Domain wall (string theory)

{{Short description|Theoretical (d−1)-dimensional singularity}}

{{Other uses|Domain wall}}

{{string theory}}

In string theory, a domain wall is a theoretical (d−1)-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, their interactions are hypothesized to emit gravitational waves that would be detectable by LIGO and similar experiments.{{cite journal |arxiv=1602.03901 |doi=10.1103/PhysRevD.94.103519 |title=Hearing the signal of dark sectors with gravitational wave detectors |date=2016 |last1=Jaeckel |first1=Joerg |last2=Khoze |first2=Valentin V. |last3=Spannowsky |first3=Michael |journal=Physical Review D |volume=94 |issue=10 |page=103519 |bibcode=2016PhRvD..94j3519J }}