Flavor hierarchy from extra dimension and gauge threshold correction Original Research Article

Dynamical quasi-localization of matter fields in extra dimension is an elegant mechanism to generate hierarchical 4-dimensional Yukawa couplings. We point out that a bulk matter field whose zero mode is quasi-localized can give a large Kaluza–Klein threshold correction to low energy gauge couplings, which is generically of the order of ln(Yukawa)/8π2, so it can significantly affect gauge coupling unification. We compute such threshold corrections in generic 5-dimensional theories compactified on S1/Z2×Z2, and apply the result to grand unified theories on orbifold generating small Yukawa couplings through quasi-localization.