Generalized Chaplygin gas as a scheme for Unification of Dark Energy and Dark Matter

Abstract

We study the cosmological scenario arising from the dynamics of a generalized Chaplygin gas. The equation of state of the system is given in terms of the energy density, $\rho$, and pressure, $p$, by the relationship $p=-A/{\rho }^{\alpha }$, where $A$ is a positive constant and $0<\alpha \le 1$. The conditions under which homogeneity arises are discussed and it is shown that this equation of state describes a universe evolving from a phase dominated by non-relativistic matter to a phase dominated by a cosmological constant via an intermediate period where the effective equation of state is $p=\alpha \rho$.

4 pages. Talk presented by O.B. at the XVIIIth IAP Colloquium "On the Nature of Dark Energy", Paris, July 2002