. The onset temperature of these orders are similar to SC. One view is that SDW and CDW are competing phases of SC, and that the system is fine tuned close to a multicriticality such that all orders have similar transition temperatures. Another view, proposed by Fradkin & Kivelson, is that this is a pair density wave (PDW) state --- a FFLO SC without magnetic fields. Such a state is characterized by a spin gap and power law SC, SDW and CDW correlations. I will talk about the two-leg Hubbard-Heisenberg model, and show that PDW appears naturally. I will briefly mention how this model is related to the cuprate superconductors.
References:
[1] E. Fradkin, S.A. Kivelson and J.M. Tranquada, arXiv:1407:4480
[2] A. Jaefari and E. Fradkin, Phys. Rev. B 85, 035104 (2012)


Tuesday, December 2nd 2014
Speaker: Yuriy Sizyuk, University of Wisconsin-Madison
Subject: Magnetism in multi-orbital systems with strong spin-orbit coupling.
12:20 pm:
Space Physics Seminar in 210 Physics
To be announced.
2:30 pm:
Biophysics Seminar in 210 Physics
There will be no seminar this week.

Wednesday, December 3rd 2014
1:25 pm:
Nuclear Physics Seminar in 435 Physics
Speaker:  Cheng-Hsien Li, University of Minnesota
Subject: Wave-Packet Treatment of Detection Rate in Accelerator Neutrino Experiments

Neutrinos are treated as point particles in Monte Carlo simulations for predicting experimental observables. In this talk, possible conflict between point-particle and wave-packet pictures in accelerator neutrino experiments will be presented. Starting from the 3D solution of a Gaussian wave packet, the detector counting rate is derived using simple quantum-mechanical treatment. Considering the geometric setup and beam profile similar to the MINOS and NOvA experiments, it is demonstrated that the transverse spreading of a neutrino wave packet would result in a shifted energy spectrum from that predicted in point particle scenario if the wave packet acquires an initial transverse width a_t \lesssim 10 fm from pion decay. Absence of such spectral shift in current or future experimental data could in turn constrain the initial transverse width of a neutrino wave packet from pion decay.

3:35 pm:
Speaker: Peter Saulson, Syracuse University
Subject: What Advanced LIGO is about to see
Refreshments served in Room 216 Physics after colloquium

For the past several decades, physicists have been working to detect gravitational waves from astrophysical sources and to open a new tool for astronomical observation. Now, Advanced LIGO is about to start its first observing run. By the time it reaches its full design sensitivity around 2018, it will be able to survey a sphere 200 Mpc in radius for signals from the coalescence of binary neutron stars, deep enough to find them. It has a good chance to find signals from binaries involving black holes, too. In this talk, I’ll explain how Advanced LIGO works and why we think that its time has finally come.

Faculty Host: Vuk Mandic

Thursday, December 4th 2014
Speaker: Vihang Mehta and Larry Rudnick
12:15 pm:
Speaker: Alexander Zhiboedov (Harvard U.)
Subject: Causality Constraints on Corrections to the Graviton Three-Point Coupling
1:25 pm:
Condensed Matter Seminar in 210 Physics
Speaker: Gabriel Kotliar, Rutgers University
Subject: Layered Iron Pnictides and Chalchogenides as Hunds metals a new class of strongly correlated materials.
CANCELLED--SPEAKER UNABLE TO TRAVEL TO MN----

The recent discovery of superconductivity in iron based materials are a subject of intensive investigations and controversy. They serve as an excellent test of the current capabilities for predicting the physical properties of correlated materials. We will describe some of the LDA+DMFT based Studies for various spectroscopies: optical conductivity, photoemission and inelastic neutron scattering and will compare them with experiments. We will argue that these materials are Hunds metals, a new class of strongly correlated materials where the correlations are controlled by the strength of the Hunds rule coupling J rather than by the Hubbard U, and will place these materials in the broader context of searching for other high temperature superconductors.

