Effect of low anisotropy on cosmological models by using supernova data

Abstract

By using the supernovae type Ia (SNIa) data we study influence of the anisotropy (although low) on the evolution of the universe and compare ΛCDM model with 6 representative parametrizations of the recent Hubble expansion history H(z). To compare these models we use the maximum likelihood method for find that the best fit dynamical w(z) and q(z) obtained from the SNIa dataset. We have performed a comparative analysis of three SNIa datasets such as, the 194 SNIa (0 ≤ z ≤ 1.75), the Supernova Legacy Survey (SNLS) dataset (238 data points 0.15 < z < 1.1) and the most recent Pantheon sample (1048 data points 0.01 < z < 2.3). In particular we find the best fit value of ΛCDM model Ωσ0=0.013±0.008, χmin2=197.56 with 194 SNIa, Ωσ0=−0.003±0.033, χmin2=230.656 with 238 SNLS and Ωσ0=0.011±0.013, χmin2=1012.55with 1048 Pantheon sample. The analysis shows that by considering the anisotropy, it leads to more best fit parameters in all models (except of SCDM) with SNIa data. We also use two statistical tests such as the usual χmin2/dof and p-test to compare different dark energy models. According to both statistical tests and considering anisotropy, the ΛCDM model that is providing the best fit to ΛCDM of FRW model. An even better fit would result with an optimization of the data using effects of anisotropy from the beginning.