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Events During the Week of October 15th through October 22nd, 2023

Monday, October 16th, 2023

Plasma Physics (Physics/ECE/NE 922) Seminar
Fluid Modeling of Runaway Electron Beams
Time: 12:00 pm - 1:15 pm
Place: 1610 Engineering
Speaker: Alex Sainterme, UW-Madison
Abstract: A now-common approach for modeling runaway electron (RE) effects on
macroscopic tokamak plasma dynamics introduces a simple fluid
description of a separate beam-like electron species traveling parallel to
magnetic field lines in a resistive MHD background plasma [Bandaru, et
al., PRE 99, 063317(2019)]. The RE beam provides a source of
resistance-free current density whose direction depends on the timeevolving
magnetic field. Sources of runaway electron density are
included to approximate the acceleration of electrons to high energies in
the presence of strong parallel electric fields. This fluid RE model has
been implemented in the non-ideal MHD code NIMROD. Some initial
calculations are shown to benchmark the implementation of the RE
source model. The model has also been used to study linear stability of a
particular MHD equilibrium supported entirely by RE current. It is
found that in addition to modifying the growth of the tearing mode, the
RE beam is itself unstable to a form of ’resistive hose’ instability
[Rosenbluth, Phys. Fluids 3, 932(1960)]. Scaling of the growth rate with
the resistivity of the bulk plasma shows that for Lundquist number less
than 104, the resistive hose is the fastest growing linear
instability in the system. This is relevant for RE beams generated in
tokamak disruptions where the background plasma is cold and resistive.
Preliminary nonlinear simulations of the hose mode are presented.

Alex Sainterme is a fifth year PhD student in the Nuclear Engineering
and Engineering Physics department working under Professor Carl Sovinec.
Alex’s research focuses focuses on simulation and modeling of runaway
electron dynamics and disruptions in tokamaks.
Host: Prof. Steffi Diem
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Tuesday, October 17th, 2023

No events scheduled

Wednesday, October 18th, 2023

Theory Seminar (High Energy/Cosmology)
Extensions of a scale separation AdS$_4$ solution and their mass spectrum.
Time: 12:00 pm - 1:00 pm
Place: 5280 Chamberlin Hall
Speaker: Georgios Tringas , Annecy, LAPTH
Abstract: In this talk we will discuss two extensions of the so-called DGKT solution, a 4d scale-separated anti-de Sitter (AdS) solution obtained as a compactification on a 6d torus orbifold. Each extension consists in a specific large n expansion beyond the DGKT solution, where n is the unbounded F4-flux parameter. One of the extensions considered generalizes the known warped, partially localized solution. We analyse the two extensions in 10d massive type IIA supergravity as well as in a 4d effective theory, using a general warped compactification formalism. The main new correction to DGKT that we get is one from F4, the other fluxes being constrained by flux quantization. In each extension, one would expect corrections to the mass spectrum, before reaching contributions from alpha-prime corrections. However the mass spectrum turns out to be robust and conformal dimensions remain unchanged.
Host: Gary Shiu
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Time: 12:00 pm - 1:00 pm
Place: Sterling B343
Abstract: We will be discussing the article "Accelerating and scaling mentoring strategies to build infrastructure that supports underrepresented groups in STEM" by Adams et al (paper pdf). We will also be going over a brief summary at the beginning of the hour and welcome attendees who have not had a chance to read the article.