Faculty Host: Rafael Fernandes

Friday, December 5th 2014
Speaker: Thomas Christian Bachlechner
Subject: CANCELLED, no seminar.
Speaker: Dr. Mark Giampapa, NSO/NOAO
Subject:  Perspectives on the Solar Cycle and Activity in Solar-Type Stars

The variability we observe in the Sun, as well as stars similar to the Sun is intimately related to the generation and emergence of magnetic fields. This process involves the interaction of convective motions, rotation and extant magnetic fields through a mechanism broadly referred to as the dynamo. Among the most visible manifestations of solar activity is the number of sunspots, which is modulated by the 11-year sunspot cycle. Similarly, solar-type stars exhibit periodic behavior analogous to the sunspot cycle on multi-year time scales along with the rotational modulation of localized regions of strong magnetic flux on their surfaces on multi-day time scales. Recently the Sun has shown indications of a decline in activity relative to previous sunspot cycles in the modern era. Is the recent behavior of the solar cycle unusual and what do current observations indicate about the nature of the next solar cycle? Could the Sun be entering a “Grand Minimum” similar to the Maunder Minimum (1645 – 1715 AD) with its prolonged period of low sunspot activity? What is the nature of cycles and activity in solar-type stars and how do stellar cycles compare to the solar cycle? These are among the questions that will be addressed from the perspective of a solar-stellar astronomer.

Speaker: Arthur Daemmrich, University of Kansas, School of Medicine, History and Philosophy of Medicine
Subject: Vulnerable Subjects, Vulnerable Knowledge: Children's Chemical Testing Programs in the United States and European Union
Refreshments served in Room 216 Physics at 3:15 p.m.

Methods for identifying health risks in children – and the very characterization of children as a vulnerable population – have undergone significant transformations in recent decades. Attention to the risks posed by industrial chemicals has expanded from waste streams to commercial products, and from surveying the environment for known toxins to mapping the ‘body burdens’ of hundreds of synthetic substances – especially potentially endocrine disrupting chemicals – found in humans. This talk presents findings from a historical and sociological research project concerning long-term testing programs in the United States and Europe. In both settings, children came to be understood as vulnerable to synthetic compounds found in breast milk or absorbed through exposure to cleaning compounds and plastic toys. Test methods, especially plans to recruit minority participants through financial incentives, proved more controversial in the United States than in the European Union. At the same time, EU member states carried out competing studies and regulators found it impossible to integrate test results. Furthermore, issues of cooperation among otherwise competing firms and between the industry and government regulators plagued efforts in the United States, while the complexity of fitting children’s testing into a major new regulatory framework for chemicals slowed testing in Europe. The talk presents an analysis of testing programs and offers historical and comparative insight on initiatives intended to generate new regulatory knowledge that is disruptive to existing governance systems and the social roles occupied by physicians, industry, government regulators, and health-oriented NGOs.

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

Monday, December 8th 2014
Speaker: TBA
Subject: TBA
12:15 pm:
Speaker: Francois Aubin, University of Minnesota
Subject:  The LABOCA/ACT survey at all redshifts

I will discuss a recent paper describing a Sunyaez Zel'dovich (SZ) effect survey on 11 galaxy clusters based on ACT, LABOCA, ACTA and CABB data. The contamination of radio sources and sub-millimetre galaxies is studied. Peculiar velocities of the galaxy clusters are extracted to constrain the kinetic SZ effect.

