Seminars in Fall 2014
All seminars are held at 4:10 PM in Bio 19, unless otherwise noted.
Refreshments will be served at 4:00 PM.
October 1, 2014
Andrew Essin, Caltech
Exotic Quantum Numbers in Exotic Phases of Matter
Thesis Start-Up Meeting
Summer Internship Talks
Yudan Guo, Self-Consistent Tomography of a Superconducting Qubit
Dan Herman, Examining Energy Transport in Solar Flares Using EUV/SXR Peak Flux Timing
Liese Maynard, Using Jet Asymmetry to Distinguish Quark 3-Pronged Decays from Background
Anna Nuxoll, Myths and Science: Research on Inclusive Climate
Summer Internship Talks
Miguel Conner, Regolith-Atmosphere Water Vapor Transfer on Mars: Comparison between Phoenix and MSL Data
Naomi Gendler, Inference on Populations of Binary Neutron Stars
Elizabeth Grace, Sensitivity Study: Measurement of Reactor Electron Antineutrino Disappearance in the Double Chooz Experiment
Kai Nalipinski/Jack Flowers, An Investigation of Lowest Energy Levels on a Square Lattice
Julia Selker, A New Method and Instrument for Cryo-Electron Microscopy Sample Preparation
Spencer Chang, University of Oregon
Dark Matter Direct Detection Experiments and Inelastic Dark Matter
In this talk, I will give an introductory overview of dark matter direct detection experiments, a class of underground experiments searching for dark matter in our galaxy. There is an elegant dark matter framework called the weakly interacting massive particle (WIMP), which suggests a detectable scattering cross section for dark matter off target nuclei. An overview of interesting past and future experiments will be given, focusing on a longstanding observation by the DAMA experiment of an annual modulation that is suggestive of dark matter. I will review both dark matter and background explanations of this modulation. In particular, I will show that cosmic ray muons, which are known to modulate, cannot be solely responsible for the signal. As a potential signal, I will discuss a scenario where the dark matter inelastically scatters with nuclei, which I will show is still allowed by current limits and should be tested in the near future.
Andrew Essin, Caltech
Exotic Quantum Numbers in Exotic Phases of Matter
Symmetries imply conservation laws and therefore provide meaningful and useful ways to label and classify states of particles and matter. Condensed matter physics traditionally classifies phases of matter by patterns of symmetry breaking. One of the most exciting areas of current research is the study of phases which break no symmetries, because the distinctions between them cannot be captured within the traditional scheme. I will focus on exotic phases of matter that are host to "fractional excitations," and will describe how fractional excitations can carry "fractional quantum numbers."
Summer Internship Talks/CAT Presentation
Jay Collins, Simulating Information Transmission at Auditory Hair Cell Synapses
Will Holdhusen, Comparing Earth's Gravity Field to Antarctic Seasonal Patterns
Nick Irvin, The Vortex Emitted from a Wind Turbine
Matthew Graham, Oregon State University
Micro-Femto Energetics; Nano-Physics in the Twinkling of an Eye
When light and matter interact, electron micro-femto energetics begin. Our just-constructed lab is able ‘film’ the excited electron’s energetic journey from light absorption to photocurrent generation with sub-micron (<10-6 m) spatial resolution and femtosecond (~10-15 s) time-resolution. By 'filming' how electrons move and relax at nanoscale interfaces, we identify the bottlenecks that inherently limit the efficiency of solar voltaics and photosensors. We will show how our ultrafast ‘moives’ give a time-space resolved microscopy map of the electronic population in materials such as graphene and single atomic layer dichalcogenides devices. For graphene, our measurements reveal how electrons relax near the Fermi energy through a radically accelerated supercollision mechanism. The discovery of this novel electronic mechanism provides the missing link required to predict current generation from electronic population in graphene.
Ian Coddington, National Institute of Standards and Technology, Boulder
Frequency Comb Measurements Outside the Laboratory
Frequency combs are a novel laser source that have been exploited in an exciting range of laboratory-bound precision measurements. I will discuss development of a fieldable frequency comb, and experiments that send comb light across outdoor air paths to explore both accurate atmospheric measurements of greenhouse gasses and optical time-frequency transfer to support navigation and geodesy.
