PURE BULK CAVITY MODES, AdS5 SHEAR RESONANCES, AND THE NON-HADRONIC X(2370) STRUCTURE: BEYOND THE GLUEBALL HYPOTHESIS (XLIII v6)

The recent high-significance (11.7σ) observation of the $X(2370)$ resonance at 2.37 GeV by the BESIII Collaboration has been widely interpreted within conventional Lattice Quantum Chromodynamics (QCD) as a candidate for a scalar/pseudoscalar "glueball"—a bound state composed purely of gauge bosons. In this paper, within the pregeometric framework of FCD-RBv6, we demonstrate that 4D gauge boson self-coupling is a effective projection of 5D bulk shear elasticity, and we formally refute the glueball paradigm. By modeling the AdS₅inter-brane throat as a closed elastic resonant cavity under free Dirichlet boundary conditions (devoid of valence quark nodes), we derive the fundamental radial-torsional shear mode driven by the Bessel root x₀₁π ≈ 7.55498. Using only the Compton centrifugal floor radius R₀ = 0.6308 fm and c, we predict an exact ab initio resonance energy of Etheoretical = 2362.41 MeV, exhibiting a deviation of merely $0.32%$ from the experimental value of 2370 MeV. Furthermore, we explain the absence of valence quarks in $X(2370)$ decays through elastic shear relaxation of the bulk, link its energy to the 2.51 MeV sub-hadronic mass quantum, and establish a falsifiable matrix predicting higher excited cavity modes (x₀₂π = 5420.73 MeV and x₀₃π = 8500.22 MeV) for upcoming collider searches.