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

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$A$isapositiveconstantand$0 < \alpha \le 1$. 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 $p=\alpha \rho$.