Colloquium Archives (before June 2017)

More recent colloquia are posted on the Physics & Astronomy Colloquia page.

Xinlin Li, Laboratory for Atmospheric and Space Physics (LASP) and Department of Aerospace Engi-neering Sciences (AES) of University of Colorado at Boulder (CU)

Title:  "Three Generations of CubeSat in University of Colorado to Address Heliospheric Physics"  (video)

Abstract: The Colorado Student Space Weather Experiment (CSSWE), a 3-unit (10cm x 10cm x 30cm) CubeSat, has been on its low earth orbit for over two years, continuing to send back high quality measurements of energetic particles: differential fluxes of 0.58 to >3.8 MeV electrons and 9-40 MeV protons. Significant science results about radiation belt physics have been produced and over a dozen peer-reviewed papers about the sciences as well as the engineering efforts have been published.

Nitin Samarth, George A. and Margaret M. Downsbrough Department Head, Department of Physics, Penn State University

Title:  "Topological Insulators: From Exotic Quantum States to Spintronics"   (video)

Abstract: The surface electrons of 3D topological insulators are known to possess a helical Dirac spin texture [1] that can be exploited for studying exotic quantum states (such as condensed matter versions of Majorana fermions, axions and supersymmetry) to pragmatic spintronic devices for information technology. I will provide a perspective on this field, with examples of how we create novel phases of matter by interfacing a topological insulator with magnetism [2] and superconductivity [3].  I will also discuss the recent emergence of "topological spintronics," demonstrating how the spin texture of a topological insulator leads to striking phenomena useful for devices, including the generation of a spin-orbit torque of record efficiency at room temperature [4].

Alexander Pines, Glenn T. Seaborg Professor of Chemistry and Faculty Affiliate, California Institute for Quantitative Biosciences, UC Berkeley

Title: Ups and downs of nuclear spins: Hyperactive NMR and MRI  (video)

Abstract: Contemporary NMR and MRI instruments are typically HUGE, immobile, hazardous and $$$.  I shall describe recent advances in our laboratory aimed at translating some of the capabilities of NMR and MRI onto mobile microfluidic chips. Components of the converging methodologies include spin hyperpolarization, sensitive detection by means of SQUIDs and laser atomic magnetometers, the development of functionalized NMR biosensors, and the implementation of NMR and MRI at zero to ultralow magnetic fields.

Stephon Alexander, Dartmouth College

Topic: "Why Might Primordial Gravitational Waves be Necessary?"  (Video)

ABSTRACT: The recent breakthrough detection of primordial gravitational waves by the BICEP2 telescope confirms a longstanding prediction from the cosmic inflationary paradigm. It is interesting the theories beyond the standard model of particle interactions, such as string theory generically predict modifications to Einsteins theory of general relativity that are left-right asymmetric (parity violating). In this colloquium I provide a pedagogical discussion of the possiblity that parity violating primordial gravitational waves can generate the observed matter anti-matter asymmetry and play a second crucial role in actually ending the epoch of cosmic inflation. I discuss the potential for detecting this form of parity violating gravitional waves in future CMB missions.

Scott Kenyon, Harvard-Smithsonian

Topic: "Pluto Strikes Back" (Video)

ABSTRACT: In the last decade, HST observations have revealed 4 small satellites orbiting the binary planet Pluto-Charon. After describing the basic system architecture, I will discuss a plausible path from the giant impact which produced Pluto-Charon to the formation of small satellites orbiting the binary. This path leads to several clear predictions for the system which the New Horizons mission will test during its 2015 flyby. To conclude, I will describe how Pluto-Charon provides a nearby laboratory for investigating the formation of planets around binary stars.

K. Birgitta Whaley, University of California-Berkeley

Topic: "Macroscopic Quantum Superposition States ---- Ideality and Reality"  (Video)

Abstract: What are macroscopic quantum superposition states, do they exist, and if not, why not? These questions have fascinated quantum physicists and chemists since the days of Schrodinger and his cat. The extreme superposition expressed by Schrödinger's cat epitomizes such states and current experiments seek to realize "cat states" made from larger and larger numbers of particles in a variety of physical systems. Studying such states tell us a lot about the nature and power of quantum mechanics, e.g., for large scale quantum information processing. Yet what do we really mean by the "size" or "Schrödinger cattiness" of a quantum superposition in a strongly interacting quantum system composed of large numbers of elementary particles? I shall discuss our current understanding of such quantum mechanical superposition states, their significance for quantum mechanics as well as experimental advances in generating and manipulating them.

Warren Brown, Smithsonian Astrophyiscal Observatory

Topic: "Hypervelocity Stars"  (Video)

Abstract: A massive black hole sits in the heart of the Milky Way. Most stars are found in multiple systems. A consequence of these two facts are "hypervelocity stars" ejected from the Milky Way at million mph velocities. I discovered the first hypervelocity star in 2005, and since then have found more than 20 unbound hypervelocity stars in a targeted survey. Recent results include new evidence for their origin, an unexplained spatial distribution on the sky, and Hubble Space Telescope proper motion measurements that may allow us constrain the shape and orientation of the Galactic potential.