Cosmological evolution driven by polytropic fluids in an inhomogeneous spacetime

Abstract Addressing the late-time accelerated expansion of the universe, known as the “dark energy problem”, remains a central challenge in cosmology. While the cosmological constant is the standard explanation, alternative models such as quintessence, phantom fluids, and Chaplygin gas have been proposed. This work investigates the generalized Chaplygin gas (GCG) model, which is characterized by a polytropic equation of state. We explore this model within the framework of an anisotropic fluid, by means of a metric that reduces to the standard form of the Friedmann–Lemaître–Robertson–Walker (FLRW) spacetime at cosmological scales. To assess the model’s viability, we derive analytical expressions for the scale factor, the Hubble parameter, and the deceleration parameter. Finally, the model is tested against observational data to constrain its parameters and evaluate its consistency.