Events at Physics |
Events During the Week of April 11th through April 18th, 2021
Monday, April 12th, 2021
- Plasma Physics (Physics/ECE/NE 922) Seminar
- Creating Astrophysically Relevant Systems in the Laboratory in the High-Energy-Density Regime
- Time: 12:00 pm
- Place: Zoom Meeting
- Speaker: Prof. Carolyn Kuranz, University of Michigan
- Abstract: High-energy-density experiments can provide insight into astrophysical processes, which are often observed from great distances under uncontrolled and unknown conditions. In order for an experiment to be well-scaled to an astrophysical process, several specific conditions must be considered, including key governing equations, specific spatial scaling, and similar global dynamics. In many cases, these conditions can be met using high-energy-density experimental facilities, such as, high-energy laser or pulsed power devices. I will discuss general scaling rules and several astrophysically-relevant high-energy-density physics experiments, specifically an experiment conducted at the National Ignition Facility relevant to core-collapse supernova SN1993J, a red supergiant, where a radiative shock is near a hydrodynamically unstable interface. We found that significant energy fluxes from radiation and thermal heat conduction affect the hydrodynamics structure at the interface. In the experiments, a blast wave structure similar to those in supernovae is created in a plastic layer. The blast wave crosses a three-dimensional interface that produces unstable growth dominated by the Rayleigh-Taylor instability. We have detected the evolution of the interface structure under these conditions and will show the resulting experimental and simulation data.
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Chris Hegna is inviting you to a scheduled Zoom meeting.
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Meeting ID: 918 3541 9103
Passcode: 578475 - Monday Science Seminar
- Multidimensional Progenitor Models For Core-collapse Supernovae
- Time: 12:00 pm - 1:00 pm
- Place:
- Speaker: Dr. Carl Fields, Michigan State University and Arizona State University
- Abstract: Core-collapse supernova explosions (CCSN) are one possible fate of a massive star. Simulations of CCSNe rely on the properties of the massive star at core-collapse. As such, a critical component is the realization of realistic initial conditions. Multidimensional progenitor models can enable us to capture the chaotic nuclear shell burning occurring deep within the stellar interior. I will discuss ongoing efforts to progress our understanding of the nature of massive stars through next-generation hydrodynamic stellar models. In particular, I will present recent results of three-dimensional hydrodynamic massive star models evolved for the final 10 minutes before collapse. These recent results suggest that realistic 3D progenitor models can be favorable for obtaining robust models of CCSN explosions and are an important aspect of massive star explosions that must be taken into consideration. I will conclude with a brief discussion of the implications our models have for predictions of multi-messenger signals from CCSNe
- Host: Melinda Soares-Furtado
- Plasma Theory Seminar
- NO SEMINAR
- Time: 4:00 pm
Tuesday, April 13th, 2021
- Network in Neutrinos, Nuclear Astrophysics, and Symmetries (N3AS) Seminar
- Nucleosynthesis in magneto-rotational driven supernovae
- Time: 2:00 pm
- Place:
- Speaker: Moritz Reichert , TU – Darmstadt
- Abstract: About half of the heavy elements in our Universe are synthesized by one process, the rapid neutron capture process (r-process). This process requires extreme and violent environments that achieve the necessary neutron-rich conditions. Therefore, we use a modern state of the art hydrodynamical simulation to investigate the synthesis of elements in a possible host scenario of the r-process, so-called magneto-rotational driven supernovae. In total, we calculate the nucleosynthesis of four models with different magnetic field strengths and rotation rates. The models host a variety of nucleosynthetic conditions and synthesize neutron-rich, but also small amounts of proton-rich isotopes. We find elements up to xenon (second r-process peak) for the model with weakest magnetic field strength, which is caused by a late change of the proto-neutron star morphology. For the model with the strongest magnetic field strength, we find a fully operating r-process. Having a detailed abundance pattern of this event calculated, we discuss possible observables.
- Host: Baha Balantekin
Wednesday, April 14th, 2021
- Department Meeting
- Department Meeting - CANCELLED
- Time: 12:15 pm - 1:15 pm
- Place: Cancelled - due to lack of urgent business.
