Events at Physics
Events During the Week of December 6th through December 13th, 2015
- Plasma Physics (Physics/ECE/NE 922) Seminar
- Dusty plasmas for fundamental physics, fusion, semiconductor manufacturing, and astronomy
- Time: 12:00 pm
- Place: 2241 Physics
- Speaker: John Goree, University of Iowa
Beyond the usual electrons and ions, low-temperature plasmas can also contain charged particles of solid matter, ranging in size from nanometers to microns. They gain a large charge by collecting more electrons than ions from the ambient plasma. In fusion these solid particles are found immersed in the plasma of the divertor region of tokamaks. In semiconductor manufacturing they are called “particulates,” and they grow spontaneously and represent a contamination problem. Astronomers call these solid particles “dust,” and they are found in the plasma of the interstellar medium where they are the precursors of terrestrial planets like Earth. In this talk I review these diverse examples of dusty plasma, and then I present a fundamental physics experiment intended to probe the extreme properties of plasmas that are dominated by Coulomb collisions. A shear flow in this “strongly coupled” plasma results in localized viscous heating, a phenomenon that has long been predicted theoretically for both plasmas and fluids but never observed until now.
- Host: Paul Terry, UW
- Physics Education Innovation Seminar
- Online Activities to Improve In Person Learning
- Time: 12:00 pm
- Place: 4274 Chamberlin
- Speaker: Tim Stelzer, University of Illinois at Urbana-Champaign
- Abstract: Students’ unprecedented access to content on the web is providing a unique opportunity to transform the role lectures in education, moving the focus from content delivery to helping students synthesize the content into knowledge. We have introduced a variety of activities to facilitate this transformation at the University of Illinois, including web-based preflight assessments of student understanding before lecture, peer instruction (clickers) to assess and facilitate student understanding during lecture, and web-based multimedia pre-lectures designed to provide students with content before lecture. In this talk I will discuss the pedagogical motivation for introducing these activities, and the impact they have had at the University of Illinois<br>
Bio: Professor Timothy Stelzer received his bachelor's degree in physics from St. John's University in 1988, and his Ph.D. in physics from the University of Wisconsin-Madison in 1993. A high-energy particle theorist, Professor Stelzer has concentrated on standard model physics at hadron colliders. He has also been heavily involved with the Physics Education Group at Illinois, where he has led the development and implementation of tools for assessing the effectiveness of educational innovations in introductory courses and expanding the use of web technology in physics pedagogy. He was instrumental in the development of the I-clicker™ and is a regular on the University's "Incomplete List of Teachers Ranked as Excellent by Their Students."<br>
He and collaborators were selected by the American Physical Society to receive the 2013 Excellence in Education Award in recognition of their creation of smartPhysics, a web-based learning environment. He also received the UW Department of Physics' Distinguished Alumni Award in May 2015.
- Chaos & Complex Systems Seminar
- Imaging around obstacles and into lunar caves using scattered light
- Time: 12:05 pm
- Place: 4274 Chamberlin (refreshments will be served)
- Speaker: Andreas Velten, UW Department of Molecular Biology
- Abstract: The Computational Optics Group at the UW Laboratory for Optical and Computational Instrumentation (LOCI) develops novel imaging systems by combining new hardware designs with novel computational image reconstruction methods. The traditional method of imaging is based on hardware that resembles the human eye to produce images suitable for analysis and pattern recognition by a human viewer. A traditional camera like this only accesses a very small fraction of the information provided by the light field. Most of the light detected by optical systems occurs in the form of multiply scattered photons that can not be used to create an image in this traditional way. In this talk I will show different systems that, using custom methods to selectively capture and control photon time of flight, allow us to capture information inaccessible to a regular camera.<br>
Our Modular Indirect Remote Imaging System (MIRIS) uses ultrafast illumination and detection to collect and utilize light transport information. A laser is used to direct a pulse train towards one of the visible surfaces in a scene. The light bounces off of this surface and reflects off objects in the scene before heading back towards the visible scene where it is imaged with high time resolution by a camera. Images of the scene are reconstructed from the collected time-encoded information using a modified backprojection algorithm.<br>
In collaboration with the NASA Jet Propulsion Lab, we are performing studies to apply this method to explore the inside of caves on the moon from a low lunar orbit.
