Creation of wormholes by quantum tunnelling in modified gravity theories

TL;DR

This paper investigates how quantum tunnelling in scalar-tensor theories with non-minimal coupling can produce wormholes via gravitational instantons with necks, revealing new geometric features and energy condition violations.

Contribution

It demonstrates that non-minimal coupling allows gravitational instantons to develop necks, leading to wormhole formation, which is not possible in minimally coupled theories.

Findings

Instantons with necks can materialize wormholes.

Neck geometries are linked to null energy condition violations.

A bound on neck size relative to instanton size is derived.

Abstract

We study the process of quantum tunnelling in scalar-tensor theories in which the scalar field is non-minimally coupled to gravity. In these theories gravitational instantons can deviate substantially from sphericity and can in fact develop a neck - a feature prohibited in theories with minimal coupling. Such instantons with necks lead to the materialisation of bubble geometries containing a wormhole region. We clarify the relationship of neck geometries to violations of the null energy condition, and also derive a bound on the size of the neck relative to that of the instanton.