1:00 pm:
CM Journal Club in 210 Tate
Speaker: Tianbai Cui
Subject: Griffith Effects at Classical and Quantum Phase Transitions

Phase transitions in a quenched disordered system behave differently from the ones in a clean system. One interesting aspect of this is the Griffiths effect, namely, the properties of the phase transition can be dramatically changed by the fluctuations of the rare large spatial regions (the so call “rare regions”) that are devoid of impurities. In generic classical systems, the Griffiths effects are very weak, therefore, were seldom observed in experiments. For quantum phase transitions, however, the Griffiths phenomena are enhanced, which can lead to power-law singularities in thermodynamic quantities. I will qualitatively talk about the Griffith effect in classical phase transitions by considering a randomly diluted Ising model. Then, I will talk about the quantum Griffiths effects by studying quantum phase transitions in itinerant magnets with Heisenberg spin symmetry in the large-N limit. References: [1] T. Vojta, J. Phys. A 39, R143 (2006). [2] T. Vojta and J. Schmalian, Phys. Rev. B 72, 045438 (2005).

Speaker: Alexei Milekhin (ITEP)
Subject: RG-Whitham dynamics in Hamiltonian systems and resurgence phenomenon

Tuesday, December 9th 2014
10:00 am:
Thesis Defense in 120 PAN
Speaker: Justin Hietala, University of Minnesota
Subject:  Ds Semileptonic Decays
This is the public portion of Mr. Hietala's Thesis Defense.

We measure six exclusive decay rates of the Ds meson using CLEO data gathered at a 4170 MeV center-of-mass energy.

There will be no seminar this week.
12:20 pm:
Space Physics Seminar in 210 Physics
Speaker: Charles McEachern, University of Minnesota
Subject: Fast Computation of Alfven Waves in a Dipole Field
There will be no seminar this week.
2:30 pm:
Biophysics Seminar in 210 Physics
Subject: There will be no seminar this week.

Wednesday, December 10th 2014
1:25 pm:
Nuclear Physics Seminar in 435 Physics
Speaker:  Michael Albright, University of Minnesota
Subject: What's up with freeze-out fluctuations?

Decades of theoretical work suggests the QCD phase diagram possesses a rich structure, including multiple phases of matter which are separated by phase transition lines. In recent years, physicists have grown increasingly confident that the phase diagram may also contain a critical point--a point of second-order phase transition which terminates a line of first-order phase transitions. Now, the search is on for the critical point. The Relativistic Heavy Ion Collider (RHIC) has completed Phase I of its critical point search, called the Beam Energy Scan (BES), and researchers are preparing a follow-up search. It is believed that freeze-out fluctuations in conserved charges, like electric charge or baryon number, may contain signatures of the critical point, providing an avenue for experimental detection. In this talk, I will report on efforts to compute freeze-out fluctuations using model equations of state developed by our research group. I will also compare our results to simpler hadron gas models reported in the literature. I will show that it is difficult to reconcile predictions of the various models with lattice QCD calculations and data reported by the STAR collaboration. I will finish with some possible explanations for the discrepancies and describe how we plan to investigate them in the future.

Speaker: Agnes Mocsy
Refreshments served in Room 216 Physics after colloquium

Thursday, December 11th 2014
12:15 pm:
There will be no seminar this week.
1:25 pm:
Condensed Matter Seminar in 210 Physics
There will be no seminar this week.
1:30 pm:
Thesis Defense in 130 PAN
Speaker: Tom Hofer, University of Minnesota
Subject: Development of CDMS-II Surface Event Rejection Techniques and Their Extensions to Lower Energy Thresholds
This is the public portion of Mr. Hofer's Thesis Defense.

The CDMS-II phase of the Cryogenic Dark Matter Search, a dark matter direct-detection experiment, was operated at the Soudan Underground Laboratory from 2003 to 2008. The full payload consisted of 30 ZIP detectors, totaling approximately 1.1 kg of Si and 4.8 kg of Ge, operated at temperatures of 50 mK. The ZIP detectors read out both ionization and phonon pulses from scatters within the crystals; channel segmentation and analysis of pulse timing parameters allowed eff ective fi ducialization of the crystal volumes and background rejection sufficient to set world-leading limits at the times of their publications.

