Inflationary quantum dynamics and backreaction using a classical-quantum correspondence

TL;DR

This paper investigates how quantum fluctuations influence inflationary dynamics using a classical-quantum correspondence, revealing a wavelength-dependent backreaction that can either stabilize or destabilize inflation.

Contribution

It introduces a novel approach employing classical-quantum correspondence to analyze quantum backreaction during inflation, highlighting a wavelength threshold effect.

Findings

Quantum backreaction renormalizes the Hubble parameter for long wavelengths.

Short-wavelength modes can destabilize inflation.

The classical-quantum correspondence aligns with traditional semiclassical methods.

Abstract

We study inflationary dynamics using a recently introduced classical-quantum correspondence for investigating the backreaction of a quantum mechanical degree of freedom to a classical background. Using specifically a coupled Einstein-Klein-Gordon system, an approximation that holds well during the very early inflationary era when modes are very deep inside the Hubble horizon, we show that the backreaction of a mode of the quantum field will renormalize the Hubble parameter only if the mode's wavelength is longer than some threshold Planckian length scale. Otherwise, the mode will destabilize the inflationary era. We also present an approximate analytical solution that supports the existence of such short-wavelength threshold and compare the results of the classical-quantum correspondence with the traditional perturbative-iterative method in semiclassical gravity.