Genericness of quantum damping of cosmological shear in modified loop quantum cosmology

TL;DR

This paper demonstrates that quantum damping of cosmological shear in modified loop quantum cosmology is a robust and generic feature under physically relevant initial conditions, supported by numerical and perturbative analyses.

Contribution

It clarifies that previous claims of non-generic damping are based on unphysical initial conditions, reaffirming the damping as a generic phenomenon in the model.

Findings

Quantum damping of shear is robust for physically relevant initial conditions.

Post-bounce evolution shows an isotropic attractor with decaying anisotropies.

Damping occurs independently of matter content if the weak energy condition holds.

Abstract

In arXiv:2603.18175, the authors argue, based on numerical studies of particular cases, that the quantum damping of cosmological shear in a modified loop quantum cosmological model (mLQC-I) that was recently found in arXiv:2510.14021 is not generic and that the universe never becomes truly classical. In this brief Note, we revisit these claims by carefully examining the underlying assumptions and the class of initial conditions considered. We show that the examples analyzed in arXiv:2603.18175 correspond to configurations that do not represent physically admissible collapsing Bianchi I universes, as they involve mixed expanding-contracting directions and lead to effectively lower-dimensional post-bounce geometries. Restricting to physically relevant initial conditions corresponding to genuine three-dimensional contraction, we find that the quantum damping of cosmological shear is a robust dynamical feature. This conclusion is supported by both numerical and perturbative analyses, which demonstrate that the post-bounce evolution admits an isotropic attractor, with anisotropies decaying exponentially and independently of the matter content, provided that the weak energy condition is satisfied. We further outline a plausible post-bounce mechanism for the onset of classicalization.