Beltrami fields, dispersive electromagnetic waves and gravitational spheromaks from chiral anomaly

Abstract: In this note, we focus on the backreaction effects due to the chiral anomaly. The chiral anomaly modifies conserved currents, introducing new contributions. For Maxwell gauge fields, this leads to a contribution to the electric current proportional to the background magnetic field, a phenomenon known as the chiral magnetic effect, which is widely discussed in the literature. In the case of gravitational fields, as we demonstrate, the anomaly induces a new contribution to the stress-energy tensor. We analyze the potential manifestations of these modifications in the gravitational field and hydrodynamics in chiral media, and we also comment on backreaction effects in electrodynamics. In each case, we observe the systematic appearance of Beltrami-type fields. In electrodynamics and hydrodynamics, a Beltrami field (e.g., magnetic field or fluid velocity) is a vector parallel to its own curl. We propose a generalization of Beltrami fields for tensorial gravitational perturbations, calling the respective solutions to the gravitational equations gravitational spheromaks by analogy with a similar phenomenon in electrodynamics. In the modified hydrodynamics of chiral media, vorticity asymptotically forms a Beltrami vector field in a generalized Gromeka-Beltrami flow.