Spectral flow on the Higgs branch and AdS/CFT duality

We use AdS/CFT duality to study the large Nc limit of the meson spectrum on the Higgs branch of a strongly coupled, = 2 supersymmetric SU(Nc) gauge theory with Nf = 2 fundamental hypermultiplets. In the dual supergravity description, the Higgs branch is described by SU(2) instanton configurations on D7-branes in an AdS background. We compute the spectral flow parameterized by the size of a single instanton. In the large Nc limit, there is a sense in which the flow from zero to infinite instanton size, or Higgs VEV, can be viewed as a closed loop. We show that this flow leads to a non-trivial rearrangement of the spectrum.