Intersecting branes and adding flavors to the Maldacena-Nunez background

TL;DR

The work develops a holographic approach to include fundamental flavors in the Maldacena–Nuñez background by introducing a small number of spacetime-filling D-branes (D9) or intersecting D5′-branes. Since flavors arise from open strings, the authors emphasize the need to twist the spectrum using open-string charge, proposing a specific identification of U(1) charges that yields 4d $N=1$ gauge theories with fundamental matter in the probe limit. They analyze the flat-spectrum content, the necessary twists, and the geometric implications in the MN background, showing that D5′-branes can serve as probe flavors while D9-branes pose tadpole considerations that may require additional ingredients for consistency. The results indicate that the MN background can holographically realize non-chiral SQCD with fundamental quarks, with the open-string sector playing a crucial role in both the spectrum and stability via KK-mode dynamics on the wrapped cycles. The approach opens avenues for studying meson spectra and chiral symmetry within these flavored holographic setups, while highlighting technical challenges such as tadpole cancellation and backreaction beyond the probe limit.

Abstract

We study adding flavors into the Maldacena-Nŭnez background. It is achieved by introducing spacetime filling D9-branes or intersecting D5$'$-branes into the background with a wrapping D5-brane. Both D9-branes and D5$'$-branes can be spacetime filling from the 5D bulk point of view. At the probe limit it corresponds to introducing non-chiral fundamental flavors into the dual N=1 SYM. We propose a method to twist the fundamental flavor which has to involve open string charge. It reflects the fact that coupling fundamental matter to SYM in the dual string theory corresponds to adding an open string sector