Events at Physics |
Events on Monday, April 16th, 2012
- Plasma Physics (Physics/ECE/NE 922) Seminar
- Kinetic Turbulence in Space and Astrophysical Plasmas: Theoretical, Numerical, and Experimental Investigations
- Time: 12:05 pm
- Place: 2535 Engineering Hall
- Speaker: Prof. Greg Howes, University of Iowa
- Abstract: In many turbulent space and astrophysical plasma environments, the
dissipation of the turbulence, and consequent conversion of turbulent
fluctuation energy to plasma heat, occurs at scales on which the plasma
dynamics is collisionless. Direct access to the near Earth solar wind provides a
unique opportunity to confront our understanding of the dynamics of kinetic
plasma turbulence, and its dissipation via collisionless damping mechanisms,
with in situ spacecraft measurements. Significant effort has recently been
focused on employing the gyrokinetic formalism to study the dissipation of
turbulence in the solar wind, taking advantage of sophisticated numerical
techniques developed for use in the fusion community. Here I will report on
some of the most recent successes of this effort, in particular the first threedimensional,
nonlinear gyrokinetic simulation of plasma turbulence resolving
scales from the ion to electron gyroradius with a realistic mass ratio, where all
damping is provided by resolved physical mechanisms. Complementing this
theoretical and numerical research program are experiments on the Large
Plasma Device (LAPD) at UCLA to measure the nonlinear interactions between
counterpropagating Alfven waves, the fundamental building block of Alfvenic
plasma turbulence. - Condensed Matter Theory Group Seminar
- Multiparticle Quantum Walks and the Graph Isomorphism Problem
- Time: 4:30 pm
- Place: 5310 Chamberlin
- Speaker: Kenny Rudinger, UW-Madison
- Abstract: We investigate the quantum dynamics of particles on graphs ("quantum walk"), with the aim of developing quantum algorithms for determining whether or not two graphs are isomorphic. We investigate such walks on strongly regular graphs (SRGs), a class of graphs with high symmetry. We explore the effects of particle number and interaction range on a walk's ability to distinguish non-isomorphic graphs. We numerically find that both non-interacting three-boson and three-fermion continuous time walks have the same distinguishing power on a dataset of 70,712 pairs of SRGs, each distinguishing over 99.6% of the pairs. We also find that increasing to four non-interacting particles further increases distinguishing power on this dataset. While increasing particle number increases distinguishing power, we prove that any walk of a fixed number of non-interacting particles cannot distinguish all SRGs.