Proton decay, Yukawa couplings and underlying gauge symmetry in string theory Original Research Article

In string theory, massless particles often originate from a symmetry breaking of a large gauge symmetry G to its subgroup H. The absence of dimension-4 proton decay in supersymmetric theories suggests that image are different from image in their origins. In this article, we consider a possibility that they come from different irreducible components in image. Requiring that all the Yukawa coupling constants of quarks and leptons be generated from the super-Yang–Mills interactions of G, we found in the context of Georgi–Glashow image unification that the minimal choice of G is image and image is the only alternative. This idea is systematically implemented in heterotic String, M theory and F theory, confirming the absence of dimension 4 proton decay operators. Not only image but also G constrain operators of effective field theories, providing non-trivial information.