E8 Cartan-kernel coupling-ratio spine
Date: 26 October 2026
Status: five ratio points promoted; one nonscalar direction promoted; perturbation tube open
Evidence: ratio ledger Certificate: spine verifier
For (r=u/U), complete-shell convergence promotes:
| (r) | promoted gap | final shell | final boundary weight |
|---|---|---|---|
| 0.25 | 0.5092198755 | 8 | (1.57\times10^{-6}) |
| 0.375 | 0.3367370326 | 10 | (9.13\times10^{-7}) |
| 0.50 | 0.2182768215 | 10 | (4.98\times10^{-6}) |
| 0.75 | 0.1177882433 | 12 | (5.52\times10^{-6}) |
| 1.00 | 0.1019267219 | 12 | (2.93\times10^{-5}) |
Each point has two successive sub-one-percent increments and preserves the same parity detector: the first state is odd and sine-bright; the second is even and cosine-bright. The rising cutoff required with (r) is physical numerics, not solver failure: stronger locking spreads charge support.
Shell-six runs at (r=2,4) have 2.8% and 5.0% boundary weight and remain reconnaissance. The five promoted points are a sampled stability spine, not a proof of every intermediate ratio. One unequal-channel direction now survives, but independent amplitude directions and metric perturbations are required before calling this an open stability tube.