Late-time reconstruction of non-minimally coupled gravity with a smoothness prior

Gen Ye; Anton Chudaykin; Camille Bonvin; Martin Kunz

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arXiv · 2605.12415

Late-time reconstruction of non-minimally coupled gravity with a smoothness prior

Gen Ye·Anton Chudaykin·Camille Bonvin·Martin Kunz

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Abstract

We present a non-parametric, model-independent reconstruction of the cosmological background and perturbation dynamics in non-minimally coupled theories of gravity. Within the Effective Field Theory of dark energy framework, we reconstruct the time-dependent cosmological constant, $\Lambda(t)$, and the non-minimal coupling function, $\Omega(t)$, from cosmological data. To ensure stability, we apply a correlated smoothness prior that restricts the reconstruction to the space of sufficiently smooth functions. Using CMB, DESI BAO, Type Ia supernovae, CMB-ISW lensing cross-correlations, and large-scale 3x2pt DES Year 3 data, we find a $2.8\sigma$ hint for a non-minimal coupling. For the dark energy equation of state, our results indicate a preference for the existence of crossing of the phantom divide, $w_{DE}=-1$, at $z<0.8$. The non-minimal coupling effect stabilizes dark energy perturbations, providing a viable physical interpretation of the phantom crossing scenario. Our work paves the way for model-agnostic searches for signatures of modified gravity in cosmological data.

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Gen Ye, Anton Chudaykin, Camille Bonvin, Martin Kunz. 2026-05-12. Late-time reconstruction of non-minimally coupled gravity with a smoothness prior. https://arxiv.org/abs/2605.12415

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