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Events on Friday, April 2nd, 2021

Academic Calendar
Spring recess (reduced for spring 2021)
Time: 12:00 am
Place:
Abstract: *Note: actual end time may vary.*
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Theory Seminar (High Energy/Cosmology)
Beyond Lorentz's Lamp-post: Amplitude Techniques for Cosmology
Time: 10:00 am
Place: For zoom link, sign up at: https://groups.google.com/a/g-groups.wisc.edu/d/forum/theoryseminars/join
Speaker: Scott Melville, University of Cambridge
Abstract: In recent years, a number of powerful techniques have been developed for scattering amplitudes, exploiting fundamental principles like unitarity and causality to place constraints on our effective field theories. However, most of this progress has been confined to Lorentz-invariant systems, and so cannot be applied to cosmology (in which the expanding spacetime background spontaneously breaks Lorentz symmetry). In this talk, I will describe how we can import these amplitude techniques to systems without Lorentz symmetry, and in particular how they impact the Effective Field of Theory of inflation, identifying a region of parameter space in which unitarity/causality guarantees new physics beyond single-field, weakly coupled inflation.
Host: Lars Aalsma
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Astronomy Special Friday Lunch Talk
"Making Use of Imaged Spotted Stellar Surfaces"
Time: 12:00 pm
Place: Zoom Meeting See Abstract for Link
Speaker: Rachael Roettenbacher, Yale University
Abstract: For stars with convective outer layers, stellar magnetism manifests as dark starspots--localized regions of stifled convection. Starspots affect measurements of fundamental stellar parameters, including temperature and radius, which lead to inaccurate estimates of age and mass. Additionally, starspots have been shown to mimic and obscure detections of planets. By imaging stellar surfaces, we begin to disentangle the signatures of stellar magnetism. The imaging efforts discussed here feature aperture synthesis imaging using interferometric data with sub-milliarcsecond resolution. Using this technique and others, I obtain images of active systems and detect magnetic structures. Here, I will discuss my work to study individual stars and survey spotted stars in order to understand how stellar magnetism changes across the Hertzsprung-Russell diagram and impacts the evidence and characterization of companions.

Zoom Link:

https://uwmadison.zoom.us/j/88513896776?pwd=Y1JtRE1KZllxWkFTamJBSGtGdm9yQT09
Host: Professor Ellen Zweibel
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Department Coffee Hour
Department Coffee Hour - CANCELLED
Time: 3:30 pm
Place: CANCELLED this week
Abstract: CANCELLED - No classes Friday, April 2, 2021 - mini break.
Host: Climate and Diversity Committee
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