Domain wall (string theory)

For other uses, see Domain wall (disambiguation).

In physics, a domain wall is any of several similar things in string theory, magnetism, or optics. These phenomena can all be generically described as topological solitons that occur whenever a discrete symmetry is spontaneously broken.

String theory

In string theory, a domain wall is a theoretical 2-dimensional singularity. A domain wall is meant to represent an object of codimension one embedded into space (a defect in space localized in one spatial dimension). 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, it seems plausible that they will violently emit gravitational waves if two such walls would collide. As the Laser Interferometer Gravitational-Wave Observatory and future observatories of its kind will search for direct evidence of gravitational waves, this phenomenon would be included as well in such searches.

See also

• Topological defect
• Cosmic string
• Membrane (M-theory)
• Gravitational singularity