Symmetry Breaking and Axionic Strings in the Warped Deformed Conifold

TL;DR

The paper shows that D-strings at the bottom of the KS warped deformed conifold are axionic strings in the dual cascading gauge theory, hosting a massless pseudoscalar glueball as the Goldstone boson of spontaneously broken U(1)B on the baryonic branch. It derives a linearized 2-form perturbation in KS that yields a normalizable zero-mode, identifies its SUSY partner as a scalar mode arising from a mixed NS-NS 2-form and metric perturbation, and argues these modes reflect baryonic-branch physics. The work connects the gravity-side Goldstone mechanism to operator expectations of baryon condensation, discusses the Higgs phase upon compactification, and explores non-commutative deformations via a double T-duality, with implications for cosmology and future SUSY backgrounds. Overall, it substantiates a baryonic-branch interpretation of the cascading theory and clarifies the dual role of D-strings as axionic/D-strings in the gauge/gravity correspondence.

Abstract

We interpret D-strings at the bottom of the warped deformed conifold as axionic strings in the dual cascading SU(N+M) x SU(N) gauge theory. The axion is a massless pseudo-scalar glueball which we find in the supergravity fluctuation spectrum and interpret as the Goldstone boson of spontaneously broken U(1) baryon number symmetry. The existence of this massless glueball, anticipated in hep-th/0101013, supports the idea that the cascading gauge theory is on the baryonic branch, i.e. the U(1)_B global symmetry is broken by expectation values of baryonic operators. We also find a massless scalar glueball, which is a superpartner of the pseudo-scalar. This scalar mode is a mixture of an NS-NS 2-form and a metric perturbation of the warped deformed conifold of a type first considered in hep-th/0012034.