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This Week at Physics

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Events During the Week of October 21st through October 28th, 2018

Monday, October 22nd, 2018

Plasma Physics (Physics/ECE/NE 922) Seminar
Dalton Schnack Memorial Lecture: Three-dimensional Coherent Plasmoids in Current-Carrying Plasmas
Time: 12:05 pm
Place: 2241 Chamberlin Hall
Speaker: Dr. Fatima Ebrahimi, Princeton Plasma Physics Lab
Abstract: Generation of coherent, current-carrying structures is prevalent in magnetically-dominated, rotating astrophysical and laboratory plasmas. Intertwining flux tubes, as well as sheet-like structures, emerging from the surface of the sun, and edge-localized filament structures in magnetically confined plasmas are examples of such current-carrying structures. In this talk, using three-dimensional simulations, I demonstrate the onset and nonlinear evolution of coherent current-carrying filaments, as well as round magnetic structures (so called plasmoids), in a global toroidal geometry. The role of magnetic reconnection, the rearrangement of the magnetic field topology, as a major underlying mechanism for the fast growth and nonlinear saturation of the localized current-carrying structures will be explained. It will be shown that 3-D magnetic fluctuations can cause either local flux amplification to trigger axisymmetric reconnecting plasmoids formation at the reconnection site or cause the local annihilation of axisymmetric current through a fluctuation-induced, bi-directional dynamo term. The instrumental role of magnetic reconnection, which enables an innovative technique for producing current in fusion plasmas, will be discussed.

Supported in part by a generous grant from the Women in Science & Engineering Leadership Institute (WISELI)
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Tuesday, October 23rd, 2018

Chaos & Complex Systems Seminar
The dynamics of mood in bipolar disorder
Time: 12:05 pm
Place: 4274 Chamberlin (Refreshments will be served)
Speaker: Amy Cochran, UW Departments of Biostatistics & Medical Informatics
Abstract: Bipolar disorder is a chronic disease of severe mood fluctuation. Longitudinal patterns are central to any patient description, but are condensed into simple attributes and categories. Although these provide a common language for clinicians, they are not supported by empirical evidence. In this talk, I will discuss modeling frameworks for providing patient-level descriptions of longitudinal patterns. Since these frameworks often represent competing hypotheses, e.g. mood is periodic or mood has distinct 'states', I will focus on a key question: how to differentiate between models when only time courses of mood are available? Through statistical analysis, we settle on the idea that BP could arise from an inability for mood to quickly return to normal when perturbed and present a model to embody this idea that can be personalized to individual with bipolar disorder. I will conclude by discussing next steps for translating this work into clinical care.
Host: Clint Sprott
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Council Meeting
council meetings
Time: 3:30 pm
Place: 2314 Chamberlin Hall
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Wednesday, October 24th, 2018

Department Meeting
Department Meeting
Time: 12:15 pm
Place: 5310 Chamberlin Hall
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Thursday, October 25th, 2018

R. G. Herb Condensed Matter Seminar
TBD
Time: 10:00 am
Place: 5310 Chamberlin
Speaker: Will Oliver , MIT-Lincoln Labs
Abstract: TBD
Host: Vavilov
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Cosmology Journal Club
Time: 12:00 pm
Place: 5242 Chamberlin Hall
Abstract: Please visit the following link for more details:
http://cmb.physics.wisc.edu/journal/index.html
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 Ross Cawthon (cawthon@wisc.edu) and Santanu Das (sdas33@wisc.edu).
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Astronomy Colloquium
How ionizing photons escape galaxies to reionize the universe
Time: 3:30 pm
Place: 4421 Sterling Hall, Coffee and cookies 3:30 PM. Talk Begins at 3:45 PM
Speaker: John Chisholm, University of Califormina - Santa Cruz
Abstract: The intergalactic medium was rapidly ionized at 6 < z < 9. However, the source of cosmic reionization is hotly debated because there appears to be an insufficient number of high-redshift active galactic nuclei, while neutral gas in star-forming galaxies efficiently absorbs the ionizing photons produced by stars. Impending observatories (e.g., JWST and ELTs) aspire to determine the source of reionization, but the large average opacity of the high-redshift intergalactic medium precludes direct observations of ionizing photons. Fortunately, local analogs can be used to develop indirect diagnostics of the escape of ionizing photons. Here, I present restframe ultraviolet observations of star-forming galaxies that emit ionizing photons at redshifts of 0 and 2. These observations encode details of how ionizing photons escape star-forming galaxies, while also accurately predicting the escape fraction of ionizing photons. These observations provide a template for JWST and ELTs to determine the source of cosmic reionization.
Host: Professor Christy Tremonti
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Friday, October 26th, 2018

Theory Seminar (High Energy/Cosmology)
Dark quark nuggets
Time: 2:00 pm
Place: 5310 Chamberlin Hall
Speaker: Sida Lu, University of Wisconsin-Madison
Abstract: "Dark quark nuggets'', a lump of dark quark matter, can be produced in the early universe for a wide range of confining gauge theories and serve as a macroscopic dark matter candidate. The two necessary conditions, a nonzero dark baryon number asymmetry and a first-order phase transition, can be easily satisfied for many asymmetric dark matter models and QCD-like gauge theories with a few massless flavors. For confinement scales from 10 keV to 100 TeV, these dark quark nuggets with a huge dark baryon number have their masses vary from $10^{23}~mathrm{g}$ to $10^{-7}~mathrm{g}$ and their radii from $10^{8}~mathrm{cm}$ to $10^{-15}~mathrm{cm}$. Such macroscopic dark matter candidates can be searched for by a broad scope of experiments and even new detection strategies. Specifically, we have found that the gravitational microlensing experiments can probe heavier dark quark nuggets or smaller confinement scales around 10 keV; collision of dark quark nuggets can generate detectable and transient electromagnetic radiation signals; the stochastic gravitational wave signals from the first order phase transition can be probed by the pulsar timing array observations and other space-based interferometry experiments; the approximately massless dark mesons can behave as dark radiation to be tested by the next-generation CMB experiments; the free dark baryons, as a subcomponent of dark matter, can have direct detection signals for a sufficiently strong interaction strength with the visible sector.
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Physics Department Colloquium
Quantum Engineering of Superconducting Qubits
Time: 3:30 pm
Place: 2241 Chamberlin Hall
Speaker: William D. Oliver, MIT-Lincoln Labs
Abstract: Superconducting qubits are coherent artificial atoms assembled from electrical circuit elements. Their lithographic scalability, compatibility with microwave control, and operability at nanosecond time scales all converge to make the superconducting qubit a highly attractive candidate for the constituent logical elements of a quantum information processor. In this talk, we review this progress and the challenges ahead as we create the future of engineered quantum systems.
Reception: following the talk
Host: Maxim Vavilov
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Physics Museum
Physics Museum 100th Anniversary Reception/Talk
Time: 4:30 pm
Place: 2241 Chamberlin Hall
Speaker: Robert Joynt & James Reardon, UW - Madison, Physics
Abstract: Reception at 4:30 PM
Talk at 5:00 PM
Host: Sridhara Dasu
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