- Speaker: Sridhara Dasu, Department Chair
- Cancelled - due to lack of urgent business.
- Host: Sridhara Dasu
- Thesis Defense
- Stellarator Beta Limits with Extended MHD Modeling Using NIMROD
- Time: 1:00 pm
- Place:
- Speaker: Torrin Bechtel, Physics PhD Graduate Student
- Abstract: The nonlinear, extended MHD code NIMROD is employed to simulate self-consistent stellarator behavior at high beta. Finite anisotropic thermal conduction allows for sustained pressure gradients within stochastic regions. The configuration under investigation is an l=2, M=10 torsatron with vacuum rotational transform near unity. Finite-beta plasmas are generated from vacuum fields using a volumetric heating source and temperature dependent resistivity. With realistic parameters the configuration is unstable to interchange, which acts to limit the achievable beta. Simulations performed in a single field period domain do not exhibit a complete crash from the instability, but otherwise closely match theorized linear and nonlinear interchange behavior. In more dissipative regimes where instability is suppressed, steady-state solutions are obtained. A conventional equilibrium beta limit is observed due to pressure induced stochastic magnetic field formation. The parametric dependence of the equilibrium limit is examined in detail. Equilibrium results are compared with several reduced models for effective collisional transport across stochastic magnetic fields and with the HINT code. Collisionality independent models also are investigated for more realistic parallel thermal conduction rates. Join Zoom Meeting Meeting ID: 913 2120 9265 Passcode: 298219
- Host: Chris Hegna, Faculty Advisor
- Thesis Defense
- Overlapping Aluminum-Gate Quantum Dots for Valley-Orbit Based Qubits in Si/SiGe
- Time: 4:00 pm
- Place:
- Speaker: JP Dodson, Physics PhD Graduate Student
- Abstract: Variability in valley-orbit state splittings will be a problem for large-scale implementations of silicon-based quantum processors. Depending on the particular qubit architecture, the role of valley-orbit states varies; however, a common theme for nearly all silicon-based qubits is that valley-orbit splittings must be precisely engineered or have large in situ tunability. Here, we investigate overlapping aluminum-gate devices for valley-orbit based qubits in Si/SiGe which enable high in situ tunability of valley-orbit states. Spectroscopic measurements of low-lying one- and two-electron valley-orbit states are taken to determine the quantitative relationship between the valley, singlet-triplet and orbital splittings. By exploiting the dependence of valley-orbit state splittings on electrostatic confinement and electron number, we show progress towards single-shot readout in the (4,1)-(3,2) electron regime, allowing for in situ tunability of the qubit frequency and enhancement of the readout window.
- Host: Mark Eriksson, Faculty Advisor
Thursday, April 15th, 2021
- Cosmology Journal Club
- Time: 12:00 pm - 1:00 pm
- Abstract: Each week, we start with a couple scheduled 15 minute talks about one's research, or an arXiv paper. The last 30 minutes 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
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- NPAC (Nuclear/Particle/Astro/Cosmo) Forum
- Ultra-high-energy cosmic rays and neutrinos, expectations for diffuse fluxes and arrival-direction correlations
- Time: 2:30 pm - 3:30 pm
- Place:
- Speaker: Arjen van Vliet, DESY Zeuthen, Germany
- Abstract: Astrophysical neutrinos can be produced by cosmic-ray interactions, either inside the sources of cosmic rays (source neutrinos) or during the propagation through extragalactic space (cosmogenic neutrinos). The expected cosmogenic neutrino flux in the EeV range depends strongly on the composition of ultra-high-energy cosmic rays (UHECRs). A larger fraction of protons will especially increase the expected cosmogenic neutrino flux. One scenario in which a significant proton fraction can be expected is if different classes of Active Galactic Nuclei (AGN) are the dominant sources of UHECRs. If that is the case, not only a large cosmogenic neutrino flux is expected, but a large source neutrino flux as well. It might therefore be interesting to look at correlations between neutrino and UHECR arrival directions. However, deflections of UHECRs in magnetic fields decrease the expected directional correlations. Even for the weakest extragalactic magnetic fields (EGMFs) the non-observation of high-energy neutrino multiplets strongly constrains the possibility to find neutrino-UHECR correlations. On the other hand, the Pierre Auger Collaboration has recently found indications for correlations between UHECR arrival directions and local star-forming galaxies or AGN. These results can be used to put limits on the EGMFs between these galaxies and the Milky Way. For a source density of star-forming galaxies relatively strong EGMFs are required to reproduce the level of anisotropy that Auger has observed.
