Inspired by the model of Jarvinen and Kiritsis, we present a simple holographic model for the onset of chiral symmetry breaking at the edge of the conformal window in QCD in the Veneziano limit. Our most naive model enforces the QCD two-loop running coupling on a D3/D7 holographic brane system. The mass of the holographic field, describing the chiral condensate in the model, is driven below the Breitenlohner-Freedman bound when the running is sufficiently strong, triggering chiral symmetry breaking for $N_f/N_c<2.9$. This model though contains too great a remnant of supersymmetry and does not correctly encode the perturbative anomalous dimensions of QCD. In a second model we impose the QCD anomalous dimension result and find chiral symmetry breaking sets in for $N_f/N_c=4$ at a Berezinsky-Kosterlitz-Thouless–type phase transition. In this case the transition is triggered when the anomalous dimension of the mass operator ${\gamma }_m=1$.

• Received 25 April 2012

DOI:https://doi.org/10.1103/PhysRevD.86.026008