Chiral anomalies and AdS/CMT in two dimensions

I clarify some recent confusion regarding the holographic description of finite-density systems in two dimensions. Notably, the chiral anomaly for symmetry currents in 2d conformal field theories (CFT) completely determines their correlators. The important exception is a CFT with a gauge theory to which we may couple an external current, as in the probe D3/D3 system or the putative dual to the charged BTZ black hole. These systems are analyzed with an eye for potential condensed matter applications.