Covariant and 3+1 Equations for Dynamo-Chiral General Relativistic Magnetohydrodynamics

TL;DR

This paper develops a covariant and 3+1 formulation of general relativistic magnetohydrodynamics equations for chiral plasmas, linking quantum effects like the Chiral Magnetic Effect to classical dynamo processes in astrophysical contexts.

Contribution

It introduces a unified covariant framework and derives the 3+1 GRMHD equations for chiral plasmas, enabling numerical studies of quantum and classical magnetic phenomena in relativistic astrophysics.

Findings

Derived the covariant generalized Ohm's law for chiral plasmas.

Formulated the 3+1 GRMHD equations including chiral effects.

Facilitates numerical simulations of CME in compact astrophysical objects.

Abstract

The exponential amplification of initial seed magnetic fields in relativistic plasmas is a very important topic in astrophysics, from the conditions in the early Universe to the interior of neutron stars. While dynamo action in a turbulent plasma is often invoked, in the last years a novel mechanism of quantum origin has gained increasingly more attention, namely the Chiral Magnetic Effect (CME). This has been recognized in semi-metals and it is most likely at work in the quark-gluon plasma formed in heavy-ion collision experiments, where the highest magnetic fields in nature, up to B~10^18 G, are produced. This effect is expected to survive even at large hydrodynamical/MHD scales and it is based on the chiral anomaly due to an imbalance between left- and right-handed relativistic fermions in the constituent plasma. Such imbalance leads to an electric current parallel to an external magnetic field, which is precisely the same mechanism of an alpha-dynamo action in classical MHD. Here we extend the close parallelism between the chiral and the dynamo effects to relativistic plasmas and we propose a unified, fully covariant formulation of the generalized Ohm's law. Moreover, we derive for the first time the 3+1 general relativistic MHD equations for a chiral plasma both in flat and curved spacetimes, in view of numerical investigation of the CME in compact objects, especially magnetars, or of the interplay among the non-ideal magnetic effects of dynamo, the CME and reconnection.