Gluon condensate effects on heavy quarkonium spectral functions and thermal dissociation

Abstract

We investigate how gluon condensate modifies thermal spectral functions and melting patterns of heavy vector mesons, specifically charmonium and bottomonium, using an improved soft-wall anti-de Sitter/quantum chromodynamics (AdS/QCD) model. The framework is extended to finite temperature via a dilaton black hole geometry that consistently incorporates the back-reaction from the gluon condensate. We numerically track the evolution of spectral resonance peaks as functions of both temperature and gluon condensate strength. Our calculations reveal that increasing temperature systematically broadens and suppresses spectral peaks, signaling in-medium dissociation. In contrast, a stronger gluon condensate significantly mitigates peak broadening and enhances the spectral weight of both ground and excited states. This behavior indicates that the gluon condensate hinders thermal dissociation, thereby stabilizing heavy quarkonia within the quark–gluon plasma. These findings are consistent with existing studies and provide new holographic evidence for the stabilizing role of the gluon condensate from the perspective of thermal spectral functions.