2008/03/31 by Claudia Quercellini, Marco Bruni, A. Balbi +3 · 2 citations
Physics and Astronomy · #Black Holes and Theoretical Physics #Cosmology and Gravitation Theories #Galaxies: Formation, Evolution, Phenomena #astro-ph #gr-qc
paper · pdf · doi:10.1103/physrevd.78.063527
published as Phys.Rev.D78:063527,2008 · 12 pages, 5 figures, considerable changes to the text
arxiv created 2008/07/21 · openalex publication_date 2008/09/15 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
We explore the dynamics of cosmological models with two coupled dark components with energy densities \ensuremathρA and \ensuremathρB and constant equation of state (EOS) parameters wA and wB. We assume that the coupling is of the form Q=Hq(\ensuremathρA,\ensuremathρB), so that the dynamics of the two components turns out to be scale independent, i.e. does not depend explicitly on the Hubble scalar H. With this assumption, we focus on the general linear coupling q=qo+qA\ensuremathρA+qB\ensuremathρB, which may be seen as arising from any q(\ensuremathρA,\ensuremathρB) at late time and leads in general to an effective cosmological constant. In the second part of the paper we consider observational constraints on the form of the coupling from SN Ia data, assuming that one of the components is cold dark matter (CDM), i.e. wB=0, while for the other the EOS parameter can either have a standard (wA>\ensuremath-1) or phantom (wA<\ensuremath-1) value. We find that the constant part of the coupling function is unconstrained by SN Ia data and, among typical linear coupling functions, the one proportional to the dark energy density \ensuremathρA is preferred in the strong coupling regime, |qA|>1. Models with phantom wA favor a positive coupling function, increasing \ensuremathρA. In models with standard wA, not only a negative coupling function is allowed, transferring energy to CDM, but the uncoupled subcase falls at the border of the likelihood.