Modified gravity bridges the cosmological tensions

Abstract

The standard model of cosmology, $\Lambda$CDM, is plagued by various tensions with recent observations. The most pressing one is the Hubble tension, where the observed expansion rate of our Universe is $5\sigma$ larger than that predicted by $\Lambda$CDM. Recently, the result from DESI also reveals a new inconsistency between the baryon acoustic oscillation and cosmic microwave background (CMB) observations in $\Lambda$CDM. It is found that these major cosmological tensions can be traced back to a common physical origin - the non-minimal coupling between gravity and matter, different from the expectation of general relativity (GR). Bayesian model comparison reveals strong evidence of non-minimally coupled gravity over GR and $\Lambda$CDM, with a Bayes factor $\ln B=+12.1$. The non-minimal coupling model predicts that gravity in the early Universe should be $\sim 5\%$ stronger on cosmological scales than it is today, which is consistent with current observation and will be tested by upcoming CMB and big bang nucleosynthesis experiments.

7 pages, 4 figures; matched published version in PRD Letters

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