Physics and Astronomy Calendar

Week of Monday, March 27th 2017

Monday, March 27th 2017
12:15 pm:
Speaker: Qi Wen, UMN
Subject:  Falling Rotation Curves of The Star-forming Galaxies Ten Billion Years Ago

In the standard model of cosmology, the mass ratio of baryons to dark matter is about 1 : 5. The mass of the outer disks in nearby (z ~0) massive galaxies are usually dominated by dark matter, which explains the observations of the common flat or slightly rising shapes of galaxies' rotation curves in the local universe. However, a recent study reported that the rotation curves of star-forming galaxies at z ~ 0.6-2.6 may commonly be falling with radius. In this talk, I will discuss this study in detail about their observations, sample selection and methodology. Finally we will look at some implications from the results obtained.

Tuesday, March 28th 2017
12:20 pm:
There will be no seminar this week.
4:30 pm:
There will be no seminar this week.

Wednesday, March 29th 2017
1:30 pm:
There will be no seminar this week.
Speaker: Aaron Mislivec, University of Minnesota
Subject: Neutrino-Nucleus Coherent Pion Production at MINERvA

Neutrino-nucleus coherent pion production is a rare neutrino scattering process that produces a lepton and pion in the forward direction while leaving the target nucleus in its initial state. Despite being rare, coherent pion production is an important background to neutrino oscillation measurements. Previous measurements of coherent pion production in the 1 to 10 GeV neutrino energy range, the energy range in which neutrino oscillation experiments operate, have been limited by either low statistics or detector capabilities. MINERvA, a dedicated neutrino-nucleus scattering experiment, has made precise measurements of neutrino and antineutrino charged current coherent pion production on carbon at 2 to 20 GeV neutrino energies. These measurements are an important input to neutrino-nucleus interaction models utilized by neutrino oscillation experiments.

4:30 pm:
CM Journal Club in PAN 120
Speaker: Mengxing Ye
Subject: Kitaev Spin Liquid
Refreshments will be served.

Reference: A. Kitaev, 'Anyons in an exactly solved model and beyond',

Thursday, March 30th 2017
10:10 am:
Biophysics Seminar in 120 PAN
Speaker: Prof. Peter Kner, University of Georgia
Subject: Wavefront Correction for Superresolution Microscopy

Superresolution microscopy is rapidly becoming an essential tool in the biological sciences allowing imaging biological structure at length scales below 250 nm. Currently, superresolution microscopy has been applied successfully on single cells achieving resolutions of 100nm down to 20nm over a few microns of depth. When superresolution microscopy is applied in thicker samples the resolution rapidly degrades. Optical aberrations and scattering distort and reduce the point spread function causing different superresolution techniques to fail in different ways. I will discuss our work on combining structured illumination microscopy and stochastic optical reconstruction microscopy with adaptive optics to achieve sub-diffraction resolution in thick tissue.

Speaker: Matt Gomer and Liliya Williams
3:35 pm:
Speaker: Alex Koulakov, Cold Spring Harbor Laboratory
Subject: Mechanism of Olfaction
Refreshments to be served outside Smith 100 after the colloquium.

Olfaction is the final frontier of our senses - the one that is still almost completely mysterious to us. Despite extensive genetic and perceptual data, and a strong push to solve the neural coding problem, fundamental questions about the sense of smell remain unresolved. Unlike vision and hearing, where relatively straightforward relationships between stimulus features and neural responses have been foundational to our understanding sensory processing, it has been difficult to quantify the properties of odorant molecules that lead to olfactory percepts. In a sense, we do not have olfactory analogs of ``red, ``green and ``blue''. The seminal work of Linda Buck and Richard Axel identified a diverse family of about 1000 receptor molecules that serve as odorant sensors in the nose. However, the properties of smells that these receptors detect remain a mystery. I will review our current understanding of the molecular properties important to the olfactory system. I will also describe a theory that explains how odorant identity can be preserved despite substantial changes in the odorant concentration.

Faculty Host: Boris Shklovskii

Friday, March 31st 2017
11:15 am:
Speaker: Cheng-Hsien Li, University of Minnesota
Subject: Density Matrix Treatment of Neutrino Oscillations In Vacuum

Motivated by our earlier estimate that shows an enormous degree of overlap among neutrino wave packets (WPs) from astrophysical sources, I will present a derivation of vacuum oscillation probability for detecting one neutrino from a pair of neutrino WPs which are described by an anti-symmetric 2-particle wave function. I will begin by briefly reviewing the oscillation probability in the one-particle framework and recast the probability as the expectation value of a projection operator which projects a neutrino WP state onto the detected WP state. In the two-particle framework, such expectation value can be computed with the help of the density matrix of the 2-particle wave function. Additional interference terms in the derived oscillation probability appear to be invariant under arbitrary re-phasing of the relevant WP states but these terms will nevertheless vanish due to the orthogonality between the two neutrino WPs. Therefore, the derived oscillation probability reduces to a simple sum of one-particle oscillation probabilities.

Speaker: Daniel Shaffer, University of Minnesota
Subject: Searching for Topological Superconductivity in MoS_2 (and other transition metal dichalcogenides)
Speaker: Alex Kamenev (UMN)
Subject: TBA
There is no colloquium this week.
Subject: Author Meets Readers: David M. Miller's "Representing Space in the Scientific Revolution"
Refreshments served at 3:25 p.m.


Katherine Brading, Philosophy, University of Notre Dame

Samuel Fletcher, Philosophy, University of Minnesota

Edward Slowik, Philosophy, Winona State University

Abstract: The novel understanding of the physical world that characterized the Scientific Revolution depended on a fundamental shift in the way its protagonists understood and described space. At the beginning of the seventeenth century, spatial phenomena were described in relation to a presupposed central point; by its end, space had become a centerless void in which phenomena could only be described by reference to arbitrary orientations. David Marshall Miller examines both the historical and philosophical aspects of this far-reaching development, including the rejection of the idea of heavenly spheres, the advent of rectilinear inertia, and the theoretical contributions of Copernicus, Gilbert, Kepler, Galileo, Descartes, and Newton. His rich study shows clearly how the centered Aristotelian cosmos became the oriented Newtonian universe, and will be of great interest to students and scholars of the history and philosophy of science.

Speaker: Dan Dahlberg, University of Minnesota
Subject: Noise in Mesoscopic Magnetic Systems
4:40 pm:
Speaker: Melissa Eblen-Zayas, Carleton College
Subject: Redesigning an advanced lab course to promote experimental design

The advanced lab course can provide students with an opportunity to develop experimental design skills. However, students often struggle with the challenges and potential for failure that come with designing their own experiments. I will describe how we used results from the Colorado Learning Attitudes About Science Survey for Experimental Physics (E-CLASS) to explore student attitudes about experimental work in a course designed to promote the development of experimental design skills and how we have modified the course through the introduction of metacognitive activities in response to E-CLASS results.

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