Equilibrium parity-violating current in a magnetic field

Abstract

It is argued that if the Hamiltonian of a system of charged fermions does not conserve parity, then an equilibrium electric current parallel to $\stackrel{\ensuremath{\rightarrow}}{\mathrm{B}}$ can develop in such a system in an external magnetic field $\stackrel{\ensuremath{\rightarrow}}{\mathrm{B}}$. The equilibrium current is calculated (i) for noninteracting left-handed massless fermions and (ii) for a system of massive particles with a Fermitype parity-violating interaction. In the first case a nonzero current is found, while in the second case the current vanishes in the lowest order of perturbation theory. The physical reason for the cancellation of the current in the second case is not clear and one cannot rule out the possibility that a nonzero current appears in other models.