Preinflationary dynamics of $\alpha-$attractor in loop quantum cosmology

TL;DR

This paper investigates the preinflationary dynamics of $ ext{alpha}$-attractor models within loop quantum cosmology, revealing universal features of the evolution and identifying conditions leading to successful slow-roll inflation.

Contribution

It provides a systematic numerical analysis of initial conditions leading to inflation in $ ext{alpha}$-attractor models in loop quantum cosmology, highlighting universal phases and comparing different potentials.

Findings

Universal three-phase evolution: bouncing, transition, slow-roll.

Viable initial conditions produce sufficient e-folds for observations.

Results are consistent across different scalar field potentials.

Abstract

We systematically study the preinflationary dynamics of the spatially flat Friedmann-Lemaitre-Robertson-Walker universe filled with a single scalar field that has the generalized $\alpha-$attractor potentials, in the framework of loop quantum cosmology, in which the big bang singularity is replaced generically by a non-singular quantum bounce due to purely quantum geometric effects. The evolution can be divided into two different classes, one is dominated initially (at the quantum bounce) by the kinetic energy of the scalar field, and one is not. In both cases, we identify numerically the physically viable initial conditions that lead to not only a slow-roll inflationary phase, but also enough $e$-folds to be consistent with observations, and find that the output of such a viable slow-roll inflationary phase is generic. In addition, we also show that in the case when the evolution of the universe is dominated initially by the kinetic energy of the scalar field (except for a very small set in the phase space), the evolution before reheating is aways divided into three different phases: {\em bouncing, transition and slow-roll inflation}. This universal feature does not depend on the initial conditions of the system nor on the specific potentials of the scalar field, as long as it is dominated initially by the kinetic energy of the scalar field at the bounce. Moreover, we carry out phase space analyses for the models under consideration and compare our results with the power-law and Starobinsky potentials.