Collective modes of chiral kinetic theory in a magnetic field

We study collective excitations in systems described by chiral kinetic theory in an external magnetic field, such as quark-gluon plasma or Fermi liquids near Dirac/Weyl points of a semimetal. We consider high-temperature weak-coupling plasma, as well as high-density Landau Fermi liquid, without restricting to weak interactions. We show that the chiral magnetic wave (CMW) emerges in the hydrodynamic regime (at frequencies smaller than the collision relaxation rate), and the CMW velocity is determined by thermodynamic properties only. We find that in a plasma of opposite chiralities, at frequencies smaller than the chirality-flipping rate, the CMW excitation turns into a vectorlike diffusion mode. In the interacting Fermi liquid, the CMW turns into the Landau zero sound mode in the high-frequency collisionless regime.