Non-Gaussianity in Loop Quantum Cosmology

TL;DR

This paper extends loop quantum cosmology to second order perturbations, revealing significant non-Gaussianity enhancements during the cosmic bounce, yet maintaining the validity of perturbative predictions for the CMB.

Contribution

It provides the first detailed analysis of second order non-Gaussianity in LQC, highlighting the impact of the bounce on primordial fluctuations.

Findings

Bounce enhances non-Gaussianity by several orders of magnitude.

Perturbative expansion remains valid despite large non-Gaussianity.

Results have implications for CMB observations and LQC phenomenology.

Abstract

We extend the phenomenology of loop quantum cosmology (LQC) to second order in perturbations. Our motivation is twofold. On the one hand, since LQC predicts a cosmic bounce that takes place at the Planck scale, the second order contributions could be large enough to jeopardize the validity of the perturbative expansion on which previous results rest. On the other hand, the upper bounds on primordial non-Gaussianity obtained by the Planck Collaboration are expected to play a significant role on explorations of the LQC phenomenology. We find that the bounce in LQC produces an enhancement of non-Gaussianity of several orders of magnitude, on length scales that were larger than the curvature radius at the bounce. Nonetheless, we find that one can still rely on the perturbative expansion to make predictions about primordial perturbations. We discuss the consequences of our results for LQC and its predictions for the cosmic microwave background.