Strong evidence for an accelerating universe

Abstract

A recent analysis of the Supernova Ia data claims a 'marginal' ($\sim3\sigma$) evidence for a cosmic acceleration. This result has been complemented with a non-accelerating $R_{h}=ct$ cosmology, which was presented as a valid alternative to the $\Lambda$CDM model. In this paper, we use the same analysis to show that a non-marginal evidence for acceleration is actually found. We compare the standard Friedmann models to the $R_{h}=ct$ cosmology by complementing SN Ia data with the Baryon Acoustic Oscillations, Gamma Ray Bursts and Observational Hubble datasets. We also study the power-law model which is a functional generalisation of $R_{h}=ct$. We find that the evidence for late-time acceleration is beyond refutable at a 4.56$\sigma$ confidence level from SN Ia data alone, and at an even stronger confidence level ($5.38\sigma$) from our joint analysis. Also, the non-accelerating $R_{h}=ct$ model fails to statistically compare with the $\Lambda$CDM having a $\Delta(\text{AIC})\sim30$.