B19: Decoherence as Interface Instability: A Structural Perspective within the BRISM Framework

Decoherence is typically described as a dynamical loss of phase coherence due to environmental coupling. This work introduces a complementary structural perspective within the BRISM (Brane Interface Substrate Model) framework. Decoherence is interpreted as a loss of Born-stable measurement projection at the interface between complex Hilbert-space states and real-valued observables, without modifying standard quantum mechanics. Within this formulation, quantum coherence corresponds to the persistence of a structurally stable measurement map, while decoherence is characterized as a deviation from this stability class. A model-independent deviation functional, δ₍Born₎(t), is introduced to quantify departures from Born-stable measurement statistics. This quantity measures instability of the measurement projection rather than state-space distance and allows comparison of decoherence processes independently of specific dynamical models. The same interface stability conditions that select the Born rule organize into a minimal symmetry structure, U(1) ⊕ SU(2) ⊕ SU(3), which defines a canonical dimensionless invariant X = 4π³ + π² + π. This invariant reproduces the inverse fine-structure constant at leading order, with a structurally induced correction reaching 10⁻⁹ agreement. This correspondence is interpreted as a manifestation of internal structural consistency rather than a predictive fit. The stability threshold ε* governing decoherence is identified as an effective, environment-dressed form of the fundamental interface scale ε₀ = 1/π², providing a bridge between microscopic interface geometry and macroscopic decoherence behavior. The present work does not replace dynamical models of decoherence but isolates a structural stability condition that applies across them, offering a unified and model-independent lens on coherence loss in quantum systems. For a current top-down overview of the BRISM framework and its wider structural context, see: Current BRISM Top‑Down Overview All BRISM papers on Zenodo >> Searchlist Supplementary structural material, dependency maps, and reproducibility notes are available in an accompanying public repository: https://github.com/swencarloheinze/brism-framework