Radiation Hydrodynamics Scaling Laws in High Energy Density Physics and Laboratory Astrophysics

accepted paperInternational audienceIn this paper, radiating fluids scaling laws are studied. We focus on optically thin and optically thick regimes which are relevant for both astrophysics and laboratory experiments. By using homothetic Lie groups, we obtain the scaling laws, the similarity properties and the number of free parameters which allow to rescale experiments in the two astrophyscial situations

Discontinuous Galerkin Time-Domain solution of Maxwell's equations on locally-refined grids with fictitious domains

The use of the prominent FDTD method for the time-domain scattering of electromagnetic waves by devices with small geometrical details can require very fine grids and lead to unmanageable computational time and storage. We propose an extension of a Discontinuous Galerkin Time-Domain (DGTD) method to locally-refined, possibly non-conforming meshes, coupled to a fictitious domain approach. The DGTD method we use is set on block-structured grids of orthogonal elements and is based on centered flux approximations for surface integrals and a second-order leap-frog scheme for advancing in time. The stability of the method has been analyzed previously, it is proved that a discrete electromagnetic energy is exactly preserved. The dispersion analysis is completed in this paper. Also, new features of the method are introduced herein: the use of PML regions in a DG context has been detailed, and a first step towards the coupling with a fictitious domain approach has been done, leading to very promising preliminary numerical results

Analytical solutions of specific classes of astrophysical radiating shocks

In this paper we study specific classes of radiating shocks which are widely spread in astrophysical environments. We present more general solutions of their structure and proceed to the analytical determination of physical quantities

Discontinuous Galerkin Time-Domain solution of Maxwell's equations on locally-refined grids with fictitious domains

The use of the prominent FDTD method for the time-domain scattering of electromagnetic waves by devices with small geometrical details can require very fine grids and lead to unmanageable computational time and storage. We propose an extension of a Discontinuous Galerkin Time-Domain (DGTD) method to locally-refined, possibly non-conforming meshes, coupled to a fictitious domain approach. The DGTD method we use is set on block-structured grids of orthogonal elements and is based on centered flux approximations for surface integrals and a second-order leap-frog scheme for advancing in time. The stability of the method has been analyzed previously, it is proved that a discrete electromagnetic energy is exactly preserved. The dispersion analysis is completed in this paper. Also, new features of the method are introduced herein: the use of PML regions in a DG context has been detailed, and a first step towards the coupling with a fictitious domain approach has been done, leading to very promising preliminary numerical results

Light Stops in the MSSM: Implications for Photino Dark Matter and Top Quark Decay

We consider the viability of the minimal supersymmetric standard model with a light ($m_{\tilde t_1} <$ 45 GeV) stop. In order for its relic abundance to be cosmologically significant, the photino as dark matter must be quite close in mass to the stop, $(m_{\tilde t_1} - m_{\tilde \gamma}) \simeq 3 - 7$ GeV. However, as we show, the photino despite its low mass is virtually undetectable by either direct or indirect means. We also discuss the implications of these masses on the top quark branching ratios.Comment: 11pages, LaTex, UMN-TH-1309/9

Les hypolipémiants (enquête de terrain sur la tolérance, l'observance et le rôle du pharmacien dans la délivrance des hypolipémiants)

POITIERS-BU Médecine pharmacie (861942103) / SudocSudocFranceF

Astrophysique de laboratoire (modélisation analytique et numérique du choc radiatif)

PARIS-BIUSJ-Thèses (751052125) / SudocPARIS-BIUSJ-Physique recherche (751052113) / SudocSudocFranceF

Similitudes et autosimilarité en physique des hautes densités d énergie (application à l astrophysique de laboratoire)

Cette thèse traite du nouveau domaine très prometteur qu est l astrophysique de laboratoire et a pour but de renforcer le lien entre expériences à l aide de lasers de puissance et situations astrophysiques. Tout d abord je justifie l approche de l astrophysique de laboratoire en élaborant de nouvelles lois d échelle en hydrodynamique radiative à partir de la théorie des groupes de Lie. Pour la première fois, il est montré rigoureusement que les plasmas en présence de rayonnement en astrophysique peuvent être reproduits de manière homologue en laboratoire par des plasmas laser. Cette étude m a conduit à proposer un nouveau projet expérimental (le projet POLAR) qui vise à mieux comprendre la physique de la colonne d accrétion des variables cataclysmiques magnétiques. Ce projet est l un des premiers visant à la création d une véritable maquette d un objet astrophysique. Dans un second temps, j ai construit un ensemble de nouvelles solutions auto-semblables décrivant la dynamique des gaz polytropiques et le collapse radiatif à partir de la transformation de Burgan-Feix-Munier. Je montre explicitement que cette dernière apparaît comme une méthode unificatrice permettant de générer un ensemble complet de solutions auto-semblables. Ces solutions m ont permis d appréhender la physique de base des phénomènes mis en jeu ainsi que de valider le code de simulation numérique que j ai développé au cours de cette thèse. Elles se révèlent également adaptées à la modélisation des expériences de jets de laboratoire réalisées auprès de l installation LULI2000 dont l objectif est la reproduction des phénomènes d éjection de plasmas que l on rencontre autour des étoiles jeunes.PARIS-Observatoire (751142302) / SudocSudocFranceF

Etude de la diffusion céphaloradienne des carbapénèmes chez le rat, en présence d'agents modifiant la perméabilité de la barrière hémato-encéphalique

POITIERS-BU Médecine pharmacie (861942103) / SudocSudocFranceF