The standard model on a domain-wall brane?

Abstract

We propose a 4+1-dimensional action that is a candidate for realising a standard-model-like effective theory for fields dynamically localised to a domain-wall brane. Our construction is based in part on the conjecture that the Dvali-Shifman mechanism for dynamically localising gauge bosons works correctly in 4+1-d. Assuming this to be so, we require the gauge symmetry to be SU(5)in the bulk, spontaneously breaking to SU(3)xSU(2)xU(1) inside the domain wall, thus dynamically localising the standard model gauge bosons provided that the SU(5) theory in the bulk exhibits confinement. The wall is created jointly by a real singlet-Higgs field eta configured as a kink, and an SU(5) adjoint-Higgs field chi that takes nonzero values inside the wall. Chiral 3+1-dimensional quarks and leptons are confined and split along the bulk direction via their Yukawa couplings to eta and chi. The Higgs doublet and its colour triplet SU(5) partner are similarly localised and split. The splittings suppress coloured-Higgs-induced proton decay and, because of the different localisation profiles, the usual SU(5) mass relation m_e = m_d does not arise. Localised gravity is generated via the Randall-Sundrum alternative to compactification.