Cubic Lower Gate Is a Monotone Reserve-Flux Barrier
For the unique hostile theta Jensen interface, set
The exact lower cubic gate becomes
Its derivative is
Thus the preceding quadratic reserve buys a strictly increasing, exactly quantified budget for negative adjacent Mellin-variance flux. The budget changes sign at the unique physical root
corresponding to . Below that reserve, the cubic gate requires positive flux; above it, negative flux is permitted only up to the explicit budget.
This splits the pre-Xi cubic theorem into reserve placement and conditional flux control, with an exact finite falsifier for each stage.
Artifact:
research/grothendieck/cubic-lower-gate-is-a-monotone-reserve-flux-barrier.md