Testing the isotropy of the Universe with type Ia supernovae

Abstract

We analyze the magnitude-redshift data of type Ia supernovae included in the Union and Union2 compilations in the framework of an anisotropic Bianchi type I cosmological model and in the presence of a dark energy fluid with anisotropic equation of state. We find that the amount of deviation from isotropy of the equation of state of dark energy, the skewness δ, and the present level of anisotropy of the large-scale geometry of the Universe, the actual shear Σ0, are constrained in the ranges −0.16 δ 0.12 and −0.012 Σ0 0.012 (1σ C.L.) by Union2 data. Supernova data are then compatible with a standard isotropic universe (δ = Σ0 = 0), but a large level of anisotropy, both in the geometry of the Universe and in the equation of state of dark energy, is allowed.

Searching for a cosmological preferred axis in complicated class of cosmological models: case study f (R, T ) model

“…The Bianchi I type cosmological model [12,50] and the Rinders-Finsler cosmological model [14,15] are two models which are consistent with the SNe Ia data. A scalar perturbation of the ΛCDM model may also break the spherical symmetry of the Universe such that a preferred axis arises.…”

“…Further results of this paper are as follows: [41,16,12,19,7,11]. It is interesting that the results of other studies are in (1 − σ) confidence level of our study (see figure 31).…”

“…However, recent observational evidence included Large Scale Velocity Flows (DarkFlow ) [29] anisotropy in the Values of the Fine Structure Constant α (α Dipole) [61,41], anisotropy in Accelerating Expansion Rate (Dark Energy Dipole) [12,19], and other effects [47,5,46] indicate that the Universe may be anisotropic on large scales. A number of authors have investigated the anisotropies of the cosmic acceleration [32,12], which was motivated in several aspects. In particular, several groups such as [51,37] have applied the hemisphere comparison method to study the anisotropy…”

Probing dark energy anisotropy

“…Here we apply them to an anisotropic universe such as the Bianchi I model just considered. (Also see [37] for fitting current data to a restricted Bianchi model.) The supernova survey is treated as independent sky areas with deep, well cadenced observations suitable for accurate distance measurement.…”

Comparison between hemisphere comparison method and dipole-fitting method in tracing the anisotropic expansion of the Universe use the Union2 data set

“…Generally speaking, there are two different ways to investigate the possible anisotropy from the data. One is directly fitting the data to a specific anisotropic cosmological model (Campanelli et al 2011;Li et al 2013;Chang et al 2013Chang et al , 2014aSchücker et al 2014). Many anisotropic cosmological models have be proposed to match the observations.…”