Events at Physics |
Events During the Week of September 25th through October 2nd, 2022
Monday, September 26th, 2022
- Plasma Physics (Physics/ECE/NE 922) Seminar
- The plasma edge and beyond: application of plasma edge diagnostics at W7-X
- Time: 12:00 pm - 6:00 pm
- Place: 1610 Engineering Hall
- Speaker: Philip Drews, Heinrich-Heine-Universitä Düsseldorf
- Abstract: The Langmuir probe diagnostic has been present since the discovery of the plasma state of matter. They are still used in contemporary experiments like EAST, JET or W7-X, both fixed on plasma facing components and mounted on manipulators for profile measurements. The diagnostic can observe the electron temperature and density, as well as flow velocities and information about the turbulence in the plasma. The main advantages of the Langmuir probe are the simple setup, analysis, as well as high spatial and temporal resolution. While the utility of the diagnostic is obvious, limitations and pitfalls of Langmuir and other probe measurements should be highlighted. The presentation will focus on results obtained from diagnostics probes utilized in conjunction with the Multipurpose Manipulator (MPM) system at W7-X. Furthermore, the practical aspects of advanced diagnostic concepts like the retarding field analyzer for ion temperature measurements are discussed. A new probe head for HSX was developed for the measurement of plasma edge parameters, like the electron density and temperature, the ion temperature and turbulence. The experiences from both W7-X and HSX were used to design a probe that should be minimally invasive during the measurement and provide good coverage of the aforementioned plasma parameters. Finally, the integration of Probe measurements at W7-X into the wider picture of other diagnostic measurements and the use of modelling will be presented.
- Host: Benedikt Geiger
Tuesday, September 27th, 2022
- Network in Neutrinos, Nuclear Astrophysics, and Symmetries (N3AS) Seminar
- Distribution Functions of Dark Matter Halos
- Time: 2:00 pm
- Place: Join Zoom Meeting Meeting ID: 912 3071 4547
- Speaker: Axel Gross , University of Minnesota
- Abstract: The spherical NFW profile provides a good approximation to the density distributions of dark matter halos. In dynamical equilibrium, this density profile should correspond to a stationary distribution function of dark matter in phase space. We derive this distribution function and show that it is a good match to those obtained from N-body simulations.
Host: Baha Balantekin
Join Zoom Meeting
Meeting ID: 912 3071 4547
- Host: A. Baha Balantekin
- Theory Seminar (High Energy/Cosmology)
- Coupling a Cosmic String to a TQFT
- Time: 4:00 pm - 5:00 pm
- Place: Chamberlin 5280
- Speaker: Sungwoo Hong, (Argonne, U. Chicago)
- Abstract: In the last few years, the notion of symmetry has been enlarged to "generalized symmetry" and these more generalized symmetries have played a critical role in deepening our understanding of QFT, notably IR phases of QFT. In this talk, I will discuss various ways of coupling the axion-Maxwell theory to a sector of topological field theory (TQFT). Contrary to common wisdom, I will show that such topological modifications can lead to direct changes in the local physics with possible observable consequences. This surprise can be realized by a dimensional reduction, namely, a coupling to a TQFT in 4d leads to a non-trivial and local impact on the 2d string world-sheet QFT. I will explain how this happens using the language of anomaly inflow, which provides a way of figuring out the IR-universal observable effect from the TQFT-coupling. There exists another topological modification of the theory, i.e. gauging a discrete subgroup of 0-form shift symmetry, and this time it results in an alteration of the spectrum of cosmic strings. If time permits, I will also discuss generalized symmetries and associated higher-groups of these theories.
- Host: George Wojcik
Wednesday, September 28th, 2022
- No events scheduled
Thursday, September 29th, 2022
- Physics Department Colloquium
- Justin Kasper: Nuclear Power (fusion and fission), Galactic Radiation, and Space Exploration
- Time: 12:00 pm - 1:00 pm
- Place: Orchard View Room, Discovery Building
- Speaker: Justin Kasper, PhD, BWX Technologies, Inc. and University of Michigan Climate & Space
- Abstract: Special joint colloquium between Physics, Engineering Physics, and Astronomy:
Nuclear Power is about to Transform our Presence in Space.
