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The anomalous transport of axial charge: topological vs non-topological fluctuations
Axial charge imbalance is an essential ingredient in novel effects associated
with chiral anomaly such as chiral magnetic effects (CME). In a non-Abelian
plasma with chiral fermions, local axial charge can be generated a) by
topological fluctuations which would create domains with non-zero winding
number b) by conventional non-topological thermal fluctuations. We provide a
holographic evaluations of medium's response to dynamically generated axial
charge density in hydrodynamic limit and examine if medium's response depends
on the microscopic origins of axial charge imbalance. We show a local domain
with non-zero winding number would induce a non-dissipative axial current due
to chiral anomaly. We illustrate holographically that a local axial charge
imbalance would be damped out with the damping rate related to Chern-Simon
diffusive constant. By computing chiral magnetic current in the presence of
dynamically generated axial charge density, we found that the ratio of CME
current over the axial charge density is independent of the origin of axial
charge imbalance in low frequency and momentum limit. Finally, a stochastic
hydrodynamic equation of the axial charge is formulated by including both types
of fluctuations.Comment: 30 pages, version accepted in JHE
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