Can varying the gravitational constant alleviate the tensions ?

Abstract

Constraints on the cosmological concordance model parameters from observables at different redshifts are usually obtained using the locally measured value of the gravitational constant G N . Here we relax this assumption, by considering G as a free parameter, either constant over the redshift range or dynamical but limited to differ from fiducial value only above a certain redshift. Using CMB data and distance measurements from galaxy clustering BAO feature, we constrain the cosmological parameters, along with G, through a MCMC bayesian inference method. Furthermore, we investigate whether the tensions on the matter fluctuation σ 8 and Hubble H 0 parameter could be alleviated by this new variable. We used different parameterisations spanning from a constant G to a dynamical G. In all the cases investigated in this work we found no mechanism that alleviates the tensions when both CMB and BAO data are used with ξ g = G/G N constrained to 1.0±0.04 (resp. ±0.01) in the constant (resp. dynamical) case. Finally, we studied the cosmological consequences of allowing a running of the spectral index, since the later is sensitive to a change in G. For the two parameterisations adopted, we found no significant changes to the previous conclusions.

Is Local $H_0$ At Odds With Dark Energy EFT?

“…While this clearly happens for the (w 0 , w a ) parametrisations in section 2, DE EFTs, even those that permit w DE < −1, are evidently more rigid, and as we have seen, the scope is limited, at least within our assumptions. In that sense, our analysis agrees with [67,74] that a varying Newton's constant may be a viable approach to alleviating H 0 tension, but this window can be expected to be severely restricted as observational constraints improve.…”

“…For this reason, one would expect increases in H 0 due to linear evolution of F(φ) with cosmic time to be marginal, and this is indeed what we found. Even though the outlook may not be good [67,74], at a technical level it is imperative to identify models that increase H 0 without relying heavily on a local H 0 prior, e. g. [72,73]. Finally, we note that increasing H 0 requires Ḟ > 0 (F 1 < 0), which implies the Newton's constant must decrease in the late universe in line with the findings of Ref.…”

“…On the minimal assumption that the coupling G 4 (φ) evolves linearly with cosmic time, while employing model agnostic techniques for the Quintessence sector, G 2 (φ, X) = X − V(φ), we show in section 3 that any increase in H 0 is expected to be negligible. In other words, despite ongoing debate about whether non-minimal couplings can alleviate H 0 tension [71][72][73], in line with [67,74], we find that a non-minimal coupling can only marginally alleviate H 0 tension, at least within reasonable assumptions. Concretely, we observe that the class of models largely fails to penetrate into the phantom regime w DE < −1 at z = 0, so it is consistent with our (w 0 , w a ) expectations.…”

Cosmology Intertwined: A Review of the Particle Physics, Astrophysics, and Cosmology Associated with the Cosmological Tensions and Anomalies

“…Other approaches considering varying gravitational constant are analysed in [907], that considering G N as a free parameter, and in [908] in the context of a cuscuta-galileon gravity theory. Finally, Ref [909] implements a sharp transition in the value of the effective gravitational constant prior recombination, effectively lowering the sound horizon at CMB last scattering and addressing both the H 0 and the S 8 tensions.…”

Testing a varying-$Λ$ model for dark energy within CPC framework

“…Refs. [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28] in the recent literature. This is a rather controversial topic [29,30,31].…”