Observational constraints on cosmological models with Chaplygin gas and quadratic equation of state

TL;DR

This paper compares various cosmological models, including Chaplygin gas and quadratic equation of state, using observational data to evaluate their fit and parameter constraints, highlighting the quadratic model's best fit but penalized complexity.

Contribution

It introduces and tests a cosmological model with a quadratic equation of state against observational data, comparing it with established models like b1CDM and Chaplygin gas models.

Findings

Quadratic equation of state model achieves the lowest b1^2 value.

Model with quadratic equation of state has the best fit but more parameters.

Akaike information criterion favors simpler models despite fit quality.

Abstract

Observational manifestations of accelerated expansion of the universe, in particular, recent data for Type Ia supernovae, baryon acoustic oscillations, for the Hubble parameter $H(z)$ and cosmic microwave background constraints are described with different cosmological models. We compare the $\Lambda$CDM, the models with generalized and modified Chaplygin gas and the model with quadratic equation of state. For these models we estimate optimal model parameters and their permissible errors with different approaches to calculation of sound horizon scale $r_s(z_d)$. Among the considered models the best value of $\chi^2$ is achieved for the model with quadratic equation of state, but it has 2 additional parameters in comparison with the $\Lambda$CDM and therefore is not favored by the Akaike information criterion.