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Events During the Week of October 10th through October 17th, 2021

Monday, October 11th, 2021

Plasma Physics (Physics/ECE/NE 922) Seminar
Time: 12:00 pm
Place: 2241 Chamberlin Hall
Speaker: Jim Schroeder (Wheaton College)
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Tuesday, October 12th, 2021

Network in Neutrinos, Nuclear Astrophysics, and Symmetries (N3AS) Seminar
An Early Cosmological Epoch of QCD Confinement
Time: 2:00 pm - 3:00 pm
Speaker: Tim Tait , UC Irvine
Abstract: I will discuss the possibility that Physics beyond the Standard Model induces an early phase of the Universe in which QCD is confined, with a larger confinement scale than is observed today. Such a phase offers a unique mechanism that can explain the matter-antimatter asymmetry of the Universe, and offers opportunities to shed light on mysteries such as the abundance of QCD axions or WIMP dark matter.
Host: Baha Balantekin
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Theory Seminar (High Energy/Cosmology)
Cutting and gluing with running couplings in N=2 QCD
Time: 4:00 pm - 5:00 pm
Place: Chamberlin 5280
Speaker: Jan Manschot, Trinity College Dublin
Abstract: A manifestation of S-duality or strong-weak coupling duality is the equivalent dynamics of a quantum field theory at distinct values of its coupling constant. A natural question for such a quantum field theory is the determination of a domain for the coupling constant parametrizing inequivalent quantum field theories. We address this question for asymptotically free N = 2 Yang-Mills theories with gauge group SU(2) and Nf ≤ 3 fundamental hypermultiplets. To this end, we consider the order parameter for the Coulomb branch, which is a function of the running coupling τ invariant under S-duality. If the domain for τ is restricted to an appropriate fundamental domain F, the function u is one-to-one. For special choices of the masses, u does not give rise to branch points and cuts, such that u is a modular function for a congruence subgroup \Gamma of SL(2,Z) and the fundamental domain is \Gamma \in H. For generic masses, however, branch points and cuts are present, and subsets of F are being cut and glued upon varying the mass. We study this mechanism for various phenomena, such as decoupling of hypermultiplets, merging of local singularities, as well as merging of non-local singularities which give rise to superconformal Argyres-Douglas theories. Joint work with Johannes Aspman and Elias Furrer ( Note: This is a hybrid event. A zoom link will be distributed via the seminar mailing list. To join, email the organizer.
Host: Lars Aalsma
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Wednesday, October 13th, 2021

No events scheduled

Thursday, October 14th, 2021

R. G. Herb Condensed Matter Seminar
The Emergence of Superconductivity in Inhomogeneous Systems
Time: 10:00 am
Place: 5310 Chamberlin
Speaker: Nadya Mason , UIUC
Abstract: Inhomogeneous superconductivity, where puddle regions or phase separation dominates behavior, is evident in materials ranging from high-temperature superconductors to complex oxides. Yet, although inhomogeneous superconductors have been intensely studied, the nature of the onset of superconductivity in these systems is still largely unknown. In this talk I will present electrical transport measurements of model inhomogeneous superconductors, and discuss the onset and ground states of superconductivity in these systems. First, I will show how superconductivity is established in granular normal-superconducting systems via a “rare-region” or extremal-grain process. I will then show how the ordering and separation of superconducting islands in a normal metal matrix can induce metallic states and other unusual phases. These results are generally relevant to how superconductivity is established in low-dimensional or disordered systems.
Host: Alex Levchenko
Presentation: Inhomogeneous superconductivity.pdf
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Astronomy Colloquium
Exploring the Interaction of Convection and Rotation in the Core Region of Massive Stars through 3-D simulations
Time: 3:30 pm - 5:00 pm
Place: 4421 Sterling Hall, Coffee and Cookies at 3:30 pm, Talk starts at 3:45 pm
Speaker: Paul Woodward, University of Minnesota
Abstract: Over the last several years, I have been simulating stellar interiors with a 3-D compressible hydrodynamics code, PPMstar. This work is a collaboration between my team at the University of Minnesota and the team of Falk Herwig, at the University of Victoria in Canada. This work focuses on the process of material mixing at the boundaries of convection zones and their potential effects upon stellar evolution. Through such mixing processes, small concentrations of nuclear fuels can be carried downward in convection zones into regions that are much hotter, where they can burn very rapidly with significant energy release. In the last two years, we have been looking at this process in massive main sequence stars, where entrainment of hydrogen fuel into the core convection zone can extend the star's main sequence life. In the case of these main sequence stars, we have observations of asteroseismology to compare with to validate our results. We obtain mixing rates that are consistently on the high side of our expectations. This has led us to explore the effects of rotation of these stars on this convective boundary mixing. I will present results of simulations of a massive star rotating at different rates and discuss how these simulations reveal the development of more rapidly rotating equatorial jets near the top of the central convection zone, with correspondingly less rapidly rotating central regions. The behavior of internal gravity waves in the stably stratified gas above the convection zone will also be discussed, with a focus on angular momentum transport.

We strongly encourage you to attend the colloquium in person. If that is impossible, it is available over zoom at the following link:

Host: Professor and Chair Richard Townsend
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Friday, October 15th, 2021

Graduate Introductory Seminar (Physics 701)
Astrophysics and Cosmology
Time: 12:05 pm - 12:55 pm
Place: 2241 Chamberlin
Speaker: Peter Timbie, UW Madison Department of Physics
Host: Sridhara Dasu
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Physics Department Colloquium
Electronic Transport in Strain-Engineered Graphene
Time: 3:30 pm - 4:30 pm
Place: 2103 Chamberlin Hall
Speaker: Nadya Mason, UIUC
Abstract: There is wide interest in using strain-engineering to modify the physical properties of 2D materials, for both basic science and applications. Deformations of graphene, for example, can lead to the opening of band gaps, as well as the generation of pseudo-magnetic fields and novel electronic states. We demonstrate how controllable, device-compatible strain patterns in graphene can be engineered by depositing graphene on corrugated substrates. We discuss several techniques for creating corrugated substrates, focusing on periodic spherical curvature patterns in the form of closely packed nanospheres. We show how the smaller nanospheres induce larger tensile strain in graphene, and explain the microscopic mechanism of this. We also present experimental results demonstrating how a nearly periodic array of underlying nanospheres creates a strain superlattice in graphene, which exhibits mini-band conductance dips and pseudomagnetic field effects that depend on the magnitude of induced strain. This control of the strain degree of freedom provides a novel platform both for fundamental studies of 2D electron correlations and for prospective applications in 2D electronic devices.
Host: Alex Levchenko
Presentation: Strain engineered 2D materials.pdf
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