Events at Physics
Events During the Week of January 24th through January 31st, 2016
- No events scheduled
- Chaos & Complex Systems Seminar
- urbulence, the manifestation of eddies and their role in conservation laws
- Time: 12:05 pm
- Place: 4274 Chamberlin Hall (Refreshments will be served)
- Speaker: George Hrabovsky, Madison Area Science and Technology
- Abstract: Only in technically dry fluids can you get away from the phenomena of turbulence. Such phenomena serve to transport important quantities across scales. Why is this important? Because two thirds of the classical states of matter are composed of fluids. Fluids exist on most scales of distance measurement—some surprising. Where there are non-perfect fluids, there is turbulence. Why is the transport of these quantities across scales important? What are the ramifications for physical and predictive modeling? Come to the talk and find out...<br>
- Host: Sprott
- Theory Seminar (High Energy/Cosmology)
- Condensed Dark Matter: An Axion Story
- Time: 3:30 pm
- Place: 5280 Chamberlin Hall
- Speaker: Chanda Prescod-Weinstein, MIT
- Abstract: Recently there has been significant interest in the claim that axions, a popular dark matter candidate, form a Bose-Einstein condensate on a scale that has consequences for structure formation. I will describe my work examining this claim. It is clear that while Bose-Einstein condensates of axions form, they don't have the structure that was initially expected. Yet again, it matters whether particles are attracted or repulsed by one another.
- Host: Amol Upadhye
- NPAC (Nuclear/Particle/Astro/Cosmo) Forum
- Discovery of a Fast Radio Burst
- Time: 4:30 pm
- Place: 5280 Chamberlin Hall
- Speaker: Peter Timbie, UW - Madison, Department of Physics
- Abstract: Fast Radio Bursts (FRBs) are short (millisecond), non-repeating pulses that have now been observed at radio frequencies by three different radio telescopes. First detected a decade ago, a total of 16 of these events have been seen. I will report on the recent serendipitous discovery of an FRB at the Green Bank Telescope during a search for large-scale cosmic structure. The source is not resolved but our measurements of dispersion, Faraday rotation, and scattering along the line of sight leads us to conclude that the source is probably extragalactic and is located either in a dense, magnetized nebula associated with the source or a location within the central region of its host galaxy.
- Host: Vandenbroucke
- Astronomy Colloquium
- The Past, Present, and Future of the Milky Way
- Time: 3:30 pm
- Place: 4421 Sterling Hall, Coffee at 3:15 PM
- Speaker: Robert Benjamin, UW Whitewater
- Abstract: Ascertaining the three-dimensional structure of our Milky Way Galaxy in all of its components (stars, gas, star formation, magnetic fields, cosmic rays, and dark matter) has been a long and tortuous journey. But there is no other galaxy that we can study in such detail and all models for the structure and evolution of Galaxies must be consistent with the physical propeties that we measure in our host galaxy. The “modern era” of Galactic stucture began at Yerkes, Washburn, and Warner and Swasey Observatories, but rapidly moved to the mapping of the neutral hydrogen component of the Galaxy. I will provide a brief review of this history (come out to dinner with me and you can hear a lot more) and then update you on the current status and implications of what we know about the structure of the Milky Way Galaxy. I will then discuss what we can expect to learn about the Milky Way in the future thanks to upcoming projects like Gaia, APOGEE-2, WFIRST, LSST, and (potentially) SPHEREx and point out areas where future investigations are needed.
- Physics Department Colloquium
- ****NOTE SPECIAL START TIME****
- Quantum trajectories and the quantum state of the past
- Time: 3:00 pm
- Place: 2241 Chamberlin Hall
- Speaker: Klaus Molmer, Aarhus University
- Abstract: The state of a quantum system is described by a wavefunction evolving in time according to the Schroedinger equation. If a measurement is carried out on the system, its wave function collapses, i.e., it changes according to the random outcome of the measurement. During a sequence of measurements on a single system, its quantum state thus follows a stochastic trajectory in which the normal quantum mechanical time evolution is interrupted by collapses at each measurement.
The resulting state of the system, at any time, successfully predicts probabilities and mean values for the measurement of physical observables. In this talk we ask whether the sequence of measurements also adds to our knowledge about the state of the system at earlier times during the experiment.
The answer is yes, and I shall show how such "hindsight" knowledge can be formally defined in quantum mechanics and how we can represent it via a time evolving (past) state, which at any time depends on both earlier and later measurement outcomes. I will show applications of the theory to experiments on atoms and superconducting qubits, and I will discuss how the concept and formalism of past quantum states touch upon both practical and foundational aspects of quantum physics.
- Host: Mark Saffman