Station 02 · method bench
A2 germ
S_q(u; α) = u³/3 − α u, F = u² − α, H = 2u, a2 = 1. Fold of this family only at (α, u) = (0, 0) = Σ_Sq. This is a method fingerprint — not CERT_ReS_fold.
Potential
S(u)
Bifurcation
α × u
For α > 0 the critical set is two Morse points u = ±√α. They meet at the fold.
Classify
PASS_GENUINE_FOLD- S
- 0
- F
- 0
- |F|
- 0
- H = a1
- 0
- a2
- 1
- n₀
- 1
- simple kernel
- true
- namespace
- Sigma_Sq only
Cuts: |F| < 1e-6, |a1| < 1e-8 simple, a2 ≠ 0. Morse bowls and off-shell dips are refused. Airy on this germ does not prove a ReS fold.