The Residual Gram-Kummer Grade Has a Nontrivial Elliptic Extension
Sequence claim: seqclaim-8a6ba83c9d9c23dcf2fbeabb.
Relative-cohomology test
Entry 1195 identifies the rank-eight associated grade as two occurrence copies of four Gram-Kummer lines. To test whether those lines split from the elliptic pair systems, retain the three oriented faces of each source-labelled residual triple.
For every one of the eight terms the exact profile is
The split face supplies the (H^0_-) pair boundary already divided out in Entry 1192. It contributes no new extension class.
Two Abel--Jacobi components
On either connected elliptic face (C_{ij}), the off-branch triple lifts to two distinct points (p_+,p_-). The relative-cohomology extension is the oriented normal function
For a smooth genus-one curve the Abel map (C\to\operatorname{Pic}^1(C)) is injective. Therefore
The retained triples are off branch, so both elliptic-face classes are generically nonzero. Across the source packet this gives 16 labelled nonzero extension components.
Result
The full coefficient object is a nontrivial extension of the rank-one Gram-Kummer quotient by existing elliptic (H^1) systems. This is precisely the H2 architecture:
Scope
This is a generic fiberwise relative-cohomology nonsplitting statement. It does not yet compute the complete Gauss--Manin off-diagonal matrices, integral extension index, or physical-chain pairing.
Next falsifier
For one representative of each (C_4) orbit, construct the two elliptic curves with their labelled point pairs and calculate the normal-function Gauss--Manin derivative. Quotient by regular triangular gauges and factor its intrinsic singular support. The decisive question is whether all poles lie on the already frozen branch/Gram/soft arrangement.
Artifacts
research/benincasa/checkers/four_site_qg_residual_abel_jacobi_extension.pyresearch/benincasa/results/four-site-qg-residual-abel-jacobi-extension.json