Dark Energy as a Forbidden Bulk Degree of Freedom in a Non-Orientable Spacetime

In standard cosmology, dark energy is modeled as a globally defined, dynamically sourced contribution to the stress–energy tensor, evolving with respect to a unique cosmic time. This paper shows that such a component is structurally forbidden in a spacetime that is globally non-orientable while reducing exactly to General Relativity in all locally orientable regions. The argument does not depend on field content, equations of state, or model-specific dynamics. Instead, it follows from the incompatibility between three simultaneously enforced conditions: (i) exact local stress–energy conservation, (ii) global non-orientability of spacetime, and (iii) the requirement of a globally integrable energy contribution evolving with respect to a unique time orientation. Building on earlier results demonstrating structural silence (Paper 26) and the failure of global conservation in non-orientable manifolds (Paper 27), this work completes the logical chain by showing that any would-be dark-energy contribution must either cancel globally, become branch-dependent, or reduce to geometric background behavior. A sourced bulk dark-energy component cannot appear as an observable degree of freedom. Cosmic acceleration, if present, must therefore be interpreted as a geometric or topological effect rather than a dynamical energy component. The paper concludes by stating clear structural conditions under which this conclusion would be falsified, making the result testable in principle. This paper is part of the Möbius Cosmology Series, a constraint-first program that preserves exact local General Relativity while enforcing global topological consistency.