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Events on 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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