Absence of a VVDZ Discontinuity in AdS_AdS

TL;DR

This paper investigates the gauge invariance and polarization states of graviton modes in an AdS4 brane within AdS5, demonstrating that the classical smooth massless limit persists quantum mechanically due to locality in the extra dimension.

Contribution

It clarifies the role of gauge invariance and locality in maintaining a smooth massless limit for graviton modes in AdS brane models, resolving previous ambiguities.

Findings

All spin-2 modes propagate five polarization states.

Classical smooth limit as mass parameter approaches zero.

Quantum level analysis supports classical results.

Abstract

We clarify the role of gauge invariance for the theory of an AdS4 brane embedded in AdS5. The presence of a nonvanishing mass parameter even for the lightest KK mode of the graviton indicates that all of the spin-2 modes propagate five polarization states. Despite this fact, it was shown earlier that the classical theory has a smooth limit as the mass parameter is taken to zero. We argue that locality in the fifth dimension ensures that this property survives at the quantum level.