# Quantum instability of an oscillating universe

## TL;DR

This paper investigates the quantum stability of an oscillating universe model with a scalar field, showing that quantum instabilities prevent stable stationary states under certain conditions.

## Contribution

It demonstrates that quantum instabilities, beyond previously known effects, hinder the existence of localized stationary states in an oscillating universe with a scalar field.

## Key findings

- Quantum instability prevents stationary states with localized wave functions.
- Previous sources of instability like particle production are assumed absent.
- The analysis is based on solutions to the Wheeler-DeWitt equation.

## Abstract

An oscillating, compact Friedmann universe with a massive conformally coupled scalar field is studied in the framework of quantum cosmology. The scalar field is treated as a perturbation and we look for solutions of the Wheeler-DeWitt equation describing stable stationary states of the model. We assume that the previous sources of quantum instability that have been discussed in the literature (particle production, and tunnelling to zero size) are absent. We then show, under rather general assumptions, that a further source of quantum instability prevents the existence of stationary states with localized wave function in the direction of the scalar-field modes.