Acoustic oscillations and viscosity

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dc.creatorMaartens, Roy
dc.creatorTriginer, Josep
dc.date1998-02-06
dc.date1998-07-08
dc.date.accessioned2026-07-07T10:51:21Z
dc.date.available2026-07-07T10:51:21Z
dc.descriptionUsing a simple thermo-hydrodynamic model that respects relativistic causality, we revisit the analysis of qualitative features of acoustic oscillations in the photon-baryon fluid. The growing photon mean free path introduces transient effects that can be modelled by the causal generalization of relativistic Navier-Stokes-Fourier theory. Causal thermodynamics provides a more satisfactory hydrodynamic approximation to kinetic theory than the quasi-stationary (and non-causal) approximations arising from standard thermodynamics or from expanding the photon distribution to first order in the Thomson scattering time. The causal approach introduces small corrections to the dispersion relation obtained in quasi-stationary treatments. A dissipative contribution to the speed of sound slightly increases the frequency of the oscillations. The diffusion damping scale is slightly increased by the causal corrections. Thus quasi-stationary approximations tend to over-estimate the spacing and under-estimate the damping of acoustic peaks. In our simple model, the fractional corrections at decoupling are $\gtrsim 10^{-3}$.
dc.descriptionImproved version with new quantitative estimates and some corrections. We show how quasi-stationary approximations based on expanding the photon distribution to first order in the Thomson time tend to under-estimate the frequency and damping of acoustic oscillations
dc.identifierhttps://arxiv.org/abs/astro-ph/9802074
dc.identifierhttp://arxiv.org/abs/astro-ph/9802074
dc.identifierPhys.Rev.D58:123507,1998
dc.identifierdoi:10.1103/PhysRevD.58.123507
dc.identifier.urihttp://salesiana.dossiersoluciones.com/handle/123456789/184794
dc.subjectAstrophysics
dc.titleAcoustic oscillations and viscosity
dc.typetext

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