Strong evidence for an accelerating Universe

Abstract

A recent analysis of supernova Ia (SN Ia) data claims a “marginal” (~ 3σ) evidence for a cosmic acceleration. This result has been complemented with a non-accelerating Rh = ct cosmology, which was presented as a valid alternative to the ΛCDM model. In this paper we use the same analysis to show that non-marginal evidence for acceleration is truly found. We compare the standard Friedmann models to the Rh = ct cosmology by complementing SN Ia data with baryon acoustic oscillations, gamma ray bursts, and observational Hubble datasets. We also study the power-law model, which is a functional generalisation of Rh = ct. We find that the evidence for late-time acceleration cannot be refuted at a 4.56σ confidence level from SN Ia data alone, and at an even stronger confidence level (5.38σ) from our joint analysis. In addition, the non-accelerating Rh = ct model fails to statistically compare with the ΛCDM, having a Δ(AIC) ~ 30.