This paper develops a source-datum framework for the quantum chromodynamics (QCD) theta phase and asks a prior structural question that is usually left implicit in discussions of the strong charge-parity (CP) problem: what exactly is the phase object whose observability, compensation, relaxation, or closure is being studied? The paper identifies the QCD phase as a gauge–determinant circle datum assembled from topological sector data, determinant and chiral phase data, representative-change rules, and admissible CP comparison of the total phase. A central result is the distinction between a theory-level phase parameter and its evaluation on a particular topological sector. The paper further defines a total gauge–determinant phase, develops descent criteria under representative changes, formulates anomaly-compatible chiral compensation through a cocycle condition, and establishes a total-phase-first notion of CP comparison. The note also introduces a unified QCD source space on which topological and determinant phase data are simultaneously defined. Within this framework, non-retuning is formulated as an invariance principle under admissible source-preserving transformations, and a verification ledger is developed to distinguish source-datum obligations established in the paper from additional physical obligations required for full strong-CP closure. As a companion to Strong CP as Completion-Locked Phase Closure, this work supplies the phase object to which the companion closure theorem applies. Its role is not to derive new QCD dynamics, but to identify and certify the structural phase datum whose observability, compensation, extension, and closure are under discussion. The result is a source-datum framework that places topological phases, determinant phases, anomaly compensation, Peccei–Quinn extensions, and strong-CP closure claims within a common structural language. License note: Distributed under CC BY-NC-ND 4.0.
Salimah H. Meghani (Sat,) studied this question.