Seminars in Fall 2016
All seminars are held at 4:10 PM in Physics 123, unless otherwise noted.
Refreshments will be served at 4:00 PM.
October 27, 2016
Kassa Betre, Stanford University
Geometry from Quantum Graphity
Johnny Powell (on sabbatical research)
There are several learning curves which are required to master N-body simulations with ChaNGa ( acronym explained in the talk ): installing Red Hat Linux, developing a robust facility with the command line including mastery of reading Man pages and a comprehensive understanding of the Linux file structure, Git ( a version control system ), Tipsy ( visualization software for ChaNGa ), and Python ( software for developing initial conditions ( IC ) for a given simulation). The nature of these learning curves will be presented in a preliminary fashion.
Brief examples of how simulations have helped our contemporary understanding galaxies will be presented. In addition, the peculiar nature of the scientific process with respect to simulations will be addressed.
The astrophysical problem addressed - but untouched by this sabbatical - is the nature of secularly-evolved galactic bars (google, NGC 1300 for an monumental HST image). A brief discussion of the conceptual development of galaxies in a cosmological context will be provided.
Results for a dark matter (DM) only simulation will be presented and compared with the canonical experimental observations: M.J.Geller and J.P. Huchra, Science, 246, 897, (1989).
The NSF supercomputing facility, XSEDE, will be briefly discussed as well as the steps to obtain a startup allocation on a supercomputer such a Comet. Very preliminary results of a hydrodynamical simulation on Comet will be presented.A live demonstration of the use of Comet will be provided. Finally, a few minutes will be devoted to the N-body Shop team and the Physics and Astronomy facility at the University of Washington
Ali Cox, Ian Fries, Farhan Hasan, Sarah Racz, Amanda Swanson
Ella Banyas, Benjamin Morrison, Edgar Perez, Tenzin Sangpo, Noah Shofer
Sabrina Appel, Kaustuv Datta, Yuka Esashi, Vincent Griffith
David Hall, Amherst College
Knots are familiar entities that appear at a captivating nexus of art, technology, mathematics, and science. They have recently attracted significant experimental interest in contexts ranging from knotted DNA and nanostructures to nontrivial vortex knots in classical fluids. In this talk I will discuss the first controlled experimental creation and detection of knot solitons, which are particle-like topological excitations possessing a knotted field character. The superfluid medium within which they exist is a Bose-Einstein condensate with a temperature some tens of billionths of a degree above absolute zero. In addition to enabling future experimental studies of their propertiesand dynamics, these knot solitons provide a striking demonstration of the celebrated Hopf fibration, which mathematically ties together many seemingly unrelated physical phenomena.
Kassa Betre, Stanford University
Quantum Graphity models have been proposed as one approach towards Quantum Gravity in which a fully quantum mechanical, background independent system in the high energy gives rise to a low energy state that looks like ordinary spacetime. The high energy states of the Quantum Graphity system are random graphs with microscopic degrees of freedom that live on the edges and vertices. In the low emergy limit, a discretized regular lattice emerges. While this program is promising, much work remains to be done to show that such a low dimensional structure and dynamics results through statistical mechanics. In this talk, I will describe how a uniform dimension emerges in the low energy starting with an assumption of a high energy Hamiltonian that is quadratic in the vertex degrees of the nodes of the graph.
Mike Solontoi, Pacific University
Dave Moore, Oculus (Facebook)
Andy Rhines, University of Washington
Lindsay Sonderhouse, University of Colorado