This Week at Physics

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This Week at Physics

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Events During the Week of October 15th through October 22nd, 2017

Monday, October 16th, 2017

Plasma Physics (Physics/ECE/NE 922) Seminar
Cosmic Ray Dynamics in Galaxies and Galaxy Clusters
Time: 12:00 pm
Place: Chamberlin 2241
Speaker: Dr. Joshua Wiener, UW Madison
Abstract: Cosmic rays (CRs) make up an important piece of many types of astronomical objects. Though few in number, they can collectively contain as much energy as the thermal gas in galaxies and galaxy clusters. It is therefore important to correctly model the transport of CRs in bulk in order to more completely understand the general dynamics of these systems. I will briefly describe a simple CR transport model where the bulk flow of CRs is limited by the streaming instability. I will then apply this model to a number of systems of different scales: in galaxy clusters, CRs are responsible for synchrotron emission seen as giant radio haloes. In galaxies, CRs may be effective drivers of massive outflows, playing a role in stellar feedback and regulation of star formation. On smaller scales, a CR-driven wind which is incident upon a cold dense cloud may be subject to a peculiar bottleneck effect, which may impart significant momentum to the cloud as well as thicken its interface with the surrounding hot gas.
Host: Stanislav Boldyrev
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Council Meeting
Council Meeting
Time: 4:00 pm
Place: 2314 Chamberlin Hall
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Tuesday, October 17th, 2017

Chaos & Complex Systems Seminar
Chaos theory from a topological perspective
Time: 12:05 pm
Place: 4274 Chamberlin (refreshments will be served)
Speaker: Anda Xiong, UW Department of Physics
Abstract: I will talk about some phenomena in chaos theory and how can they be viewed by topology, such as the connection between fractals and topological subdivision, and calculating the self-linking number of attractors. Furtherly I will give an example for how persistence homology can be helpful to research in chaos theory.
Host: Clint Sprott
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Wednesday, October 18th, 2017

Department Meeting
Department Meeting
Time: 12:15 pm
Place: 5310 Chamberlin Hall
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Wednesday Nite @ the Lab
Time: 7:00 pm
Place: 425 Henry Mall, Room 1111 (UW Biotechnology Center)
Speaker: Carsten Rott, IceCube
Abstract: Most of the mass of our universe is in dark matter, but what is it? To shed light on this great unsolved mystery, researchers are using accelerators, detectors in the deep underground, and large telescopes to find dark-matter particles. <br>
This talk will describe what we know so far about dark matter, with a particular focus on how scientists from the IceCube Neutrino Telescope are looking for it.
Host: UW Biotechnology Center
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Thursday, October 19th, 2017

R. G. Herb Condensed Matter Seminar
Cyclotron resonance in graphene: Kohn’s theorem, many-particle physics, and more
Time: 10:00 am
Place: 5310 Chamberlin
Speaker: Erik Henriksen , Washington University in St. Louis
Abstract: Cyclotron resonance—the resonant absorption of infrared light by charge carriers in a strong magnetic field– is one of the more basic measurements that can be made on semiconductors. First demonstrated on germanium in the early ‘50s, CR proved to be enormously useful in determining semiconductor band structures and, from the ‘70s, was instrumental in probing two-dimensional systems in Si and GaAs heterostructures. However, early on W. Kohn pointed out a limitation of the CR technique: in translationally invariant parabolic systems, CR is insensitive to electron-electron interactions, with the consequence that CR has been useless in investigating such remarkable phenomena as the fractional quantum Hall effect. We have performed CR measurements over the past decade that demonstrate how to evade Kohn’s theorem by breaking translational invariance, or working in graphene whose linear dispersion can be viewed as an extreme case of a non-parabolic band structure. In our most recent work we find direct evidence of many-particle physics in the cyclotron resonance of high mobility graphene. This exciting development suggests that infrared spectroscopy will provide a new window on interacting electron phenomena in graphene including (fractional) quantum Hall effects, Hofstadter’s butterfly, hydrodynamic transport, and perhaps even cavity QED.

Host: Brar
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Round Table Discussion of Recruitment and Retention of Women in the Graduate Program
Time: 2:00 pm
Place: B343 Sterling Hall Conference room
Speaker: Jenni Strabley
Abstract: Round Table Discussion of Recruitment and Retention of Women in the Graduate Program
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Astronomy Colloquium
Climate Cycles and the History of Our Solar System
Time: 3:30 pm
Place: 4421 Sterling Hall, Coffee and cookes 3:30 PM. Talk begins at 3:45 PM
Speaker: Stephen Meyers, Department of Geoscience, UW Madison
Abstract: Quasiperiodic variations in Earth’s orbit and spin vector influence the distribution of sunlight on Earth’s surface, causing cyclic climate change on time scales >10,000 years. The geologic record preserves evidence of these astronomical-climate rhythms, which are expressed as physical, chemical and paleobiologic variability in sedimentary strata. In this seminar, I will discuss how these “fossilized” astronomical signals can be used to test hypotheses about the behavior of the Solar System, and its evolution over the past several billion years. One of the most fundamental questions that we can address with the geological archive pertains to the proposed chaotic dynamical nature of the Solar System that is predicted by numerical and analytical models of the planetary orbits. New geological data from the Cretaceous period (~86 million years ago) provides the first unambiguous confirmation of this chaotic motion. Another question that the geologic record is uniquely poised to address is the history of the Earth-Moon system, including changes in Earth-Moon separation and length of day. To address this research problem, I will present results from a new Bayesian inversion approach that uses the astronomical signals preserved in very ancient strata (> 1 billion years old) to reconstruct the Earth-Moon history, as well as the fundamental frequencies of the Solar System. A byproduct of this work is the development of high-resolution geological time scales that can be used to assess rates of Earth system processes, including climate change and biological evolution. Taken together, these examples highlight the close interlink between geology and astronomy, and how these fields can fundamentally inform each other.
Host: UW Astronomy Deparment
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Friday, October 20th, 2017

R. G. Herb Condensed Matter Seminar
Ultra-high Q Superconducting RF Cavities: from particle accelerators to quantum computing
Time: 11:00 am
Place: 5310 Chamberlin Hall
Speaker: Alex Romanenko, Fermilab
Abstract: “Superconducting radio frequency (SRF) cavities are an enabling technology for all modern accelerators where they serve as a primary means to accelerate charged beams. Extremely high quality factors Q=10^10-10^11 of SRF cavities in the broad range of fields up to tens of MV/m allow continuous wave operation of accelerators for various applications, i.e. SNS, CEBAF, LCLS-II, PIP-II and others, as well as make SRF cavities an attractive option for various non-accelerator applications ranging from quantum computing to dark sector photon searches. In this talk I will review the underlying science achievements and challenges in SRF, as well as describe the new SRF ‘quantum’ regime effort at Fermilab.”
Host: McDermott
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Graduate Introductory Seminar
Theoretical Condensed Matter Physics
Time: 12:00 pm
Place: 4274 Chamberlin Hall
Speaker: Coppersmith, Ioffe, Joynt, Levchenko, Vavilov
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Physics Department Colloquium
An Economically Attractive Path to Commercializing Nuclear Fusion and Bettering our World
Time: 3:30 pm
Place: 2241 Chamberlin Hall
Speaker: Greg Piefer, SHINE Technologies
Abstract: An Economically Attractive Path to Commercializing Nuclear Fusion and Bettering our World
Host: Albrecht Karle
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