Michael S. Murillo

Theory and simulation of strong correlations in quantum Coulomb systems

Strong correlations in quantum Coulomb systems (QCS) are attracting increasing interest in many fields ranging from dense plasmas and semiconductors to metal clusters and ultracold trapped ions. Examples are bound states in dense plasmas (atoms, molecules, clusters) and semiconductors (excitons, trions, biexcitons) or Coulomb crystals. We present first-principle simulation results of these systems including path integral Monte Carlo simulations of the equilibrium behaviour of dense hydrogen and electron– hole plasmas and molecular dynamics and quantum kinetic theory simulations of the nonequilibrium properties of QCS. Finally, we critically assess potential and limitations of the various methods in their application to Coulomb systems.

Static local field correction description of acoustic waves in strongly coupling dusty plasmas

The kinetic equations for an interacting dust system with external time-dependent forces is considered from the Born–Bogolyubov–Green–Kirkwood–Yvon equations. A kinetic equation is obtained by writing the two-particle distribution function as a product of two one-particle distribution functions and the equilibrium radial distribution function. It is shown that a Vlasov-like equation is recovered with a collision term which is a functional of the pair correlation function. Wave behavior from the corresponding fluid equations is considered for a dusty plasma. The results are in qualitative agreement with previously obtained dispersion relations based on generalized hydrodynamics and the quasilocalized charge approximation.

Molecular dynamics simulations of temperature equilibration in dense hydrogen.

The temperature equilibration rate between electrons and protons in dense hydrogen has been calculated with molecular dynamics simulations for temperatures between 10 and 600eV and densities between 10;{20}cm;{-3}to10;{24}cm;{-3} . Careful attention has been devoted to convergence of the simulations, including the role of semiclassical potentials. We find that for Coulomb logarithms L greater, similar1 , a model by Gericke-Murillo-Schlanges (GMS) [D. O. Gericke, Phys. Rev. E 65, 036418 (2002)] based on a T -matrix method and the approach by Brown-Preston-Singleton [L. S. Brown, Phys. Rep. 410, 237 (2005)] agrees with the simulation data to within the error bars of the simulation. For smaller Coulomb logarithms, the GMS model is consistent with the simulation results. Landau-Spitzer models are consistent with the simulation data for L>4 .

Two-dimensional wake potentials in sub- and supersonic dusty plasmas

Hot electrons and sub- and supersonic flows of cold ions around a charged dust particle create steady state wake and Debye screening fields. These linear, electrostatic fields are studied in two-dimensional planar or cylindrical geometry. An asymptotic analysis in the limit of large (compared to Debye length) downstream coordinate z yields analytic wakefields that are in good agreement with numerical integrations of the linear, steady state response function.

Instability growth in magnetically imploded high-conductivity cylindrical liners with material strength

Magnetically imploded cylindrical metal shells (z-pinch liners) are attractive drivers for experiments exploring hydrodynamics and properties of materials at extreme conditions. As in all z-pinches, the outer surface of a liner is unstable to magneto Rayleigh-Taylor (RT) modes during acceleration, and large-scale distortion arising from RT modes could make such liners unuseable. On the other hand, material strength in the liner should, from first principles, reduce the growth rate of RT modes, and material strength can render some combinations of wavelength and amplitude analytically stable. A series of experiments has been conducted in which high-conductivity, soft, cylindrical aluminum liners were accelerated with 6-MA, 7-/spl mu/s rise-time driving currents. Small perturbations were machined into the outer surface of the liner and perturbation growth monitored. Two-dimensional magneto-hydrodynamic (2-D-MHD) calculations of the growth of the initial perturbations were in good agreement with experimentally observed perturbation growth through the entire course of the implosions. In general, for high-conductivity and soft materials, theory and simulation adequately predicted the behavior of magneto-RT modes in liners where elastic-plastic behavior applies. This is the first direct verification of the growth of magneto-RT in solids with strength known to the authors.

Longitudinal collective modes of strongly coupled dusty plasmas at finite frequencies and wavevectors

Dusty plasmas offer a unique method for testing dynamical wave theories in the strong Coulomb coupling regime. Recently, there have been many theoretical models, based on either a generalized hydrodynamic or on kinetic descriptions, developed to describe dust acoustic waves under conditions of strong coupling. These theories attempt to extend the usual acoustic wave dispersion relation to the strong coupling regime and, in some cases, to finite frequencies and wave vectors beyond the hydrodynamic limit. Here a multicomponent kinetic theory is used to obtain the dust acoustic wave dispersion relation in terms of an approximate dynamic local field correction, and comparison is made with the viscoelastic Navier–Stokes description.

Towards multiscale modeling of influenza infection

Aided by recent advances in computational power, algorithms, and higher fidelity data, increasingly detailed theoretical models of infection with influenza A virus are being developed. We review single scale models as they describe influenza infection from intracellular to global scales, and, in particular, we consider those models that capture details specific to influenza and can be used to link different scales. We discuss the few multiscale models of influenza infection that have been developed in this emerging field. In addition to discussing modeling approaches, we also survey biological data on influenza infection and transmission that is relevant for constructing influenza infection models. We envision that, in the future, multiscale models that capitalize on technical advances in experimental biology and high performance computing could be used to describe the large spatial scale epidemiology of influenza infection, evolution of the virus, and transmission between hosts more accurately.

Ion kinetic effects on the wake potential behind a dust grain in a flowing plasma

The structure of the wake potential downstream of a stationary dust grain in a flowing plasma is studied on ion time scales using particle-in-cell simulation methods. The scaling of the wake is investigated as a function of Mach number and other parameters as well as the dimensionality of the system. The results are compared and discussed in relation to various theoretical expressions for the wake. Consistent with theory, in one dimension the wake wavelength scales as MλDe(1−M2)−1/2 for M 1. In two dimensions, a wake is formed for both M 1, while the wake wavelength scales as MλDe in both regimes. The amplitude of the wake peaks at M≈1 in both the one- and two-dimensional simulations.

Strongly coupled plasma physics and high energy-density matter

High energy–density matter—matter with pressures in excess of a megabar—covers a wide range of parameter space. Many laboratory experiments span a large portion of this parameter space as they evolve from a liquid or solid phase through the strongly coupled plasma phase to a hot plasma phase. This tutorial will introduce the basic physics of the intermediate, strongly coupled plasma phase from a very general point of view, including a discussion of experiments, such as laser-cooled ions, dusty plasmas, and white dwarfs. Basic definitions and results will be given for simple strongly coupled plasmas in the context of concepts familiar from weakly coupled plasma physics, to the extent possible. Definitions relevant to high energy–density physics are then introduced before focusing on dense plasmas, which form the overlap between the strongly coupled and high energy–density regions.

Fast electric microfield distribution calculations in extreme matter conditions

Abstract Spectral line shapes provide a powerful tool for characterizing strongly coupled plasmas that have become experimentally more accessible in recent years. Line shape calculations in turn require as input the electric microfield distribution at the emitting atom or ion. The APEX approximation for microfield distributions is computationally fast and suited for weakly as well as strongly coupled plasmas. The currently available APEX program, however, contains computationally difficulties that restrict its range of applicability. Consequently, the code has been improved removing many of its shortcomings. An important new feature is the incorporation of the HNC integral equation solution to the radial distribution functions necessary for the APEX approximation.