Meson Spectroscopy in AdS/CFT with Flavour

TL;DR

The paper analyzes mesons in an N=2 gauge theory with dynamical quarks using the AdS/CFT framework by embedding a D7-brane in AdS5×S5. It derives the full meson spectrum from quadratic fluctuations of the D7-brane worldvolume fields (spin-0 and spin-1) and complements this with a semiclassical treatment of high-spin mesons via rotating open strings, revealing a mass gap scale m_q/√(g_sN) and Regge behavior for moderate spin transitioning to Coulombic binding at large spin. An unexpected SO(5) structure appears in the free spectrum, with implications for representation content and operator mappings, while interactions and baryons are discussed through higher-order DBI terms and a D5-brane baryon vertex, respectively. The work connects meson dynamics to both the quark-antiquark potential and broader string-theoretic constructs, offering predictions and insights into flavor physics in holographic contexts.

Abstract

We compute the meson spectrum of an N=2 super Yang-Mills theory with fundamental matter from its dual string theory on AdS_5 x S_5 with a D7-brane probe. For scalar and vector mesons with arbitrary R-charge the spectrum is computed in closed form by solving the equations for D7-brane fluctuations; for matter with non-zero mass m_q it is discrete, exhibits a mass gap of order m_q / sqrt(g_s N) and furnishes representations of SO(5) even though the manifest global symmetry of the theory is only SO(4). The spectrum of mesons with large spin J is obtained from semiclassical, rotating open strings attached to the D7-brane. It displays Regge-like behaviour for J << sqrt(g_s N), whereas for J >> sqrt(g_s N) it corresponds to that of two non-relativistic quarks bound by a Coulomb potential. Meson interactions, baryons and `giant gauge bosons' are briefly discussed.