Probing the isotropy of cosmic acceleration using different supernova samples

TL;DR

This study investigates the isotropy of cosmic acceleration using three supernova datasets, finding some anisotropic signals in two datasets but not in the third, and analyzing the effects of data distribution on these results.

Contribution

It provides a comparative analysis of supernova datasets to probe cosmic acceleration isotropy and examines how data distribution affects dipole measurements.

Findings

Dipole in Union2.1 dataset suggests anisotropy.

No significant dipole detected in JLA dataset.

Anisotropic coordinate distribution influences dipole magnitude.

Abstract

Recent studies have indicated that an anisotropic cosmic expansion may exist. In this paper, we use three datasets of type Ia supernovae (SNe Ia) to probe the isotropy of cosmic acceleration. For the Union2.1 dataset, the direction and magnitude of the dipole are $(l=309.3^{\circ} {}^{+ 15.5^{\circ}}_{-15.7^{\circ}} ,\ b = -8.9^{\circ} {}^{ + 11.2^{\circ}}_{-9.8^{\circ}} ),\ A=(1.46 \pm 0.56) \times 10^{-3}$. For the Constitution dataset, the results are $(l=67.0^{\circ}{}^{+ 66.5^{\circ}}_{-66.2^{\circ}},\ b=-0.6^{\circ}{}^{+ 25.2^{\circ}}_{-26.3^{\circ}}),\ A=(4.4 \pm 5.0) \times 10^{-4}$. For the JLA dataset, no significant dipolar deviation is found. We also explore the effects of anisotropic distributions of coordinates and redshifts on the results using Monte-Carlo simulations. We find that the anisotropic distribution of coordinates can cause dipole directions and make dipole magnitude larger. Anisotropic distribution of redshifts is found to have no significant effect on dipole fitting results.