Holographic spectral functions in metallic AdS/CFT

Abstract

We study the holographic D3/D7 setup dual to = 4 supersymmetric Yang-Mills with quenched fundamental matter. We extend the previous analyses of conductivity and photoproduction to the case where there is a finite electric field. Due to the electric field a special region in the D7-brane geometry, labelled the singular shell, appears generically, and the computation of correlators involves a careful study of the indicial exponents both at this singular region and at the horizon. We show that there is a unique choice consistent with the known expression for the electrical conductivity found by Karch and O'Bannon [1]. We explore the parameter space spanned by the quark mass, the baryon density and the electric field. We find a region where the conductivity and photoproduction change rapidly and trace this behavior to competing effects which manifest themselves as a rapid change in behavior in the probe brane embeddings, related to possible thermodynamic instabilities. © SISSA 2009.