Events at Physics
Events During the Week of October 25th through November 1st, 2015
- Plasma Physics (Physics/ECE/NE 922) Seminar
- Badger Gyrokinetics: Recent Advances in Plasma Microturbulence
- Time: 12:00 pm
- Place: 2241 Physics Bldg
- Speaker: M.J. Pueschel, Physics, UW
- Abstract: This presentation gives an overview of select gyrokinetics-based results
that have been produced at UW-Madison over the last few years. In scope,
they cover a wide array of topics related to microinstabilities and
turbulence. The failure of ion-temperature-gradient-driven turbulence to
saturate at large beta is explained through field line decorrelation and
the depletion of zonal flows. Turbulent transport in the MST
reversed-field pinch and the HSX stellarator are investigated: critical
gradients in the former are lowered drastically by residual tearing mode
activity, whereas the latter exhibits nonlinear structure formation.
Generic stellarator research reveals a rich spectrum of subdominant
eigenmodes, which in aggregate govern transport characteristics and
which have to be included in quasilinear transport modeling. Heating in
the solar corona is studied through simulations of turbulent
reconnection, where heating rates match observations and nanoflares can
be explained by plasmoid mergers. A new plasma instability is presented,
which, in addition to affecting reconnection rates, appears to dominate
pressure-gradient-driven experiments at the LAPD device.
- Host: Plasma Physics
- Chaos & Complex Systems Seminar
- Cosmic rays from the simple to the complex
- Time: 12:05 pm
- Place: 4274 Chamberlin (refreshments will be served)
- Speaker: Justin Vandenbroucke, UW Department of Physics
- Abstract: Cosmic rays and their siblings, astrophysical gamma rays and neutrinos, are fundamentally simple objects: high energy subatomic particles. However, they arrive at Earth bearing information about some of the most energetic and enigmatic phenomena in the universe, including exploding stars, giant black holes at the center of distant galaxies, and dark matter. I will discuss recent progress and open questions, including the prospects for answering some of them with a new instrument called the Cherenkov Telescope Array. Finally, I will present the Distributed Electronic Cosmic-ray Observatory, an app and website that enable members of the public to detect cosmic rays with cell phone camera sensors.
- Host: Sprott
- Theory Seminar (High Energy/Cosmology)
- Z'-portal for dark mesons in the SIMP scheme
- Time: 3:30 pm
- Place: 5280 Chamberlin Hall
- Speaker: Min-Seok Seo, Seoul National University
- Abstract: Recently, it has been proposed that dark mesons with Wess-Zumino-Witten term realizes the SIMP scheme, in which dark matter relic density is determined by freeze-out of 3 -> 2 self annihilation, in a natural way. This model can be completed after considering communication between dark sector and Standard Model sector in order to prevent the dark matter over-heating. In this talk, kinetic mixing between dark U(1) and hypercharge U(1) gauge bosons is suggested as a plausible interaction satisfying such requirement. Possible ways of assigning U(1) charge are restricted by the presence of Wess-Zumino-Wittern term, so more information on dark sector can be extracted. Requirement of sufficient interaction between dark- and Standard Model sector provides lower bound of the dark photon mass and the magnitude of kinetic mixing. Several additional issues concerning the model is also visited.
- Host: Amol Upadhye
- Department Meeting
- Time: 12:15 pm
- Place: 5310 Chamberlin Hall
- Cosmology Journal Club
- An Informal discussion about a broad variety of arXiv papers related to Cosmology
- Time: 12:15 pm
- Place: 5242 Chamberlin Hall
- Abstract: Please visit the following link for more details:
Please feel free to bring your lunch!
If you have questions or comments about this journal club, would like to propose a topic or volunteer to introduce a paper, please email Amol Upadhye (firstname.lastname@example.org).
- Host: Amol Upadhye
- Astronomy Colloquium
- Understanding Galaxy Evolution with Massive Starburst Galaxies
- Time: 3:45 pm
- Place: 4421 Sterling Hall, Cookies and Coffee at 3:30 PM
- Speaker: Hai Fu, University of Iowa
- Abstract: We are constantly intrigued by how dramatically galaxies evolve when we probe closer to the cosmic dawn. Ten billion years ago, galaxies were forming stars ten times more fiercely than they do today. This phenomenon can be understood in the framework of cold dark matter simulations only if star formation is suppressed in massive dark matter halos. However, the physical mechanisms responsible for the suppression are unclear. Starburst galaxies in massive halos offer a unique laboratory to constrain the suppression processes, because, unlike most galaxies, such processes have apparently failed to operate in these starbursts. Thanks to the Herschel Space Telescope and the South Pole Telescope, for the first time we have identified a rare sample of gravitationally lensed or hyperluminous starbursts at the peak epoch of cosmic star formation. I will show how high-resolution multi-phase observations have helped us gain a comprehensive understanding of these unusual galaxies. I will also describe an ongoing project aimed at constraining the halo-scale gas supply of such massive starbursts. By contrasting with normal galaxies, the results of these studies will be fundamental to a physical understanding of galaxy evolution.
- Host: Prof Tremonti
- Special Friday Lunch Talk
- Widespread buried ice in Arcadia Planitia, Mars
- Time: 12:00 pm
- Place: 4421 Sterling Hall
- Speaker: Ali Bramson, University of Arizona
- Abstract: The distribution and concentration of subsurface water ice on Mars are key constraints on past climate and the processes that led to the ice’s deposition. We investigate the subsurface of Arcadia Planitia by measuring the depth of terraces in simple impact craters and mapping a widespread subsurface reflection in radar sounding data. Our mapping of these data sets has allowed us to constrain the thickness, latitude range and volume of an extensive subsurface layer. We have also constrained the composition of the layer by combining these data, and results are consistent with a widespread deposit of excess ice in the northern mid-latitudes of Mars. Understanding the conditions that formed and preserved this thick, extensive layer of ice will improve our understanding of the Martian climate system and the deposit may also serve as a resource for future human exploration to Mars.
- Physics Department Colloquium
- The Future of Nuclear Power: Safety and Economics
- Time: 3:30 pm
- Place: Chamberlin 2241 (Coffee & Cookies at 3:15pm)
- Speaker: Greg Jaczko
- Abstract: What will the future be for nuclear power? The economics, policy and politics of small modular reactors will be discussed. I will discuss whether this technology can make it and revive the United States role as a leader in commercial nuclear power.
- Host: Albrecht Karle