Domain wall (string theory)
In string theory, a domain wall is a theoretical -dimensional singularity. A domain wall is meant to represent an object of codimension one embedded into space. For example, D8-branes are domain walls in type II string theory. In M-theory, the existence of Horava–Witten domain walls, "ends of the world" that carry an E8 gauge theory, is important for various relations between superstring theory and M-theory.
If domain walls exist, their interactions are hypothesized to emit gravitational waves that would be detectable by LIGO and similar experiments.
