Testing the isotropy of the Universe by using the JLA compilation of Type Ia supernovae

Abstract

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