Events at Physics
Events During the Week of September 11th through September 18th, 2016
Monday, September 12th, 2016
- Plasma Physics (Physics/ECE/NE 922) Seminar
- An Introduction to Bayesian Analysis for Fusion Science
- Time: 12:00 pm
- Place: 2241 Chamberlin Hall
- Speaker: Lisa Reusch, UW Madison
- Abstract: The harsh conditions that will exist in fusion devices that are in full nuclear environments will place severe limits on the diagnostics. Integrated data analysis (IDA) provides methods to maximize the scientific value of the diagnostic data, and is a growing area of research in the fusion community. The goal of IDA is to combine information from different diagnostics to get the most reliable measurement of physical parameters of interest in a standardized and transparent way. A natural framework in which to develop IDA is Bayesian probability theory or Bayesian analysis. On its own, Bayesian analysis of a diagnostic can offer advantages over traditional approaches to analysis, in particular when the analysis involves complex inversions. In the context of IDA, the probabilistic focus of Bayesian analysis allows an IDA technique to be developed modularly, one diagnostic at a time. It automatically includes error analysis and provides a method for including background information into the analysis quantitatively. This talk presents an introduction to a Bayesian approach to data analysis using concrete examples. It focuses on explaining the terms in Bayes’ Rules, the foundation for Bayesian analysis, and will highlight important considerations that need to be made when applying Bayesian analysis to a particular diagnostic. Its function as a framework for IDA will also be illustrated.
- Host: Cary Forest
Tuesday, September 13th, 2016
- Chaos & Complex Systems Seminar
- Correspondence between intonation and expression in music
- Time: 12:05 pm
- Place: 4274 Chamberlin Hall (refreshments will be served)
- Speaker: Trevor Stephenson, Madison Bach Musicians
- Abstract: For demonstration in the lecture I will bring my 17th-century Italian harpsichord and tuning lever (this harpsichord weighs only 40 pounds and has a lovely, clear sound). I will explain and demonstrate how various temperament systems are created (with a wee-bit of the math behind them) and show how different temperaments affect the expressive possibilities of a piece.
- Host: Clint Sprott
- Theory Seminar (High Energy/Cosmology)
- Baryogenesis from Decaying Magnetic Helicity
- Time: 3:30 pm
- Place: 5280 Chamberlin
- Speaker: Andrew Long, University of Chicago, Kavli Institute for Cosmological Physics (KICP)
- Abstract: Due to quantum anomalies in the Standard Model, baryon number is violated in the early universe in the presence of a helical (hyper)magnetic field. I will discuss how the matter / anti-matter asymmetry of the universe may have been created from the decaying helicity of a primordial (hyper)magnetic field. This scenario has the interesting feature that baryogenesis occurs without the violation of (B-L), since the (B+L) asymmetry generated by the hypermagnetic field counteracts the washout by electroweak sphalerons. After the electroweak crossover, the hypermagnetic field becomes an electromagnetic field. Thus, observations of the relic, intergalactic magnetic field today may inform our understanding of the cosmological excess of matter over anti-matter.
- Host: Joshua Berger
Wednesday, September 14th, 2016
- High Energy Seminar
- An Effective Field Theory Analysis of LUX and Other Direct Dark Matter Searches
- Time: 4:00 pm
- Place: 5280 Chamberlin hall
- Speaker: Nicole Larsen, Kalvi Institute for Cosmological Physics, Univ Chicago
- Abstract: The Large Underground Xenon (LUX) dark matter search is a 370-kg dual-phase xenon-based time projection chamber that operates by detecting light and ionization signals from particles incident upon a xenon target. With its 2013 report of the world’s first sub-zeptobarn spin-independent WIMP-nucleon cross section limit, LUX emerged as a frontrunner in the field of dark matter direct detection. In December 2015, LUX released an updated analysis of its 2013 dataset leading to an overall 23% increase in sensitivity for high-mass WIMPs and even more significant improvement for low-mass WIMPs. And in July 2016, LUX released results from an extended 332-day dataset, finding no evidence of WIMPs and improving its limit to a minimum of 0.2 zeptobarns for 50-GeV WIMPs. However, tension between experiments and the absence of a definitive positive detection suggest it would be prudent to search for WIMPs outside the standard spin-independent/spin-dependent analyses. Recent effective field theory work has identified a complete set of 14 possible independent WIMP-nucleon interaction operators restricted only by basic symmetries. These operators produce not only spin-independent and spin-dependent nuclear responses but also novel nuclear responses such as angular-momentum-dependent and spin-orbit couplings. Here we report on the extension of the LUX analysis to search for all 14 of these interactions, comment on the possible suppression of event rates due to operator interference, and investigate several other prominent direct detection experiments to show that under this new framework, LUX again exhibits world-leading sensitivity.
- Host: Kimberly Palladino
Thursday, September 15th, 2016
- R. G. Herb Condensed Matter Seminar
- Quantum annealing--advantages and pitfalls
- Time: 10:00 am
- Place: 5310 Chamberlin
- Speaker: Hari Krovi, BBN Technologies
We will review the framework of quantum annealing and quantum adiabatic algorithms. We will describe the evidence that they give speed-ups over classical algorithms for optimization problems and the need for non-stoquasticity in the Hamiltonian. We also present some negative results showing evidence that they do not give an exponential speed-up over classical algorithms for these problems. Finally, we present some recent work on constructing annealing algorithms with non-stoquastic terms.
- Host: Vavilov
- Astronomy Colloquium
- Cosmic Rays in Galaxies - Drivers of Winds?
- Time: 3:30 pm
- Place: 4421 Sterling Hall, Coffee and cookies 3:30 pm, Talk starts 3:45 PM
- Speaker: Joshua Wiener, UW Madison Astronomy Dept
- Abstract: Cosmic rays are often cited as an appealing driver of galactic winds. Cosmic rays(CRs) have some advantages as a wind-driving mechanism, such as long cooling times which allow the CRs to keep their energy for long periods of time. In this talk I will summarize the physics of CR transport, and how CRs interact with the ambient gas in a galaxy. I present numerical simulations of isolated galaxies, which reveal how the characteristics galactic winds depend strongly on how the CR physics are modeled.
- Host: Astronomy Dept
Friday, September 16th, 2016
- Physics Department Colloquium
- The Signal Above the Noise: the Importance of Physics Policy and Advocacy
- Time: 3:30 pm
- Place: 2241 Chamberlin
- Speaker: Gregory Mack , APS Physics
- Abstract: Science is only one of many competing priorities for policymakers, so physicists and members of the physics community must be vocal in order to have their needs met. The American Physical Society's Office of Public Affairs (OPA) handles policy and advocacy issues for the society in order to foster the progress of the field of physics. OPA's activities range from helping to craft APS policy position statements to going directly to Capitol Hill with APS members to meet with Senate and House offices to advocate for the needs of the physics community. This talk will discuss the different aspects of OPA's activities and how members of the physics community can get involved to help ensure a positive future for the field of physics.
- Host: Lisa Everett and Peter Timbie