Testing dark matter warmness and quantity via the reduced relativistic gas model

Abstract

We use the framework of a recently proposed model of reduced relativistic gas to obtain the bounds for $\ensuremath{\Omega}$'s of dark matter and dark energy (in the present case, a cosmological constant), taking into consideration an arbitrary warmness of dark matter. An equivalent equation of state has been used by Sakharov to predict the oscillations in the matter power spectrum. Two kinds of tests are accounted for in what follows, namely, the ones coming from the dynamics of the conformal factor of the homogeneous and isotropic metric and also the ones based on linear cosmic perturbations. The reduced relativistic gas model demonstrated its high effectiveness, permitting to explore a large volume in the space of mentioned parameters in a rather economic way. Taking together the results of such tests as supernova type Ia (Union2 sample), $H(z)$, cosmic microwave background ($R$ factor), baryon acoustic oscillation, and large-scale structure data (2dFGRS data), we confirm that $\ensuremath{\Lambda}\mathrm{CDM}$ is the most favored model. At the same time, for the 2dFGRS data alone we found that an alternative model with a very small quantity of dark matter is also viable. This output is potentially relevant in view of the fact that the large-scale structure data is the only test which cannot be affected by the possible quantum contributions to the low-energy gravitational action.