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Events During the Week of October 17th through October 24th, 2021

Monday, October 18th, 2021

Plasma Physics (Physics/ECE/NE 922) Seminar
“Overcoming challenges in atmospheric pressure plasma studies: instabilities, self-organization and complex interfaces”
Time: 12:00 pm
Place:
Speaker: Peter Bruggeman (Univ of MN)
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Tuesday, October 19th, 2021

Theory Seminar (High Energy/Cosmology)
Jet Timing
Time: 4:00 pm
Place: Chamberlin 5280
Speaker: Matthew Low, University of Pittsburgh
Abstract: The measurement of the arrival time of a particle, such as a lepton or photon, reaching the detector provides valuable information. A similar measurement for a hadronic final state, however, is much more challenging as one has to extract the relevant information from a collection of particles. In this talk, I will explore the most effective ways to combine the times of particles into a single time for a jet. First, prompt jets will be discussed, then the more complicated case of delayed jets will be studied. Choosing a good definition of the time of a jet offers a new complementarity probe into hadronic physics at colliders. 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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Network in Neutrinos, Nuclear Astrophysics, and Symmetries (N3AS) Seminar
Exploring Axion-like Particles with Nearby Supernovae
Time: 6:00 pm
Place: Zoom:
Speaker: Kanji Mori , Fukuoka University, Japan
Abstract: Axion-like particles (ALPs) are hypothetical pseudo-Nambu-Goldstone bosons which are a candidate of dark matter. Since they are thought to couple with photons, ALPs can be produced in hot astrophysical plasma. Once produced, ALPs decay into photons which may be observable with gamma-ray telescopes. I calculated the ALP emission from a thermonuclear (i.e. type Ia) supernova and a massive star in the final stage of stellar evolution. It is shown that gamma-rays that originate from ALPs can be a target of next-generation gamma-ray telescopes and provide an independent constraint on ALP parameters. Also, ALPs may affect energy transfer in core-collapse supernovae. I will mention a preliminary result on supernova explosion aided by heavy ALPs.
Host: Baha Balantekin
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Wednesday, October 20th, 2021

Physics ∩ ML Seminar
Machine Learning Application for the Event Horizon Telescope
Time: 11:00 am
Place: Chamberlin 5280 (Zoom link also available for online participants who signed up on our mailing list)
Speaker: Joshua Yao-Yu Lin , University of Illinois at Urbana-Champaign
Abstract: The Event Horizon Telescope (EHT) recently released the first horizon-scale images of the black hole in M87. Combined with other astronomical data, these images constrain the mass and spin of the hole as well as the accretion rate and magnetic flux trapped on the hole. An important question for EHT is how well key parameters such as spin and trapped magnetic flux can be extracted from present and future EHT data alone. In the first half of the talk, we explore parameter extraction using a neural network trained on high-resolution synthetic images drawn from state-of-the-art simulations. We find that the neural network is able to recover spin and flux with high accuracy. We are particularly interested in interpreting the neural network output and understanding which features are used to identify, e.g., black hole spin. Using feature maps, we find that the network keys on low surface brightness feature in particular. In the second half of the talk, I will also mention an ongoing project VLBInet, in which we propose a data-driven approach to analyze complex visibilities and closure quantities for radio interferometric data with neural networks. Using mock interferometric data, we show that our neural networks are able to infer the accretion state as either high magnetic flux (MAD) or low magnetic flux (SANE), suggesting that it is possible to perform parameter extraction directly in the visibility domain without image reconstruction.
Host: Gary Shiu
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Thursday, October 21st, 2021

Astronomy Colloquium
“Star Formation, Solar Physics, and Stellar Astrophysics: A Data-Intensive Approach”
Time: 3:30 pm
Place: 4421 Sterling Hall, Coffee and Cookies at 3:30 pm, Talk starts at 3:45 pm
Speaker: Keivan Stassun, Vanderbilt University
Abstract: Large time-domain surveys, from the ground and from space, are enabling new data-intensive approaches to a variety of problems in stellar and solar astrophysics. This talk describes four projects, each serving as a vignette of a different but complementary mode of data-intensive research into the formation and evolution of Sun-like stars. The SLoWPoKES project extracts from the Sloan Digital Sky Survey the largest sample of wide low-mass binaries ever assembled, which we use to constrain binary star formation theory and the role of third bodies in the formation of tight binaries. The EB Factory project seeks to identify rare, but astrophysically very interesting, case studies from among the large numbers of eclipsing binaries being harvested by surveys for transiting exoplanets. We use a set of rare low-mass and brown-dwarf eclipsing binaries to elucidate the role
of magnetic activity in altering the basic properties of low-mass stars and brown dwarfs, affecting our understanding of the stellar initial mass function and the frequency of brown dwarfs in stellar populations. The X10000 Project studies the structures of young stellar coronae in order to understand the role of extreme coronal mass ejections in the angular momentum evolution of young stars. As a by-product of this work, we have determined the first robust empirical relationship between X-ray flare energy and coronal mass loss for the Sun. Finally, we use the Kepler database of precision light curves for 150,000 stars to present a new, “photometric variability HR diagram” which enables accurate determination
of stellar surface gravities, improves our knowledge of exoplanet
properties, and enhances our ability to identify the most radial-velocity quiet stars for exoplanet discovery.

