Non-minimally coupled gravity constraints from DESI DR2 data

Abstract

It has been observed that the hint about dynamical dark energy in the DESI BAO observation might point to non-minimally coupled gravity. We report the first $3\sigma$ evidence for non-minimal coupling in a model-agnostic effective field theory (EFT) approach. In a non-parametric reconstruction approach, we detect a clear departure from the General Relativity expectation of non-minimal coupling based on a combined analysis of DESI DR2 BAO together with CMB and Type Ia supernova data. Also, it is found that current data can constrain up to the quadratic order $(n=2)$ if the EFT function representing non-minimal coupling is Taylor expanded as a general function of the dark energy fraction $\Omega_{\rm DE}$, i.e. $\Omega^{\rm EFT}(a)=\sum_{i=0}^{n} c^{\rm EFT}_i \Omega^i_{\rm DE}(a)$. Our findings constitute a detection of modified-gravity effects and call for a more flexible parametrization of the EFT functions than commonly used ones in literature.