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| 1 | +# Semantic Hardening Plan (D.1 -> I.1) |
| 2 | + |
| 3 | +## Goal |
| 4 | + |
| 5 | +Replace compile-safe placeholders with mathematically meaningful Lean proofs across the production chain: |
| 6 | + |
| 7 | +- no `axiom` |
| 8 | +- no `sorry` |
| 9 | +- no proxy theorem statements of the form `: True` |
| 10 | + |
| 11 | +## Scope |
| 12 | + |
| 13 | +Production proof chain files: |
| 14 | + |
| 15 | +- `Collatz/Foundations/Core.lean` |
| 16 | +- `Collatz/Epochs/Core.lean` |
| 17 | +- `Collatz/Epochs/APStructure.lean` |
| 18 | +- `Collatz/Epochs/Homogenization.lean` |
| 19 | +- `Collatz/Epochs/NumeratorCarry.lean` |
| 20 | +- `Collatz/Epochs/LongEpochs.lean` |
| 21 | +- `Collatz/SEDT/Core.lean` |
| 22 | +- `Collatz/SEDT/Theorems.lean` |
| 23 | +- `Collatz/Mixing/Semigroup.lean` |
| 24 | +- `Collatz/Mixing/PhaseMixing.lean` |
| 25 | +- `Collatz/Mixing/TouchFrequency.lean` |
| 26 | +- `Collatz/CycleExclusion/CycleDefinition.lean` |
| 27 | +- `Collatz/CycleExclusion/PeriodSum.lean` |
| 28 | +- `Collatz/CycleExclusion/PureE1Cycles.lean` |
| 29 | +- `Collatz/CycleExclusion/MixedCycles.lean` |
| 30 | +- `Collatz/CycleExclusion/RepeatTrick.lean` |
| 31 | +- `Collatz/CycleExclusion/Main.lean` |
| 32 | +- `Collatz/Convergence/Coercivity.lean` |
| 33 | +- `Collatz/Convergence/FixedPoints.lean` |
| 34 | +- `Collatz/Convergence/NoAttractors.lean` |
| 35 | +- `Collatz/Convergence/MainTheorem.lean` |
| 36 | + |
| 37 | +## Workstreams |
| 38 | + |
| 39 | +### W1. Foundations Hardening |
| 40 | + |
| 41 | +Target: |
| 42 | + |
| 43 | +- Replace proxy definitions (`OddPred`, simplified `collatz_step`, etc.) with canonical forms. |
| 44 | +- Prove foundational arithmetic and parity lemmas needed by all downstream modules. |
| 45 | + |
| 46 | +Done criteria: |
| 47 | + |
| 48 | +- Core definitions match paper-level intent. |
| 49 | +- No theorem/lemma in this file uses `: True`. |
| 50 | +- Downstream files can import these lemmas without introducing local stubs. |
| 51 | + |
| 52 | +### W2. Epoch Semantics (D.1 + G.5 prerequisites) |
| 53 | + |
| 54 | +Target: |
| 55 | + |
| 56 | +- Replace synthetic epoch quantities (`p_touch`, `long_epoch_density`, etc.) with derivable definitions. |
| 57 | +- Formalize AP structure, homogenization, and numerator carry lemmas with exact hypotheses. |
| 58 | + |
| 59 | +Done criteria: |
| 60 | + |
| 61 | +- D-level lemmas are real statements with executable hypotheses/conclusions. |
| 62 | +- Long-epoch machinery has a mathematically interpretable statement that can feed SEDT/mixing. |
| 63 | + |
| 64 | +### W3. SEDT Core (E.2) |
| 65 | + |
| 66 | +Target: |
| 67 | + |
| 68 | +- Remove proxy numeric constants and bind them to explicit assumptions/derived bounds. |
| 69 | +- Replace placeholder bounds and witness-only proofs with inequalities used in subsequent modules. |
| 70 | + |
| 71 | +Done criteria: |
| 72 | + |
| 73 | +- `SEDT/Core` and `SEDT/Theorems` expose theorem statements that correspond to paper E.2 objects. |
| 74 | +- No placeholder existential witnesses (`⟨-1, by norm_num⟩` style) remain unless mathematically intended. |
| 75 | + |
| 76 | +### W4. Mixing Layer (F.6/F.7) |
| 77 | + |
| 78 | +Target: |
| 79 | + |
| 80 | +- Formalize semigroup and phase-mixing statements as actual measure/frequency bounds. |
| 81 | +- Connect touch-frequency and mixing conclusions to SEDT inputs. |
| 82 | + |
| 83 | +Done criteria: |
| 84 | + |
| 85 | +- F.6/F.7 equivalent statements are explicit and consumed by H-level modules. |
| 86 | +- No vacuous proofs. |
| 87 | + |
| 88 | +### W5. Cycle Exclusion (H.main) |
| 89 | + |
| 90 | +Target: |
| 91 | + |
| 92 | +- Replace `False`-based proxy predicates for cycle properties with real definitions. |
| 93 | +- Prove exclusion via period-sum and repeat-trick arguments over those real predicates. |
| 94 | + |
| 95 | +Done criteria: |
| 96 | + |
| 97 | +- `Cycle.is_pure_e1`, `Cycle.is_nontrivial`, and related notions are semantically meaningful. |
| 98 | +- `Main.lean` excludes nontrivial cycles from proven premises, not from definitional falsity. |
| 99 | + |
| 100 | +### W6. Convergence Closure (I.1) |
| 101 | + |
| 102 | +Target: |
| 103 | + |
| 104 | +- Strengthen coercivity/fixed-point/no-attractor modules to formal implications. |
| 105 | +- Derive global convergence theorem from hardened D/E/F/G/H stack. |
| 106 | + |
| 107 | +Done criteria: |
| 108 | + |
| 109 | +- `Convergence/MainTheorem.lean` theorem statement corresponds to I.1 and depends only on proven lemmas. |
| 110 | + |
| 111 | +### W7. CI and Acceptance |
| 112 | + |
| 113 | +Target: |
| 114 | + |
| 115 | +- Keep existing no-`sorry`/no-`axiom` gate. |
| 116 | +- Add semantic gate that rejects vacuous theorem signatures in production chain. |
| 117 | + |
| 118 | +Done criteria: |
| 119 | + |
| 120 | +- CI fails on new `: True` theorem declarations in production files. |
| 121 | +- `lake build Collatz` passes in CI and locally. |
| 122 | + |
| 123 | +## Execution Order |
| 124 | + |
| 125 | +1. W1 Foundations |
| 126 | +2. W2 Epoch semantics |
| 127 | +3. W3 SEDT core |
| 128 | +4. W4 Mixing |
| 129 | +5. W5 Cycle exclusion |
| 130 | +6. W6 Convergence |
| 131 | +7. W7 CI hardening |
| 132 | + |
| 133 | +## Risk Notes |
| 134 | + |
| 135 | +- Tight coupling between W2, W3, and W4 can cause theorem churn; stabilize interfaces early. |
| 136 | +- Avoid introducing new broad axiomatizations; prefer local assumptions and explicit parameter records. |
| 137 | +- Keep theorem names stable where possible to reduce cross-file rewrite overhead. |
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