Novel Parity Violating Transport Coefficients in 2+1 Dimensions from Holography

TL;DR

This paper develops a holographic model to study parity-violating transport phenomena in 2+1 dimensional fluids, revealing novel transport coefficients influenced by Chern-Simons terms and scalar dynamics.

Contribution

It introduces a new holographic framework incorporating Chern-Simons terms and a pseudo scalar to analyze parity violation in 2+1D hydrodynamics, highlighting mechanisms of spontaneous and explicit parity breaking.

Findings

Transport coefficients exhibit unusual behaviors compared to ordinary materials.

Parity can be broken spontaneously or explicitly, affecting the transport properties.

The model connects bulk scalar dynamics with boundary fluid parity violation.

Abstract

We construct a 3+1 dimensional holographic model dual to a parity violating hydrodynamic system in 2+1 dimensions. Our model contains gravitational and electrodynamic Chern-Simons terms coupled to a neutral pseudo scalar $\theta$, and a potential composed of quadratic and quartic terms in $\theta$. The background is a charged black brane. We study the hydrodynamics to first order in spacetime derivatives near the probe limit of the pseudo scalar, by extracting the transport coefficients from the scalar, vector, and tensor modes of bulk perturbations. We study two mechanisms for breaking the parity of the boundary fluid: the parity is either spontaneously broken by the nonzero vev of the dual pseudo scalar operator, or by the pseudo scalar source on the boundary. The resulting transport coefficients have unusual behaviors compared to those in ordinary materials.