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Events During the Week of March 28th through April 4th, 2021

Monday, March 29th, 2021

Plasma Physics (Physics/ECE/NE 922) Seminar
The Centrifugal Mirror Fusion Experiment (CMFX): Parameter Space Design, Diagnostics and Construction Process
Time: 12:00 pm
Place: Zoom Meeting
Speaker: Prof. Carlos Romero-Talamas, Univ of Maryland-Baltimore County
Abstract: Chris Hegna is inviting you to a scheduled Zoom meeting. Join Zoom Meeting Meeting ID: 918 3541 9103 Passcode: 578475 One tap mobile +13126266799,,91835419103#,,,,*578475# US (Chicago) +19292056099,,91835419103#,,,,*578475# US (New York) Dial by your location +1 312 626 6799 US (Chicago) +1 929 205 6099 US (New York) +1 301 715 8592 US (Washington D.C) +1 346 248 7799 US (Houston) +1 669 900 6833 US (San Jose) +1 253 215 8782 US (Tacoma) Meeting ID: 918 3541 9103 Passcode: 578475 Find your local number: Join by SIP Join by H.323 (US West) (US East) (India Mumbai) (India Hyderabad) (Amsterdam Netherlands) (Germany) (Australia) (Singapore) (Brazil) (Canada) (Japan) Meeting ID: 918 3541 9103 Passcode: 578475
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Plasma Theory Seminar
Time: 4:00 pm
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Tuesday, March 30th, 2021

Network in Neutrinos, Nuclear Astrophysics, and Symmetries (N3AS) Seminar
Theory of Fast Flavor Conversion of Supernova Neutrinos
Time: 2:00 pm - 3:00 pm
Place: hosted by Baha Balantekin
Speaker: Soumya Bhattacharyya, Tata Institute of Fundamental Research
Abstract: A supernova natively emits neutrinos and antineutrinos of all flavors with different luminosities and energy spectra. These neutrinos can undergo neutrino-neutrino forward-scattering inside the dense anisotropic interior of the star and can lead to ``Fast Neutrino Flavor Conversion''. We present the first ever theory of ``Fast Neutrino Flavor Conversion'' beyond the linear regime to show how the different neutrino flavors are brought closer to each other or in other words ``Flavor Depolarizes'' due to irreversible decoherence-like processes occurring at a Tera-Hz rate, determined by the large neutrino density. Our theory explains how depolarization happens, when does it happen, what determines the epoch and finally describes a method to calculate the extent of depolarized fluxes. This new result allows detailed implementation of flavor-dependent neutrino transport in supernova simulations and paves the way for supernova neutrino phenomenology.
Host: Baha Balantekin
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Wednesday, March 31st, 2021

Department Meeting
Time: 12:15 pm - 1:15 pm
Place: Virtual see "abstract" for connection info
Speaker: Sridhara Dasu, Department Chair
AIMEE N LEFKOW is inviting you to a scheduled Zoom meeting.

Topic: Department Meeting
Time: Jan 13, 2021 12:15 PM Central Time (US and Canada)
Every week on Wed, until May 12, 2021, 18 occurrence(s)
Jan 13, 2021 12:15 PM
Jan 20, 2021 12:15 PM
Jan 27, 2021 12:15 PM
Feb 3, 2021 12:15 PM
Feb 10, 2021 12:15 PM
Feb 17, 2021 12:15 PM
Feb 24, 2021 12:15 PM
Mar 3, 2021 12:15 PM
Mar 10, 2021 12:15 PM
Mar 17, 2021 12:15 PM
Mar 24, 2021 12:15 PM
Mar 31, 2021 12:15 PM
Apr 7, 2021 12:15 PM
Apr 14, 2021 12:15 PM
Apr 21, 2021 12:15 PM
Apr 28, 2021 12:15 PM
May 5, 2021 12:15 PM
May 12, 2021 12:15 PM
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Meeting ID: 924 9932 5588
Passcode: 337209
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+19292056099,,92499325588#,,,,*337209# US (New York)
+13017158592,,92499325588#,,,,*337209# US (Washington D.C)

Dial by your location
+1 929 205 6099 US (New York)
+1 301 715 8592 US (Washington D.C)
+1 312 626 6799 US (Chicago)
+1 669 900 6833 US (San Jose)
+1 253 215 8782 US (Tacoma)
+1 346 248 7799 US (Houston)
Meeting ID: 924 9932 5588
Passcode: 337209
Find your local number:
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Join by H.323 (US West) (US East) (India Mumbai) (India Hyderabad) (Amsterdam Netherlands) (Germany) (Australia) (Singapore) (Brazil) (Canada) (Japan)
Meeting ID: 924 9932 5588
Passcode: 337209

Host: Sridhara Dasu
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Thursday, April 1st, 2021

Cosmology Journal Club
Time: 12:00 pm - 1:00 pm
Abstract: Each week, we start with a couple scheduled 15-20 minute talks about one's research, or an arXiv paper. The last part will typically be open to the group for anyone to discuss an arXiv paper.

