Observational constraints on Rastall’s cosmology
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Rastall’s theory is a modification of General Relativity, based on the non-conservation of the stress-energy tensor. The latter is encoded in a parameter γ such that γ=1 restores the usual ∇ ν T μν =0 law. We test Rastall’s theory in cosmology, on a flat Robertson–Walker metric, investigating a two-fluid model and using the type Ia supernovae Constitution dataset. One of the fluids is pressure-less and obeys the usual conservation law, whereas the other is described by an equation of state p x =w x ρ x , with w x constant. The Bayesian analysis of the Constitution set does not strictly constrain the parameter γ and prefers values of w x close to −1. We then address the evolution of small perturbations and show that they are dramatically unstable if w x ≠−1 and γ≠1, i.e. General Relativity is the favored configuration. The only alternative is w x =−1, for which the dynamics becomes independent from γ.
KeywordsDark Matter Dark Energy Dark Sector Matter Component Luminosity Distance
We thank CNPq (Brazil) and FAPES (Brazil) for partial financial support. This research has made use of the CfA Supernova Archive, which is funded in part by the National Science Foundation through grant AST 0907903.
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