Inflationary Cosmology as a Probe of Primordial Quantum Mechanics

TL;DR

This paper proposes that inflationary cosmology can test quantum mechanics at early universe scales, especially for hidden-variable theories like pilot-wave, by examining potential anomalies in cosmic microwave background power spectra.

Contribution

It demonstrates how inflation can transfer microscopic quantum nonequilibrium to observable scales, providing a novel way to test hidden-variable theories against cosmological data.

Findings

Inflation can produce observable signatures of quantum nonequilibrium in the CMB.

Nonequilibrium may cause scale invariance breaking in the primordial power spectrum.

Possible explanation for large-scale low-power anomalies in the CMB.

Abstract

We show that inflationary cosmology may be used to test the statistical predictions of quantum theory at very short distances and at very early times. Hidden-variables theories, such as the pilot-wave theory of de Broglie and Bohm, allow the existence of vacuum states with non-standard field fluctuations ('quantum nonequilibrium'). We show that inflationary expansion can transfer microscopic nonequilibrium to macroscopic scales, resulting in anomalous power spectra for the cosmic microwave background. The conclusions depend only weakly on the details of the de Broglie-Bohm dynamics. We discuss, in particular, the nonequilibrium breaking of scale invariance for the primordial (scalar) power spectrum. We also show how nonequilibrium can generate primordial perturbations with non-random phases and inter-mode correlations (primordial non-Gaussianity). We address the possibility of a low-power anomaly at large angular scales, and show how it might arise from a nonequilibrium suppression of quantum noise. Recent observations are used to set an approximate bound on violations of quantum theory in the early universe.