A Phase–Geometric Origin of Quantum Uncertainty in a C3–Extended Hilbert Space

Abstract Quantum uncertainty is conventionally presented as an intrinsic limitation arising from noncommuting observables. This work proposes an alternative, yet fully compatible, perspective based on an extended phase geometry. Quantum mechanics is formulated on the cyclic phase algebra C₃, in which the state space naturally decomposes into a measurable (visible) subspace and an orthogonal hidden phase channel. Crucially, the definition of uncertainty remains identical to that of standard quantum mechanics: variances are computed solely from the measurable sector using the conventional expression for variance, without modifying the Born rule or the measurement postulates. We demonstrate that the C₃-extended Schrödinger dynamics constrains the visible and hidden components on physical solution manifolds. As a result, the numerical value of the standard quantum uncertainty can be reformulated, without redefining it, in terms of second moments associated with the hidden phase channel. Within this framework, uncertainty is interpreted as a geometric projection effect arising from an unobservable phase degree of freedom. Consistency with the standard complex (C₂) formulation is recovered in the appropriate limit, and implications for angular momentum observables and the structure of quantum fluctuations are briefly outlined.