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Events at Physics

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Events During the Week of October 4th through October 11th, 2015

Monday, October 5th, 2015

Plasma Physics (Physics/ECE/NE 922) Seminar
Turbulence Dynamo and Origin of Magnetic Fields in Galaxy Clusters.
Time: 12:00 pm
Place: 2241 Physics Bldg
Speaker: Professor Jungyeon Cho, Chungnam National University, Korea
Abstract: In usual astrophysical circumstances, magnetic diffusivity is very low and, as a result, magnetic fields lines are tied to fluid elements. Therefore random turbulence motions can efficiently stretch magnetic field lines, which results in amplification of magnetic field. This turbulence dynamo is believed to play important roles in the origin of cosmic magnetism. For turbulence dynamo, a weak seed magnetic field is required. If the seed field has a primordial origin, it could be regarded as uniform (or homogeneous) at the scale of galaxy clusters. On the other hand, if the seed field is ejected from an astrophysical body, it could be highly localized in space at the beginning. In this talk I'll discuss growth of uniform and localized seed magnetic fields in turbulence. I will demonstrate that growth of both uniform and localized seed magnetic fields in clusters of galaxies is very similar. Therefore, it is difficult to tell whether or not the seed magnetic field has a cosmological or an astrophysical origin in clusters of galaxies. However, I'll show that it is possible to tell the difference in filaments. I’ll also claim that turbulence dynamo models favor an astrophysical origin of cosmic magnetism, rather than a primordial origin.
Host: Paul Terry
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Tuesday, October 6th, 2015

Chaos & Complex Systems Seminar
Making computer networks work
Time: 12:05 pm
Place: 4274 Chamberlin (refreshments will be served)
Speaker: Aditya Akella, UW Department of Computer Sciences
Abstract: We depend on computer networks for literally every aspect of our daily lives, e.g., work, family, education, socializing, entertainment, and finances. Yet, the quality of experience that we as users derive from these networks is far from satisfactory. We're routinely hit by poor or variable page-load times and download speeds, and even outright unavailability of critical network-accessible services. Researchers and practitioners alike work round the clock to develop fixes, but disruptive applications, protocols, and hardware quickly render them ineffective.<br>
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In this talk, I will argue that design and operational deficiencies in key components of the network infrastructure play a crucial role in this unfortunate predicament. I will then describe two sets of technologies my group has developed to ensure that network infrastructure offers good performance, and remains robust and agile, even in the face of unforeseen disruptive trends. One is a suite of analytics-driven management plane designs for ensuring robust and flexible operation of complex networks. The other is content-aware systems that ensure bandwidth-efficient and low-latency content delivery. These technologies have been incorporated into a variety of commercial systems in operation today.
Host: Sprott
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Wednesday, October 7th, 2015

No events scheduled

Thursday, October 8th, 2015

R. G. Herb Condensed Matter Seminar
TBD
Time: 10:00 am
Place: 5310 Chamberlin Hall
Speaker: Kurt Jacobs , Army Research Lab
Abstract: TBD
Host: Saffman
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R. G. Herb Condensed Matter Seminar
Quantum Control and Quantum Networks
Time: 10:00 am
Place: Chamberlin 5310
Speaker: Kurt Jacobs, Army Research Lab
Abstract: I will give an overview of topics that our group at ARL is interested in,
and then describe some recent work on the application of numerical search
methods to quantum information transfer in linear networks.
Host: Saffman
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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:
    http://cmb.physics.wisc.edu/journal/index.html
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 Le Zhang (lzhang263@wisc.edu)
Host: Peter Timbie
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Astronomy Colloquium
Stellar Forensics with Explosions: Supernovae, Gamma-Ray Bursts, and their Environments
Time: 3:45 pm
Place: 4421 Sterling Hall
Speaker: Maryam Modjaz, New York University
Abstract:
Nature's two magnificent explosions, long-duration gamma-ray bursts (GRBs) and stripped-envelope supernovae (SNe), are both products of collapsing massive stars. Yet, over the last 15 years, we have not determined the detailed make-up of the stellar progenitors of each kind of explosion, nor the conditions that lead to each kind of explosion in massive stripped stars. While long-duration GRBs emit relativistic jets of high-energy radiation, stripped SNe are core-collapse explosions whose massive progenitors have been stripped of their outer hydrogen and helium envelopes.

I will present a number of comprehensive observational studies that probe the progenitor environments, their metallicities and the explosion parameters of SNe with and without GRBs, as well as those of normal Stripped SNe, with the goal of constraining their progenitor systems and explosions mechanisms. I will conclude with an outlook on how the most promising venues of research - using the many existing and upcoming innovative surveys such as the Palomar Transient Factory and LSST - have shed new light on the diverse deaths of massive stars, and will continue to do so.
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Graduate Introductory Seminar
Atomic, Molecular, and Optical Physics
Time: 4:30 pm
Place: 5280 Chamberlin Hall
Speaker: Lawler, Lin, Saffman, Walker, Yavuz
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Friday, October 9th, 2015

Physics Department Colloquium
Building a galactic scale gravitational wave observatory
Time: 3:30 pm
Place: 2241 Chamberlin Hall (Coffee & Cookies at 3:15pm)
Speaker: Xavier Siemens, University of Wisconsin-Milwaukee
Abstract: For the better part of the last decade, the North American Nanohertz Observatory for Gravitational Waves (NANOGrav) has been using the Green Bank and Arecibo radio telescopes to monitor millisecond pulsars. NANOGrav aims to directly detect low-frequency gravitational waves which cause small changes to the times of arrival of radio pulses. In this talk I will discuss the work of the NANOGrav collaboration and our sensitivity to gravitational waves from astrophysical sources. I will show that a detection is possible in the next few years.
Host: Peter Timbie
Poster: https://www.physics.wisc.edu/events/posters/2015/3746.pdf
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