False Vacuum Decay With Gravity in Non-Thin-Wall Limit

TL;DR

This paper introduces a wave-function approach to false vacuum decay with gravity, providing a new method that effectively handles thick-wall bubbles and offers clearer interpretation of instantons, surpassing traditional Euclidean path-integral techniques.

Contribution

A novel wave-function based method for calculating tunneling amplitudes in false vacuum decay with gravity, applicable to thick-wall scenarios and offering improved interpretability.

Findings

Method agrees with Euclidean path-integral results in thin-wall limit

Capable of analyzing thick-wall bubble nucleation

Provides insights into boundary conditions of the wave function

Abstract

We consider a wave-function approach to the false vacuum decay with gravity and present a new method to calculate the tunneling amplitude under the WKB approximation. The result agrees with the one obtained by the Euclidean path-integral method, but gives a much clearer interpretation of an instanton (Euclidean bounce solution) that dominates the path integral. In particular, our method is fully capable of dealing with the case of a thick wall with the radius of the bubble comparable to the radius of the instanton, thus surpassing the path-integral method whose use can be justified only in the thin-wall and small bubble radius limit. The calculation is done by matching two WKB wave functions, one with the final state and another with the initial state, with the wave function in the region where the scale factor of the metric is sufficiently small compared with the inverse of the typical energy scale of the field potential at the tunneling. The relation of the boundary condition on our wave function for the false vacuum decay with Hartle-Hawking's no-boundary boundary condition and Vilenkin's tunneling boundary condition on the wave function of the universe is also discussed.