Adiabatic expansion of polytropic universe with varying cosmological constant: Models tested with observational data

Abstract

We use two large collections of observational data of supernovae type Ia (SNe Ia) to investigate the polytropic Universe including the situation with a varying cosmological constant; details of our new derivations are presented. We examine the fitness of our new models of a polytropic Universe with two sets of SNe Ia data to test if these are better descriptions than the current standard model of cosmology. Beginning with the established relationships for polytropic matter we derive new equations describing the influence of polytropic matter on the expanding Universe including the situation with a varying cosmological constant. When the models derived here are tested with large sets of supernovae type I a data we find a significant influence of polytropic matter on the state of our expanding Universe. We find that one of our models with a varying {\Lambda} describes the SNe Ia data significantly better than the, {\Lambda}CDM, standard model.