Events at Physics

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Events During the Week of March 6th through March 13th, 2016

Monday, March 7th, 2016

Plasma Physics (Physics/ECE/NE 922) Seminar
"Nonlinear Convective Transport in Magnetized Temperature Filaments: Theory, Simulation and Experiments
Time: 12:00 pm - 1:00 pm
Place: 1153 Mechanical Engineering
Speaker: Dr. Richard Sydora, University of Alberta, University of Alberta
Host: UW Madison
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Tuesday, March 8th, 2016

Chaos & Complex Systems Seminar
Cultural-responsivity, education, and health in Anishinaabe communities
Time: 12:05 pm - 1:00 pm
Place: 4274 Chamberlin Hall (refreshments will be served)
Speaker: Tim Frandy, UW Department of Medicine and Public Health
Abstract: For the past few decades, culture and cultural-responsivity have increasingly been viewed as important within indigenous communities to improve educational systems and public health outcomes. More than a decade of research has shown the positive impacts of culturally-responsive teaching in Native communities, and recent research has shown correlation with language and cultural maintenance programs in First Nations communities to dramatically lower diabetes rates. This presentation will discuss discuss research conducted in partnership between UW-Madison and the Lac du Flambeau Anishinaabe community that has used indigenous methodologies and cultural revitalization to improve health and educational outcomes. This work raises new possibilities for interdisciplinary collaborative research and lower-cost solutions to improve complex social problems in marginalized communities.
Host: Clint Sprott
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Wednesday, March 9th, 2016

Department Meeting
Time: 12:15 pm - 1:15 pm
Place: 5310 Chamberlin Hall
Host: Albrecht Karle
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Thursday, March 10th, 2016

R. G. Herb Condensed Matter Seminar
Phonon-mediated decay of singlet-triplet qubits in double quantum dots in GaAs/AlGaAs and Si/SiGe heterostructures
Time: 10:00 am - 11:00 am
Place: Chamberlin 5310
Speaker: Viktoriia Kornich, University of Basel
Abstract: We study theoretically the phonon-induced relaxation and decoherence times of singlet-triplet qubits in lateral double quantum dots (DQDs) in GaAs/AlGaAs and Si/SiGe heterostructures. We show that the two-phonon processes can dominate over the one-phonon processes even at rather low temperature, e.g. for the decoherence time at 50 mK for biased GaAs/AlGaAs DQDs. We find that when the DQD is unbiased the qubit lifetimes are orders of magnitude longer than for the case of biased DQD. The lifetimes of the qubits in Si/SiGe DQDs are remarkably longer than the ones in GaAs/AlGaAs DQDs, and following interest in S-T_- qubits we consider the phonon-induced decoherence and relaxation particularly in the region of the singlet-triplet anticrossing. We show that the hybridization of the singlet state plays a crucial role. Among other parameters of the system, we study the effect of micromagnet-induced magnetic field gradient on the qubit, which reveals an non-trivial behavior of the relaxation and decoherence times as a result of interplay between one-phonon and two-phonon processes. We suggest how our theory can be tested experimentally.
Host: Vavilov
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Cosmology Journal Club
An Informal discussion about a broad variety of arXiv papers related to Cosmology
Time: 12:15 pm - 1:15 pm
Place: 5242 Chamberlin Hall
Abstract: Please visit the following link for more details:
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 Amol Upadhye (
Host: Amol Upadhye
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Astronomy Colloquium
Toward a physically-predictive theory of galaxy formation: resolved stellar and black hole feedback
Time: 3:30 pm - 5:00 pm
Place: 4421 Sterling Hall, Coffee and Cookies 3:30 PM, Talk at 3:45 PM
Speaker: Claude-Andre Faucher-Giguere, Northwestern University
Abstract: Over the past few years, cosmological hydrodynamic simulations have begun to produce galaxy populations with properties that agree broadly with observations. The successes of most existing simulations however rely on carefully tuning parameters of sub-grid models for core physical processes such as star formation, stellar feedback, and supermassive black holes. I will describe a research program that aims to greatly improve the predictive power of galaxy formation models by directly resolving some of the key physical processes in the ISM of galaxies and developing approximations for unresolved processes that are directly calibrated using small-scale calculations. This approach largely eliminates the need for tunable parameters. I will present some key results from the FIRE ("Feedback In Realistic Environments") cosmological simulations developed using this approach, including on the physics shaping the galaxy stellar mass function, the generation of galactic winds, the chemical enrichment of galaxies, and observational diagnostics of circum-galactic gas flows. I will conclude by outlining our on-going work to model supermassive black hole growth and feedback, from galactic nucleus to cosmological scales.<br>
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Friday, March 11th, 2016

