Effective Action and Soft Supersymmetry Breaking for Intersecting D-brane Models

TL;DR

This work develops a general framework to analyze spontaneous SUSY breaking in hidden sectors of N=1 orientifold compactifications with intersecting D-branes, deriving the four-dimensional effective action and soft terms without specifying the breaking mechanism. It provides explicit expressions for the Kähler potential components $\hat{\cal K}$, $\tilde{\cal K}^{[aa]}$, and $\tilde{\cal K}^{[ab]}$, and for the gauge kinetic functions $f_a$, showing how flux and brane data enter the moduli dependence through $s,t_m,u_m$ and flux-related quantities $\Delta_a^{(m)}$ and $\nu_{ab}^{(m)}$. Soft breaking parameters are then computed in the standard SUGRA way, yielding gaugino masses $M_a$, scalar masses, and trilinears $A^0_{\alpha\beta\gamma}$ that depend on the auxiliary fields $F^I$ and on the moduli; simplifications occur in aligned modulus limits where gaugino masses become universal. The analysis reveals that gauge coupling unification is not automatic and only arises in restricted regions of moduli space, while FCNC, CP violation, EDMs, and dark matter appear with a rich but controllable dependence on intersection angles and flux. Overall, the work provides a practical bridge between intersecting D-brane constructions and low-energy phenomenology, with explicit formulas ready for confrontation with data.

Abstract

We consider a generic scenario of spontaneous breaking of supersymmetry in the hidden sector within N=1 supersymmetric orientifold compactifications of type II string theories with D-branes that support semi-realistic chiral gauge theories. The soft breaking terms in the visible sector of the models are computed in a standard way without specifying the breaking mechanism, which leads to expressions that generalize those formerly known for heterotic or type I string models. The elements of the effective tree level supergravity action relevant for this, such as the Kahler metric for the matter fields, the superpotential of the visible sector and the gauge kinetic functions, are specified by dimensional reduction and duality arguments. As phenomenological applications we argue that gauge coupling unification can only occur in special regions of the moduli space; we show that flavor changing neutral currents can be suppressed sufficiently for a wide range of parameters, and we briefly address the issues of CP violation, electric dipole moments and dark matter, as well.