Hydrodynamic modes in holographic multiple-axion model

TL;DR

This paper studies how multiple axions in a holographic model affect shear viscoelasticity and hydrodynamic modes, revealing enhanced shear modulus at high temperatures and increased diffusive modes with more axions.

Contribution

It introduces a holographic solid model with multiple axions and analyzes their impact on shear properties and hydrodynamic modes, extending previous single-axion models.

Findings

Shear modulus is increased at high temperatures with more axions.

Shear viscosity is suppressed by additional axions.

Adding axions increases diffusive modes without changing sound modes.

Abstract

In this paper we investigate the shear viscoelasticity and the hydrodynamic modes in a holographic solid model with several sets of axions that all break the translations spontaneously on boundary. Comparing with the single-axion model, the shear modulus is enhanced at high temperatures and the shear viscosity is always suppressed in the presence of additional axions. However, the different sets of axions exhibit competitive relationship in determining the shear modulus at low temperatures. Furthermore, by calculating the black hole quasi-normal modes, it is found that adding more axions only increases the amount of diffusive modes. The number of the sound modes always remains unchanged.