Non-homogeneity-driven universe acceleration

A 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 centre of the models is barotropic (p(t) = alphap(t)) and the function k(t) playing the role of spatial curvature is proportional to the Stephani version of the Friedmann-Robertson-Lemaitre-Walker scale factor R(t) (k(t) = beta R(t)). A classification of the cosmological models is performed depending on different values and signs of parameters alpha and beta. It is shown that for beta < 0 (hyperbolic geometry) a dust-like (alpha = 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. The redshift-magnitude relation m(z) is calculated and discussed in the context of SnIa observational data. It is noted that the most distant supernovae of type la fit quite well to the relation in (z) calculated in the considered model (Ho = 65 km s(-1) Mpc(-1), Omega (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 Ho and (0) parameters.