Conformal symmetries and MOTS stability

Abstract

Let $\{\hat{I}{\pounds }_t\}$ be a spacelike foliation of a spacetime $\mathcal{M}$, and suppose each $\hat{I}{\pounds }_t$ is foliated by 2-surfaces $\mathcal{S}$ with spacelike unit normal in $\hat{I}{\pounds }_t$. We show that under mild energy conditions, a MOTS $\mathcal{S}$ that intersects integral curves of past-pointing conformal Killing vector field lying in the normal space of $\mathcal{S}$ is strictly stable and evolves smoothly to a spacelike horizon. We also show that if the restriction of the divergence of the vector field to $\mathcal{S}$ is non-negative, $\mathcal{S}$ is unstable, and if negative and $\mathcal{S}$ is a 2-sphere, $\mathcal{S}$ must be strictly stable.

8 pages, 3 figures, two-column format, comments welcome