Non-homogeneity-driven Universe acceleration

TL;DR

This paper investigates Stephani cosmological models with barotropic equations of state, demonstrating that certain hyperbolic models can naturally produce accelerated expansion and fit supernova data without a cosmological constant.

Contribution

It introduces a classification of Stephani models based on parameters and shows their potential to explain universe acceleration and supernova observations without dark energy.

Findings

Hyperbolic dust-like models exhibit late-time acceleration.

Distant galaxies show negative deceleration parameters.

Supernova data fit well without cosmological constant.

Abstract

Class of spherically symmetric Stephani cosmological models is examined in the context of evolution type. It is assumed that the equation of state at the symmetry center of the models is barotropic. Classification of cosmological models is performed depending on different values and signs of two free parameters. It is shown that for (hyperbolic geometry) dust-like cosmological model exhibits accelerated expansion at later stages of evolution. The Hubble and deceleration parameters are defined in the model and it is shown that the deceleration parameter decreases with the distance becoming negative for sufficiently distant galaxies. Redshift-magnitude relation is calculated and discussed in the context of SnIa observational data. It is noticed that the most distant supernovae of type Ia fit quite well to the redshift-magnitude relation calculated in the considered model without introducing the cosmological constant. It is also shown that the age of the universe in the model is longer than in the Friedmann model corresponding to the same Hubble and energy density parameters.