Events at Physics
Events During the Week of March 30th through April 6th, 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 (firstname.lastname@example.org)
- Host: Peter Timbie
- Plasma Physics (Physics/ECE/NE 922) Seminar
- Exploring Boundary Plasma and PMI Research at MIT with New Diagnostics and Experiments
- Time: 12:00 pm
- Place: 2241 Chamberlin
- Speaker: Dennis Whyte, Massachusetts Institute of Technology
- Host: Cary Forest
- Atomic Physics Seminar
- Rydberg-atom trapping and spectroscopy in optical trapping fields
- Time: 3:30 pm
- Place: 5280 Chamberlin Hall
- Speaker: Georg Raithel, University of Michigan
- Abstract: Trapped, cold Rydberg atoms are important in future applications in high-precision measurement, field sensing and quantum information processing. The following topics will be discussed. (1) We use high-resolution atom imaging to measure the Rydberg-Rydberg correlation function in Rydberg-atom samples prepared within the spatially-varying light shifts of a laser trap. We study the pair-correlation behavior as well as direct two-photon excitation of correlated Rydberg-atom pairs in the trap. (2) We employ a standing-wave laser trap in combination with Rydberg-atom position control within the standing wave to show that optical photoionization of a Rydberg atom does not occur within the main lobes of the Rydberg electron’s wave-function, but only within a relatively small volume around the nucleus. This evidence is consistent with the (sometimes unexpected) validity of the electric-dipole approximation for optical Rydberg-atom photoionization. (3) Modulated, spatially inhomogeneous light fields, such as amplitude-modulated optical lattices, can be used to drive multipole microwave transitions between Rydberg levels in a minimally invasive manner. This enables high-precision measurements of atomic properties. I will show first results with this new type of spectroscopy. (4) High-precision spectroscopy will be most promising with circular, Bohr-like Rydberg states. These have long lifetimes and low electric polarizabilities, among other nice features. Towards this, we have recently produced and trapped such atoms with an adiabatic “crossed-fields” state-switching method. Looking ahead, I will briefly discuss how these methods could be combined to perform specific high-precision measurements.
- Host: Saffman
- Chaos & Complex Systems Seminar
- Modeling issues in emergency medical services and their implications
- Time: 12:05 pm
- Place: 4274 Chamberlin (refreshments will be served)
- Speaker: Laura McLay, UW Department of Industrial and Systems Engineering
- Abstract: In this talk, I will discuss issues that affect models for optimally allocating scarce resources for public services (such as fire and emergency medical services) including issues involving performance benchmarks, equity, natural disasters, and the modeling of human servers in queuing models. I will include stories from my research and from the field.
- Host: Clint Sprott
- Physics Education Innovation Seminar
- Flexible Physics Mobile videos: Physics 109, 103-4, 201-2, and 207-8 on Youtube and Turning a Large Lecture into a Blended Classroom: First Results from Physics 207
- Time: 11:00 am
- Place: 5310 Chamberlin Hall
- Abstract: Flexible Physics Mobile videos:
Physics 109, 103-4, 201-2, and 207-8 on Youtube
Turning a Large Lecture into a Blended Classroom:
First Results from Physics 207
(Peter Timbie, Jake Feintzeig, and Josh Weber)
- R. G. Herb Condensed Matter Seminar
- Measuring topological transitions in superconducting qubits
- Time: 10:00 am
- Place: Chamberlin 5310
- Speaker: Michael Kolodrubetz, Boston University
- Abstract: The field of topological insulators sprung from the realization that in the presence of spin-orbit coupling, non-interacting electrons can have a band structure that non-trivially wraps the first Brillouin zone. From the gauge-invariant Berry curvature that locally defines the geometry of this wrapping, one can define an integer topological invariant – the Chern number – from which all other invariants derive. We investigate the Berry curvature and Chern number of an even simpler case: single and double spin-1/2 systems (qubits) in a rotating magnetic field. We show that these simple systems undergo topological transitions of their Chern number, which for the case of the single qubit can be directly mapped to the topological transitions of the Haldane model of graphene. Furthermore, we experimentally demonstrate such a topological transition in a single superconducting qubit, measuring the Berry curvature as a leading order correction to linear response. We then generalize the methods to two-qubit systems, where we experimentally measure the topological phase diagram and demonstrate interaction-driven topological transitions.
