The assumption of homogeneity and isotropy on large scales is one of the main hypothesis of the standard cosmological model. In this paper, we revisit a test of cosmological isotropy using type Ia supernova (SN Ia) distances provided by the latest SN Ia compilation available, namely, the Pantheon compilation. We perform a model-independent analysis by selecting low-redshift subsamples lying in two redshift intervals, i.e., z ≤ 0.10 and z ≤ 0.20. By mapping the directional asymmetry of cosmological parameters across the sky, we show that the current SN Ia data favours the hypothesis of cosmic isotropy, as the anisotropy found in the maps can be mostly ascribed to the non-uniform sky coverage of the data rather than an actual cosmological signal. These results confirm that there is null evidence against the cosmological principle in the low-redshift universe.

We use the most recent type Ia supernovae (SNe Ia) observations to perform a statistical comparison between the standard ΛCDM model and its extensions [wCDM and w(z)CDM] and some alternative cosmologies: namely, the Dvali-Gabadadze-Porrati (DGP) model, a power-law f (R) scenario in the metric formalism and an example of vacuum decay [Λ(t)CDM] cosmology in which the dilution of pressureless matter is attenuated with respect to the usual a −3 scaling due to the interaction of the dark matter and dark energy fields. We perform a Bayesian model selection analysis using the MultiNest algorithm. To obtain the posterior distribution for the parameters of each model, we use the joint light-curve analysis (JLA) SNe Ia compilation containing 740 events in the interval 0.01 < z < 1.3 along with current measurements of baryon acoustic oscillations (BAO). The JLA data are analyzed with the SALT2 light-curve fitter and the model selection is then performed by computing the Bayesian evidence of each model and the Bayes factor of the ΛCDM cosmology related to the other models. The results indicate that the JLA data alone are unable to distinguish the standard ΛCDM model from some of its alternatives but its combination with current measurements of baryon acoustic oscillations shows up an ability to distinguish them. In particular, the DGP model is practically not supported by both the BAO and the joint JLA + BAO data sets compared to the standard scenario. Finally, we provide a rank order for the models considered.

The cosmographic expansion history of the universe is investigated by using the 557 type Ia supernovae from the Union2 Compilation set along with the current estimates involving the product of the CMB acoustic scale ℓA and the BAO peak at two different redshifts. Using a well-behaved parameterization for the deceleration parameter, q(z) = q0 +q1z/(1+z), we estimate the accelerating redshift zacc = −q0/(q0 + q1) (at which the universe switches from deceleration to acceleration) and investigate the influence of a non-vanishing spatial curvature on these estimates. We also use the asymptotic value of q(z) at high-z to place more restrictive bounds on the model parameters q0 and q1, which results in a more precise determination of the epoch of cosmic acceleration.PACS numbers: 95.36.+x, 98.80.Es