Comparison of $R_h=ct$ and $\Lambda$CDM using DESI DR1 measurements

Abstract

We use DESI DR1 BAO measurements of the ratio of tranvserse comoving distance to Hubble distance in order to test the compatibility of $R_h=ct$ over flat $\Lambda$CDM. For this purpose, we used Bayesian model selection to evaluate the efficacy of these models given the observed data. When we consider the BAO measurements up to redshift of 1.3, both models are equally favored. However, when we consider the Lyman-$\alpha$ QSO measurement at redshift of 2.33, we find Bayes factors of greater than 100 for flat $\Lambda$CDM over $R_h=ct$ using two different priors for $\Omega_m$, indicating that $\Lambda$CDM is decisively favored over $R_h=ct$. The same is the case when we combine all the measurements. Therefore, the DESI DRI measurements rule out $R_h=ct$ cosmology, albeit this is driven by the Lyman-$\alpha$ QSO measurement at $z=2.33$.