Creation of massive particles in a tunneling universe

TL;DR

This paper investigates particle creation during quantum tunneling in cosmology, showing that particle production is minimal and the universe's creation from nothing can be viewed as tunneling from a small recollapsing universe.

Contribution

It introduces a semiclassical wave function for tunneling in quantum cosmology with a massive scalar field, demonstrating minimal particle creation and justifying the semiclassical approximation.

Findings

Particle production is small during tunneling.

Quantum states remain close to the adiabatic vacuum.

Backreaction on the metric is negligible.

Abstract

We examine the particle production during tunneling in quantum cosmology. We consider a minisuperspace model with a massive, conformally coupled scalar field and a uniform radiation background. In this model, we construct a semiclassical wave function describing a small recollapsing universe and a nucleated inflating universe (``tunneling from something''). We find that the quantum states of the scalar field in both the initial and the nucleated universe are close to the adiabatic vacuum, the number of created particles is small, and their backreaction on the metric is negligible. We show that the use of the semiclassical approximation is justified for this wave function. Our results imply that the creation of the universe from nothing can be understood as a limit of tunneling from a small recollapsing universe.