- Host: Lu Lu
- Astronomy Colloquium
- Planets, Patterns, and the Origin of Life
- Time: 3:30 pm - 5:00 pm
- Place: Zoom meeting(see Abstract ) Coffee and tea 3:30pm, Talk 3:45 PM
- Speaker: Lauren Weiss, University of Hawaii at Monoa
- Abstract: Exoplanet science is an explosive new field catalyzed by the discovery of over 4000 extrasolar planets via the NASA Kepler and MIT-led TESS missions. The field will continue to evolve rapidly over the next several decades as we push observational techniques toward the discovery of Earth-like planets. Along the way, we are learning about diverse types of planets, their interior and atmospheric compositions, their orbital properties, the systems in which they reside, and how the planets form and change over time. Recent discoveries of patterns have reshaped our understanding of planet formation, with possible implications for the origins of Earth-like planets and life. I will discuss my past, present, and future experiments with observational astronomy to address these topics.
Zoom Link:
- Host: Professor Ellen Zweibel
- High Energy Seminar
- First results from the Muon g-2 experiment at Fermilab
- Time: 4:00 pm - 5:00 pm
- Place:
- Speaker: Liang Li, Shanghai Jiao Tong University
- Abstract: The Fermilab Muon g-2 experiment measures the muon anomalous magnetic moment with high precision. Together with recent improvements on the theory front, the first results of the experiment confirm the long-standing discrepancy between the experimental measurements and the Standard Model predictions. The combined significance of the discrepancy is at 4.2 sigma. This talk presents the first results and current status of the Muon g-2 experiment at Fermilab.
- Host: Yang Bai
Friday, April 16th, 2021
- Theory Seminar (High Energy/Cosmology)
- The Impact of a Midband Gravitational Wave Experiment On Detectability of Cosmological Stochastic Gravitational Wave Backgrounds
- Time: 2:00 pm - 3:00 pm
- Place: For zoom link, sign up at:
- Speaker: Yanou Cui, UC Riverside
- Abstract: I will discuss the impact of a future midband gravitational wave experiment on improving detectability of a cosmologically sourced stochastic GW background. Specific proposed midband experiments considered are TianGo, B-DECIGO and AEDGE. We propose a combined power-law integrated sensitivity (CPLS) curve combining GW experiments over different frequency bands, which shows significant improvement in sensitivity to SGWBs with the aid of a midband experiment. We consider GW emission from cosmic strings and phase transitions as benchmark examples of cosmological SGWBs. We explicitly model various astrophysical SGWB sources, most importantly from unresolved black hole mergers. Based on analysis using Markov Chain Monte Carlo, we demonstrated that midband experiments can, when combined with LIGO A+ and LISA, can significantly improve sensitivities to cosmological SGWBs and better separate them from astrophysical SGWBs.
- Host: Lars Aalsma
- Department Coffee Hour
- Department Coffee Hour (Virtual)
- Time: 3:30 pm - 4:30 pm
- Place: Virtual (see abstract for connection info)
- Abstract: Topic: Department Coffee Hour
Time: Jan 29, 2021 03:30 PM Central Time (US and Canada)
Every week on Fri, until May 14, 2021, 16 occurrence(s)
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Meeting ID: 979 8528 1970
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- Host: Climate and Diversity Committee
- Academic Calendar
- GRADUATE SCHOOL SPRING 2021: Request for all Master's and Ph.D. Degree Warrants
- Time: 4:00 pm - 5:00 pm
- Abstract: CONTACT: 262-2433, gsacserv@grad.wisc.edu