Events at Physics
Events During the Week of April 20th through April 27th, 2014
- Cosmology Journal Club
- An Informal discussion about a broad variety of arXiv papers related to Cosmology
- Time: 12:00 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 Le Zhang (email@example.com)
- Host: Peter Timbie
- Plasma Physics (Physics/ECE/NE 922) Seminar
- Pressure Anisotropy in Reconnection
- Time: 12:00 pm
- Place: 2241 Chamberlin
- Speaker: Paul Cassak, West Virginia University
- Host: Jan Egedal
- Chaos & Complex Systems Seminar
- Now you see him, now you don’t — a hitchhiker’s guide to high dimensional data analysis
- Time: 12:05 pm
- Place: 4274 Chamberlin (refreshments will be served)
- Speaker: Ming Yuan, UW Department of Statistics
- Abstract: The analysis of high-dimensional data now commonly arising in scientific investigations poses many statistical challenges not present in smaller scale studies. In this talk, I will survey some main ideas and problems, in particular, in recovering high dimensional sparse signals and estimating large matrices -- two classes of problems that have attracted much recent interests in a range of fields including statistics, applied math and electrical engineering. Time permitting, I will also discuss their implications in other scientific domains.
- Host: Clint Sprott
- Department Meeting
- Time: 12:15 pm
- Place: 5310 Chamberlin Hall
- NPAC (Nuclear/Particle/Astro/Cosmo) Forum
- The Mystery and Promise of Fast Radio Bursts
- Time: 2:30 pm
- Place: 5280 Chamberlin
- Speaker: Albert Stebbins, FermiLab
- Abstract: The newly discovered phenomena of Fast Radio Bursts is discussed as well as their possible origins. If these bursts originate at cosmological distances then they may provide a tool to probe a variety of different phenomena apart from the bursts themselves. This includes neutrino masses, cosmological distances, and the intergalactic medium on parsec scales.
- Host: Peter Timbie
- Astronomy Colloquium
- Deep Surveys with GISMO : Searching for submillimeter galaxies at the highest redshifts
- Time: 3:30 pm - 5:00 am
- Place: 4421 Sterling Hall
- Speaker: Johannes Staguhn, John Hopkins University
The GISMO 2 mm camera at the IRAM 30m telescope is available to the astronomical community through the semi-annual IRAM call for proposals. GISMO provides a general capability across a wide range of astronomical sources, including observations of galactic dust and free-free emission, the characterization of the SEDs of nearby galaxies, and detecting dusty galaxies at high redshifts. The 2 mm band is in particular well suited to trace the first dusty galaxies in the universe, since their redshifted SEDs peak close to GISMO's observing frequency, whereas the medium redshift galaxy foreground is almost invisible in this band. This effect makes GISMO's deep field observations a valuable complement, rather than a redundancy, to the HERSCHEL far-infrared and sub-mm surveys. There are two ongoing deep sky surveys with GISMO. Following a brief summary of a sample of current projects, I will describe one of those surveys in detail: the GISMO Deep Field (GDF) survey, which is centered on the Hubble Deep Field North. This survey by now has reached the confusion limit (we measure a confusion noise of 60 microJy) and we have extracted 12 + 3 sources in a 7 arcminute wide field, of which roughly half have known submillimeter galaxy counterparts, including the enigmatic submillimeter galaxy SCUBA-850.1. Our detailed statistical analysis of the GDF data provides a solid estimate of the expected rate of false detections among those source identifications. Furthermore, numerical simulations were used, to estimate the "completeness" of our set of extracted sources. A comparison of our observations with model predictions shows that our results are in good agreement with galaxy count models. Simple models predict an appreciable number to be at very high redshifts (z~5-6 and above) with intrinsic luminosities of a few 10^12 L_sol.
Targeted GISMO observations of even more extreme high redshift galaxies have been obtained during our most recent observing run. I will present preliminary results from these observations, which have the potential to put strong constraints on the formation of dark matter halos and the production of metals in the early universe.
Finally, I will give an outlook into the future by outlining the variety of science questions we anticipate to address with the dual band (1 mm and 2 mm) bolometer camera GISMO-2, which we expect will replace GISMO at the IRAM 30 m telescope in the second half of 2014.
- Host: Professor and Dept Chair, Ellen Zweibel
- Theory Seminar (High Energy/Cosmology)
- Soft R-Parity Violation
- Time: 2:15 pm
- Place: 5280 Chamberlin Hall
- Speaker: Yuhsin Tsai, Univ. of California-Davis
- Abstract: Supersymmetric (SUSY) models with R-parity generically predict sparticle decays with invisible neutralinos, which yield distinctive missing energy events at colliders. Since most LHC searches are designed with this expectation, the putative bounds on sparticle masses become considerably weaker if R-parity is violated so that squarks and gluinos decay to jets with large QCD backgrounds. In this talk I will introduce a scenario in which baryonic R-parity violation (RPV) arises effectively from soft SUSY-breaking interactions. The model features a global R-symmetry that initially forbids RPV interactions, a hidden R-breaking sector, and a heavy mediator that communicates this breaking to the visible sector. After R-symmetry breaking, the mediator is integrated out and an effective RPV A-term arises at tree leve. Although this mediator must be heavy compared to soft masses, the model introduces no new hierarchy since viable RPV can arise when the mediator mass is near the SUSY breaking scale. In generic regions of parameter space, a light thermally-produced gravitino is stable and can be a viable dark matter candidate.
- Physics Department Colloquium
- Searching for new physics at the LHC: The story you haven't heard
- Time: 3:30 pm
- Place: 2241 Chamberlin Hall (coffee at 4:30 pm)
- Speaker: Michael Williams , MIT
- Abstract: There are two ways to discover new particles: we can make them in the lab and observe their decays or we can observe discrepancies between precision measurements and theoretical predictions. Both methods are being employed by the LHCb experiment at CERN to search for what lies beyond the Standard Model (SM) of particle physics. The LHCb experiment has published over 170 papers since 2011. The core physics program involves making precise measurements of observables whose SM predictions are well known and that are expected to be extremely sensitive to a wide range of beyond the SM theories, e.g., supersymmetry. The magic of quantum mechanics permits particles that are too massive to be produced in the lab, even at the LHC, to make significant contributions to the observables measured at LHCb. If, in fact, the lightest new particles cannot be produced directly at the LHC, then our only hope for discovery at a collider in the coming decades is via such indirect observations. I will also discuss direct searches for light dark matter candidates and other future prospects for discovery.
- Host: Westerhoff