The completed Chronoflux Atlas recovers inertia as the lawful resistance carried by matter when its admitted motion is changed relative to temporal transport. Continuity supplies the conserved current and temporal order, but it does not by itself fix the coefficient multiplying acceleration. That coefficient is recovered only when temporal and matter variables belong to one common action. The physical fibre Hessian of the reduced action is then the local inertial operator, as such, because it isthe Jacobian which maps a change of velocity into a change of momentum. I construct the selected coupled branch from a conserved temporal U(1) current, a positive temporal modulation of the matter kinetic term, and a retained actuator sector. The same action returns the current, the complete stress tensor and all internal exchange. For a localised matter configuration, collective-coordinate reduction gives an inertial tensor equal to the matter deformation overlap weighted by the temporal state. A uniform temporal state therefore rescales the inertial tensor through the positive kinetic modulation. This is the recovered origin of inertia within the branch: inertia is the positive curvature of the matter action against displacement through the temporal medium. The derivation also fixes the boundary. A physical inertial eigenvalue may become very small while remaining positive, producing a large but finite response. Exact zero drives the Legendre map to degeneracy, introduces a new constraint, or destroys deterministic acceleration. The same obstruction appears in scalar worldline and field-kinetic branches. Frequency-dependent effective inertia may cross zero near resonance, but that is a causal dynamic cancellation accompanied by phase, dispersion and loss, not vanishing rest mass. Finally, total energy and four-momentum remain closed across matter, temporal and actuator sectors, so no isolated internal cycle produces reactionless momentum. Admissibility, Recoverability and Persistence distinguish a lawful inertial response from singular dynamics or incomplete metrology. The result closes inertia as temporal resistance while preserving the exact zero, universality and empirical boundaries. Keywords: inertia; temporal transport; kinetic geometry; fibre Hessian; effective mass; Noether current; energy exchange; Chronoflux Atlas
Roy Herbert (2026) studied this question.