FRW TYPE OF COSMOLOGY WITH A CHAPLYGIN GAS

Abstract

The evolution of a universe modeled as a mixture of generalized Chaplygin gas (GCG) and ordinary matter field is studied for a Robertson–Walker type of spacetime. This model could interpolate periods of radiation-dominated, matter-dominated and cosmological constant-dominated universes. Depending on the arbitrary constants appearing in our theory, the instant of flip changes. Interestingly, we also get a bouncing model when the signature of one of the constants changes. The velocity of sound may become imaginary under certain situations pointing to a perturbative state and consequently the possibility of structure formation. We also discuss the whole situation in the backdrop of the well-known Raychaudhuri equation and a comparison is made with the previous results.