On chiral magnetic effect and holography

We point out that there is a difference between the behavior of fermionic systems (and their holographic analogs) in a background axial vector field, on the one hand, and at finite chiral chemical potential, on the other. In the former case, the electric current induced by constant background axial field A₀ and magnetic field B vanishes, while in the latter it is given by the anomaly-prescribed formula j = μA/2π²e² Nc B.