Mass and Gauge Invariance IV (Holography for the Karch-Randall Model)

TL;DR

This paper demonstrates that the Karch-Randall model is holographically dual to a 4D conformal field theory coupled to gravity, revealing a mass spectrum without massless spin-2 states and challenging the link between general covariance and massless gravitons.

Contribution

It provides a purely 4D interpretation of the Karch-Randall compactification, showing it as the first local 4D field theory lacking a massless graviton despite general covariance.

Findings

No massless spin-2 states in the spectrum

First example of a local 4D theory with general covariance but no massless graviton

Holographic duality between Karch-Randall model and 4D CFT coupled to gravity

Abstract

We argue that the Karch-Randall compactification is holographically dual to a 4-d conformal field theory coupled to gravity on Anti de Sitter space. Using this interpretation we recover the mass spectrum of the model. In particular, we find no massless spin-2 states. By giving a purely 4-d interpretation to the compactification we make clear that it represents the first example of a local 4-d field theory in which general covariance does not imply the existence of a massless graviton. We also discuss some variations of the Karch-Randall model discussed in the literature, and we examine whether its properties are generic to all conformal field theory.