Extremal and weakly trapped submanifolds in Generalized Robertson-Walker spacetimes

In this article we obtain new rigidity results for spacelike submanifolds of arbitrary codimension in Generalized Robertson-Walker spacetimes. Namely, under appropriate assumptions such as parabolicity we prove by means of some maximum principles that they must be contained in a spacelike slice. This enables us to characterize extremal and weakly trapped submanifolds in these ambient spacetimes.