This November 4th at the Niles Gallery @ 4PM join us for a Poetry Recital by Ricardo Pau-Llosa, the most prominent Cuban-American poet today!
Title: The topology of graphs
Abstract: Topologists consider two spaces (think: shapes of any possible dimension) to be weakly equivalent if one can be easily deformed into the other. For example, to a topologist, a sphere is weakly equivalent to a cube. However, it becomes very difficult to determine whether two spaces are weakly equivalent when the dimension of the spaces is greater than three. In this talk, I will introduce one tool that topologists use to distinguish between spaces called homotopy groups. Then I will describe how we can use ideas from topology to study graphs.
Presenter: Dr. Deborah Vicinsky is a Visiting Assistant Professor of Mathematics in Mathematics & Computer Science Department at Wabash College. She received her PhD from the University of Oregon in 2015. Her research interests include model categories, Goodwilie calculus and homotopy of graphs.
The observed large transverse single-spin asymmetries in hadronic collisions pose a challenge to theory since four decades. Phenomena and basic general features of these asymmetries will be discussed. In particular, the current status of QCD calculations will be presented. Recent developments in this area indicate that, in contrast to a long-standing belief, the parton fragmentation could play a crucial role in explaining these intriguing observables.
Entanglement entropy has recently been recognized to be useful in many purposes, but its general behavior is not well understood because it has been analytically calculated only for limited shapes. To examine its general behavior, we numerically calculated entanglement entropies of an annular region, or its equivalent notion ``mutual information across the annular region'', by space discretization and by the holographic formula.
As a result, we found two interesting features. One is the role of the mutual information as a measure of the UV degrees of freedom in the small width limit. The other is an exponentially small correction to the existing mass expansion formula of the entanglement entropies for gapped theories. Based on these observations, we discuss a possibility that the mutual information can be a measure of degrees of freedom of field theories.
This talk will discuss energy resources, options for portable fuels for transportation needs, and requirements and limitations of a practical automobile powered by electricity. Battery development is a significant obstacle--nature does not always give us what we want. A new model for transportation will be proposed that uses the electric cars we already have to solve our transportation issues--without having to wait for a breakthrough in battery chemistry.
Refreshments will be served in CP179 at 3:15pm
Most galaxies harbor weakly- or non-active central super-massive black holes (BHs). Roughly once every 10^4 - 10^5 years in each galaxy, a star enters the BH's tidal disruption radius within which the tidal force of the BH exceeds the star's self gravity, and hence the star gets tidally disrupted. In these so-called tidal disruption events (TDEs), the stellar debris feeds a burst of super-Eddington accretion that generates a bright flare of electromagnetic radiation. In the recent ~ 10 years, several dozen such flares have been discovered by transient surveys in various wavelengths from gamma/X-ray to UV and optical, and ~ 10 of them have optical spectra. In addition, the discoveries of Sw J1644+57 and Sw J2058+05 showed that the TDE accretion disk can launch relativistic jets, and these events are called jetted TDEs.
TDEs offer a new window of studying many astrophysical puzzles, such as super-Eddington MHD accretion physics, population of non-active super-massive BHs in the universe, composition and radiation mechanism of relativistic jets, etc. I'll talk about a few ongoing works with my advisor and collaborators. (1) If a relativistic jet is launched from the accretion disk, the electrons in the jet will inverse-Compton scatter external photons from the disk. We calculated the inverse-Compton luminosity and found it consistent with the X-ray observations from the jetted TDE Sw J2058+05. (2) A typical TDE emits about 10^51 - 10^52 erg of UV/optical energy, which will most likely be absorbed by pc-scale dust at the galactic center. Dust grains will re-radiate this energy in the mid-IR at a luminosity of 10^42 - 10^43 erg/s. Observations and applications of this mid-IR component will be discussed. (3) From the ~ 10 TDE candidates with optical spectra, but we see a large diversity of emission and absorption lines. We study the line formation physics in these spectra and have drawn some general conclusions about the gas properties (e.g. density, temperature and mass).
Recent advances in both experimental and theoretical atomic, molecular, and optical physics provide remarkable new opportunities for precision measurements and tests of fundamental physics, including searches for permanent electric-dipole moments, parity violation studies, searches for variation of fundamental constants, testing gravity and searching for gravitational waves, tests of local Lorentz invariance and the Einstein equivalence principle and many others. I will give a systematic overview of searches for new physics with atoms and molecules, recent key results, and highlight select future proposals.
Lorentz symmetry is one of the cornerstones of modern physics. However, a number of theories aiming at unifying gravity with other fundamental interactions including string field theory suggest violation of Lorentz symmetry. While the energy scale of such strongly Lorentz symmetry-violating physics is much higher than that currently attainable by particle accelerators, Lorentz violation (LV) may nevertheless be detectable via precision measurements at low energies. I will give an overview of such tests with atomic systems, describing the most recent experiment with trapped Ca+ ions in more detail. I will also discuss a systematic study of LV sensitivities in atomic systems that identified ytterbium ion as an idea system with high sensitivity as well as excellent experimental controllability. By applying quantum information inspired technology to Yb+, we expect tests of LLI violating physics in the electron-photon sector to reach levels of 10-23, five orders of magnitude more sensitive than the current best bounds.
Fred will present an introduction to synchrotron radiation and its unique properties, which arise from Maxwell’s Equations. He will discuss technology of light sources, beamlines, and experimental techniques.
He will present an example of an experiment: the search for quantum chaos in doubly excited states of the helium atom. The result reflects on the transition from a quantum description of matter on an atomic scale to a classical description on a planetary scale.
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Dr. Schlachter is a physicist employed as a consultant and policy analyst by the American Physical Society following his retirement from Lawrence Berkeley National Laboratory. He was co-author of a 2008 APS report on energy efficiency; he wrote the chapter on transportation. He has since published several articles on batteries and electric cars, including pieces in Proceedings of the National Academy of Sciences, and APS News.
