Decoherence in the cosmic background radiation

TL;DR

This paper investigates whether quantum effects in the cosmic background radiation's temperature anisotropies can be detected, and finds that scalar-tensor interactions cause decoherence, making scalar fluctuations appear classical.

Contribution

It demonstrates that scalar-tensor interactions induce sufficient decoherence in scalar fluctuations, rendering them classical and affecting the detectability of quantum phenomena in CBR observations.

Findings

Scalar-tensor interactions cause decoherence of scalar fluctuations.

Decoherence makes scalar fluctuations appear classical.

Quantum effects in CBR are challenging to detect due to decoherence.

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 temperatures. 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.