Events During the Week of October 27th through November 3rd, 2024
Monday, October 28th, 2024
- Climate & Diversity
- Climate and Diversity Committee Open Hours
- Time: 12:00 pm - 2:00 pm
- Place: Chamberlin 5310
- Speaker: Rachel Zizmann, UW-Madison Physics
- Abstract: Open Hours are welcome for everyone in the department! During these sessions, we have the option to discuss the topic listed, that is not required or necessary for attending
- Host: Rachel Zizmann
- Plasma Physics (Physics/ECE/NE 922) Seminar
- Realta Fusion's axisymmetric mirror development program
- Time: 12:05 pm - 1:00 pm
- Place: 1610 Engineering Hall
- Speaker: Sam Frank, Realta Fusion
- Abstract: Realta Fusion is a startup spun out from the University of Wisconsin - Madison aiming to decarbonize industrial heat and power with axisymmetric magnetic mirror fusion power plants. Realta Fusion actively sponsors magnetic mirror research on the Wisconsin HTS Axisymmetric Mirror (WHAM), which had its first plasma in July 2024, and is working to develop a tandem mirror fusion pilot plant, Hammir. In this presentation, we will discuss Realta Fusion's mirror development roadmap, early experimental results from WHAM with comparisons to simulations using Realta Fusion's RealTwin modeling framework, and a number of aspects of the Hammir tandem mirror pilot plant design.
- Host: John Sarff
Tuesday, October 29th, 2024
- Theory Seminar (High Energy/Cosmology)
- Detecting Ultrashort Gamma-ray Bursts Originated from Ultraheavy Dark Matter Collisions
- Time: 11:00 am - 12:00 pm
- Place: 5310 Chamberlin Hall
- Speaker: Xuheng Luo, Johns Hopkins University
- Abstract: Dark matter may exist today in the form of ultraheavy composite bound states. Collisions between such dark matter states can release intense bursts of gamma-rays. Thus, indirect-detection signals of dark matter may include unconventional gamma-ray bursts. Such bursts may have been missed not necessarily because of their low arriving gamma-ray fluxes, but rather their ultrashort duration and rareness. In this talk, I will discuss the strategies and prospects for detecting such ultrashort gamma-ray burst. I will also present a concrete dark matter model that produces bursts potentially detectable by the current instruments.
- Host: Yang Bai
- Network in Neutrinos, Nuclear Astrophysics, and Symmetries (N3AS) Seminar
- SIMP Miracles and WIMP Dead Ends: Navigating the Freeze-Out of MeV Dark Matter
- Time: 2:00 pm - 3:00 pm
- Place:
- Speaker: Joseph Pradler, HEPHY, Vienna
- Abstract: In this talk we consider both the possibility of dark matter being either a strongly or a weakly interacting thermal relic. For strongly interacting massive particles (SIMPs) we study the influence of bound states X on their cosmology, finding a "catalysis" of mass-depleting processes in the hidden sector, adding a qualitative change to SIMP freeze-out once X exist, hence broadening the options for SIMP dark matter. In turn, for weakly interacting massive particles (WIMPs) we study the low mass frontier of thermal relics where freeze-out happens during the cosmological non-trivial epochs of neutrino decoupling and primordial nucleosynthesis. Here we present a first self-consistent calculation of the cosmological Neff parameter that is expected to be measured with much improved accuracy in upcoming CMB experiments.
NOTE: All participants and hosts are now required to sign into a Zoom account prior to joining meetings hosted by UC Berkeley.
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Meeting ID: 912 3071 4547 - Host: Balantekin
- High Energy Seminar
- Road to Minimal WIMPs
- Time: 3:00 pm - 4:00 pm
- Place: 5280 Chamberlin
- Speaker: Rodolfo Capdevilla Roldan, FNAL
- Abstract: Minimal WIMP models extend the Standard Model with an electroweak multiplet whose neutral component $\chi_0$ serves as Dark Matter (DM). Direct Detection (DD) and Indirect Detection (ID) searches probe these models especially when $\chi_0$ accounts for 100% of DM (the thermal target). Colliders aim to produce the charged members of the multiplet, which produce interesting signals when they decay. These searches are more effective when $\chi_0$ accounts for a fraction of DM, as this leads to a lower mass multiplet and larger production cross sections. This shows an interesting complementarity between DD, ID, and colliders. In this talk, I discuss the role that present and future colliders can play in discovering Minimal WIMPs. I show how a 3 TeV muon collider can discover the elusive doublet (Higgsino-like) state up to its thermal target. As the collider energy increases, larger multiplets become accessible. A 10 TeV muon collider could discover the triplet (Wino-like) state up to its thermal target as well as a quintuplet state that accounts for ~10% of DM. These results indicate an interesting path ahead towards the possible discovery of the long standing minimal WIMPs.
