Rapid transition of Geff at zt ≃ 0.01 as a possible solution of the Hubble and growth tensions

The mismatch in the value of the Hubble constant from low- and high-redshift observations may be recast as a discrepancy between the low- and high-redshift determinations of the luminosity of Type Ia supernovae, the latter featuring an absolute magnitude which is approximate to 0.2 mag lower. Here, we propose that a rapid transition in the value of the relative effective gravitational constant mu(G) = G(eff)/G(N) at z(t) similar or equal to 0.01 could explain the lower luminosity (higher magnitude) of local supernovae, thus solving the H-0 crisis. In other words, here the tension is solved by featuring a transition at the perturbative rather than background level. A model that features mu(G) = 1 for z less than or similar to 0.01 but mu(G) similar or equal to 0.9 for z greater than or similar to 0.01 is trivially consistent with local gravitational constraints but would raise the Chandrasekhar mass and so decrease the absolute magnitude of type Ia supernovae at z greater than or similar to 0.01 by the required value of approximate to 0.2 mag. Such a rapid transition of the effective gravitational constant would not only resolve the Hubble tension but it would also help resolve the growth tension as it would reduce the growth of density perturbations without affecting the Planck/Lambda CDM background expansion.

Automated summary

The discrepancy in the value of the Hubble constant between low- and high-redshift observations may be explained by a rapid transition in the relative effective gravitational constant around z=0.01, which could account for the differences in the luminosity of Type Ia supernovae. This transition not only resolves the Hubble tension, but also helps ease the growth tension by reducing density perturbations without affecting the background expansion.