The Morrow Frequency: Natural Curvature Cut–Off of Mass–Energy Coherence in 5D SpaceTime+

This paper extends the 5D SpaceTime+ programme by demonstrating that the boundary between inertial and radiative behaviour is not arbitrary but geometrically fixed by the Morrow Frequency, ωM =mc2h α¯.At this turning point, curvature phase executes a quarter–turn (π/2) rotation, where closed (mechanical) and open (electromagnetic) curvatures exchange dominance. Appendix A derives the asymptotic law mem(ω)∼(ωM/ω) directly from the determinant of the coupled curvature system, while Appendix B provides a geometric interpretation of the phase rotation.Together, these results establish the natural coherence limit of mass–energy, linking the constants m, c, h, α (and implicitly π) within one invariant expression. The Morrow Frequency therefore represents a major unification milestone connecting inertia, radiation, and geometric quantisation within the continuous curvature of 5D SpaceTime+.