Constraining Modified Chaplygin gas parameters

TL;DR

This paper constrains the parameters of a modified Chaplygin gas cosmological model using observational data, analyzing its viability, stability, and consistency with the recent acceleration of the universe.

Contribution

It provides the first detailed parameter constraints for the modified Chaplygin gas model based on observational data and explores its implications for cosmic acceleration and structure formation.

Findings

Transition from deceleration to acceleration occurs at low redshift.

Parameter A near zero or slightly negative fits observational data.

Instability may arise depending on initial conditions, affecting structure formation.

Abstract

We investigate the evolution of a FRW model fuelled by a modified Chaplygin gas with an equation of state $p = A\rho -\frac{B}{\rho^\alpha}$. An attempt is made here to constrain the free parameters of MCG model through the wellknown contour plot technique using observational data. The permissible range of values of the pair of free parameters are determined to study the viability of cosmological models \emph{vis-a-vis} observational results. Aside from allowing the desirable feature of \emph{flip} of the sign of deceleration parameter we also find that the transition from the decelerating to the accelerating phase occurs at relatively low value of redshift in accordance with the observational prediction that the acceleration is a recent phenomenon. It is found that the effective acoustic speed may become imaginary depending upon the initial conditions signalling that perturbations associated with instability sets in resulting in structure formation. As one considers more negative values of $A$ the \emph{flip} in sign is delayed resulting the density parameter to change fast. Again it is found from the contour plot that compatibility with observational results is admitted with a value of $A$ which is very near to zero or a small negative number.