T-branes and Yukawa couplings
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We consider various configurations of T-branes which are non-abelian bound states of branes and were recently introduced by Cecotti, Cordova, Heckman and Vafa. They are a refinement of the concept of monodromic branes featured in phenomenological F-theory models. We are particularly interested in the T-branes corresponding to Z 3 and Z 4 monodromies, which are used to break E 7 or E 8 gauge groups to SU(5) GUT . Our results imply that the up-type and down-type Yukawa couplings for the breaking of E 7 are zero, whereas up-type and down-type Yukawa couplings, together with right handed neutrino Yukawas are non-zero for the case of the breaking of E 8. The dimension four proton decay mediating term is avoided in models with either E 7 or E 8 breaking.
KeywordsF-Theory Intersecting branes models Supersymmetric gauge theory
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