Glueballs and Their Kaluza-Klein Cousins

TL;DR

The paper investigates whether Kaluza-Klein states on the S^5 of the AdS5 black hole × S^5 dual to 3D QCD via gauge/gravity duality decouple in the continuum limit. It computes the SO(6) non-singlet dilaton KK masses in the supergravity limit, finding they are of the same order as the glueball spectrum, and then evaluates the leading $\alpha'$ corrections, which decrease these masses by factors $[1 - c_l \zeta(3) \alpha'^3]$ but do not cause KK states to become heavier than glueballs. This indicates that, at the perturbative level considered, KK decoupling is not evident and that the holographic glueball spectra may require non-perturbative effects to fully align with the lattice results. The work thus urges caution in interpreting supergravity-based glueball spectra as direct proxies for QCD behavior and hints at possible non-perturbative decoupling mechanisms in the sigma-model description.

Abstract

Spectra of glueball masses in non-supersymmetric Yang-Mills theory in three and four dimensions have recently been computed using the conjectured duality between superstring theory and large N gauge theory. The Kaluza-Klein states of supergravity do not correspond to any states in the Yang-Mills theory and therefore should decouple in the continuum limit. On the other hand, in the supergravity limit g_{YM}^2 N -> \infty, we find that the masses of the Kaluza-Klein states are comparable to those of the glueballs. We also show that the leading (g_{YM}^2N)^{-1} corrections do not make these states heavier than the glueballs. Therefore, the decoupling of the Kaluza-Klein states is not evident to this order.