Electrical conductivity of the Quark-Gluon Plasma in the presence of strong magnetic fields

TL;DR

This study calculates the electrical conductivity of the Quark-Gluon Plasma under strong magnetic fields using lattice QCD simulations, revealing anisotropic behavior likely related to the Chiral Magnetic Effect.

Contribution

It provides the first lattice QCD computation of the QGP electrical conductivity in strong magnetic fields, highlighting anisotropic effects and the behavior of the relaxation time associated with the CME.

Findings

Conductivity is enhanced parallel to the magnetic field.

Conductivity is suppressed orthogonal to the magnetic field.

Relaxation time for the CME is lower than previously expected.

Abstract

We compute the electrical conductivity of the strongly interacting medium in the presence of strong magnetic background fields, $eB=4,9~GeV^2$, and for different values of the temperature, both in the confined and in the deconfined Quark-Gluon Plasma (QGP) phase. The conductivity is obtained from the Euclidean lattice time correlator of the electrical current, computed on gauge configurations sampled from Monte-Carlo simulations of an improved staggered discretization of $N_f = 2+1$ QCD. We perform the inverse Laplace transform of the correlator adopting a recently-proposed version of the standard Backus--Gilbert procedure for the inversion. The results obtained in the QGP phase show a sizable enhancement of the conductivity in the direction parallel to the magnetic field, as well as a suppression in the direction orthogonal to it. Such enhancement could be attributed to the manifestation of the Chiral Magnetic Effect (CME): following this guess, we extract the behaviour of the relaxation time of this process, extrapolate it to the continuum limit and compare it to previous results, finding it lower than expected in the explored range of temperatures.