Testing the isotropy of the Universe by using the JLA compilation of type-Ia supernovae

TL;DR

This study tests the isotropy of the Universe using supernova data and finds no significant evidence of anisotropy, supporting the cosmological principle.

Contribution

It applies MCMC methods to constrain anisotropy parameters across multiple cosmological models using the JLA supernova compilation.

Findings

Anisotropic amplitude is consistent with zero at 68% CL.

Dipole directions are opposite to those in Union2 data.

Results support a isotropic Universe.

Abstract

We probe the possible anisotropy of the Universe by using the JLA compilation of type-Ia supernovae. We apply the Markov Chain Monte Carlo (MCMC) method to constrain the amplitude and direction of anisotropy in three cosmological models. For the dipole-modulated $\Lambda$CDM model, the anisotropic amplitude is consistent with zero at $68\%$ C.L., and has an upper bound $A_D<1.98\times10^{-3}$ at $95\%$ C.L. Regardless of much larger uncertainty, we find the dipole direction of JLA is amazingly opposite to that of Union2. Similar results are found for the dipole-modulated $w$CDM and CPL models. Thus, the Universe is still well consistent with the isotropy according to the JLA compilation.