Admissibility Gaps: Spectral Conditions for Constraint-Induced Mass in Massless Field Propagation

This note defines the admissibility gap functional and gives a coercivity criterion for whenconstraint enforcement produces a strictly positive spectral gap. The result isolates the structural condition underlying constraint-induced effective mass inmassless field propagation, and serves as a companion note to: Charles Wood, “Constraint-Induced Effective Mass in Massless Field Propagation”,arXiv:2601.09642 (2026), DOI: 10.48550/arXiv.2601.09642. The admissibility gap functions as an operational invariant distinguishing gapped (coercive)constraints from gapless (non-coercive) rank reductions, with spectral examples.