Possible Resolution of the Hubble Tension with Weyl Invariant Gravity
release_zdvisxl2ozgnbdrb7lcxe67hkm
by
Meir Shimon
2020
Abstract
We explore cosmological implications of a genuinely Weyl invariant (WI)
gravitational interaction. The latter reduces to general relativity in a
particular conformal frame for which the gravitational coupling and active
gravitational masses are fixed. Specifically, we consider a cosmological model
in this framework that is dynamically identical to the standard model
(SM) of cosmology. However, kinematics of test particles traveling in the
new background metric is modified thanks to a new fundamental mass scale,
γ, of the model. Since the lapse-function of the new metric is
radially-dependent any incoming photon experiences (gravitational)
red/blueshift in the comoving frame, unlike in the SM. Distance scales
are modified as well due to the scale γ. The claimed 4.4σ tension
level between the locally measured Hubble constant, H_0, with SH0ES and the
corresponding value inferred from the cosmic microwave background (CMB) could
then be significantly alleviated by an earlier-than-thought recombination.
Assuming vanishing spatial curvature, either one of the Planck 2018 (P18) or
dark energy survey (DES) yr1 data sets subject to the SH0ES prior imply that
γ^-1 is O(100) times larger than the Hubble scale, H_0^-1.
Considering P18+SH0ES or P18+DES+SH0ES data set combinations, the odds against
vanishing γ are over 1000:1 and 2000:1, respectively, and the model is
strongly favored over the SM with a deviance information criterion (DIC) gain
≳ 10 & ≳ 12, respectively. The tension is reduced in this
model to ∼ 1.5 & 1.3 σ, respectively. We conclude that the H_0
tension may simply result from a yet unrecognized fundamental symmetry of the
gravitational interaction – Weyl invariance. (abridged)
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