Dynamical homogenization in effective loop quantum cosmology

TL;DR

This paper demonstrates that effective loop quantum gravity dynamics can resolve singularities and homogenize inhomogeneities in cosmological models, leading to large, smooth regions compatible with observations after a cosmic bounce.

Contribution

It shows that inhomogeneities are dynamically homogenized after the bounce in loop quantum cosmology, with implications for early universe structure formation.

Findings

Singularity is replaced by a cosmic bounce.

Homogeneous regions of a few Planck lengths form after the bounce.

Inflation can expand these regions to cosmic scales, suppressing perturbations.

Abstract

The effective dynamics of loop quantum gravity for marginally bound Lema\^itre-Tolman-Bondi spacetimes predict that the big-bang singularity is resolved and replaced by a cosmic bounce. Numerics show that these effective dynamics also homogenize small regions soon after the bounce when inhomogeneities before the bounce are sufficiently large. These homogeneous regions typically have a width of a few Planck lengths where relative perturbations in the energy density remain less than 15%. If the bounce is followed by an inflationary period, the homogeneous region can reach cosmic scales and the amplitude of relative perturbations can be suppressed to a value compatible with observations.