Dynamical behaviors of FRW Universe containing a positive/negative potential scalar field in loop quantum cosmology

TL;DR

This paper analyzes the stability and bounce behaviors of a flat FRW universe with positive or negative potential scalar fields within loop quantum cosmology, revealing quantum effects lead to non-singular bounces and possible cyclic universe scenarios.

Contribution

It provides a phase-plane analysis of scalar field dynamics in loop quantum cosmology, highlighting differences from classical cosmology and identifying conditions for stable bounces and cyclic universe behavior.

Findings

Positive potential scalar fields lead to a single quantum bounce.

Negative potential scalar fields result in two bounce points and possible cyclic universe.

Quantum geometry effects prevent singularities and enable non-singular bounces.

Abstract

The dynamical behaviors of FRW Universe containing a posivive/negative potential scalar field in loop quantum cosmology scenario are discussed. The method of the phase-plane analysis is used to investigate the stability of the Universe. It is found that the stability properties in this situation are quite different from the classical cosmology case. For a positive potential scalar field coupled with a barotropic fluid, the cosmological autonomous system has five fixed points and one of them is stable if the adiabatic index $\gamma$ satisfies $0<\gamma<2$. This leads to the fact that the universe just have one bounce point instead of the singularity which lies in the quantum dominated area and it is caused by the quantum geometry effect. There are four fixed points if one considers a scalar field with a negative potential, but none of them is stable. Therefore, the universe has two kinds of bounce points, one is caused by the quantum geometry effect and the other is caused by the negative potential, the Universe may enter a classical re-collapse after the quantum bounce. This hints that the spatially flat FRW Universe containing a negative potential scalar field is cyclic.