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Fall 2017 Colloquium Series


Date:  Thursday, November 30th, 2017
Speaker: Ben Farr, UO Physics

Title: GW170817: Astronomy’s First Talkie

Abstract: On August 25, 2017, after collecting 117 days of simultaneous two-detector observing time, the LIGO observatories ended their second observing run (O2).  Having started on November 30, 2016, O2 had progressed relatively uneventfully for 260 calendar days. That is, until August 17, 2017, when LIGO detected its first binary neutron star merger, GW170817. Beyond being LIGO’s first binary neutron star detection, and its longest and loudest detection so far, it was also detected by telescopes across the entire electromagnetic spectrum, emphatically kicking off the era of multi-messenger astronomy using gravitational waves.  With more than 70 ground- and space-based observatories joining in the discovery, GW170817 quickly became one of the most observed transients in the history of astronomy.  I will discuss some of what GW170817 and its EM counterpart, particularly its kilonova signature, has taught us (so far) about neutron star collisions, the expansion of the universe, and fundamental physics.

Host:  Ray Frey


Date:  Thursday, November 16th, 2017
Speaker: David Curtin, University of Toronto

Title: Flashes of Hidden Worlds at Colliders

Abstract:  After briefly reviewing the Standard Model of particle physics, I explain why the fundamental reasons to expect New Physics are more urgent than ever. Null results of searches at the Large Hadron Collider (LHC) and other experiments are therefore especially puzzling. I argue that this points us towards new theories for addressing these fundamental mysteries, and new experimental approaches for discovering them. I will discuss how theories of Hidden Sectors can address the Hierarchy Problem, the universe’s matter-antimatter asymmetry, and Dark Matter. I outline why these scenarios could have gone undiscovered so far, but also why their hidden nature is also the key to their discovery, since they give rise to the production of exotic Long-Lived Particles (LLPs) at the LHC. Exploring this Lifetime Frontier requires a new systematic search program, as well as new detectors. Our proposed MATHUSLA experiment will boost the sensitivity of the HL-LHC by orders of magnitude.

Host:  Tim Cohen


Date:  Thursday, November 9th, 2017
Speaker:  Ajay Gopinathan, UC Merced

Title: Unstructured Proteins: Extracting Function from Disorder

Abstract: Intrinsically unstructured or disordered proteins (IDPs), which form over a third of human proteins, challenge the structure-function paradigm in biology that relates the function of proteins to their unique 3-d structure, because they function without ever folding into a unique structure. This presents an interesting opportunity to use the tools of polymer physics to gain insight into IDP dynamics and function. I shall present an overview of IDPs and a couple of examples of our recent efforts to understand how IDPs can exploit conformational entropy for functional purposes. One particularly fascinating context for IDP function is the nuclear pore complex (NPC) which gates nanoscale pores in the nuclear envelope of cells. The NPC controls all traffic into and out of the nucleus using a barrier composed of a large number of IDPs that fill the pore. Despite numerous studies, the actual structure of the barrier and its mechanism of operation are poorly understood primarily because of the disordered nature of these proteins. Here, I will present our “bottom-up” approach using sequence analysis, coarse-grained simulations and polymer brush theory which points to a novel form of gated transport in operation within the nuclear pore complex based on polymer brush physics. Another striking example of the use of conformational entropy is in the translocation across the cell wall of certain bacterial IDPs. I will present evidence that this translocation depends only on cell geometry and protein length indicating that bacteria can exploit purely physical entropic mechanisms to perform this function.

Host: Raghu Parthasarathy


Date:  Thursday, November 2nd, 2017
Speaker:  Christopher Monroe, University of Maryland and IonQ

Title: Building a Quantum Computer, Atom by Atom

Abstract: Laser-cooled and trapped atomic ions are standards for quantum information science, acting as qubits with unsurpassed levels of quantum coherence while also allowing near-perfect measurement. When qubit state-dependent optical forces are applied to a collection of ions, their Coulomb interaction is modulated in a way that allows entanglement operations that form the basis of a quantum computer. Similar forces allow the simulation of quantum magnetic interactions, and recent experiments have implemented tunable long-range interacting spin models with up to 50 trapped ions. Scaling to even larger numbers can be accomplished by coupling trapped ion qubits to optical photons, where entanglement can be formed over remote distances for applications in quantum communication, quantum teleportation, and distributed quantum computation. By employing such a modular and reconfigurable architecture, it should be possible to scale up ion trap quantum networks to useful dimensions, for future quantum applications that are impossible using classical processors.

