The Dynamics of Reheating in Loop Quantum Cosmology

TL;DR

This paper integrates the reheating phase into loop quantum cosmology, demonstrating its consistency with observational data and constraining the total e-folds from the bounce to today.

Contribution

It presents the first comprehensive modeling of reheating within the LQC framework, connecting quantum bounce dynamics with observable cosmological parameters.

Findings

Reheating in LQC is compatible with Planck and ACT data.

The total number of e-folds from bounce to now is constrained.

Reheating parameters influence observable scalar and tensor perturbations.

Abstract

In loop quantum cosmology (LQC), the initial singularity is replaced by a quantum bounce, leading to a universal post-bounce evolution characterized by three distinct epochs: bouncing, transition, and slow-roll inflation, before the hot big-bang universe starts. While the generic nature of inflation in LQC is well-established, the subsequent reheating phase-the process that thermalizes the universe and marks the beginning of the hot big bang has remained unexplored in this quantum gravitational framework. This paper presents the first comprehensive integration of the (generalized) reheating mechanism into the LQC paradigm. Using the Power Law Plateau potential and comparing predictions with the latest Planck 2018 and ACT 2025 data, we demonstrate that the inclusion of a reheating phase with a generic equation of state is fully consistent with the cosmological constraints. In addition, using the observational data for the amplitude and spectral index of the scalar perturbations and the tensor-to-scalar ratio, we also constrain the total number of e-folds from the bounce to the present day and find a lower bound, which is less constrained than that obtained previously from the fitting of the high-$l$ CMB temperature power spectrum (TT), the polarization data (TT, TE, EE) and the low-$l$ polarization data (lowP).