SUSY breaking mediation by D-brane instantons

TL;DR

<p>We introduce a novel mechanism for SUSY-breaking mediation in string theory: D-brane (instantonic) mediation, where Euclidean D-branes stretched between hidden and visible sectors generate non-perturbative operators that communicate SUSY breaking across sector boundaries. The framework is developed in Type IIB toroidal orientifolds, with explicit analysis of E3-brane instantons and their zero-mode structure, yielding superpotential and Kähler corrections that produce soft terms in the visible sector. Concrete examples include a Polonyi hidden sector realized via an E3 instanton and a full ZZ_3 orientifold model demonstrating mediation of SUSY breaking through instanton-induced A-terms, with detailed discussion of volumes, hierarchies, and tadpole cancellations. The work also discusses phenomenological implications, notably the potential misalignment between instanton-generated A-terms and non-perturbative Yukawas, and proposes ways to broaden instanton orientation to realize aligned or diagonalizable soft terms, highlighting the role of geometry in shaping mediation.</p>

Abstract

It is well known that D-brane instantons can generate contributions to the effective superpotential of gauge theories living on D-branes which are perturbatively forbidden by global U(1) symmetries. We extend this idea to theories with supersymmetry breaking, studying the effect of D-brane instantons stretched between the SUSY-breaking and visible sectors. Analogously to what happens in the SUSY case, this mechanism can give rise to perturbatively forbidden soft terms (among other effects). We introduce and discuss general properties of instanton mediation. We illustrate our ideas in simple Type IIB toroidal orientifolds. As a bi-product, we present a string theory realization of a Polonyi hidden sector.

Figures (7)

• Figure 1: Extended quiver diagram for the basic E-brane configuration that generates a superpotential contribution. Dotted arrows indicate charged fermionic zero modes. The figure presents the simplest case, in which the fermionic zero modes couple to a single bifundamental field between a pair of nodes. In the generic situation, charged zero modes can couple to more general operators, associated with an open path in the quiver.
• Figure 2: The basic configuration for mediation. It consists of visible and hidden sectors $V$ and $H$, their orientifold images $V'$ and $H'$, and and O-plane $O$. All of them are intersected by a Euclidean D-brane, depicted in yellow.
• Figure 3: Extended quiver diagram for the basic mediating configuration. Dotted arrows indicate charged fermionic zero modes. The figure presents the simplest case in which these fermionic zero modes couple to single bifundamental fields between pairs of nodes in the visible and hiden sectors. Generically, charged zero modes can couple to more general operators, associated with open paths in the quiver.
• Figure 4: The basic configuration realizing a Polonyi model. It consists of an O3-plane and a D3-brane away from it, connected by a finite size E3-brane with $O(1)$ CP projection.
• Figure 5: A Polonyi model is also obtained when two D3-branes sit on top of an O3-plane. A finite size E3-brane with $O(1)$ CP projection generates the superpotential.