Non-homogeneity-driven universe acceleration

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 (p(t) = αρ(t)) and the function k(t) playing role of spatial curvature is proportional to Stephani version of the Friedmann-Robertson-Lemaitre-Walker scale factor R(t) (k(t) = βR(t)).Classification of cosmological models is performed depending on different values and signs of parameters α and β. It is shown that for β < 0 (hyperbolic geometry) dust-like (α = 0) 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 m(z) 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 relation m(z) calculated in the considered model (H 0 = 65 km/sMpc, Ω 0 ≤ 0.3) 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 H 0 and Ω 0 parameters.PACS numbers: 98.62. Py, 98.80.Es, 98.80.Hw 1

Dark side of the universe in the Stephani cosmology

“…However, it is possible to choose a time parameter in which the spatial dependence of the Hubble and deceleration parameters can vanish [33]. Consequently, the above definition for the Hubble parameter reduces to…”

“…With n = 1 Eq. (27) corresponds to the age of the universe obtained in the work by Stelmach and Jakacka [33]. For the present epoch we assume that the universe is only composed of dust (w 0 = 0) and for simplicity in our calculations we put k 0 = 0 as we do in flat FLRW models.…”

“…The evolution of the model depends on some arbitrary functions, accordingly it can be named a private universe [32]. In the work by Stelmach and Jakacka [33], they assume that the curvature parameter relates to the scale factor by K (t) = β R(t) where β is a constant. They showed that with β < 0 a cosmological model with dust source can lead to the accelerated expansion at later times of evolution.…”

Stephani–Schutz quantum cosmology

“…[31], correspond with choosing Λ = 0 and N = 1. In this case (Λ = 0, N = 1) the constraint equation H = 0 reduces to…”

Quantum Stephani exact cosmological solutions and the selection of time variable

“…[31], are corresponding with choosing the gauge N = 1. In this gauge the constraint equation H = 0 reduces to…”