MG12 - Talk detail
 

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Abstract

Vacuum thin-shell solutions in five-dimensional Lovelock theory of gravity

We discuss junction conditions for vacuum solutions in Einstein-Gauss-Bonnet gravity in five-dimensions. These come from considering boundary terms in the Lovelock action. 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. For those cases, new global structures with surprising features are seen to arise. In particular, we show that vacuum spherically symmetric wormholes do exist in this theory. These can be regarded as gravitational solitons connecting two asymptotically (Anti) de-Sitter spaces.

Weyl's tube formula and gravity

It is often stated that the most natural generalisation of GR in higher dimensions is Lovelock's theory. They share many physical properties. But there are also key differences and problems, such as the breakdown of determinism which can occur when when the matrix of coefficients of second time derivatives of the metric degenerates. This can be avoided by imposing inequalities on the curvature. Here it is argued that such inequalities occur naturally if the Lovelock action is obtained from Weyl's formulae for the volume and surface area of a tube. In this talk I will give a treatment of the Weyl tube formula in terminology familiar to relativists and to give an appropriate (straightforward) generalisation to a tube embedded in Minkowski space.

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