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.
Highlights
Heavy-ion collisions create an interesting new state of matter, quark-gluon plasma of QCD, where confinement is effectively lost due to high temperature above the QCD cross-over line
We extend the previous studies in two important aspects: we study Chiral Magnetic Effect and Chiral Magnetic Wave in out-of-equilibrium conditions and in non-hydrodynamic regimes
For the parameters we explored, the group velocity receives most of its contribution from the first term in (5.77), which is significantly larger than the group velocity of the equilibrium chiral magnetic wave
Summary
Heavy-ion collisions create an interesting new state of matter, quark-gluon plasma of QCD, where confinement is effectively lost due to high temperature above the QCD cross-over line. We study the time evolution of the Chiral Magnetic Wave dispersion relation in the neutral falling mass shell geometry, again in the quasi-static approximation In this case, we assume a homogeneous, static background magnetic field which solves the equations of motion trivially, and we are interested in how chiral charge fluctuations behave under this condition, treating them as linearized small fluctuations. We are interested in the low momentum regime, and in non-hydrodynamic regime of finite spatial momenta, envisioning that the relevant charge fluctuations in the heavy-ion collisions may be highly inhomogeneous in the transverse plane For such large frequency-momentum regime, the quasi-static approximation is better justified. We will look for wave-like excitations in the spectral function below the lightcone, which is the region we expect to see chiral magnetic wave
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