Holographic Flavor Transport in Arbitrary Constant Background Fields

TL;DR

This paper uses gauge-gravity duality to calculate a new transport coefficient for massive hypermultiplet fields in a super-Yang-Mills plasma under arbitrary constant electromagnetic fields, including a novel conductivity component.

Contribution

It introduces a generalized calculation of the conductivity tensor in gauge-gravity duality with parallel electric and magnetic fields, revealing a previously uncalculated component.

Findings

Computed all components of the baryon number conductivity tensor.

Identified divergences in the flavor contribution to the stress-energy tensor.

Found a divergence-free current that becomes anomalous with parallel electric and magnetic fields.

Abstract

We use gauge-gravity duality to compute a new transport coefficient associated with a number Nf of massive N=2 supersymmetric hypermultiplet fields propagating through an N=4 SU(Nc) super-Yang-Mills theory plasma in the limits of large Nc and large 't Hooft coupling, with Nf << Nc. We introduce a baryon number density as well as arbitrary constant electric and magnetic fields, generalizing previous calculations by including a magnetic field with a component parallel to the electric field. We can thus compute all components of the conductivity tensor associated with transport of baryon number charge, including a component never before calculated in gauge-gravity duality. We also compute the contribution that the flavor degrees of freedom make to the stress-energy tensor, which exhibits divergences associated with the rates of energy and momentum loss of the flavor degrees of freedom. We discuss two currents that are free from these divergences, one of which becomes anomalous when the magnetic field has a component parallel to the electric field and hence may be related to recent study of charge transport in the presence of anomalies.