Mechanism for the suppression of quantum noise at large scales on expanding space

TL;DR

This paper introduces an exactly-solvable model demonstrating how the expansion of space can naturally suppress quantum noise at large scales, potentially explaining large-scale features in the cosmic microwave background.

Contribution

It provides a novel analytical solution showing suppression of quantum noise in expanding space within the pilot-wave quantum framework, linking it to cosmological observations.

Findings

Suppression of quantum noise occurs at super-Hubble scales.

Expansion causes a retardation of relaxation to the Born rule.

Potential explanation for large-scale power deficits in the CMB.

Abstract

We present an exactly-solvable model for the suppression of quantum noise at large scales on expanding space. The suppression arises naturally in the de Broglie-Bohm pilot-wave formulation of quantum theory, according to which the Born probability rule has a dynamical origin. For a scalar field on a radiation-dominated background we construct the exact solution for the time-evolving wave functional and study properties of the associated field trajectories. It is shown that the time evolution of a field mode on expanding space is mathematically equivalent to that of a standard harmonic oscillator with a 'retarded time' that depends on the wavelength of the mode. In the far super-Hubble regime the equivalent oscillator evolves over only one Hubble time, yielding a simple mechanism whereby relaxation to the Born rule can be suppressed on very large scales. We present numerical simulations illustrating how the expansion of space can cause a retardation of relaxation in the super-Hubble regime. Given these results it is natural to expect a suppression of quantum noise at super-Hubble wavelengths. Such suppression could have taken place in a pre-inflationary era, resulting in a large-scale power deficit in the cosmic microwave background.