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Events During the Week of December 10th through December 17th, 2017

Monday, December 11th, 2017

Plasma Physics (Physics/ECE/NE 922) Seminar
Exploring the universe through discovery science on NIF
Time: 12:00 pm - 1:00 pm
Place: Chamberlin 2241
Speaker: Dr. Bruce A. Remington, Lawrence Livermore National Laboratory
Abstract: New regimes of science are being experimentally studied at high energy density facilities around the world, spanning drive energies from microjoules to megajoules, and time scales from femtoseconds to microseconds. The ability to shock and ramp compress samples to very high pressures and densities allows new states of matter relevant to planetary and stellar interiors to be studied. Shock driven hydrodynamic instabilities evolving into turbulent flows relevant to the dynamics of exploding stars (such as supernovae), accreting compact objects (such as white dwarfs, neutron stars, and black holes), and planetary formation dynamics (relevant to the exoplanets) are being probed. The dynamics of magnetized plasmas relevant to astrophysics, both in collisional and collisionless systems, are starting to be studied. High temperature, high velocity interacting flows are being probed for evidence of astrophysical collisionless shock formation, the turbulent magnetic dynamo effect, magnetic reconnection, and particle acceleration. And new results from thermonuclear reactions in hot dense plasmas relevant to stellar and big bang nucleosynthesis are starting to emerge. A selection of examples providing a compelling vision for frontier science on NIF in the coming decade will be presented.
Host: Ellen Zweibel
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Tuesday, December 12th, 2017

Chaos & Complex Systems Seminar
Fractal occupancy of human landscapes: The concept of profit in Evansville, WI
Time: 12:05 pm - 1:00 pm
Place: 4274 Chamberlin (refreshments will be served)
Speaker: Tim Allen, UW Department of Botany
Abstract: Systems are predictable on two criteria: the thermodynamics of process; rate-independent constraints. The economics of this distinction is high gain, straight consumption of quality fuel, versus low gain where low quality material is processed to make quality fuel. A quality resource might sit on a hot spot. Evansville, WI, is a low gain system that depended on rail road (which is planned). Janesville and Madison are high gain depending or roads and fossil fuel. Roads are not planned, they simply straighten and widen in response to the flux of traffic. Railroads and roads end up with roughly the same fractal dimension, but railroads branch out from the main line, while roads emerge up scale from small roads to turnpikes. Evansville depends on a diffuse low quality landscape, while amassing capital by concentration. Janesville and Madison depend on high quality, locally focused resources. The argument turns on my satellite repairman based in Evansville, servicing a diffuse landscape with information and constraint structure.
Host: Clint Sprott
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NPAC (Nuclear/Particle/Astro/Cosmo) Forum
Evidence for the Higgs Boson Decay to a Bottom Quark-Antiquark Pair
Time: 2:30 pm
Place: 4274 Chamberlin Hall
Speaker: Stephane Cooperstein, Princeton
Abstract: A search for the standard model (SM) Higgs boson (H) decaying to bb when produced in association with an electroweak vector boson is reported for the following processes: Z(νν)H, W(μν)H, W(eν)H, Z(μμ)H, and Z(ee)H. The search is performed in data samples corresponding to an integrated luminosity of 35.9 fb−1 at √s = 13 TeV recorded by the CMS experiment at the LHC during Run 2 in 2016. An excess of events is observed in data compared to the expectation in the absence of a H → bb signal. The significance of this excess is 3.3 standard deviations, where the expectation from SM Higgs boson production is 2.8. The signal strength corresponding to this excess, relative to that of the SM Higgs boson production, is 1.2 ± 0.4. When combined with the Run 1 measurement of the same processes, the signal significance is 3.8 standard deviations with 3.8 expected. The corresponding signal strength, relative to that of the SM Higgs boson, is 1.06+0.31. −0.29
Host: Sridhara Dasu
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Council Meeting
Time: 4:00 pm
Place: 2314 Chamberlin Hall
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Wednesday, December 13th, 2017

NPAC (Nuclear/Particle/Astro/Cosmo) Forum
Search for New Physics with the Top Quark
Time: 2:30 pm
Place: 4274 Chamberlin Hall
Speaker: Kevin Black , Boston University
Abstract: The top quark is the heaviest known elementary particle: with a mass as large as an entire gold atom and the only fermion with a natural Yukawa coupling. Millions of top quarks have been produced at the LHC allowing precise measurements of its properties that have been compared with Standard Model predictions. The high center-of-mass energy of the LHC can also be exploited for dedicated searches for new heavy particles decaying preferentially to top quarks. I will review the latest ATLAS results searching for evidence of new physics in the production and decay of top quarks at the LHC with the ATLAS detector.
Host: Sridhara Dasu
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Thursday, December 14th, 2017

R. G. Herb Condensed Matter Seminar
Graphene in the extreme quantum limit
Time: 10:00 am
Place: 5310 Chamberlin Hall
Speaker: Cory Dean, Columbia University
Abstract: Soon after the discovery of monolayer graphene, it was shown that bilayer graphene (BLG), consisting of two bernal stacked monolayers, could theoretically support an even-denominator fractional quantum Hall state equivalent to the 5/2 Moore-Read Pfaffian first identified in GaAs . Owing to the unique landau level spectrum in BLG, the Pfaffian in this system is expected to be tunable by electric and magnetic fields, with the potential to be stronger than in GaAs for accessible field parameters. In my talk I will discuss recent magnetotransport studies of high mobility, BLG. Utilizing a dual gate geometry to tune through different orbital and layer polarizations, we find four even denominator states appearing within the N = 1 orbital branches of the lowest LL. We investigate how these states evolve with varying parameters and provide the first mapping of the B – D phase diagram. Our results confirm the unique tunability of the even denominator state in BLG, and we reach a regime where the energy gap is found to exceed several kelvin. I will also present recent measurements of bilayer systems in which we separate the two layers by a thin BN spacer. Here, by tuning the interlayer interaction strength via the layer separation, we are able to stabilize new correlated states in the double layer systems formed from interlayer excitons.
Host: Alex Levchenko
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Friday, December 15th, 2017

Department Meeting
Time: 9:00 am
Place: 5310 Chamberlin Hall
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Physics Department Colloquium
The Missing Metals in the Universe
Time: 3:30 pm
Place: 2241 Chamberbelin
Speaker: Joel Bregman, Univ. Michigan - Ann Arbor
Abstract: After the Big Bang nucleosynthesis period, H and He were present, but not significant amounts of heavier materials, such as C, N, O, Si, Fe, or Pb. These heavier elements, known collectively as “metals” to astronomers, were produced by several types of stars and stellar events, including low and high mass supernovae and the merger of neutron stars (kilonovae). The cosmic mass density of such metals is inferred from direct observations of supernovae and from the cosmic history of star formation. Previous observations to detect these metals in the local Universe find that 70-90% are unaccounted for (“missing metals”). This missing metals problem can be resolved if most of the metals lie in hot dilute gas surrounding galaxies and in the cosmic web. We discuss the detection of these metals in hot environments using X-ray astronomy and the tools needed for future observations.
Host: McCammon
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