- Host: Vavilov
- NPAC (Nuclear/Particle/Astro/Cosmo) Forum
- Cosmic voids as cosmological laboratories
- Time: 2:00 pm
- Place: 4274 Chamberlin
- Speaker: Paul Sutter, IAP
- Abstract: Voids are the large, underdense regions in the cosmic web, and they are potentially powerful cosmological probes due to their intimate connection to the growth of structure, their domination by dark energy, and their relative lack of systematics. I will present our latest work to identify voids in galaxy redshift surveys, our efforts to understand their fundamental nature and their connection to dark matter underdensities, and an overview of many diverse cosmological applications, including gravitational lensing, the ISW effect, and the Alcock-Paczynski effect.
- Host: Peter Timbie
- Astronomy Colloquium
- The Gaseous Environments of Galaxies: Toward Lower Halo Masses and Absorption Morphology
- Time: 3:30 pm
- Place: 4421 Sterling Hall
- Speaker: Kate Rubin, Harvard-Smithsonian Center for Astrophysics
- Abstract: The environments extending several hundred kiloparsecs from galaxies contain the fuel that feeds galactic star formation, and act as the reservoir into which ejecta from stellar and AGN feedback are driven. Observations of the cool hydrogen and metal content of these regions (i.e., the circumgalactic medium, or CGM) can therefore provide incisive tests of our understanding of these processes. I will briefly discuss current constraints on the content of the CGM around massive, &gt; L* galaxies from z~2 to ~0. I will then describe a new technique that pinpoints much fainter, sub-luminous systems at z~2, allowing us to probe the gas in their surroundings in absorption toward background QSOs for the first time. I will also discuss prospects for new constraints on the sizes of CGM absorbers, and provide a first glimpse into the small-scale distribution of this diffuse material. Such measurements represent important steps toward a complete, detailed empirical picture of the CGM.
- Host: Aleks Diamond Stanic
- Physics Department Colloquium
- Looking for Dark Matter, Here, There and Everywhere
- Time: 3:30 pm
- Place: 2241 Chamberlin Hall (coffee at 4:30 pm)
- Speaker: Patrick Fox , Fermilab
- Abstract: The hunt for physics beyond the standard model at the LHC is in full swing. We already know of the existence of (at least) one new particle that is not in the standard model, dark matter. The existence of dark matter was first inferred from astrophysical observations and later confirmed by cosmological measurements. There is considerable ongoing effort to see the effects of dark matter, which makes up the majority of the matter in our galaxy, in a more terrestrial setting. I will outline what is, and what is not, known about dark matter, and explain how we may soon learn a lot more, as well as explaining how the conventional search methods can be complemented by searches at the LHC, and elsewhere.
- Host: Bai
- Digital Planetarium show & tell
- Time: 4:00 pm
- Place: Sterling Hall Planetarium
- Speaker: Jim Madsen, WIPAC, UW-River Falls
- Abstract: Join colleagues from the Wisconsin IceCube Particle Astrophysics Center (WIPAC) and others for a drop-in “show and tell” of a digital planetarium system from 4 to 6 pm in the Sterling Hall planetarium on Friday, April 4.
This system allows visitors to explore more of the cosmos in new ways and provides colleagues in other disciplines a new platform for teaching and learning in an enriching and engaging environment. Whether it's a tour of the universe or a trip through the human heart, there are growing numbers of datasets and interactive tools finding their way into the domed learning environment. This system allows for real-time data access, professional rendering, custom production, and remote domecasting presentations. Hear about plans to bring this technology to the UW system with the help of the Growth Agenda. Stop over and meet Joel Halvorson, a seasoned digital dome professional, and see how you can better tell your story in a domed environment.