The impact of domain walls on the chiral magnetic effect in hot QCD matter

TL;DR

This paper investigates how domain walls influence the chiral magnetic effect in hot QCD matter, revealing that boundary conditions and oscillations significantly alter the CME's behavior compared to infinite media.

Contribution

It introduces an analytical model showing the impact of domain walls on CME, highlighting boundary effects and oscillatory charge separation currents in finite domains.

Findings

No electric current flows across the domain boundary.

Charge separation current is a dissipative Ohm current.

CME can arise from boundary conditions or anomalous currents.

Abstract

The Chiral Magnetic Effect (CME) -- the separation of positive and negative electric charges along the direction of the external magnetic field in quark-gluon plasma and other topologically non-trivial media -- is a consequence of the coupling of electrodynamics to the topological gluon field fluctuations that form metastable $CP$-odd domains. In phenomenological models it is usually assumed that the domains are uniform and the influence of the domain walls on the electric current flow is not essential. This paper challenges the latter assumption. A simple model consisting of a uniform spherical domain in a uniform time-dependent magnetic field is introduced and analytically solved. It is shown that (i) no electric current flows into or out of the domain, (ii) the charge separation current, viz. the total electric current flowing inside the domain in the external field direction, is a dissipative Ohm current, (iii) the CME effect can be produced either by the anomalous current or by the boundary conditions on the domain wall and (iv) the charge separation current oscillates in plasma long after the external field decays. These properties are qualitatively different from the CME in an infinite medium.