Every Veblen level is a normal function; φ_{α+1} enumerates fixed points of φ_α (BH climb rung 5)#246
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…erates fixed points of φ_α (BH climb rung 5)
Target-side climb toward ψ₀(Ω_ω) (BH order-type fidelity, open problem
D-2026-06-14). Builds on VeblenBinary (binary φ + generic fixed-point
engine) and VeblenPhiNormal (ω^^-monotonicity).
New module proofs/agda/Ordinal/Brouwer/VeblenBinaryNormal.agda
(--safe --without-K, zero postulates, structural recursion):
VeblenBinary proved continuity (φ-cont) + base-of-tower fixed-point
correctness (nextFix-fixed-{≤,≥}). This slice closes the two remaining
normal-function properties FOR EVERY LEVEL, by induction on the level α
through the generic engine:
* φ-mono₂ — every φ_α is monotone in its argument;
* φ-infl — every φ_α is inflationary (β ≤′ φ_α β).
With VeblenBinary.φ-cont this gives: EVERY Veblen level is a normal
function.
And the defining property of the hierarchy:
* φ-level-fixed-{≤,≥} — φ_{α+1}(β) IS a fixed point of φ_α
(φ_α (φ_{α+1} β) ≃ φ_{α+1} β, bi-≤′).
Generic engine lemmas proved once for an arbitrary monotone/continuous g
and instantiated at each level (the VeblenPhiNormal reuse pattern, now
generic): g-tower-mono, nextFix-mono, deriv-step-≤, deriv-oz-least,
deriv-mono, commonStep-mono; deriv-infl; deriv-fixed-≤ (continuous g),
deriv-fixed-≥ (monotone + inflationary g); plus ≡→≤′.
Design note: every deriv-mono / ≤′-lim / ω^^-mono-≤′ call (and the ⊤-valued
≤′-zero) pins its implicit source explicitly — _≤′_ is a reducing relation.
Honest scope: this is the normal-function backbone for "Γ₀ is the LEAST
diagonal fixed point" (the next slice) and the eventual ordinal-collapsing
layer. It does NOT prove Γ₀ least, does NOT reach the collapsing layer,
and closes NO postulate. Order-type fidelity (ψ₀(Ω_ω)) REMAINS OPEN
(D-2026-06-14).
Wiring: All.agda import; Smoke.agda pin block (9 headlines).
agda proofs/agda/All.agda and proofs/agda/Smoke.agda exit 0 under
--safe --without-K; kernel-guard.sh PASS; zero postulates.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Rw1RpYXU5Q7rzy2bVofVeB
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## What & why Next rung toward ψ₀(Ω_ω) (BH order-type fidelity, open problem `D-2026-06-14`). Builds on `VeblenBinary` + `VeblenBinaryNormal` (#245/#246 — every level a normal function, the Veblen recurrence, the generic fixed-point engine). The diagonal **Γ₀** was *defined* in rung 4 with only `≤′`-upper-bound sanity. Showing it is a **fixed point** of the diagonal `D(α) = φ_α(0)` needs monotonicity of φ in its **first** argument — this rung proves the two forms the diagonal needs and uses them to close **one direction** of the Γ₀ fixed point. ## New module `Ordinal/Brouwer/VeblenBinaryMono.agda` `--safe --without-K`, **zero postulates**: | Theorem | Statement | |---|---| | `commonStep-absorb` | a fixed point of `commonStep F` is a fixed point of every family member | | `commonStep-cont` | `commonStep F` is continuous when every member is | | **`φ-mono₁-step`** | adjacent levels ordered: `φ_α x ≤′ φ_{α+1} x` | | **`φ-mono₁-into-lim`** | a level below a limit is dominated: `φ_{h m} x ≤′ φ_{olim h} x` | | **`Γ₀-prefixed`** | **`Γ₀ ≤′ φ_Γ₀(0)`** — Γ₀ is a pre-fixed point of the diagonal | Both monotonicity results rest on one mechanised idea: `φ_β(x)` is a fixed point of every lower level `φ_α`, so `φ_α x ≤′ φ_α (φ_β x) = φ_β x`. For successors the absorbing fixed point is the Veblen recurrence (`φ-level-fixed`); for limits it comes from `commonStep` correctness + `deriv-fixed-≤`. ## Honest scope This closes only the `≤′` direction **`Γ₀ ≤′ φ_Γ₀(0)`**. The reverse `φ_Γ₀(0) ≤′ Γ₀` (closure from above) and full **"Γ₀ is the *least* diagonal fixed point"** need general first-argument monotonicity / common-fixed-point-from-above and remain **OPEN** — the next slice. **ψ₀(Ω_ω) sits far above Γ₀** behind the collapsing layer; **order-type fidelity REMAINS OPEN (`D-2026-06-14`)**. No postulate closed. ## Wiring `All.agda` import; `Smoke.agda` pin block (5 headlines). ## Verification - `agda proofs/agda/All.agda` → exit 0 - `agda proofs/agda/Smoke.agda` → exit 0 - `scripts/kernel-guard.sh` → **PASS** - zero postulates; `--safe --without-K` 🤖 Generated with [Claude Code](https://claude.com/claude-code) https://claude.ai/code/session_01Rw1RpYXU5Q7rzy2bVofVeB --- _Generated by [Claude Code](https://claude.ai/code/session_01Rw1RpYXU5Q7rzy2bVofVeB)_ Co-authored-by: Claude <noreply@anthropic.com>
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What & why
Next rung of the target-side climb toward ψ₀(Ω_ω) (BH order-type fidelity, open problem
D-2026-06-14). Builds onVeblenBinary(#245 — binary φ + the generic fixed-point engine) andVeblenPhiNormal(ω^^-monotonicity).VeblenBinaryproved continuity (φ-cont) and base-of-tower fixed-point correctness (nextFix-fixed-{≤,≥}). This slice closes the two remaining normal-function properties for every level, by induction on the level α through the generic engine.New module
Ordinal/Brouwer/VeblenBinaryNormal.agda--safe --without-K, zero postulates, structural recursion:φ-mono₂a ≤′ b → φ_α a ≤′ φ_α b)φ-inflβ ≤′ φ_α β)φ-level-fixed-≤/≥φ_α (φ_{α+1} β) ≃ φ_{α+1} β, bi-≤′)With
VeblenBinary.φ-cont, this establishes that every Veblen level φ_α is a normal function (monotone + inflationary + continuous).The generic engine lemmas are proved once for an arbitrary monotone/continuous
gand instantiated at each level (theVeblenPhiNormalreuse pattern, now generic):g-tower-mono,nextFix-mono,deriv-step-≤,deriv-oz-least,deriv-mono,commonStep-mono;deriv-infl;deriv-fixed-≤(continuous g),deriv-fixed-≥(monotone + inflationary g); plus≡→≤′.Honest scope
This is the normal-function backbone for "Γ₀ is the least diagonal fixed point" (the next slice) and the eventual ordinal-collapsing layer. It does not prove Γ₀ least, does not reach the collapsing layer, and closes no postulate. Order-type fidelity (ψ₀(Ω_ω)) REMAINS OPEN (
D-2026-06-14).Wiring
All.agdaimport;Smoke.agdapin block (9 headlines).Verification
agda proofs/agda/All.agda→ exit 0agda proofs/agda/Smoke.agda→ exit 0scripts/kernel-guard.sh→ PASS--safe --without-K; structural recursion🤖 Generated with Claude Code
https://claude.ai/code/session_01Rw1RpYXU5Q7rzy2bVofVeB
Generated by Claude Code