All are welcome and all fields of cosmology are appropriate.

Contact Ross Cawthon, cawthon@wisc, for more information.

Zoom info
Meeting ID: 93592708053, passcode: cmbadger

Or click:
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NPAC (Nuclear/Particle/Astro/Cosmo) Forum
New results from the Hydrogen Epoch of Reionization Array
Time: 2:30 pm - 3:30 pm
Speaker: Danny Jacobs, Arizona State University
Abstract: Observations of the 21cm hydrogen line in the early universe (redshifts 25 to 5) are expected to shed light on the origins of stars, inflation, and dark matter. First generation interferometers have placed ever-lower limits on the fluctuation power spectrum and the EDGES experiment has reported a potential global absorption trough at redshift 18. The Hydrogen Epoch of Reionization Array (HERA) is a second generation instrument which aims for a high significance power spectrum measurement between redshifts 5.5 and 12 and experimental observations to redshift 18. In 2016 HERA was operated with 20% of its collecting area. This data has been used to develop a pipeline which has produced what is currently the lowest power spectrum upper limit. I will report on these results and describe our upgrade campaign for the full array aimed at lowering systematic floors and expanding the redshift range to 25.

The speaker will be available for one-on-one meetings on Monday April 5 - Weds April 7. If you would like to meet with the speaker, please contact Peter Timbie to set up an appointment.
Host: Peter Timbie
Presentation: zoom_20210401.txt
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Astronomy Colloquium
How do galaxies in the nearby Universe grow?
Time: 3:30 pm - 5:00 pm
Place: Zoom meeting(see Abstract ) Coffee and tea 3:30pm, Talk 3:45pm
Speaker: Sanchayeeta Borthakur,, Arizona State
Abstract: Galaxy growth is a slow but continuous process. The observed properties of galaxies suggest that accretion must continue to support star formation. However, direct observational evidence of gas flows into galaxies have been extremely hard to come by. One of the most promising regions in our search has been the disk-halo interface, where we are uncovering signs of gas condensation.

In this talk, I will discuss the results from our ongoing DIISC (Deciphering the Interplay between the ISM, Stars, and the CGM) survey, which probes the disk-halo interface. I'll discuss our findings in terms of the signpost of gas accretion and galactic feedback. I'll also show evidence that structures such as high-velocity clouds and extra-planar gas seen in the Milky Way and a few other galaxies are indeed prevalent in most galaxies. These gaseous structures represent a pathway for gas accretion into galaxies and can be one of the primary ways how galaxies accrete gas in the nearby Universe.
Zoom Link
Host: Professor Amy Barger UW Astronomy
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Thesis Defense
Exploring the Use of Signal Envelopes for Neutrino Detection with In-Ice Radio Arrays
Time: 4:00 pm
Speaker: Benjamin Hokanson-Fasig, Physics PhD Graduate Student
Abstract: Neutrinos are unique cosmic messengers that can be used to probe the universe for sources of ultra-high energy cosmic rays. In order to detect the highest energy neutrinos, which are expected to interact very rarely, a large detector volume is necessary. The Askaryan Radio Array (ARA) and similar neutrino detectors use the Antarctic ice as their detector volume, searching for radio signals from neutrino-induced particle showers in the ice. This detection technique results in radio neutrino detectors that are highly sensitive to neutrinos with energies above 10 PeV. This thesis explores the possibility of using envelopes of the voltage signals from antennas in ARA to perform neutrino searches. A detector making use of signal envelopes could have a significantly lower power consumption, making it an attractive option in power-limited regions like Antarctica. By reproducing the reconstruction method used in previous ARA analyses, a reconstruction using signal envelopes is shown to be able to reconstruct the location of a neutrino event in the ice with an error of 1--2 degrees. However, since the ARA stations are not optimized for this method, the use of signal envelopes for a complete analysis of ARA data is ultimately found to be unrealistic. In the absence of a direct comparison between the previous ARA analysis and a signal-envelope analysis, further applications of the signal envelope are proposed, including detector geometries that are more optimized for envelope analysis as well as options for using signal envelopes to lower the trigger threshold of radio neutrino detectors.
Host: Kael Hanson, Faculty Advisor
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Friday, April 2nd, 2021

Academic Calendar
Spring recess (reduced for spring 2021)
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 - 11:00 am
Place: For zoom link, sign up at:
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 - 1:30 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:

Host: Professor Ellen Zweibel
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Department Coffee Hour
Department Coffee Hour - CANCELLED
Time: 3:30 pm - 4:30 pm
Place: CANCELLED this week
Abstract: CANCELLED - No classes Friday, April 2, 2021 - mini break.
Host: Climate and Diversity Committee
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Saturday, April 3rd, 2021

Academic Calendar
Spring recess (reduced for spring 2021)
Abstract: *Note: actual end time may vary.*
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Sunday, April 4th, 2021

Academic Calendar
Spring recess (reduced for spring 2021)
Abstract: *Note: actual end time may vary.*
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