Non-singular Ekpyrotic/Cyclic model in Loop Quantum Cosmology

TL;DR

This paper demonstrates that loop quantum cosmology effects can resolve singularities in the Ekpyrotic/Cyclic model, leading to a non-singular, cyclic universe with bounded anisotropies and no null energy condition violation.

Contribution

It introduces a non-singular cyclic universe model within loop quantum cosmology, including anisotropies, with novel features like moduli field turn-around and multiple bounces.

Findings

Classical singularity is resolved by quantum geometric effects.

The universe undergoes multiple small bounces near the Planck scale.

A natural turn-around of the moduli field leads to cyclic behavior.

Abstract

We study the role of non-perturbative quantum gravity effects in the Ekpyrotic/Cyclic model using the effective framework of loop quantum cosmology in the presence of anisotropies. We show that quantum geometric modifications to the dynamical equations near the Planck scale as understood in the quantization of Bianchi-I spacetime in loop quantum cosmology lead to the resolution of classical singularity and result in a non-singular transition of the universe from the contracting to the expanding branch. In the Planck regime, the universe undergoes multiple small bounces and the anisotropic shear remains bounded throughout the evolution. A novel feature, which is absent for isotropic models, is a natural turn around of the moduli field from the negative region of the potential leading to a cyclic phenomena as envisioned in the original paradigm. Our work suggests that incorporation of quantum gravitational effects in the Ekpyrotic/Cyclic model may lead to a viable scenario without any violation of the null energy condition.