- Host: Yang Bai and Sridhara Dasu
Wednesday, October 30th, 2024
- No events scheduled
Thursday, October 31st, 2024
- R. G. Herb Condensed Matter Seminar
- Optical signatures of interlayer electron coherence in a bilayer semiconductor
- Time: 10:00 am - 6:00 pm
- Place: 5310 Chamberlin
- Speaker: Pavel Dolgirev , Harvard University
- Abstract: Emergent strongly-correlated electronic phenomena in atomically-thin transition metal dichalcogenides are an exciting frontier in condensed matter physics, with examples ranging from bilayer superconductivity and electronic Wigner crystals to the ongoing quest for exciton condensation. Here, we experimentally investigate the properties of indirect excitons in naturally-grown MoS2-homobilayer, integrated in a dual-gate device structure allowing independent control of the electron density and out-of-plane electric field. Under conditions when electron tunneling between the layers is negligible, upon electron doping the sample, we observe that the two excitons with opposing dipoles hybridize, displaying unusual behavior distinct from both conventional level crossing and anti-crossing. We show that these observations can be explained by static random coupling between the excitons, which increases with electron density and decreases with temperature. We argue that this phenomenon is indicative of a spatially fluctuating order parameter in the form of interlayer electron coherence, a theoretically predicted many-body state that has yet to be unambiguously established experimentally outside of the quantum Hall regime. Implications of our findings for future experiments and quantum optics applications are discussed.
- Host: Ilya Esterlis
- Astronomy Colloquium
- Building a Multidisciplinary Community: The Impact of Sonification World Chat in Astronomy
- Time: 3:30 pm - 4:30 pm
- Place: 4421 Sterling Hall
- Speaker: Kate Meredith, Geneva Lake Astrophysics and STEAM
- Abstract: The Sonification World Chat (SWC), initiated in February 2020, addresses the growing need for collaboration and information sharing among diverse sonification projects in astronomy. Central to SWC's mission is the inclusion of blind and low-vision (BLV) individuals, whose insights are crucial for the development of effective sonification tools, interfaces, and algorithms.
Developers without extensive accessibility experience may unintentionally adopt paternalistic approaches, missing critical insights from the BLV community. SWC was established to counteract this by promoting advocacy, project support, and collaboration.
SWC fosters a diverse professional community, including experts in science, accessibility, user-centered design, audio-acoustical engineering, music, education, and the cultural dimensions of sound perception. This diversity ensures that sonification projects can address both technical and human aspects comprehensively.
This session will provide an overview of the multidisciplinary nature of sonification and highlight key projects developed under SWC. Kate will present high-level overviews of initiatives such as Astronify (Space Telescope Science Institute), Star Sound and Vox Magellan (Swinburne University), SonoUno and Sensing the Dynamic Universe (Harvard University), and her work with the Audible Universe Meetings sponsored by the Lorentz Institute at Leiden University, Netherlands.
- Host: Melinda Soares-Furtado
Friday, November 1st, 2024
- Physics Department Colloquium
- The emergent "graviton" of the fractional quantum Hall effect
- Time: 3:30 pm - 5:00 pm
- Place: Chamberlin 2241
- Speaker: Dam T. Son, University of Chicago
- Abstract: In fractional quantum Hall states, electrons self-organize into a strongly interacting fluid with nontrivial emergent properties. It has recently been understood that fractional quantum Hall fluids accommodate one or several spin-2 excitations, which have been argued to be condensed-matter analogues of the graviton. In this talk we will review the origin of the idea of the graviton and the basic physics of the fractional quantum Hall effect. We then discuss a recent experiment claiming observation of "chiral graviton modes" and its broader implications.
- Host: Ilya Esterlis
