Constraining the Anisotropic Expansion of Universe

TL;DR

This paper investigates potential anisotropy in the universe's accelerated expansion using supernova and gamma-ray burst data, constraining the anisotropy's direction and strength, and discussing methods to differentiate it from velocity effects.

Contribution

It introduces a direction-dependent dark energy model to constrain anisotropy in cosmic expansion using observational data.

Findings

Maximum anisotropic deviation at (l, b) = (126°, 13°)

Current anisotropy level g_0 ≈ 0.03

No strong evidence for anisotropic dark energy

Abstract

We study the possibly existing anisotropy in the accelerating expansion universe with the Union2 Type Ia supernovae data and Gamma-ray burst data. We construct a direction-dependent dark energy model and constrain the anisotropy direction and strength of modulation. We find that the maximum anisotropic deviation direction is $(l,\,b)=(126^{\circ},\,13^{\circ})$ (or equivalently $(l,\,b)=(306^{\circ},\,-13^{\circ})$), and the current anisotropy level is $g_0=0.030_{+0.010}^{-0.030}$ ($1\sigma$ confidence level with Union2 data). Our results do not show strong evidence for the anisotropic dark energy model. We also discuss potential methods that may distinguish the peculiar velocity field from the anisotropic dark energy model.