A larger value for H0 by an evolving gravitational constant

Matteo Braglia, Mario Ballardini, William T. Emond, Fabio Finelli, A. Emir Gumrukcuoglu, Kazuya Koyama, Daniela Paoletti

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We provide further evidence that a massless cosmological scalar field with a non-minimal coupling to the Ricci curvature of the type M2pl(1+ξσn/Mnpl) alleviates the existing tension between local measurements of the Hubble constant and its inference from CMB anisotropies and baryonic acoustic oscillations data in presence of a cosmological constant. In these models, the expansion history is modified compared to ΛCDM at early time, mimicking a change in the effective number of relativistic species, and gravity weakens after matter-radiation equality. Compared to ΛCDM, a quadratic (n=2) coupling increases the Hubble constant when Planck 2018 (alone or in combination with BAO and SH0ES) measurements data are used in the analysis. Negative values of the coupling, for which the scalar field decreases, seem favored and consistency with Solar System can be naturally achieved for a large portion of the parameter space without the need of any screening mechanism. We show that our results are robust to the choice of n, also presenting the analysis for n=4.
Original languageEnglish
Article number023529
Number of pages12
JournalPhysical Review D
Issue number2
Early online date15 Jul 2020
Publication statusPublished - 17 Jul 2020


  • astro-ph.CO
  • RCUK
  • STFC
  • ST/S000550/1
  • ST/P000703/1


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