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This Week at Physics

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Events During the Week of September 8th through September 15th, 2013

Monday, September 9th, 2013

No events scheduled

Tuesday, September 10th, 2013

Chaos & Complex Systems Seminar
Multistability and hidden attractors
Time: 12:05 pm
Place: 4274 Chamberlin
Speaker: Clint Sprott, UW Department of Physics
Abstract: One characteristic of nonlinear dynamical systems is that they can have more than one stable equilibrium. Perturbations of the variables or changes in the parameters can cause the system to abruptly switch from one equilibrium to the other from which it is hard to recover (what Al Gore calls a &amp;quot;tipping point&amp;quot;). Furthermore, equilibria can become unstable and give birth to periodic oscillations and even chaos. Hence, in addition to static attractors, there can be limit cycles and strange attractors, and several such attractors can coexist in even simple systems. Sometimes these attractors are &amp;quot;hidden&amp;quot; in the sense that they cannot be found by starting from the vicinity of an unstable equilibrium. Such hidden attractors can be catastrophic if the system is a building, a bridge, or an airplane wing. Examples of such behavior will be illustrated in very simple systems of differential equations and with simple demonstrations.
Host: Clint Sprott
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Atomic Physics Seminar
Atomic clocks, fundamental symmetries, and the search for new physics
Time: 2:00 pm
Place: 5310 Chamberlin Hall
Speaker: Marianna Safronova, University of Delaware
Abstract: I will give an overview of searches for new physics with atomic systems, including the study of parity violation, search for EDM, and the search for variation of fundamental constants. The study of parity nonconservation in cesium led to a first measurement of the nuclear anapole moment and allowed to place constraints on weak meson-nucleon couplings. I will review the present status of atomic parity violation studies and the implications for searches for physics beyond the standard model and study of weak hadronic interactions. In the second part of my talk, I will discuss the state-of-the art atomic clock development focusing on the issue of the blackbody radiation shifts as well as application of clocks to the searches for variation of the fine-structure constant.
Host: Saffman
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Wednesday, September 11th, 2013

No events scheduled

Thursday, September 12th, 2013

Astronomy Colloquium
The Physics of Starburst Galaxies
Time: 3:30 pm
Place: 4421 Sterling Hall
Speaker: Todd Thompson, Ohio State
Abstract: Star formation in galaxies is regulated by feedback processes. I
discuss the physics and implications of momentum injection via
radiation pressure on dust grains and supernovae, including
predictions for the galaxy-scale winds driven by rapidly star-forming galaxies and the characteristic surface density of star formation in ultra-luminous infrared galaxies. I discuss the disruption of giant molecular clouds, with implications for their star formation efficiency. I also present constraints on the magnetic field and cosmic ray energy densities in starbursts derived from the far-infrared--radio correlation and the gamma-ray emission of the local starbursts M82 and NGC 253.

Host: Prof Snezana Stanimirovic
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Friday, September 13th, 2013

Theory Seminar (High Energy/Cosmology)
"A simple, yet subtle, invariance of the two body decay"
Time: 2:00 pm
Place: 5280 Chamberlin Hall
Speaker: Roberto Franceschini, University of Maryland
Abstract: In this talk I shall review common issues in the reconstruction of Lorentz invariants of the two body decay, in particular the problems that arise when the boost connecting the rest frame of the decaying particle and the observer (laboratory) frame is not known.
I shall discuss how certain Lorentz _variant_ quantities such as the Energy of one of the decay product encodes Lorentz _invariant_ quantities of the decay in a simple and measurable way. I will describe a method to access these invariants that allow to determine the mass of the decaying particle by observing only one of the two decay products. Not requiring the observation of both decay products, the described method can be applied when traditional quantities as the invariant mass cannot be used. I shall show concrete results about mass measurements for the leptonic decay of the top quark and supersymmetric decay chains of the gluino. Possible uses of this observation to study the stabilization symmetry of the Dark Matter at colliders will be discussed as well.
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Physics Department Colloquium
Project Poltergeist, a Ghostly Neutrino and a Specter
Time: 3:30 pm
Place: 2241 Chamberlin Hall (coffee at 4:30 pm)
Speaker: Patrick Huber, Virginia Polytechnic Institute & State University
Abstract: It is not quite Halloween yet... In this talk we will discuss how
Project Poltergeist shaped neutrino physics for decades to come and made nuclear reactors the workhorse of early oscillation searches. A renaissance of reactor neutrino experiments around 2010 lead to the very precise measurement of one of the mixing parameters, theta13 -- in the run-up to this measurement flux calculations from the 1980's were scrutinized and surprisingly the flux was found to be higher than previously expected leading to the so-called reactor anomaly. The reactor anomaly points a type of neutrino even more elusive than regular neutrinos, the ghostly sterile neutrino. We will review the calculations performed so far and highlight some of the open questions. In the final part of the talk we will point out how current attempts to settle the question of the sterile neutrino will impact our future ability to use neutrinos to peer into the cores of nuclear reactors to safeguards against the diversion of plutonium, which may play an important role in banishing the specter of nuclear terrorism.
Host: Everett
Poster: http://www.physics.wisc.edu/twap/posters/2013/3044.pdf
Video: http://www.physics.wisc.edu/vod/2013/09/13.html
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"This Week at Physics" poster: http://www.physics.wisc.edu/twap/posters/2013/2013-09-09.pdf

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