title: A strong diffusive ion mode in dense ionized matter predicted by Langevin dynamics.
abstract: The state and evolution of planets, brown dwarfs and neutron star crusts is determined by the properties of dense and compressed matter. Due to the inherent difficulties in modelling strongly coupled plasmas, however, current predictions of transport coefficients differ by orders of magnitude. Collective modes are a prominent feature, whose spectra may serve as an important tool to validate theoretical predictions for dense matter. With recent advances in free electron laser technology, X-rays with small enough bandwidth have become available, allowing the investigation of the low-frequency ion modes in dense matter. Here, we present numerical predictions for these ion modes and demonstrate significant changes to their strength and dispersion if dissipative processes are included by Langevin dynamics. Notably, a strong diffusive mode around zero frequency arises, which is not present, or much weaker, in standard simulations. Our results have profound consequences in the interpretation of transport coefficients in dense plasmas.
authors.affiliation: Department of Physics, University of Oxford, Parks Road, Oxford OX1 3PU, UK.
authors.forename: P
authors.initials: P
authors.lastname: Mabey
authors.affiliation: Department of Physics, University of Oxford, Parks Road, Oxford OX1 3PU, UK.|AWE, Aldermaston, Reading, Berkshire RG7 4PR, UK.
authors.forename: S
authors.initials: S
authors.lastname: Richardson
authors.affiliation: Department of Physics, University of Oxford, Parks Road, Oxford OX1 3PU, UK.
authors.forename: T G
authors.initials: TG
authors.lastname: White
authors.affiliation: SLAC National Accelerator Laboratory, 2575 Sand Hill Road, MS 19, Menlo Park, California 94025, USA.|Physics Department, University of California Berkeley, Berkeley, California 94709, USA.
authors.forename: L B
authors.initials: LB
authors.lastname: Fletcher
authors.affiliation: SLAC National Accelerator Laboratory, 2575 Sand Hill Road, MS 19, Menlo Park, California 94025, USA.
authors.forename: S H
authors.initials: SH
authors.lastname: Glenzer
authors.affiliation: Institute of Radiation Physics, Helmholtz-Zentrum Dresden-Rossendorf, 01328 Dresden, Germany.
authors.forename: N J
authors.initials: NJ
authors.lastname: Hartley
authors.affiliation: Institute of Radiation Physics, Helmholtz-Zentrum Dresden-Rossendorf, 01328 Dresden, Germany.
authors.forename: J
authors.initials: J
authors.lastname: Vorberger
authors.affiliation: Centre for Fusion, Space and Astrophysics, Department of Physics, University of Warwick, Coventry CV4 7AL, UK.
authors.forename: D O
authors.initials: DO
authors.lastname: Gericke
authors.affiliation: Department of Physics, University of Oxford, Parks Road, Oxford OX1 3PU, UK.
authors.forename: G
authors.initials: G
authors.lastname: Gregori