Holographic approach to transport in dense QCD matter

TL;DR

This paper employs holographic models to study the transport properties of dense QCD matter, providing new insights into electrical, thermal conductivities, and viscosities relevant for neutron star physics.

Contribution

It introduces a holographic approach to calculate transport coefficients in dense QCD matter, contrasting with traditional perturbative methods and revealing violations of established bounds.

Findings

Holographic models yield specific values for conductivities and viscosities.

The bulk to shear viscosity ratio violates the Buchel bound.

Results differ significantly from perturbative QCD predictions.

Abstract

The transport properties of dense QCD matter play a crucial role in the physics of neutron stars and their mergers, but are notoriously difficult to study with traditional quantum field theory tools. Specializing to the case of unpaired quark matter in beta equilibrium, we approach the problem through the machinery of holography, in particular the V-QCD and D3-D7 models, and derive results for the electrical and thermal conductivities and the shear and bulk viscosities. In addition we compare the bulk to shear viscosity ratio to the speed of sound and find that it violates the so-called Buchel bound. Our results differ dramatically from earlier predictions of perturbative QCD, the root causes and implications of which we analyze in detail.