Stability of marginally outer trapped surfaces and existence of marginally outer trapped tubes

The present work extends our short communication [1]. For smooth marginally outer trapped surfaces (MOTS) in a smooth spacetime we define stability with respect to variations along arbitrary vectors v normal to the MOTS. After giving some introductory material about linear non self-adjoint elliptic operators, we introduce the stability operator Lv and we characterize stable MOTS in terms of sign conditions on the principal eigenvalue of Lv. The main result shows that given a strictly stable MOTS S0 ⊂ Σ0 in a spacetime with a reference foliation Σt, there is an open marginally outer trapped tube (MOTT), adapted to the reference foliation, which contains S0. We give conditions under which the MOTT can be completed. Finally, we show that under standard energy conditions on the spacetime, the MOTT must be either locally achronal, spacelike or null.