# FitzHugh–Nagumo Coordination Transfer — Phase-1A Report

**Status:** Completed developmental external-model transfer.  
**Scope:** Standard FitzHugh–Nagumo excitable-medium simulation; not a biological prediction, medical guidance, hardware result, novel physics, or proof of CCT distinctiveness.

## External model

The plant uses the two-state excitable dynamics introduced by
[FitzHugh (1961)](https://pubmed.ncbi.nlm.nih.gov/19431309/) and the
distributed active-pulse interpretation demonstrated by
[Nagumo, Arimoto and Yoshizawa (1962)](https://www-sop.inria.fr/members/Mathieu.Desroches/teaching/MTSN/Articles/Nagumo_etal_ProcIRE_1962.pdf).
The latter explicitly reports thresholded pulse propagation, waveform shaping,
bidirectional transmission, and annihilation of opposing pulses.

## Frozen prediction

At fixed amplitude, duration and per-channel energy, stimulate electrode 2
first and electrode 1 second. Refractory history should reduce the
counter-propagating branch while preserving the target-facing pulse. The exact
reverse (`1→2`) was frozen as the destructive ablation. This is a **2T temporal
coordination** and process-quality prediction, not an access or energy claim.

## Held-out result

- Candidate minus exact reverse: **+0.0835**
  (paired bootstrap 95% interval
  **+0.0790 to
  +0.0889**).
- Candidate minus marginal-matched destructured schedule:
  **+0.0524**
  (95% interval **+0.0447 to
  +0.0594**).
- Best noncandidate policy: **temporal_2_0**.
- Candidate minus best noncandidate: **+0.0398**.
- Nuisance sign: **9/9** cases.
- Equal nominal total drive energy: **3.9015**.

## Frozen gates

| Gate | Result |
|---|---:|
| External transfer | PASS |
| Temporal mechanism | PASS |
| Nuisance sign | PASS |
| Numerical | PASS |
| CCT distinctiveness | fail |

## Incumbent closure

| Workflow | Frozen selection | Same as CCT |
|---|---|---:|
| CCT sparse causal-path rule | temporal_2_1 | yes |
| Linearized native | coactive_1_2 | no |
| Five-policy black-box search | factorial | no |
| Full factorial/sequence search | temporal_2_1 | yes |
| Sector-native refractory-wave rule | temporal_2_1 | yes |

The strongest domain-informed incumbent made the same zero-search decision as
the CCT rule. Therefore, even if the transfer and mechanism gates pass, this
phase cannot establish a uniquely CCT predictive advantage.

## Interpretation

The useful result is narrower: the coordination-order grammar transferred from
an abstract correlation benchmark to an externally anchored nonlinear
excitable medium. It correctly framed the relevant distinction as **temporal
path quality at equal channel energy**, rather than more energy, a new state of
matter, or nonstandard physics.

The remaining CCT burden is unchanged but sharper. A future test must use an
observer/resource boundary or a cross-domain decision rule that changes the
decision relative to the best domain-native workflow—not merely redescribe the
same refractory-wave reasoning.

## Integrity

- Frozen manifest: `46fa54172c6e3e42f6f62ebf06256b17c93b36ddb4a6a79ed88113c3a74b9555`.
- Nominal and nuisance records: `432`.
- Numerical comparisons: `8`.
- Process-sign disagreements under step refinement:
  `0`.
- Maximum refined score change:
  `0.005026`.
