On the choice of the collapse operator in cosmological Continuous Spontaneous Localisation (CSL) theories

TL;DR

This paper investigates the impact of the collapse operator choice in cosmological CSL theories, concluding that a linear, odd operator in field variables is necessary for consistent wavefunction collapse and Gaussian measurement outcomes.

Contribution

It constrains the form of the collapse operator in cosmological CSL theories, advocating for a linear, odd operator based on generic and measurement considerations.

Findings

Even operators cannot induce collapse.

Odd operators with linearity produce Gaussian statistics.

Results inform the selection of collapse operators in cosmology.

Abstract

The Continuous Spontaneous Localisation (CSL) theory in the cosmological context is subject to uncertainties related to the choice of the collapse operator. In this paper, we constrain its form based on generic arguments. We show that, if the collapse operator is even in the field variables, it is unable to induce the collapse of the wavefunction. Instead, if it is odd, we find that only linear operators are such that the outcomes are distributed according to Gaussian statistics, as required by measurements of the cosmic microwave background. We discuss implications of these results for previously proposed collapse operators. We conclude that the cosmological CSL collapse operator should be linear in the field variables.