Abstract
We study the realization of axion electrodynamics in QCD in the presence of a background magnetic field at temperatures high enough for the occurrence of topological charge transitions that are reflected in the presence of a $\theta$-vacuum term in the action. We show that in this system, the Maxwell equations contain two equal and opposite electric currents that are proportional to the time derivative of the axion field $\theta$. One of these currents comes directly from the Abelian chiral anomaly term in the action and can be interpreted as a polarization current due to the magnetoelectricity of the system with CP-broken symmetry. The other current is obtained from the regular tadpole diagrams and can be understood as produced by the medium chiral imbalance and the single spin projection of the quarks in the lowest Landau level. Since the two currents cancel out, the net electric charge separation along the magnetic field, a phenomenon known as the Chiral Magnetic Effect, does not take place in hight-T QCD at least in equilibrium, in sharp contrast with many claims in the literature. We discuss the similarities and differences with Weyl semimetals in a magnetic field.
Highlights
In recent years, the discovery of anomalous transport in theoretical studies of QCD under extreme conditions and in the presence of electric and magnetic fields has opened the possibility to connect microscopic properties of new quark matter phases to observable macroscopic effects, becoming a hot topic of investigation [1]
The chiral magnetic effect (CME) has been predicted to occur in the quark-gluon plasma (QGP) in a magnetic field when there is chiral imbalance, which manifests as a nonzero chiral “chemical potential” μ5
Following the procedure described above, we find that the Maxwell equations in the hot QGP in a magnetic field are those of axion electrodynamics
Summary
The discovery of anomalous transport in theoretical studies of QCD under extreme conditions and in the presence of electric and magnetic fields has opened the possibility to connect microscopic properties of new quark matter phases to observable macroscopic effects, becoming a hot topic of investigation [1]. It was argued that the net CME current induced by a constant background axial vector AA0 and a magnetic field is zero, but if instead, one introduces a chiral chemical potential for the conserved axial charge, meaning the one that incorporates the regular and anomalous terms together, the CME current is regained [18].
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
