Gravitational solitons and $C^0$ vacuum metrics in five-dimensional Lovelock gravity

TL;DR

This paper explores vacuum solutions and gravitational solitons in five-dimensional Lovelock gravity, revealing new global structures like wormholes and analyzing their stability, existence, and uniqueness.

Contribution

It introduces a method of geometric surgery for constructing $C^0$ vacuum solutions, including novel wormhole solutions, in five-dimensional Lovelock gravity.

Findings

Vacuum spherically symmetric wormholes exist in the theory.

New global structures with surprising features are identified.

A new type of instability in the theory is discussed.

Abstract

Junction conditions for vacuum solutions in five-dimensional Einstein-Gauss-Bonnet gravity are studied. We focus on those cases where two spherically symmetric regions of space-time are joined in such a way that the induced stress tensor on the junction surface vanishes. So a spherical vacuum shell, containing no matter, arises as a boundary between two regions of the space-time. A general analysis is given of solutions that can be constructed by this method of geometric surgery. Such solutions are a generalized kind of spherically symmetric empty space solutions, described by metric functions of the class $C^0$. New global structures arise with surprising features. In particular, we show that vacuum spherically symmetric wormholes do exist in this theory. These can be regarded as gravitational solitons, which connect two asymptotically (Anti) de-Sitter spaces with different masses and/or different effective cosmological constants. We prove the existence of both static and dynamical solutions and discuss their (in)stability under perturbations that preserve the symmetry. This leads us to discuss a new type of instability that arises in five-dimensional Lovelock theory of gravity for certain values of the coupling of the Gauss-Bonnet term. The issues of existence and uniqueness of solutions and determinism in the dynamical evolution are also discussed.