Open AccessScalar perturbations in two‐temperature cosmological plasmas
Author(s) -
Moortgat J.,
Marklund M.
Publication year - 2006
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1111/j.1365-2966.2006.10419.x
Subject(s) - physics , isotropy , plasma , long wavelength limit , wavelength , perturbation (astronomy) , general relativity , classical mechanics , covariant transformation , gravitation , quantum electrodynamics , mathematical physics , quantum mechanics
We study the properties of density perturbations of a two‐component plasma with a temperature difference on a homogeneous and isotropic background. For this purpose, we extend the general relativistic gauge‐invariant and covariant (GIC) perturbation theory to include a multifluid with a particular equation of state (ideal gas) and imperfect fluid terms due to the relative energy flux between the two species. We derive closed sets of GIC vector and subsequently scalar evolution equations. We then investigate solutions in different regimes of interest. In particular, we study long‐wavelength and arbitrary‐wavelength Langmuir and ion‐acoustic perturbations. The harmonic oscillations are superposed on a Jeans‐type instability. We find a generalized Jeans criterion for collapse in a two‐temperature plasma, which states that the species with the largest sound velocity determines the Jeans wavelength. Furthermore, we find that within the limit for gravitational collapse, initial perturbations in either the total density or charge density lead to a growth in the initial temperature difference. These results are relevant for the basic understanding of the evolution of inhomogeneities in cosmological models.