The high-density regime of kinetic-dominated loop quantum cosmology

TL;DR

This paper analyzes the dynamics of perturbative states in loop quantum cosmology with a scalar field, showing that quantum moments influence the bounce properties, especially when the potential is non-negligible.

Contribution

It provides a perturbative analysis of quantum moments in loop quantum cosmology and explores their impact on the bounce in the presence of a scalar potential.

Findings

Quantum moments affect the bounce density.

The bounce persists for semi-classical states.

Potential influences the occurrence of the quantum bounce.

Abstract

We study the dynamics of states perturbatively expanded about a harmonic system of loop quantum cosmology, exhibiting a bounce. In particular, the evolution equations for the first and second order moments of the system are analyzed. These moments back-react on the trajectories of the expectation values of the state and hence alter the energy density at the bounce. This analysis is performed for isotropic loop quantum cosmology coupled to a scalar field with a small but non-zero constant potential, hence in a regime in which the kinetic energy of matter dominates. Analytic restrictions on the existence of dynamical coherent states and the meaning of semi-classicality within these systems are discussed. A numerical investigation of the trajectories of states that remain semi-classical across the bounce demonstrates that, at least for such states, the bounce persists and that its properties are similar to the standard case, in which the moments of the states are entirely neglected. However the bounce density does change, implying that a quantum bounce may not be guaranteed to happen when the potential is no longer negligible.