Brans-Dicke Gravity with a Cosmological Constant Smoothes Out ΛCDM Tensions

We analyze Brans-Dicke gravity with a cosmological constant, Λ, and cold dark matter (BD-ΛCDM) 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 cosmic microwave background likelihood. Our analysis includes both the background and perturbations equations. We find that BD-ΛCDM is observationally favored as compared to the concordance ΛCDM model, which is traditionally defined within General Relativity (GR). In particular, some well-known persisting tensions of the ΛCDM with the data, such as the excess in the mass fluctuation amplitude {σ }₈ and especially the acute H ₀-tension with the local measurements, essentially disappear in this context. Furthermore, viewed from the GR standpoint, BD-ΛCDM cosmology mimics quintessence at ≳ 3σ c.l. near our time.