# n236 — Gate F, leg 2: the dynamical test body — two clean facts and one classic wall

**Date:** 2026-07-12 · **Follows n235** (the energy wall and Cherenkov brake, established at imposed kinematics — those results stand and do not suffer tonight's pathology).

## The two clean facts

1. **The dressed particle is a composite, and the kick experiment proves it.** A momentum kick delivered to the bare core alone does not translate the particle — it launches internal oscillations of the core inside its own dressing well (v(t) swinging 1.4 → −0.7 → +0.5): textbook polaron physics, observed here in the vacuum-dressing context. "Particle" in this theory means core + cloud, dynamically and not just rhetorically.
2. **The inertia is cloud-dominated.** Momentum bookkeeping on the released states gives M_eff/M₀ ≈ 40–100 before the method degrades: the dressing outweighs the bare core by two orders. This is the dynamical face of the theory's oldest inertia claim (mass = dressing, the information-metric route): what resists acceleration is overwhelmingly the cloud, not the core.

## The wall, named

The naive self-consistent release dynamics exhibits the **classic self-force runaway** (Abraham–Lorentz class): the core rides the near-field of its own slightly-lagging cloud, accelerates, overshoots — v(t) spikes unphysically (×6 at one supersonic point) before collapsing. This is not a defect of the theory; it is the known pathology of point-core + instantaneous self-force dynamics, present in classical electrodynamics for a century. The proper tool is the **collective-coordinate method** (treat the composite's position and cloud shape as the slow variables, integrate out the fast field) — registered as Gate F's next leg, with the polaron literature as the map.

## Gate F status after two legs

- Energy wall at the field cone: **established** (n235, imposed kinematics — clean).
- Cherenkov brake above the cone: **established** (n235).
- Cone inheritance (matter ceiling = the common k-cone): **standing, conditional** (n235's condition unchanged).
- Composite structure + cloud-dominated inertia: **established** (tonight).
- Free inertial glide of the dressed composite: **not yet demonstrated** — blocked on the runaway wall; collective coordinates owed.
- The relativistic M(v) curve: owed to the same method.

**Class: facts 1–2 [A-model, the observations are the oscillation record and the momentum bookkeeping]; the runaway diagnosis [named, classic]; no claim of inertial motion is made until the collective-coordinate leg runs.**