Constraining modified Chaplygin gas parameters

摘要

We study the evolution of a FRW model fueled by a modified Chaplygin gas (MCG) with the equation of state p=A rho-B/rho(alpha). An attempt is made to constrain the free parameters of MCG model through the well-known contour plot technique using observational data. The permissible range of values of two free parameters is determined to study the viability of cosmological models against the observational results. Aside from allowing the desirable feature of a flip of the sign of the deceleration parameter, we also find that a transition from deceleration to acceleration occurs at relatively low value of the redshift in accordance with the observational prediction that the acceleration is a recent phenomenon. Stability of the model against density perturbation is studied in some detail, and it is found that the effective acoustic speed may become imaginary depending on the initial data, signalling that perturbations associated with instability set in, resulting in structure formation. As one considers more negative values of A, the flip in sign is delayed making the density parameter change fast. Again, it is found from the contour plot that compatibility with observational data is admitted with a value of A which is very near zero or is a small negative number.