Robert Knapp, Evergreen College
Physics and Sustainable Buildings
Buildings account for roughly 40% of energy use and large fractions of water, materials and other dimensions of the national and global sustainability challenge. Physics imposes limits and creates opportunities for reducing resource demands and impacts while maintaining high performance. Using measured energy flows in instrumented buildings as one guide, and fundamental physics as another, this talk will highlight key aspects of the critical thermal, optical, fluid and electrical processes used in the current generation of high-performing buildings such as the Packard Foundation’s and Bullitt Foundation’s new “net zero” office buildings. Topics will include heat engines and heat exchangers, blackbody and selective absorption and radiation, and photovoltaic performance.
Anne Trehu, College of Earth, Ocean and Atmospheric Science, Oregon State University
Earthquakes, Tsunamis and the Cascadia Subduction Zone
The Cascade volcanoes are evidence that the Juan de Fuca plate is subducting beneath the North America. Seafloor topography indicates that the Cascadia subduction zone extends from Cape Mendocino at least to northern Vancouver Island. The one element of a typical subduction zone that is missing is earthquakes on the plate boundary during the age of seismological instrumentation (i.e. since ~1900). Although the ends of the subduction zone are seismically active, and there is considerable earthquake activity within the subducting Juan de Fuca and overriding North American plates, low-angle thrust earthquakes on the plate boundary have not been recorded from the central part of the subduction zone (~Cape Blanco to central Vancouver Island), with the exception of the region offshore Cape Perpetua, OR (44 to 44.5°N). An "orphan tsunami" observed in Japan on January 26, 1700, has been modeled as being the result of an earthquake in Cascadia with magnitude of at least 8.5, and geologic evidence indicates that very large, tsunamigenic earthquakes have occurred ~18 times in the past 10,000 years. High-resolution GPS and seismic arrays that have been installed in the past 10-15 years indicate that the plates are locked together at present above a depth of ~30 km, but that they are sliding past each other at greater depth, "loading" the plate boundary. Similar high-resolution data sets that recorded deformation prior to, during and after recent large subduction zone earthquakes after Chile and Japan provide clues about the physics of the "earthquake cycle" and provide guidance to efforts to develop more detailed models of what to expect in Cascadia. I will provide an overview of the geological and geophysical setting of the Cascadia subduction zone and of recent research on megathrust earthquakes.
Ben McMorran, University of Oregon
Experiments with Free Electron Vortices
Electron vortex beams are composed of free electrons in quantized orbital states. Each electron wave packet in the beam has a helical shape, with a resulting quantized orbital angular momentum (OAM) and a corresponding magnetic moment. To produce such states, we use nanofabricated diffraction gratings to holographically “sculpt” a phase vortex onto free electron matter waves in a transmission electron microscope (TEM). We also use this approach to place free electrons in coherent superpositions of orbital states. These beams can interact with surfaces and materials in unique, albeit subtle, ways. For example, electron vortex beams can transfer quantized OAM to another system through inelastic scattering. In the TEM this can result in OAM-dependent signals and images that can provide new magnetic, plasmonic, and structural information about a material. These applications, the new technologies developed to achieve them, and the fundamental physics of free electron orbital states will be discussed.
Alex Emerman Thesis Talk/Phil Mass, Lightcraft Technology
Phil Mass Talk: Cleaning Robots and German Soap Operas - The Strange Places a Physics Education Can Lead
Not all Physics graduates end up with a career in Physics. Yet, fear not, there is still plenty of fun and interesting work to be had. As a programmer with a degree in Physics, I've found that it can provide a good basis for a career in coding. In this talk, I'll cover a couple of the projects I've had the good fortune to work on over the years. I'll delve into some of what went into creating the Roomba robotic vacuum cleaner. The control system of the Roomba was designed to behave like an insect, which allowed it to clean most homes with an operating system of only ten thousand bytes. From robotics, I'll jump over to the world of visual effects and the Previzion 'virtual production' system. Previzion allows directors to set shows anywhere in the world using greenscreen, and to see the results in real-time. Explaining aspects of the same technology used in video games, I'll show some of the math behind the pixels that might just show up as images on your TV screen.
Max Schlosshauer, University of Portland
A New "No-Go" Result for Quantum Mechanics
I describe a new theorem that shows that whenever you consider a pair of quantum systems, the whole is different from the sum of the parts even in the absence of entanglement. (Reference: Phys. Rev. Lett. 112, 070407 (2014), arXiv:1306.5805 [quant-ph])