Fermion Dipole Moment and Holography

TL;DR

This paper investigates how a fermion with a magnetic dipole moment behaves in a charged AdS black hole background and finds that certain coupling strengths can lead to superluminal modes in the dual boundary theory, constraining the model's parameters.

Contribution

It introduces a study of fermion dipole moments in holography and derives bounds on dipole coupling to ensure physical consistency in the dual CFT.

Findings

Superluminal modes appear for certain dipole couplings.

An upper bound on dipole strength is established.

Implications for holographic non-Fermi liquids are discussed.

Abstract

In the background of a charged AdS black hole, we consider a Dirac particle endowed with an arbitrary magnetic dipole moment. For non-zero charge and dipole coupling of the bulk fermion, we find that the dual boundary theory can be plagued with superluminal modes. Requiring consistency of the dual CFT amounts to constraining the strength of the dipole coupling by an upper bound. We briefly discuss the implications of our results for the physics of holographic non-Fermi liquids.