Does the Universe Accelerate Equally in all Directions?

TL;DR

This study investigates whether the universe's acceleration is isotropic by analyzing supernova data for directional dependence, employing a simple method that accounts for measurement errors, but finds only a low-significance dipole likely due to chance.

Contribution

The paper introduces a computationally efficient, largely model-independent method to detect anisotropies in cosmic acceleration using supernova data.

Findings

A low-significance dipole aligned with the CMB dipole

No strong evidence for anisotropic acceleration

Method effectively weights supernovae by measurement error

Abstract

We employ the Union compilation of Type Ia supernovae with a maximum likelihood analysis to search for a dark energy dipole. To approach this problem, we present a simple, computationally efficient, and largely model independent method. We opted to weight each SN by its observed error estimate, so poorly measured SNe that deviate substantially from the Hubble law do not produce spurious results. We find, with very low significance, a dipole in the cosmic acceleration directed roughly towards the cosmic microwave background dipole, but this is almost certainly coincidental.