Cosmic Decoherence: Massive Fields

TL;DR

This paper investigates how massive fields decohere during inflation, showing that heavy fields tend to stay quantum while lighter fields decohere quickly, impacting inflationary quantum information studies.

Contribution

It provides a detailed analysis of decoherence rates for massive fields during inflation using the density matrix approach and one-loop calculations.

Findings

Heavy fields with mass ≥ H remain quantum and do not decohere easily.

Light fields with mass < H decohere within 5-10 e-folds after Hubble crossing.

Decoherence behavior depends on the mass relative to the Hubble scale.

Abstract

We study the decoherence of massive fields during inflation based on the Zurek's density matrix approach. With the cubic interaction between inflaton and massive fields, the reduced density matrix for the massive fields can be calculated in the Schr\"odinger picture which is related to the variance of the non-Gaussian exponent in the wave functional. The decoherence rate is computed in the one-loop form from functional integration. For heavy fields with $m\gtrsim \mathcal{O}(H)$, quantum fluctuations will easily stay in the quantum state and decoherence is unlikely. While for light fields with mass smaller than $\mathcal{O}(H)$, quantum fluctuations are easily decohered within $5\sim10$ e-folds after Hubble crossing. Thus heavy fields can play a key role in studying problems involving inflationary quantum information.