Host: Michael Raymer


Date:  Thursday, October 26th, 2017
Speaker:  Nicolas Cowan, McGill University

Title: The Climate and Habitability of Short-Period Planets

Abstract: Planet hunters have discovered thousands of exoplanets (planets orbiting other stars). We now know that most temperate terrestrial planets orbit close to dim red stars and experience dramatically different stellar forcing than the Earth, notably permanent day and night hemispheres. Since we have no analogs to these worlds in our Solar System, we must observe them to understand their atmospheric composition, clouds, and wind patterns. To date, we have been able to study the climates of a few dozen exoplanets, all of which are far too hot to be habitable. I will present recent highlights from my team, including a remarkably black planet, a planet where the winds blow the wrong way, and a planet with impossibly cold nights. In short, these planets are stranger than anyone imagined. Cutting-edge analysis techniques and next-generation instruments should allow us to extend our methods to temperate terrestrial planets orbiting nearby red dwarfs. In the coming decade, we will be able to determine which of these planets are, in fact, habitable and we will start to search them for signs of life.

Host: Ben Farr


Date:  Thursday, October 19th, 2017
Speaker: Charles Clark, NIST

Title: Neutron Particles and Neutron Waves

Abstract: I present a simple overview of the particle and wave properties of the neutron, with emphasis on their similarities to and differences from light. Neutron interferometry enables one to realize the quantum limit of the Young double slit experiment, when only one neutron is ever present in the interferometer. How can only one neutron go through both slits?  We have used neutron interferometry and holography to address some of the questions of structured waves of light and matter that have been studied with electrons, atoms and photons.

Host: Benjamin McMorran


Date:  Tuesday, October 10th, 2017
Speaker: Jayanth R. Banavar, UO provost and senior vice president

Title: Geometry of Life

Banavar, whose research frequently involves interdisciplinary collaboration with the life sciences, is currently focused on applying the techniques of statistical physics to solve interdisciplinary problems, explaining, for example, why biological molecules tend to curl up into helices or to understand the rich biodiversity of tropical forests and coral reefs. Banavar earned his doctorate in physics from the University of Pittsburgh.

Host: Ray Frey


Date: Thursday, October 5th, 2017
Speaker:  Hari Shroff, National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health

Title: High Speed Imaging at and Beyond the Diffraction Limit

Abstract: I will discuss our efforts to improve structured illumination microscopy (SIM) and light-sheet microscopy. SIM doubles the spatial resolution of light microscopy, requiring lower light intensities and acquisition times than other super-resolution techniques. I will present SIM implementations that enable resolution doubling in live samples > 10-20x thicker than possible with conventional SIM, as well as hardware modifications that enable effectively ‘instant’ SIM imaging at rates 10-100x faster than other SIM. New applications of instant SIM, including combination with total internal reflection (TIRF) and with adaptive optics will also be discussed. The second half of the talk will focus on the development of inverted selective plane illumination microscopy (iSPIM), and subsequent application to the noninvasive study of neurodevelopment in nematodes. I will discuss progress that quadruples the axial resolution of iSPIM by using a second specimen view, enabling imaging with isotropic spatial resolution (dual-view iSPIM, or diSPIM). Newer multiview microscopes with more objectives and more views, further improving spatial resolution, will also be described. Applications of these technologies will be presented, including computational methods for untwisting worm embryos and calcium imaging in freely moving embryos.

Host: Tristan Ursell


Date: Thursday, September 28th, 2017
Speaker: Ray Frey, University of Oregon

Title: State of the Department, and Gravitational-­Wave Astronomy

Host: Ray Frey