Fluctuation energies in quantum cosmology

TL;DR

This paper explores how quantum fluctuations influence energy in quantum cosmology, affecting density bounds and stability, and demonstrates the effectiveness of effective methods through comparisons and extensions.

Contribution

It provides an effective framework for analyzing quantum fluctuations in loop quantum cosmology, including comparisons with numerical results and extensions to squeezed states.

Findings

Effective methods accurately describe quantum fluctuations.

Quantum fluctuations can cancel holonomy modifications.

Comparison confirms the reliability of canonical effective approaches.

Abstract

Quantum fluctuations or other moments of a state contribute to energy expectation values and can imply interesting physical effects. In quantum cosmology, they turn out to be important for a discussion of density bounds and instabilities of initial-value problems in the presence of signature change in loop-quantized models. This article provides an effective description of these issues, accompanied by a comparison with existing numerical results and an extension to squeezed states. The comparison confirms that canonical effective methods are well-suited for computations of properties of physical states. As a side product, an example is found for a simple state in which quantum fluctuations can cancel holonomy modifications of loop quantum cosmology.