Effects of the Ekpyrotic Mechanism on Inflationary Phase in mLQC-II
Abstract
Bouncing cosmological models replace the big bang singularity with a regular bounce, but face a well-known obstacle: the anisotropic shear grows as a^(-6) during contraction, where a is the average expansion factor, threatening to dominate before a homogeneous, isotropic universe can emerge from the bounce. A standard remedy is a scalar field with an ekpyrotic-like potential that turns negative near the bounce, pushing its effective equation of state above unity so it outgrows the shear. Here we examine how this mechanism affects the subsequent inflationary phase within mLQC-II, a modified loop quantum cosmology (LQC) model in which inflation is otherwise generic. Taking a potential combining ekpyrotic and inflationary components, we numerically evolve the dynamical equations across the bounce for various parameter choices. We find that while some choices of the free parameters of the theory allow the ekpyrotic potential to dominate near the bounce and resolve the shear problem, it substantially reshapes the post-bounce evolution. In particular, parameter choices that yield sufficient inflation without the ekpyrotic mechanism now often fail to do so. Sufficiently long inflation remains possible but appears to require fine-tuning. As our results are numerical, a more systematic analysis will be needed to establish their generality.
Related
- Cycles Without End: An Ekpyrotic Braneworld Bounce with a Kinetically Coupled Entropic Mechanism
- High-Accuracy Semi-Analytic Mode Functions, Ultraviolet Regularity, and Particle Creation in the Hybrid Approach to mLQC-I
- The alternative scalar field dark sector of the Universe: Cosmological inflation, quintessence and ekpyrotic model in the framework of scalar-tensor cosmology
- Torsion, Frames and Quantum Bounces: Inflation and Ekpyrotic Contraction in Quantum Trajectory Cosmology with a Non-Minimally Coupled Scalar
- A Mechanism for the Rényi Hierarchy of Decoherence-Induced Phase Transitions
BibTeX
@misc{fier2026effects,
title = {{Effects of the Ekpyrotic Mechanism on Inflationary Phase in mLQC-II}},
author = {Jared Fier and Aqsa Fareed and Reena Danika Bendukuri and Anzhong Wang},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.13447},
eprint = {2609.13447},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.13447},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Effects of the Ekpyrotic Mechanism on Inflationary Phase in mLQC-II
AU - Jared Fier
AU - Aqsa Fareed
AU - Reena Danika Bendukuri
AU - Anzhong Wang
PY - 2026
DA - 2026/09/11
PB - arXiv
DO - 10.48550/arxiv.2609.13447
UR - https://arxiv.org/abs/2609.13447
AB - Bouncing cosmological models replace the big bang singularity with a regular bounce, but face a well-known obstacle: the anisotropic shear grows as a^(-6) during contraction, where a is the average expansion factor, threatening to dominate before a homogeneous, isotropic universe can emerge from the bounce. A standard remedy is a scalar field with an ekpyrotic-like potential that turns negative near the bounce, pushing its effective equation of state above unity so it outgrows the shear. Here we examine how this mechanism affects the subsequent inflationary phase within mLQC-II, a modified loop quantum cosmology (LQC) model in which inflation is otherwise generic. Taking a potential combining ekpyrotic and inflationary components, we numerically evolve the dynamical equations across the bounce for various parameter choices. We find that while some choices of the free parameters of the theory allow the ekpyrotic potential to dominate near the bounce and resolve the shear problem, it substantially reshapes the post-bounce evolution. In particular, parameter choices that yield sufficient inflation without the ekpyrotic mechanism now often fail to do so. Sufficiently long inflation remains possible but appears to require fine-tuning. As our results are numerical, a more systematic analysis will be needed to establish their generality.
ER -