Solving the curvature and Hubble parameter inconsistencies through structure formationinduced curvature
Abstract
Recently it has been noted by Di Valentino, Melchiorri and Silk (2019) that the enhanced lensing signal relative to that expected in the spatially flat ΛCDM model poses a possible crisis for the FriedmannLemaîtreRobertsonWalker (FLRW) class of models usually used to interpret cosmological data. The 'crisis' amounts to inconsistencies between cosmological datasets arising when the FLRW curvature parameter Ω_{k0} is determined from the data rather than constrained to be zero a priori. Moreover, the already substantial discrepancy between the Hubble parameter as determined by Planck and local observations increases to the level of 5σ. While such inconsistencies might arise from systematic effects of astrophysical origin affecting the Planck cosmic microwave background (CMB) power spectra at small angular scales, it is an option that the inconsistencies are due to the failure of the FLRW assumption. In this paper we recall how the FLRW curvature ansatz is expected to be violated for generic relativistic spacetimes. We explain how the FLRW conservation equation for volumeaveraged spatial curvature is modified through structure formation, and we illustrate in a simple framework how the curvature tension in a FLRW spacetime can be resolved—and is even expected to occur—from the point of view of general relativity. Requiring earlytime convergence towards a Friedmannian model with a spatial curvature parameter Ω_{k0} equal to that preferred from the Planck power spectra resolves the Hubble tension within our dark energyfree model.
 Publication:

Classical and Quantum Gravity
 Pub Date:
 August 2020
 DOI:
 10.1088/13616382/ab954b
 arXiv:
 arXiv:2002.10831
 Bibcode:
 2020CQGra..37p4001H
 Keywords:

 relativistic cosmology;
 scalar curvature;
 Hubble tension;
 backreaction;
 General Relativity and Quantum Cosmology;
 Astrophysics  Cosmology and Nongalactic Astrophysics
 EPrint:
 23 pages, 1 figure and 1 table