- Host: Sprott
- Theory Seminar (High Energy/Cosmology)
- Gauge and fermion preheating and the end of axion inflation
- Time: 3:30 pm
- Place: 5280 Chamberlin Hall
- Speaker: Evangelos Sfakianakis, University of Illinois, Urbana-Champaign
- Abstract: Axions are attractive candidates for theories of large-field inflation that are capable of generating observable primordial gravitational wave backgrounds. These fields enjoy shift-symmetries that protect their role as inflatons from being spoiled by coupling to unknown UV physics. This symmetry also restricts the couplings of these axion fields to other matter fields. At lowest order, the only allowed interactions are derivative couplings to gauge fields and fermions. These derivative couplings lead to the biased production of fermion and gauge-boson helicity states during and after inflation. I will describe some recent work on preheating in axion-inflation models that are derivatively coupled to Abelian gauge-fields and fermion axial-currents.
For an axion coupled to U(1) gauge fields it is found –analytically and numerically- that preheating is efficient for a wide range of parameters. In certain cases the inflaton is seen to transfer all its energy to the gauge fields within a few oscillations. In most cases, three-dimensional lattice simulations showed that the gauge fields on sub-horizon scales end preheating in an unpolarized state due to the existence of strong rescattering between the inflaton and gauge-field modes.
Coupling an axion to Majorana fermions leads to the biased production of fermion helicity-states which can have interesting phenomenological implications for leptogenesis.
- Host: Amol Upadhye
- Department Meeting
- Time: 12:15 pm
- Place: 5310 Chamberlin Hall
- R. G. Herb Condensed Matter Seminar
- Design and modeling of superconducting hardware for quantum computation and simulation
- Time: 10:00 am
- Place: Chamberlin 5310
- Speaker: Jens Koch, Northwestern University
- Abstract: Despite extraordinary challenges, research worldwide has led to remarkable advances in the exquisite control of individual quantum systems. Today, microwave-controlled superconducting circuits represent one of the “hot” candidates for the quantum hardware needed in a future quantum computer. I will give a brief review of the history, summarize how quantum mechanics manifests in these circuits, and then present theory work on developing a next generation of superconducting qubits using superinductor circuit elements. The new devices may realize intrinsic error protection by employing energy-degenerate wave functions with disjoint support. I will end with an outlook on the use of superconducting qubits in photon-based quantum simulation.
- Host: Vavilov
- Astronomy Colloquium
- Effects of Radial Mixing on Galactic Disks
- Time: 3:45 pm
- Place: 4421 Sterling Hall, Coffee at 3:30 PM, Talk at 3:45 PM
- Speaker: Carlos Vera-Ciro, UW Astronomy Department
- Abstract: I will talk about secular evolution in disk galaxies, in particular we will discuss the effects of radial migration on the overall structure of galactic disks. Over the past few years this mechanism has been argued to be a natural, intrinsically driven, way of explaining observations such as the existence of a thick disk or the bias in the distribution of metals at different galactocentric distances in the Milky Way. In this talk I will show results that confront some of these interpretations, in particular in casting some questions about the role of radial migration in the assembly of the galactic thick disk.
- Physics Department Colloquium
- Holiday Colloquium
- Time: 3:30 pm
- Place: 2103 Chamberlin Hall
- Speaker: Graduate Students, UW Department of Physics
- Abstract: Friday, December 11, 2015
Pizza & Soda 3:30 | Program 4:00 pm | 2103 Chamberlin
Wristband is needed for admittance.
Please pick up wristband from Renee (2320E Chamberlin) starting at 8:30 am Friday.
- Host: Walker