Physics and Astronomy Calendar

Week of Monday, April 23rd 2018


Monday, April 23rd 2018
12:15 pm:
Speaker: Qi Wen, UMN
Subject: Broadband anti-reflection coatings using “moth-eye” structures in millimeter and submillimeter astronomy

Wasting is evil, let alone wasting the light signal from billions years ago that can potentially reveal the secrets of the Universe. Unfortunately, optical elements in a telescope, such as lenses and filters, reflect part of the light back to sky. In millimeter and submillimeter astronomy, broadband anti-reflection coatings (ARC) are more desired than ever for foreground modeling. In this talk, I will introduce the subwavelength structures (SWS) or so called “moth-eye” structures as an emerging type of broadband ARC in millimeter and submillimeter astronomy.

Faculty Host: Shaul Hanany
4:40 pm:
Speaker: Irene Moskowitz (University of Minnesota)
Subject: Bolometer Response to Elevation Angle in EBEX: How can we detect evidence of inflation in the early universe?
Faculty Host: Paul Crowell

Tuesday, April 24th 2018
12:20 pm:
Space Physics Seminar in Tate 301-20
Speaker: Zac Cohen, University of Minnesota
Subject:  STEREO Observations of Waves in the Ramp Regions of Interplanetary Shocks
This is seminar is also the public portion of Mr. Cohen's Masters' Thesis Defense.

Wednesday, April 25th 2018
1:15 pm:
Speaker: Vlad Pribiag (University of Minnesota)
Subject: Spin-Dependent Transport and Superconductivity in SrTiO3-Based Heterostructures
NOTE SPECIAL TIME: Seminar starts at 1:15
Faculty Host: Paul Crowell

Thursday, April 26th 2018
10:10 am:
Biophysics Seminar in 120 PAN
Speaker: Gianluigi Veglia, Department of Biochemistry, Molecular Biology & Biophysics, University of Minnesota
Speaker: Sourabh Chauhan
3:35 pm:
Speaker: John Bush, MIT
Subject: Hydrodynamic quantum analogs

Droplets walking on a vibrating fluid bath exhibit several features previously thought to be exclusive to the microscopic, quantum realm. These walking droplets propel themselves by virtue of a resonant interaction with their own monochromatic wavefield, and represent the first macroscopic realization of a pilot-wave system of the form proposed for microscopic quantum dynamics by Louis de Broglie in the 1920s. New experimental and theoretical results allow us to rationalize the emergence of quantum-like behavior in this hydrodynamic pilot-wave system in a number of settings, and explore its potential and limitations as a quantum analog.

Faculty Host: J. Woods Halley

Friday, April 27th 2018
10:10 am:
Nuclear Physics Seminar in Tate 201-20
To be announced.
12:20 pm:
Speaker: Kexin Feng, University of Minnesota
Subject: Signatures of unusual edge physics in the specific heat of Kitaev spin liquids

Some new candidate Kitaev spin liquid material has recently been found in the experiment. Qualitative signatures of spin liquids are important to identify them. We try to explore the features of unusual edge physics in the specific heat. We find that, the fluxe excitation has some edge effects in specific heat. We also show that there is zero-temperature degenerate entropy which indicates the existence of gapless edge mode.

Speaker: Mustafa Amin (Rice U)
Subject: Inflation Ends, What’s next ?

How did inflation end? For a broad class of "simple", observationally consistent inflationary models, I will present results regarding: (1) Nonlinear fragmentation and soliton formation in the inflaton field, (2) the equation of state of the universe after inflation. For sufficiently complex models, I will highlight some universal results from stochastic particle production during inflation and reheating, and discuss their implications for initial curvature perturbations from the early universe.

2:00 pm:
Speaker: Masaaki Matsuda, ORNL
Subject: Magnetic correlations in the vicinity of the superconducting state in CrAs and MnP
Please note time and date change for this seminar. This week only.

CrAs and MnP exhibit superconductivity under pressure with a maximum transition temperature of ~2 K at 2 GPa and ~1 K at 8 GPa, respectively. Since Cr and Mn have the spin degree of freedom, elucidating the magnetic contribution to the superconductivity is crucial to understand the pairing mechanism. A helical structure is the magnetic ground state at ambient pressure in both materials. We performed neutron scattering studies in both materials under pressure. With applying pressure, the helicity and magnetic moment of the helical structure gradually change in CrAs [1], whereas MnP shows a more complicated phase diagram [2]. Most importantly, we found that both materials show helical structure in the vicinity of the superconducting phase, although the directions of the propagation vectors are different. We also studied the chemical pressure effect on static and dynamic magnetic properties in CrAs [1]. The results suggest a coupling between the magnetism and the superconductivity.

[1] M. Matsuda et al., submitted to PRX.
[2] M. Matsuda et al., Phys. Rev. B 93, 100405(R) (2016).

Speaker: Dr. Christian Veillet, Large Binocula Telescope Observatory (LBTO)
Faculty Host: Charles E. Woodward
Speaker: Richard Samuels, Department of Philosophy, The Ohio State University
Subject: "How to Acquire Number Concepts: A New Puzzle (With Stewart Shapiro and Eric Snyder)"
Refreshments served at 3:15 p.m.

Philosophers and psychologists have long been interested in how human beings learn mathematical concepts in general, and natural number concepts, in particular. Efforts to explain how such concepts are learned, however, have resulted in a number of puzzles and problems, which have led some to conclude that these concepts cannot be learned. In this talk, we first sketch some of the more important of these puzzles, and then articulate a new one that rests upon an apparent tension between two of the best empirical probes into our natural number concepts – linguistic semantics and developmental psychology. On the face of it, the dominant views in these respective fields are in tension with each other, so that if the semanticists are right, then our best accounts of how natural number concepts are learned must be wrong. Having set out this puzzle in some detail, we argue that a structuralist conception of the naturals offers a partial resolution of this apparent tension.

4:40 pm:
Speaker: Carolyn Bishoff, Physics, Astronomy and Earth Sciences Librarian
Subject: Workshop on data management

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