%0 Journal Article
%T Consistency of modified gravity with a decreasing $G_{\rm eff}(z)$ in a $\Lambda$CDM background
%+ Laboratoire Charles Coulomb (L2C)
%A Gannouji, Radouane
%A Kazantzidis, Lavrentios
%A Perivolaropoulos, Leandros
%A Polarski, David
%< avec comité de lecture
%@ 1550-7998
%J Physical Review D
%I American Physical Society
%V 98
%N 10
%P 104044
%8 2018
%D 2018
%Z 1809.07034
%R 10.1103/PhysRevD.98.104044
%K General relativity
%K alternative theories of gravity
%K gravitation: model
%K cosmological model: background
%K dark energy: equation of state
%K dark energy: phantom
%K gravitation: fundamental constant
%K scalar tensor
%K cosmological constant
%K Friedman model
%K space-time: Robertson-Walker
%K gravitation: f(R)
%K Brans-Dicke model
%K gravitation: lens
%Z Physics [physics]/General Relativity and Quantum Cosmology [gr-qc]
%Z Physics [physics]/Astrophysics [astro-ph]
%Z Physics [physics]/High Energy Physics - Phenomenology [hep-ph]
%Z Physics [physics]/High Energy Physics - Theory [hep-th]Journal articles
%X Recent analyses [S. Nesseris et al., Phys. Rev. D 96, 023543 (2017)PRVDAQ2470-001010.1103/PhysRevD.96.023543; L. Kazantzidis and L. Pervolaropoulos, Phys. Rev. D 97, 103503 (2018)PRVDAQ2470-001010.1103/PhysRevD.97.103503] have indicated that an effective Newton’s constant Geff(z) decreasing with redshift may relieve the observed tension between the Planck15 best fit ΛCDM cosmological background (i.e., Planck15/ΛCDM) and the corresponding ΛCDM background favored by growth fσ8 and weak lensing data. We investigate the consistency of such a decreasing Geff(z) with some viable scalar-tensor models and f(R) theories. We stress that f(R) theories generically cannot lead to a decreasing Geff(z) for any cosmological background. For scalar-tensor models we deduce that in the context of a ΛCDM cosmological background, a decreasing Geff(z) is not consistent with a large Brans-Dicke parameter ωBD,0 today. This inconsistency remains and amplifies in the presence of a phantom dark energy equation of state parameter (w<-1). However, it can be avoided for w>-1. We also find that any modified gravity model with the required decreasing Geff(z) and Geff,0=G would have a characteristic signature in its growth index γ with 0.61≲γ0≲0.69 and large slopes γ0′, 0.16≲γ0′≲0.4, which is a characteristic signature of a decreasing (with z) Geff(z)<G on small redshifts. This is a substantial departure today from the quasistatic behavior in ΛCDM with (γ0,γ0′)≈(0.55,-0.02).
%G English
%L hal-01886014
%U https://hal.science/hal-01886014
%~ CNRS
%~ L2C
%~ MIPS
%~ UNIV-MONTPELLIER
%~ UM-2015-2021