Collective excitations of massive flavor branes

TL;DR

This paper investigates the collective excitations and phase transitions in a holographic model of massive flavor branes, revealing critical behavior, sound modes, and transport properties in a strongly coupled gauge theory with flavor.

Contribution

It provides a detailed analysis of the thermodynamics, sound modes, and quantum phase transitions in a D-brane setup with massive flavors, including non-zero temperature and magnetic field effects.

Findings

Identified a quantum phase transition at critical chemical potential.

Calculated non-relativistic critical exponents for the phase transition.

Matched diffusion constants with Einstein relation predictions.

Abstract

We study the intersections of two sets of D-branes of different dimensionalities. This configuration is dual to a supersymmetric gauge theory with flavor hypermultiplets in the fundamental representation of the gauge group which live on the defect of the unflavored theory determined by the directions common to the two types of branes. One set of branes is dual to the color degrees of freedom, while the other set adds flavor to the system. We work in the quenched approximation, i.e., where the flavor branes are considered as probes, and focus specifically on the case in which the quarks are massive. We study the thermodynamics and the speeds of first and zero sound at zero temperature and non-vanishing chemical potential. We show that the system undergoes a quantum phase transition when the chemical potential approaches its minimal value and we obtain the corresponding non-relativistic critical exponents that characterize its critical behavior. In the case of (2+1)-dimensional intersections, we further study alternative quantization and the zero sound of the resulting anyonic fluid. We finally extend these results to non-zero temperature and magnetic field and compute the diffusion constant in the hydrodynamic regime. The numerical results we find match the predictions by the Einstein relation.