Physical Geometry: Quantum Mechanics V — Composite Transport Systems and the Geometry of Decoherence

This paper develops the geometric origin of composite systems, decoherence, and the emergence of classical behavior within the holonomy-based transport framework introduced in Physical Geometry: Quantum Mechanics I–IV. A holonomy calculus for composite transport structures is constructed, and it is shown that restriction of representational access to subsystems induces effective loss of phase information. This restriction suppresses interference terms and yields additive invariant weights for invariantly distinguishable components in the accessible description. As a consequence, classical behavior and decoherence arise as structural consequences of composite transport and invariant projection, without requiring stochastic dynamics or additional postulates. This work completes the representational reconstruction of quantum mechanics from transport geometry and establishes the geometric basis for the emergence of classicality. This Zenodo record establishes priority and archival timestamp. Public release via arXiv is in progress.