Related papers: Realistic Yukawa Couplings through Instantons in I…
We introduce a new approach to investigate the selection rules governing the contributions of fluxed M5-instantons to the F-theory four-dimensional effective action, with emphasis on the generation of charged matter F-terms. The structure…
We discuss the role of the top-quark Yukawa coupling $y_t$ concerning the hierarchy problem and construct an alternative scheme to the conventional solutions with top partners. In traditional models, like SUSY or composite Higgs, top…
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…
We examine the flavor structure of the trilinear superpotential couplings which can result from embedding the Standard Model within D brane sectors in Type IIB orientifold models, which are examples within the Type I string framework. We…
We discuss non-perturbative corrections to the gauge kinetic functions in a four-dimensional N=2 gauge theory realized with a system of D7/D3-branes in a compactification of type I' theory on T_4/Z_2 x Z_2. The non-perturbative…
We present a conformal field theory calculation of four-point and three-point correlation functions for the bosonic twist fields arising at the intersections of D-branes wrapping (supersymmetric) homology cycles of Type II orientifold…
Supersymmetric configurations of type II D-branes with nonzero gauge field strengths in general supersymmetric backgrounds with nonzero B fields are analyzed using the kappa-symmetric worldvolume action. It is found in dimension four or…
We determine the instanton corrected hypermultiplet moduli space in type IIB compactifications near a Calabi-Yau conifold point where the size of a two-cycle shrinks to zero. We show that D1-instantons resolve the conifold singularity…
It is known that chiral fermions naturally appear at certain intersections of branes at angles. Motivated by this fact, we propose a string scenario in which different standard model gauge interactions propagate on different (intersecting)…
All five-dimensional non-abelian gauge theories have a $U(1)_I$ global symmetry associated with instantonic particles. We describe an obstruction to coupling $U(1)_I$ to a classical background gauge field that occurs whenever the theory has…
In this talk, gauge coupling evolution is analyzed in D-brane inspired models with two Higgs doublets and a U(3)xU(2)xU(1)^N gauge symmetry. In particular, we focus on D-brane configurations with two or three abelian factors. We find that…
We analyse the structure of Yukawa couplings in local SU(5) F-theory models with $E_8$ enhancement. In this setting the $E_8$ symmetry is broken down to SU(5) by a 7-brane configuration described by T-branes, all the Yukawa couplings are…
Hypermultiplet couplings in type IIA string theory on a Calabi-Yau space can be quantum corrected by D2-brane instantons wrapping special Lagrangian cycles. On the other hand, hypermultiplet couplings in the heterotic string on a K3 surface…
We discuss the structure of Yukawa couplings in D-brane models in which the SM fermion spectrum appears at the intersections of D-branes wrapping a compact space. In simple toroidal realistic examples one can explicitly compute the Yukawa…
Several dimensionful parameters needed for model building can be engineered in a certain class of SU(5) F-theory GUTs by adding extra singlet fields which are localized along pairwise intersections of D7-branes. The values of these…
We review the construction and phenomenology of intersecting brane worlds. The breaking of chiral and supersymmetry together with a reduction of gauge symmetry by introducing D-branes at generic angles into type I or type II string…
Unitarity constraints on anomalous top-Higgs couplings are examined. We also compare the unitarity constraints with the constraints from electroweak baryogenesis and electric dipole moments derived earlier.
We construct a large class of SU(5) orientifold vacua with tadpole cancellation both for the standard and the flipped case. We give a general analysis of superpotential couplings up to quartic order in orientifold vacua and identify the…
We examine the structure of the Yukawa couplings in the 11 dimensional Horava-Witten M-theory based on non-standard embeddings. We find that the CKM and quark mass hierarchies can be explained in M Theory without introducing undue fine…
In this talk, an alternative to top partner solutions and its consequences on phenomenology are discussed. The hierarchy problem from the top loop contribution is solved by mitigating the top Yukawa coupling at high scales. In this…