SU(5) grand unification on a domain-wall brane from an E6-invariant action

An SU(5) grand unification scheme for effective 3+1-dimensional fields dynamically localized on a domain-wall brane is constructed. This is achieved through the confluence of the clash-of-symmetries mechanism for symmetry breaking through domain-wall formation, and the Dvali-Shifman gauge-boson localization idea. It requires an E6 gauge-invariant action, yielding a domain-wall solution that has E6 broken to differently embedded SO(10) U(1) subgroups in the two bulk regions on opposite sides of the wall. On the wall itself, the unbroken symmetry is the intersection of the two bulk subgroups, and contains SU(5). A 4+1-dimensional fermion family in the 27 of E6 gives rise to localized left-handed zero modes in the 5* 10 1 1 representation of SU(5). The remaining ten fermion components of the 27 are delocalized exotic states, not appearing in the effective 3+1-dimensional theory on the domain-wall brane. The scheme is compatible with the type-2 Randall-Sundrum mechanism for graviton localization; the single extra dimension is infinite.