Cosmological particle production in quantum gravity

TL;DR

This paper investigates how quantum gravity effects in an anisotropic early universe can lead to gravitational particle production, impacting the universe's evolution during the Planck era.

Contribution

It introduces a framework to analyze particle production of massive modes on a quantum-gravity-induced anisotropic background, linking quantum fluctuations to observable phenomena.

Findings

Massive modes experience anisotropic Bianchi type I backgrounds.

Quantum fluctuations influence the dressed metric for field propagation.

Particle production could significantly affect early universe dynamics.

Abstract

Quantum theory of a test field on a quantum cosmological spacetime may be viewed as a theory of the test field on an emergent classical background. In such a case, the resulting dressed metric for the field propagation is a function of the quantum fluctuations of the original geometry. When the backreaction is negligible, massive modes can experience an anisotropic Bianchi type I background. The field modes propagating on such a quantum-gravity-induced spacetime can then unveil interesting phenomenological consequences of the super-Planckian scales, such as gravitational particle production. The aim of this paper is to address the issue of gravitational particle production associated to the massive modes in such an anisotropic dressed spacetime. By imposing a suitable adiabatic condition on the vacuum state and computing the energy density of the created particles, the significance of the particle production on the dynamics of the universe in Planck era is discussed.