GREAT IDEAS stands for Group for Reading, Educating, And Talking about Inclusion, Diversity, Equity, & Advocacy in Science. It is a multimedia reading group dedicated to amplifying the experiences of underrepresented groups in science and academia in order to become better advocates for our peers. GREAT IDEAS is open to everyone (students/ faculty/ staff/ etc), and all are welcome and encouraged to engage with the material and contribute to the discussions. To keep a welcoming and safe environment for everyone, we ask that everyone understand and adhere to our community guidelines for the discussions.
Host: GMaWiP (contact Faizah with questions)
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Thursday, October 19th, 2023

R. G. Herb Condensed Matter Seminar
Time: 10:00 am
Place: 5310 Chamberlin
Speaker: Luca Delacretaz, U Chicago
Host: Ilya Esterlis
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Astronomy Colloquium
Uncovering Hidden Worlds: Challenges and Statistical Solutions in Detecting Low-Mass Exoplanets Amidst Stellar Activity
Time: 3:30 pm - 4:30 pm
Place: 4421 Sterling Hall
Speaker: Jessi Cisewski-Kehe, University of Wisconsin - Madison
Abstract: Thousands of exoplanets have been discovered contributing to an improved understanding of our universe.  However, a critical challenge remains related to the limited number of low-massed exoplanet detections.  When a planet has a low mass (akin to the mass of the Earth or lower), the small signal is difficult to detect. Furthermore, stellar activity may hide a planetary signal or mimic a planetary signal leading to false detections.   

Though a variety of methods have been developed to address these challenges, a sufficient and general methodology to uncover the population of low-mass exoplanets is not available.  During this presentation, I plan to discuss the statistical challenge in the detection of low-mass exoplanets in the presence of stellar activity using extreme precision radial velocity spectra and introduce statistical methodology that has potential to address this challenge by focusing on absorption line modeling. 

General comments about the field of astrostatistics will also be made, along with a possible brief discussion on topological data analysis and its relevance to astronomy.
Host: Ke Zhang
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Friday, October 20th, 2023

Theory Seminar (High Energy/Cosmology)
CP violating top-Higgs coupling in SMEFT
Time: 1:00 pm - 2:00 pm
Place: Chamberlin 5310
Speaker: Ya-Juan Zheng, Iwate U.
Abstract: The total cross section of the process mu- mu+ > vm vm~ ttH has strong dependence on the CP phase (xi) of the top Yukawa coupling, where the ratio of xi=pi and xi=0 (SM) grows to 630 at rts=30 TeV, 3300 at 100 TeV. We study the cause of the strong energy dependence and identied its origin as the (E/mW)2 growth of the weak boson fusion sub-amplitudes, WL- WL+ > ttH, when the two W's are longitudinally polarized. We repeat the study in the SMEFT framework where the EW gauge invariance is manifest, and find that the highest energy cross section is reduced to a quarter of the complex top Yukawa model result, with the same energy power. By applying the Goldstone boson (GB) equivalence theorem, we identied the origin of this strong energy growth of the SMEFT amplitudes as the contact dimension-6 pi-pi+ttH vertex, where pi^+- denotes the GB of W^+-. We obtain the Unitarity bound on the coecient of the SMEFT operator by using the optical theorem.
Host: Yoshihiko Abe
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Saturday, October 21st, 2023

No events scheduled

Sunday, October 22nd, 2023

Saving Coral Reefs from Climate Change Through Science and Art
Time: 2:00 pm - 3:00 pm
Place: Madison Museum of Contemporary Art, 227 State Street Madison, WI, 53703
Speaker: Pupa Gilbert, UW–Madison physics
Abstract: At first look, Federico’s Uribe’s Plastic Reef (2018-2023) appears to be an underwater world filled with corals, mussels, and schools of fish. However, everything has been created and replicated using thousands of pieces of upcycled plastic carefully cut, dyed, and arranged. Discarded plastic bottles, cutlery, flip flops, and other plastic detritus that finds its way to the oceans, where it collects into “garbage islands” highlights the damage done to the oceans by pollution.

Pupa Gilbert will use the coral reef on display in Federico Uribe: Metamorphosis | Metamorfosis as a jumping off point to discuss how to save coral reefs and counter the damage of humans through from climate change. Gilbert is a Professor of Physics at the University of Wisconsin-Madison and a visiting faculty scientist at the Lawrence Berkeley National Laboratory.

This talk is presented in conjunction with the Wisconsin Science Festival. For more info:
Host: MMoCA, Wisconsin Science Festival
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