A full re-analysis of the CDMS-II data was motivated by an improvement in the event reconstruction algorithms which improved the resolution of ionization energy and timing information. The Ge data were re-analyzed using three distinct background-rejection techniques; the Si data from runs 125 - 128 were analyzed for the fi rst time using the most successful of the techniques from the Ge re-analysis. The results of these analyses prompted a novel "mid-threshold" analysis, wherein energy thresholds were lowered but background rejection using phonon timing information was still maintained. This technique proved to have signifi cant discrimination power, maintaining adequate signal acceptance and minimizing background leakage.

The primary background for CDMS-II analyses comes from surface events, whose poor ionization collection make them difficult to distinguish from true nuclear recoil events. The novel detector technology of SuperCDMS, the successor to CDMS-II, uses interleaved electrodes to achieve full ionization collection for events occurring at the top and bottom detector surfaces. This, along with dual-sided ionization and phonon instrumentation, allows for excellent fi ducialization and relegates the surface-event rejection techniques of CDMS-II to a secondary level of background discrimination. Current and future SuperCDMS results hold great promise for mid- to low-mass WIMP-search results

Speaker: Agnes Mocsy, Pratt Institute
Subject: Unexplored Cross Sections: A Physicist’s Dip into the Art World
NOTE: Due to flight delay, Colloquium has been rescheudled on Thursday, December 11

The discoveries and wonder of science have great capacity to inspire. I will discuss how as a physicist and professor at an art and design university, I have been able to share that inspiration with students from diverse backgrounds and use it to build cross-sections between the physics and art world. At the center of my efforts is the desire to find new ways to communicate important lessons from science and advocate for a more evidenced-based approach to solving problems in society. I argue that by breaking down barriers between art and science, we can better propagate the scientific way of seeing the world.


Friday, December 12th 2014
Speaker: Agnes Mocsy, Pratt Institute
Subject: On Being a Woman in Physics: My Experiences Where the Sidewalk Ends
Talk is at 1 pm. Lunch (by reservation) is at 12:30

Please go to our eventbrite page to RSVP for this event.

There will be no Colloquium this week.
There will be no Colloquium this week.
There will be no seminar this week.

Tuesday, December 16th 2014
Speaker: Alberto Hinojosa Alvarado
Subject: Gap structure in Fe-based superconductors with accidental nodes

Thursday, December 18th 2014
08:00 am:
09:30 am:
Thesis Defense in 120 PaN
Speaker: Scott Fallows, University of Minnesota
Subject: Measurement of Nuclear Recoils in the CDMS II Dark Matter Search
This is the public portion of Mr. Fallows Thesis Defense

The Cryogenic Dark Matter Search (CDMS) experiment is designed to
directly detect elastic scatters of weakly-interacting massive dark
matter particles (WIMPs), on target nuclei in semiconductor crystals
composed of Si and Ge. These scatters would occur very rarely, in an
overwhelming background composed primarily of electron recoils from
photons and electrons, as well as a smaller but non-negligible
background of WIMP-like nuclear recoils from neutrons, which must be
carefully limited. The CDMS II generation of detectors simultaneously
measure ionization and athermal phonon signals from each scatter, which
together allow effective discrimination against electron recoil
backgrounds.
Nuclear recoils have suppressed ionization signals relative to electron
recoils of the same recoil energy. The overall normalization and
linearity of the energy scale for electron recoils in CDMS II detectors
is clearly established by peaks of known gamma energy in the ionization
spectrum of 133Ba calibration data. This electron-equivalent (keVee)
energy scale enables relative calibration of the total phonon signal by
enforcing unity yield for electron recoils, in aggregate. Subtracting an
event's Luke phonon contribution from its calibrated total phonon
energy, as measured by the ionization signal, results in a valid measure
of the true recoil energy (keVr) for both electron and nuclear recoils.
Systematic uncertainties affecting this energy scale for nuclear recoils
are presented, along with several methods to constrain their magnitude.
The resulting adjusted WIMP limits from CDMS II are presented.


Thursday, December 25th 2014

Friday, December 26th 2014

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