Out-of-Equilibrium Chiral Magnetic Effect at Strong Coupling

TL;DR

This paper investigates the out-of-equilibrium chiral magnetic effect at strong coupling using holography, revealing how charge transport and wave dynamics evolve during thermalization in heavy-ion collisions.

Contribution

It constructs a holographic model of out-of-equilibrium charged plasma and analyzes the dynamical behavior of chiral magnetic phenomena during thermalization.

Findings

Charge density slows down thermalization.

Chiral magnetic conductivity increases during out-of-equilibrium.

Out-of-equilibrium chiral magnetic wave propagates faster than in equilibrium.

Abstract

We study the charge transports originating from triangle anomaly in out-of-equilibrium conditions in the framework of AdS/CFT correspondence at strong coupling, to gain useful insights on possible charge separation effects that may happen in the very early stages of heavy-ion collisions. We first construct a gravity background of a homogeneous mass shell with a finite (axial) charge density gravitationally collapsing to a charged blackhole, which serves as a dual model for out-of-equilibrium charged plasma undergoing thermalization. We find that a finite charge density in the plasma slows down the thermalization. We then study the out-of-equilibrium properties of Chiral Magnetic Effect and Chiral Magnetic Wave in this background. As the medium thermalizes, the magnitude of chiral magnetic conductivity and the response time delay grow. We find a dynamical peak in the spectral function of retarded current correlator, which we identify as an out-of-equilibrium chiral magnetic wave. The group velocity of the out-of-equilibrium chiral magnetic wave is shown to receive a dominant contribution from a non-equilibrium effect, making the wave moving much faster than in the equilibrium, which may enhance the charge transports via triangle anomaly in the early stage of heavy-ion collisions.