D6-brane splitting on type IIA orientifolds

Abstract

We study the open-string moduli of supersymmetric D6-branes, addressing both the string and field theory aspects of D6-brane splitting on type IIA orientifolds induced by open-string moduli higgsing (i.e., their obtaining VEVs). Specifically, we focus on the Z 2 × Z 2 orientifolds and address the symmetry breaking pattern for D6-branes parallel with the orientifold 6-planes as well as those positioned at angles. We demonstrate that the string theory results, i.e., D6-brane splitting and relocating in internal space, are in one to one correspondence with the field theory results associated with the higgsing of moduli in the antisymmetric representation of Sp ( 2 N ) gauge symmetry (for branes parallel with orientifold planes) or adjoint representation of U ( N ) (for branes at general angles). In particular, the moduli higgsing in the open-string sector results in the change of the gauge structure of D6-branes and thus changes the chiral spectrum and family number as well. As a by-product, we provide the new examples of the supersymmetric standard-like models with the electroweak sector arising from Sp ( 2 N ) L × Sp ( 2 N ) R gauge symmetry; and one four-family example is free of chiral Standard Model exotics.