Glueballs vs. Gluinoballs: Fluctuation Spectra in Non-AdS/Non-CFT

TL;DR

This paper computes the fluctuation spectra of glueballs and gluinoballs in non-AdS/Non-CFT holographic models, revealing quadratic confinement and limitations of the hardwall approximation.

Contribution

It introduces a numerical method for calculating mass spectra in non-conformal holographic backgrounds and applies it to the Maldacena-Nunez and Klebanov-Strassler models.

Findings

States exhibit quadratic confinement with m^2 ~ n^2 for large n.

Hardwall approximation poorly matches full spectra.

Universal proportionality constant in mass-squared dependence.

Abstract

Building on earlier results on holographic bulk dynamics in confining gauge theories, we compute the spin-0 and spin-2 spectra of gauge theories dual to the non-singular Maldacena-Nunez and Klebanov-Strassler supergravity backgrounds. We construct and apply a numerical recipe for computing mass spectra from certain determinants. In the Klebanov-Strassler case, states containing the glueball and gluinoball obey "quadratic confinement", i.e. their mass-squareds depend on consecutive number as m^2 ~ n^2 for large n, with a universal proportionality constant. The hardwall approximation appears to work poorly when compared to the unique spectra we find in the full theory with a smooth cap-off in the infrared.