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


Host: THIS IS A ZOOM TALK.
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Friday, October 22nd, 2021

Wonders of Physics
Lab Escape
Time: 10:00 am
Place: Ingersoll Physics Museum
Abstract: World-renowned quantum physicist Professor Alberta Pauline Schrödenberg desperately needs your help — the fate and security of the entire world (and more importantly, her funding!) hang in the balance. You’ll have to search her lab, solve mind-blowing puzzles to reveal clues, and hopefully find a way to complete your mission!

For more information, see our listing on the Wisconsin Science Festival website:
Host: Wonders of Physics
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Graduate Introductory Seminar (Physics 701)
Linking the theory and observation of astroparticles
Time: 12:05 pm
Place: 2241 Chamberlin
Speaker: Ke Fang, UW Madison Department of Physics
Host: Sridhara Dasu
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Physics Department Colloquium
Extremely out-of-equilibrium 1D gases
Time: 3:30 pm
Place: 2103 Chamberlin Hall
Speaker: David Weiss, Penn State
Abstract: It is notoriously hard to calculate the out-of-equilibrium dynamics of many-body quantum systems. While confining particles to one dimension sometimes simplifies dynamics, even in 1D, dynamical solutions have usually been elusive. A new approximate theory, generalized hydrodynamics (GHD), can model previously intractable dynamics. But are GHD’s approximations valid? I will describe a series of experiments with 1D Bose gases taken very far from equilibrium by, for instance, making sudden trap changes that lead them to compress 35-fold. We study the evolving distribution of rapidities, which are the momenta of the quasiparticles that emerge in these many-body systems, and which we only recently first experimentally observed for equilibrium 1D gases. These out-of-equilibrium experiments allow us to test the underlying assumptions of GHD across coupling regimes. As I will show, we find excellent agreement between our experiments and GHD theory.
Host: Alex Levchenko
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Wonders of Physics
The Wonders of Physics Traveling Show
Time: 6:00 pm
Place: Top of State Street, near the Historical Museum
Speaker: Haddie McLean, UW Physics Department
Abstract: The Wonders of Physics traveling show is back! Join Haddie McLean for a fast-paced, interactive presentation as part of the Wisconsin Science Festival.
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Wonders of Physics
The Wonders of Physics Traveling Show
Time: 7:00 pm
Place: Top of State Street, near the Historical Museum
Speaker: Haddie McLean, UW Physics Department
Abstract: The Wonders of Physics traveling show is back! Join Haddie McLean for a fast-paced, interactive presentation as part of the Wisconsin Science Festival.
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Saturday, October 23rd, 2021

Wonders of Physics
Lab Escape
Time: 9:00 am
Place: Ingersoll Physics Museum
Abstract: World-renowned quantum physicist Professor Alberta Pauline Schrödenberg desperately needs your help — the fate and security of the entire world (and more importantly, her funding!) hang in the balance. You’ll have to search her lab, solve mind-blowing puzzles to reveal clues, and hopefully find a way to complete your mission!

For more information, see our listing on the Wisconsin Science Festival website:
Host: Wonders of Physics
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Sunday, October 24th, 2021

Wonders of Physics
Lab Escape
Time: 10:00 am
Place: Ingersoll Physics Museum
Abstract: World-renowned quantum physicist Professor Alberta Pauline Schrödenberg desperately needs your help — the fate and security of the entire world (and more importantly, her funding!) hang in the balance. You’ll have to search her lab, solve mind-blowing puzzles to reveal clues, and hopefully find a way to complete your mission!

For more information, see our listing on the Wisconsin Science Festival website:
Add this event to your calendar