Joshua Burby, “A novel interacting particle system: plasma fragments”
Please join us on Tuesday, April 4, 2023 at 12:00pm in CLARK HALL, Room 110 and on ZOOM for the CIS & MINDS Seminar Series:
Guest: Joshua W. Burby, PhD
Staff Scientist
Los Alamos National Laboratory
Topic: “A novel interacting particle system: plasma fragments”
Virtually over Zoom
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https://wse.zoom.us/j/93822965644?pwd=dDNHYVZGY096QU9Dem45STBsQWQ2dz09
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Joshua W. Burby, PhD
Staff Scientist
Los Alamos National Laboratory
“A novel interacting particle system: plasma fragments”
Abstract: The main statistical model for the dynamics of a rarefied plasma is by now well established. The single-plasma-particle probability density obeys a nonlinear transport equation, attributed to Vlasov and Landau, whose validity hinges on the assumption of weak correlations among plasma particles. On the other hand, dense plasmas, which can be “strongly-coupled,” present serious theoretical and computational challenges that persist to this day. I will describe a modeling approach for strongly-coupled plasmas that interpolates between the well-established Vlasov-Landau formalism and the full Coulomb many-body formalism for a single-species, fully-ionized plasma. The set of N plasma particles is partitioned into M “fragments,” each comprising a K-tuple of particles. Then correlations between fragments are assumed to be weak. In this manner, correlations among particles in a given fragment are treated non-perturbatively, implying a more accurate resolution of correlations as the fragment length K increases. When correlations between fragments are completely ignored, the single-fragment probability density obeys a Hamiltonian transport equation that generalizes the Vlasov-Poisson system. When the first perturbative effects of fragment correlations are accounted for, the mean-field equations are corrected by a collision integral that produces entropy while conserving energy. When K=1 the collision integral reproduces the well-known result due to Landau. But more generally the collision integral cannot be evaluated in closed form due to the non-integrability of the Coulomb K-body problem. I will argue that data-driven methods offer a compelling practical path toward incorporating the effects of fragment collisions into fragment kinetic simulations.
Biography: Joshua W. Burby has been a Staff Scientist at Los Alamos National Laboratory since 2019. After earning his degree in plasma physics from Princeton University in 2015, his postdoctoral research was funded by a series of distinguished fellowships at the Courant Institute of Mathematical Sciences, the Mathematical Sciences Research Institute, and Los Alamos. His research covers mathematical plasma physics, dynamical systems, and structure-preserving machine learning.