Hydrodynamical transports in generic AdS Gauss-Bonnet-scalar Gravity

TL;DR

This paper develops a holographic model with higher-derivative corrections to better describe the temperature-dependent viscosities of quark-gluon plasma, revealing deviations from the KSS bound and demonstrating the importance of such corrections.

Contribution

It introduces a novel Einstein-Scalar-Maxwell-Gauss-Bonnet holographic model with analytic viscosity formulas derived via entropy analysis, validated by Green function computations.

Findings

Viscosity formulas show deviation from KSS bound.

Temperature dependence of viscosities is captured.

Analytic and numerical methods agree on shear viscosity.

Abstract

The experimentally observed temperature-dependent shear and bulk viscosities of the quark-gluon plasma (QGP), along with its apparent violation of the Kovtun-Son-Starinets (KSS) bound $\eta/s=1/(4\pi)$, necessitate a holographic description that incorporates higher-derivative corrections. We propose a five-dimensional Einstein-Scalar-Maxwell-Gauss-Bonnet model in which a scalar-Gauss-Bonnet coupling $H(\phi)$ encodes leading curvature corrections. Although no closed-form black hole solution is available, we employ an entropy-production analysis at the event horizon to derive exact analytic formulas for the shear viscosity $\eta$ and bulk viscosity $\zeta$. These expressions exhibit apparent deviation from the KSS bound and nontrivial temperature dependence. We then perform an independent computation via the retarded Green function (Kubo) method, finding perfect agreement for $\eta$ and isolating a single constant in $\zeta$ that requires numerical determination. Our dual derivation underscores the pivotal role of higher-derivative terms in realistic QGP modeling and demonstrates the efficacy of nonanalytic holographic backgrounds in capturing the dynamics of strongly coupled fluids.