branelocalized

Branelocalized, or brane-localized, refers to fields or interactions that are confined to a brane—a lower-dimensional hypersurface embedded in a higher-dimensional spacetime. In many braneworld scenarios inspired by string theory, standard model particles and forces are assumed to be branelocalized, meaning they propagate primarily along the four-dimensional worldvolume of the brane, while gravity and possibly other fields can extend into the surrounding extra dimensions (the bulk).

Mechanisms for localization include the dynamics of open versus closed strings in string theory, where gauge fields and matter arising from open strings end on D-branes and thus are confined to the brane. In field-theoretical approaches, localization can occur through topological defects, such as domain walls, or through potential wells in extra dimensions that trap zero modes of fields near the brane. These mechanisms determine how strongly branelocalized fields interact with bulk fields and how their Kaluza-Klein excitations behave.

The branelocalized picture has several phenomenological implications. It offers a potential framework to address hierarchy problems by separating gravity from the standard model fields in extra dimensions. The presence of bulk gravity leads to a tower of Kaluza-Klein gravitons and possibly other bulk modes, which can modify Newtonian gravity at short distances and produce distinctive collider signatures. Models such as the Randall–Sundrum brane-worlds and large extra dimensions (ADD) exemplify branelocalization concepts, as do various string-theoretic constructions with SM fields confined to D-branes.

Challenges include ensuring stable localization, controlling backreaction on the geometry, and meeting experimental constraints from precision gravity tests and collider data.