Emergent Universe Scenario in the Modified Chaplygin gas : Towards an Exact Solution and Observational Constraints

TL;DR

This paper develops an exact analytical solution for a cosmological model based on the Modified Chaplygin Gas, demonstrating an emergent universe scenario that aligns with observational data and approaches LambdaCDM behavior.

Contribution

It introduces an innovative approximation method to derive an exact scale factor solution in the MCG model, enabling detailed analysis of the emergent universe scenario.

Findings

Universe begins with finite size and evolves smoothly

Model parameters constrained by Hubble data

Effective equation of state transitions from positive to minus one

Abstract

The Modified Chaplygin Gas (MCG) model is revisited to examine its ability to describe the full cosmic evolution within a single framework. Because the field equations are highly nonlinear, no closed analytical solution for the scale factor in terms of cosmic time exists. To address this limitation and determine the flip time along with other physical characteristics, we introduce an alternative first order approximation that yields an exact analytical expression for the scale factor. This approach gives rise to an emergent, non singular cosmological scenario in which the universe begins with a finite minimum size and evolves smoothly from a quasi static phase to a de Sitter like expansion at late times, naturally approaching the LambdaCDM limit. Using Hubble observational data, we constrain the equation of state parameters and obtain the viable ranges 0 < alpha < 1 and 0 < A < 1/3. The effective equation of state parameter evolves from a positive value in the early matter dominated era to approximately minus one at late times, consistent with observations. A complementary analysis based on the Raychaudhuri equation further supports the robustness of the model.