We are a decade into a revolution in our ability to access, explore, and use space. The cost of rockets and spacecraft and the time between launches have dropped by orders of magnitude. Advanced technologies allow us to send probes into harsh environments like the atmosphere of the Sun, the frozen craters of the lunar poles and the icy moons of the outer planets. Our ambitions are limited by the amount of energy we can carry into space, or more precisely the density of that energy. We need heat and electricity to operate on the moon at night or in permanently shadowed craters, and more efficient rockets to transport humans and cargo to Mars, and nuclear power is the solution. A small fission reactor can continuously power a base on the moon or Mars for a decade, and nuclear propulsion is several times more efficient than chemical rockets, halving the duration of a crewed mission. This talk will review the amazing work in nuclear technology and design under way right now to deploy nuclear power and propulsion in space.
- Host: Cary Forest
- NPAC (Nuclear/Particle/Astro/Cosmo) Forum
- Tau appearance and quantum gravity with high-energy neutrinos
- Time: 2:30 pm - 3:30 pm
- Place: Chamberlin 4274
- Speaker: Alfonso Garcia , Harvard University
- Abstract: In this seminar, we will discuss two studies in the context of the high-energy neutrino detection. First, we address the impact of tau appearance from high-energy muon and electron neutrinos interaction as they propagate through Earth. This component is predicted to be significantly larger than the atmospheric background, and it alters current and future neutrino telescopes’ capabilities to discover a cosmic tau-neutrino flux. Second, we explore the capabilities to detect neutrino-nucleon soft interactions induced by TeV-scale gravity with the next generation of radio telescopes. In this elastic regime, the commonly used method to measure the total cross section breaks down, so we explore new proxies.
- Host: Lu Lu
- Astronomy Colloquium
- Galactic HII Regions and Structure in the Milky Way
- Time: 3:30 pm - 4:30 pm
- Place: Sterling Hall 4421; or via Zoom:
- Speaker: Trey Wenger, NSF Astronomy & Astrophysics Postdoctoral Fellow
- Abstract: Radio recombination lines (RRLs) are an unobscured tracer of ionized gas in both the diffuse interstellar medium (ISM) as well as high-mass star forming regions. The Green Bank Telescope HII Region Discovery Survey (HRDS) and its successors have more than doubled the number of known high-mass star forming regions in the Milky Way by detecting RRL emission toward infrared-identified HII region candidates. HII regions are the classic tracer of structure in galaxies, and their physical conditions (e.g., metallicity, internal kinematics) inform models of high-mass star formation and Galactic chemodynamical evolution. I will give a brief overview of our latest HRDS project, the Southern HII Region Discovery Survey, and some preliminary results with the first Galaxy-wide flux-limited HII region sample, including a novel technique to constrain Milky Way spiral structure. In the SHRDS, we serendipitously discovered a population of HII regions with ionized gas velocity gradients. I will discuss both the origin and implications of this discovery on models of high-mass star formation as well the future of Galactic structure and HII region science (both Galactic and extragalactic) in the era of ALMA and ngVLA.
Friday, September 30th, 2022
- Academic Calendar
- Deadline for students (except Graduate) to change variable credits
- Abstract: *Note: actual end time may vary.* CONTACT: 262-3811, registrar@em.wisc.edu URL:
- Academic Calendar
- Deadline for students (except Graduate) to request pass/fail or credit/audit options for a Fall term course
- Abstract: *Note: actual end time may vary.* CONTACT: 262-3811, registrar@em.wisc.edu URL:
- Academic Calendar
- Deadline for students to drop a Fall term course and receive 50% tuition adjustment
- Abstract: *Note: actual end time may vary.* CONTACT: 262-3811, registrar@em.wisc.edu URL:
- Physics Department Colloquium
- Black holes and quantum information
- Time: 3:30 pm - 4:30 pm
- Place: 2241 Chamberlin Hall
- Speaker: Tom Hartman, Cornell
- Abstract: The black hole information paradox, discovered by Hawking in 1976, is that black hole evaporation seems to violate quantum mechanics by creating too much entropy. I will describe the current status of this problem and discuss recent progress, including a new calculation of the entropy of Hawking radiation that is compatible with unitary quantum mechanics. There are two key ingredients: a link between classical geometry and quantum entanglement, and higher topologies in quantum gravity known as replica wormholes. I will also discuss the prospects for applying similar methods to cosmology in the early universe, which is similar in some ways to the inside of a black hole.
- Host: Gary Shiu