R. G. Herb Condensed Matter Seminar
Microwave response and photon emission of a voltage baised Josephson junction
Time: 10:00 am - 11:00 am
Place: 5310 Chamberlin Hall
Speaker: Salha Jebari, CEA Grenoble
Abstract: The readout of superconducting qubits and other quantum devices operating at microwave frequencies requires amplifiers combining noise close to the quantum limit[1 ], high gain, large bandwidth, and sufficient dynamic range[2 ]. Josephson parametric amplifiers using Josephson junctions in the 0-voltage state, driven by a large microwave signals, begin to perform sufficiently well in all 4 of these aspects to be of practical use, but remain difficult to optimize and use. Recent experiments with superconducting circuits consisting of a DC voltage-biased Josephson junction in series with a resonator, showed that a tunneling Cooper pair can emit one or several photons with a total energy of 2e times the applied voltage[3 ]. We present microwave reflection measurements on this device in [3], indicating that amplification is possible with a simple DC voltage-biased Josephson junction.<br>
We compare these measurements with the noise power emitted by the junction and show that, for low Josephson energy, transmission and noise emission can be explained within the framework of P(E) theory of inelastic Cooper pair tunneling. Combined with a theoretical model, our results indicate that voltage-biased Josephson junctions might be useful for amplification near the quantum limit, offering simpler design and a different trade-off between gain, bandwidth and dynamic range, which could be advantageous in some situations.
Host: Robert McDermott
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Theory Seminar (High Energy/Cosmology)
Compactifying M-theory on a G2 manifold to describe our world
Time: 1:30 pm
Place: 5280 Chamberlin Hall
Speaker: Gordon Kane, University of Michigan
Abstract: Compactified M-theory generically describes many features of our world, including gravity; Yang-Mills forces like S(U3)xSU(2)xU(1); chiral fermions (so parity violation); softly broken supersymmetry; a solution to the hierarchy problem; electroweak symmetry breaking and Higgs physics (including the ratio of the Higgs boson mass to the Z mass, and Higgs decay branching ratios); grand unification; small EDMs; no flavor changing problems and more. It predicts a non-thermal cosmological history and addresses the form(s) of dark matter and the ratio of matter to dark matter. And it predicts the superpartner spectrum: heavy (tens of TeV) squarks and sleptons, light (~ TeV) gluino and LSP. Superpartners should not have been found in Run I at LHC, and can be found in Run II (gluinos about 1..5 TeV, winos about 640 GeV). Five general assumptions are made, and there are no parameters to vary. There has been good progress in calculating and elucidating the predictions, but there is still much to do. I will explain the Higgs and superpartner predictions in some detail.
Host: lisa Everett
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Physics Department Colloquium
Status and Future of Tau physics at the LHC
Time: 3:30 pm - 4:30 pm
Place: 2241 Chamberlin Hall
Speaker: Isobel Ojalvo, University of Wisconsin - Madison
Abstract: The observation of a Higgs boson by the LHC experiments through its decays
to vector bosons was an extremely significant milestone in particle physics
research; one which redefined the research priorities in the field. After
this discovery the first step was to test the compatibility of the new
particle with the SM Higgs by searching for the different possible Higgs
couplings. The decay to fermions is of fundamental importance since it
proves the presence of Yukawa couplings in the theory. Since Higgs couples
to mass, it breaks lepton universality, therefore decays to tau leptons are
enhanced. The next step is to use the Higgs as a tool for new physics
searches through its decays (i.e. lepton flavor violation) or through its
associated production with other particles (A->Zh, H->hh, etc.)

The experimental challenges of triggering and identifying tau leptons will
be described. Then the recent Higgs results will be presented for the SM
Higgs and the SUSY extensions. Finally, the future prospects of Higgs and
tau physics will be summarized.
Host: Lisa Everett
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