Decoherence of scalar cosmological perturbations

TL;DR

This paper investigates how quantum decoherence affects scalar cosmological perturbations, showing that interactions during inflation make these fluctuations classical, impacting the interpretation of cosmic background radiation observations.

Contribution

It demonstrates that scalar-tensor interactions during inflation induce sufficient decoherence to classicalize scalar fluctuations, affecting cosmological data analysis.

Findings

Scalar-tensor interactions cause decoherence of scalar fluctuations.

Decoherence renders scalar perturbations effectively classical.

Implications for interpreting cosmic background radiation data.

Abstract

In this paper we analyze the possibility of detecting nontrivial quantum phenomena in observations of the temperature anisotropy of the cosmic background radiation (CBR), for example, if the Universe could be found in a coherent superposition of two states corresponding to different CBR temperature self-correlations. Such observations are sensitive to scalar primordial fluctuations but insensitive to tensor fluctuations, which are therefore converted into an environment for the former. Even for a free inflaton field minimally coupled to gravity, scalar-tensor interactions induce enough decoherence among histories of the scalar fluctuations as to render them classical under any realistic probe of their amplitudes.