Phenomenological Varying Modified Chaplygin Gas with Variable $G$ and $\Lambda$: Toy Models for Our Universe

TL;DR

This paper explores cosmological models with a varying modified Chaplygin gas, incorporating variable gravitational and cosmological constants, analyzing their effects on universe evolution through two toy models with different fluid compositions.

Contribution

It introduces two novel toy models of the universe with variable G and Lambda, considering a modified Chaplygin gas and a fluid-matter mixture with sign-changing interactions.

Findings

Analysis of the equation of state parameter over cosmic time.

Deceleration parameter behavior indicating acceleration phases.

Impact of variable G and Lambda on cosmological evolution.

Abstract

This article motivated by the recent articles and results of two authors. Recently, J. Sadeghi and H. Farahani presented a work [1], where they include viscosity and analyze general model, by this way they extended models considered by M. Khurshudyan [2] and [3]. In this article, We tempt to consider varying Modified Chaplygin gas model in case of variable $G$ and $\Lambda$. It is well known, that varying $G$ and $\Lambda$ gives rise to modified field equations and modified conservation laws. We will consider two different toy models. First model is a Universe with one component phenomenological gas of our consideration, while for the second model we assume existence of a composed fluid of gas and a matter with $P=\omega(t)\rho_{m}$. Sign changeable interaction between fluids is accepted. We will analyze important cosmological parameters like EoS parameter of a fluid, deceleration parameter $q$ of the model.