The hadron spectrum — the discrete sequence of meson and baryon masses — is a central experimental fact of Quantum Chromodynamics. Why is the linear Regge trajectory J ∝ M² so universal? How does tube resonance determine the spin–mass relation of hadrons? These questions have so far lacked analytic answers. This paper presents the mechanical interpretation of the hadron spectrum within the Gluon Elastic Lattice Theory (GELT): hadrons are not "particle bound states" of quarks, but different resonance modes of the elastic vibration of the confinement tube. The tube is anchored at its ends by color charges, and its transverse size is determined by the correlation length ℓc of the medium. The standing-wave condition on the tube cross section naturally yields the discrete mass spectrum: Mₙ² = M₀² + n·ΔM², where the mass-squared spacing ΔM² ∝ σ/ℓc is uniquely fixed by the string tension and the correlation length. This formula is strictly consistent with the linear Regge trajectory in analytic form. Meson tubes have both ends fixed (Dirichlet boundary condition), while baryon tubes form a Y-shaped triple junction — different combinations of the resonance modes of the three arms give a richer hadron spectrum structure. With this, the G2 series of GELT — string tension (confinement), mass gap (spectral gap), glueball radius (localized configuration), asymptotic freedom (running coupling), and hadron spectrum (discrete resonances) — all emerge from one and the same nonlinear elastic constitutive relation K (ρ).
卓冰 蒋 (Fri,) studied this question.