# E8 channel-amplitude perturbation

**Date:** 26 October 2026

**Status:** one unequal-channel direction promoted; open perturbation tube not certified

**Evidence:** [perturbation ledger](../../../evidence/data/translation-free-e8-channel-amplitude-perturbation-v1.json)
**Certificate:** [perturbation verifier](../../../verification/verify/verify_translation_free_e8_channel_amplitude_perturbation.mjs)

The scalar coupling spine is no longer the only evidence for stability. At
fixed mean locking strength 0.5, replace the eight equal amplitudes by

\[
(u_1,\ldots,u_8)=(0.55,0.45,0.54,0.46,0.53,0.47,0.52,0.48).
\]

This breaks equal-channel locking while preserving positivity and global
inversion. Complete-shell gaps at cutoffs 6, 8 and 10 are respectively
0.2185344832, 0.2173316417 and 0.2172388980. Successive relative changes are
0.550% and 0.0427%; final low-state boundary leakage is below
\(5.1\times10^{-6}\). Relative to the symmetric mean-coupling result, the
final gap moves by only -0.476%.

The detector survives in a more informative form. The ground state remains
even; the first excitation remains odd, cosine-dark and sine-bright, but its
eight sine weights become unequal. The second excitation remains even and
cosine-bright. Thus the perturbation changes the channel fingerprint without
destroying the selection rule.

This is one certified ray through parameter space, not a neighbourhood. A
[second non-collinear direction](E8_CHANNEL_AMPLITUDE_STENCIL.md) now forms a
finite stencil, but does not fill the region between samples. It
does not establish arbitrary channel disorder, metric stability, an
intercell or thermodynamic gap, E8 response, or material E8. Independent
amplitude directions and positive quadratic-metric perturbations are the next
gates; only then is an open compact-cell tube a defensible target.