Gravitation and tunnelling: Subtleties of the thin-wall approximation and rapid decays

TL;DR

This paper explores how gravitation and technical subtleties influence tunneling decay rates in scalar potentials, revealing that many instantons decay faster than previously thought, challenging assumptions about the longevity of de Sitter vacua.

Contribution

It clarifies the conditions under which the thin-wall approximation is valid and uncovers that decay rates are often underestimated in prior models, especially for potentials with small differences between maxima and minima.

Findings

Decay rates for thin-wall instantons are much larger than Coleman-de Luccia predictions.

Potentials with small differences between maxima and minima decay rapidly.

The thin-wall approximation is valid only under specific conditions, often overlooked.

Abstract

I provide some simple physical arguments that, once gravitation and some subtleties are taken into account, rather broad classes of potentials result in instantons which tunnel relatively rapidly between perturbatively stable minima. In particular, due to some previously unappreciated technical subtleties, the decay rates for instantons which may be well-described as thin-wall are much larger than the usual Coleman-de Luccia result. I discuss with some level of rigor when the thin-wall approximation holds and clarify some misconceptions regarding the application of this approximation and its meaning. I also point out potentials involving small differences between the maxima and minima generically decay relatively rapidly. These two classes of potentials include those usually used to argue for the existence of a string landscape and in light of these results it is not clear that de Sitter vacua presently understood will generically be cosmologically long-lived.