Reconstruction of a Scale-dependent Gravitational Phase Transition

• Published in: The Astrophysical journal Vol. 958; no. 1; p. 6
• Main Authors: Farhang, Marzieh, Khosravi, Nima
• Format: Journal Article
• Language: English
• Published: Philadelphia The American Astronomical Society 01-11-2023; IOP Publishing
• Subjects: Astrophysics; Cosmic microwave background; Cosmological constant; Cosmology; Dark energy; Deviation; Einstein equations; General relativity; Parameter modification; Perturbation; Phase transitions; Principal component analysis; Relativity; Sky surveys (astronomy)
• ISSN: 0004-637X; 1538-4357
• DOI: 10.3847/1538-4357/acfa6e

In this work we extend our earlier phenomenological model for a gravitational phase transition and its generalization to early times by letting the modifications in the linearly perturbed Einstein equations be scale dependent. These modifications are characterized as deviations of the parameters
μ
(
z
,
k
) and
γ
(
z
,
k
) from their values in general relativity (GR). The scale-dependent amplitudes of modified
μ
(
z
,
k
) and
γ
(
z
,
k
) and the parameters defining the phase transition, along with the standard cosmological parameters, are measured by various data combinations. Out of the perturbation parameters, we construct gravity eigenmodes that represent patterns of perturbations best detectable by data. We detect no significant deviation from GR in these parameters. However, the larger parameter space produced due to the new degrees of freedom allows for the reconciliation of various data sets that are in tension in ΛCDM. In particular, we find
H
0
= 71.9 ± 9.2 from anisotropies of the cosmic microwave background as measured by Planck (and various measurements of the baryonic acoustic oscillations, in agreement with local Hubble measurements). We also find that the
σ
8
tension between the measurements of the Dark Energy Survey and Planck is reduced to less than 1
σ
.