Brans-Dicke gravity with a cosmological constant smoothes out $\Lambda$CDM tensions

TL;DR

This paper demonstrates that Brans-Dicke gravity with a cosmological constant better fits current cosmological data than standard Lambda-CDM, resolving key tensions like the Hubble constant and matter fluctuation amplitude.

Contribution

It introduces and tests a Brans-Dicke gravity model with a cosmological constant against observational data, showing it alleviates existing cosmological tensions.

Findings

BD-ΛCDM model is favored over ΛCDM by data.

Resolves the H0 and σ8 tensions present in ΛCDM.

Mimics quintessence near current epoch.

Abstract

We analyze Brans-Dicke gravity with a cosmological constant, $\Lambda$, and cold dark matter (BD-$\Lambda$CDM for short) in the light of the latest cosmological observations on distant supernovae, Hubble rate measurements at different redshifts, baryonic acoustic oscillations, large scale structure formation data, gravitational weak-lensing and the cosmic microwave background under full Planck 2015 CMB likelihood. Our analysis includes both the background and perturbations equations. We find that BD-$\Lambda$CDM is observationally favored as compared to the concordance $\Lambda$CDM model, which is traditionally defined within General Relativity (GR). In particular, some well-known persisting tensions of the $\Lambda$CDM with the data, such as the excess in the mass fluctuation amplitude $\sigma_8$ and specially the acute $H_0$-tension with the local measurements, essentially disappear in this context. Furthermore, viewed from the GR standpoint, BD-$\Lambda$CDM cosmology mimics quintessence at $\gtrsim3\sigma$ c.l. near our time.