Events Archive

Sep
28
2011
"New Exciting Approaches to Particle Scattering Amplitudes"
Particle scattering processes at experiments such as the Large Hadron Collider at CERN are described by scattering amplitudes. In quantum field theory classes, students learn to calculate amplitudes using Feynman diagram methods. This is a wonderful method for a process like electron + positron -> muon^- + muon^+, but it is a highly challenging for a process like gluon+gluon -> 5 gluons, which requires 149 diagrams even at the leading order in perturbation theory. It turns out, however, that the result for such gluon scattering processes is remarkably simple, in some cases it is just a single term! This has lead to new methods for...
Sep
27
2011
"Complex fluids at complex surfaces: simply complicated?" by Prof. Jose Manuel Romero
We study wetting and filling of patterned surfaces by a nematic liquid crystal. We focus on three important classes of periodic surfaces: saw-toothed, sinusoidal and stepwise, which have been considered in the literature as promising candidates to develop less-consuming zenithal bistable switches for practical applications. For saw-toothed substrates, geometry induces the nucleation of disclination lines on the wedges and apexes of the substrate, so  the nematic surface free energy density develops an elastic contribution which scales as qlnq (with q being the wavenumber associated with the substrate periodicity). This leads to a large departure from...
Sep
21
2011
"Spinor Bose-Einstein condensates and Quantum Antiferromagnetism"
Bose-Einstein condensates (BECs) have revolutionized atomic physics, a revolution which, sixteen years after their discovery, shows little sign of stopping.  The attention of the quantum gases community has increasingly shifted from studies of broad features of the many-body condensed state to more specific realizations based upon control of spin state, trapping geometry, dimensionality and temporal behavior.  In many regards quantum gases have no direct counterpart in condensed matter, although many parallels do exist, and these serve to guide efforts at the interface between disciplines....
Sep
12
2011
From Colliding Black Holes To Data Mining in the Cloud, a perspective from Industry
As a student of numerical relativity who planned to work the rest of his life in academia, I had never envisioned the possibility of finding myself working in the commercial sector. The perception exists that opportunities to do novel research or to direct one's own career path are limited in industry, but I have found that this is largely not true. Rather, different constraints on your time and resources are imposed, with different challenges and rewards. In this talk, I will describe how I came to find myself leading the development of a cloud-scale information extraction and retrieval application for a customer within the Intelligence Community, share my experiences working with...
Sep
07
2011
"Measuring Everything You've Always Wanted to Know About a Laser Pulse"
Measuring an event in time seems to require a shorter one. As a result, the development of a technique for measuring ultrashort laser pulses—the shortest events ever created—has been particularly difficult. We have, however, developed simple methods for fully characterizing these events, that is, for measuring a pulse's intensity and phase vs. time. One involves making an optical spectrogram of the pulse by using nonlinear optic. The mathematics involved is equivalent to the two-dimensional phase-retrieval problem—a problem that’s solvable because the Fundamental Theorem of Algebra fails for polynomials of two variables.  We call...
Sep
01
2011
"Radio pulse measurements of high energy neutrinos: ANITA and ARA experiments"
We'll look at two novel experiments that are looking for ultrahigh energy neutrinos in the Antarctic ice. ANITA is a balloon-borne experiment which has twice flown over Antarctica making observations of ultrahigh energy cosmic rays and neutrinos. ARA is a new englacial project, under construction at the South Pole with similar goals. Both utilize the Askaryan Effect, coherent radio Cherenkov emission from particle cascades in matter, for neutrino detection.
Aug
31
2011
Annual School of Physics Gathering
Aug
29
2011
"Simulating condensed matter systems with interacting photons"
Photons do not interact strongly in nature, and have thus been relegated to a role as a tool rather than an object of study in condensed matter physics.However, in cavity quantum electrodynamics, the strong interaction of light with a single atom can lead to strong atom-mediated photon-photoninteractions, even when the light and atomic transitions are not resonant. Recent theoretical proposals have predicted phase transitions in arrays ofthese cavities, demonstrating that complex matter-like phenomena can emerge from a sea of interacting photons. I will present our recent measurements demonstrating strong photon-photon interactions in superconducting cavity QED...
Aug
24
2011
"Vulcanized matter: Its statistics, its physics, and its statistical physics"
As Goodyear discovered, when he first vulcanized rubber in 1839, a viscous liquid of macromolecules becomes an unusual, utterly random, solid, provided that enough chemical bonds are introduced between the molecules.  Perhaps surprisingly, given the randomness of their architectures, solids formed by the vulcanization process exhibit a number of rather simple and universal features -- both structural and elastic -- that are not exhibited by the apparently simpler, crystalline solids.  In this colloquium, I shall give an overview of current approaches to the physical properties of vulcanized matter and other random-network-forming media, paying special attention to...
Jun
23
2011
"The NINJA project"
Two important advances have occurred in recent years which have brought us closer to the goal of observing and interpreting gravitational waves from coalescing compact objects: the successful construction and operation of a world-wide network of ground-based gravitational-wave detectors and the impressive success of numerical relativity in successfully simulating the merger phase of Binary Black Hole (BBH) coalescence. The aim of the Numerical INjection Analysis (NINJA) project is to study the sensitivity of gravitational-wave analysis pipelines to numerical simulations of waveforms and foster close collaboration between numerical relativists and data analysts.  NINJA-1 was a huge...

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