Anisotropic non-singular quantum bounce as a seesaw and amplification mechanism for magnetic fields

TL;DR

This paper explores how anisotropic quantum bounces in loop quantum cosmology can amplify or modify magnetic fields, revealing a seesaw mechanism and conditions for magnetic field enhancement during the early universe.

Contribution

It introduces a detailed numerical analysis of magnetic field evolution through anisotropic quantum bounces, highlighting a novel seesaw amplification mechanism in Bianchi-I models.

Findings

Seesaw mechanism amplifies magnetic fields across the bounce for small initial values.

Scalar field dominance leads to magnetic field amplification instead of seesaw behavior.

Point-like approach to the big bang lacks the seesaw mechanism, affecting magnetic field evolution.

Abstract

We investigate the evolution of a homogeneous magnetic field within Bianchi-I loop quantum cosmology, in which the big bang singularity is replaced with an anisotropic quantum bounce. Using effective spacetime description, we conduct extensive numerical simulations with randomized initial conditions for two cases: first in the presence of a pure homogeneous magnetic field and then adding a massless scalar field that effectively captures the bounce regime even in the presence of inflationary potentials. For a cigar-like approach to the classical big bang, which is far more prevalent than a point-like approach, the quantum geometric bounce acts as a seesaw mechanism for magnetic field energy density. Due to the seesaw mechanism, the magnetic field energy density gets amplified by several orders of magnitude across the bounce for a small pre-bounce value of magnetic field energy density, or vice versa. In the presence of the scalar field, the seesaw mechanism is completely replaced by amplification of the magnetic field across the bounce when the initial energy density of the scalar field significantly dominates. When the universe has a point-like approach to the classical big bang, the seesaw mechanism is absent, and magnetic field energy density experiences amplification or suppression across the non-singular bounce depending on initial densities.