Black string

A black string is a higher dimensional ("D">4) generalization of a black hole in which the event horizon is topologically equivalent to "S"² × "S"¹ and spacetime is asymptotically "M"^"d"−1 × "S"¹.

Perturbations of black string solutions were found to be unstable for "L" (the length around "S"¹) greater than some theshold "L"′. The full non-linear evolution of a black string beyond this theshold might result in a black string breaking up into separate black holes which would coalesce into a single black hole. This scenario seems unlikely because it was realized a black string could not pinch off in finite time, shrinking "S"² to a point and then evolving to some Kaluza-Klein black hole. When perturbed, the black string would settle into a stable, static non-uniform black string state.