Holographic Constraints on a Vector Boson

TL;DR

This paper demonstrates that holography imposes specific restrictions on the electromagnetic and gravitational couplings of a vector boson in AdS space, ensuring the dual CFT remains consistent and free of superluminal modes.

Contribution

It reveals how holographic principles constrain the multipole moments of vector bosons, particularly bounding the gyromagnetic ratio to avoid pathologies in the dual CFT.

Findings

Generic dipole moments cause superluminal modes in the dual CFT.

Bounding the gyromagnetic ratio around g=2 ensures causality.

Constraints on higher-spin fields' couplings are derived from holography.

Abstract

We show that holography poses non-trivial restrictions on various couplings of an interacting field. For a vector boson in the AdS Reissner-Nordstrom background, the dual boundary theory is pathological unless its electromagnetic and gravitational multipole moments are constrained. Among others, a generic dipole moment afflicts the dual CFT with superluminal modes, whose remedy bounds the gyromagnetic ratio in a range around the natural value g=2. We discuss the CFT implications of our results, and argue that similar considerations can shed light on how massive higher-spin fields couple to electromagnetism and gravity.