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- Formalizes coprime sieve observers and CRT reconstruction - depth_token_coprime_intersect: two coprime observations uniquely determine the semantic coordinate modulo ℓ₁·ℓ₂ - Witness: human ℓ=7 and dolphin ℓ=11 reconstruct shared coordinate 61 mod 77 - Add to Semantics.lean imports; builds under Compiler surface
112 lines
5.9 KiB
Text
112 lines
5.9 KiB
Text
/-
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SieveLemmas.lean -- Number-theoretic lemmas for coprime sieve observers
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This module formalizes the CRT reconstruction principle referenced in
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ImaginarySemanticTime.lean: two observers with coprime native sieve moduli
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hold independent, complementary shadows of the same underlying manifold
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coordinate. Neither observer can recover the other's view without a CRT
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exchange, but together they reconstruct the coordinate modulo the product.
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Key lemma: depth_token_coprime_intersect — the observations of two coprime
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sieves intersect in exactly one residue class modulo ℓ₁·ℓ₂, which is the
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original semantic coordinate's residue class.
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-/
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import Mathlib.Data.Nat.GCD.BigOperators
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import Mathlib.Data.ZMod.Basic
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namespace Semantics.SieveLemmas
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open Nat
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-- ═══════════════════════════════════════════════════════════════════════════
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-- §1 Sieve observations and coprimality
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-- ═══════════════════════════════════════════════════════════════════════════
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/-- A sieve modulus is a positive natural number used as a native resolution.
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We bundle the positivity proof so that modular operations are well-behaved. -/
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structure SieveModulus where
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val : Nat
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pos : val > 0
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deriving Repr
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/-- Observation of a semantic coordinate `x` through a sieve modulus `ℓ`. -/
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def observe (ℓ : SieveModulus) (x : Nat) : Nat := x % ℓ.val
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/-- Two sieve moduli are coprime observers when their values are coprime. -/
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def CoprimeObservers (ℓ1 ℓ2 : SieveModulus) : Prop :=
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Coprime ℓ1.val ℓ2.val
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instance {ℓ1 ℓ2 : SieveModulus} : Decidable (CoprimeObservers ℓ1 ℓ2) := by
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unfold CoprimeObservers; infer_instance
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/-- An observation is always smaller than its sieve modulus. -/
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lemma observe_lt (ℓ : SieveModulus) (x : Nat) : observe ℓ x < ℓ.val := by
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simp only [observe]
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apply mod_lt
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exact ℓ.pos
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-- ═══════════════════════════════════════════════════════════════════════════
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-- §2 CRT reconstruction
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-- ═══════════════════════════════════════════════════════════════════════════
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/-- Reconstruct the unique residue modulo ℓ₁·ℓ₂ that projects to `r1` and `r2`.
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Returns 0 if either modulus is invalid (defensive, since SieveModulus is positive). -/
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def crtReconstruct (ℓ1 ℓ2 : SieveModulus) (r1 r2 : Nat) (hc : CoprimeObservers ℓ1 ℓ2) : Nat :=
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(chineseRemainder hc r1 r2).val
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/-- The CRT reconstruction is correct modulo the first observer's modulus. -/
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theorem crtReconstruct_mod_ℓ1 (ℓ1 ℓ2 : SieveModulus) (r1 r2 : Nat)
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(hc : CoprimeObservers ℓ1 ℓ2) :
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crtReconstruct ℓ1 ℓ2 r1 r2 hc % ℓ1.val = r1 % ℓ1.val := by
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simp [crtReconstruct]
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exact (chineseRemainder hc r1 r2).property.left
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/-- The CRT reconstruction is correct modulo the second observer's modulus. -/
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theorem crtReconstruct_mod_ℓ2 (ℓ1 ℓ2 : SieveModulus) (r1 r2 : Nat)
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(hc : CoprimeObservers ℓ1 ℓ2) :
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crtReconstruct ℓ1 ℓ2 r1 r2 hc % ℓ2.val = r2 % ℓ2.val := by
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simp [crtReconstruct]
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exact (chineseRemainder hc r1 r2).property.right
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-- ═══════════════════════════════════════════════════════════════════════════
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-- §3 The coprime-intersection theorem (depth-token view)
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-- ═══════════════════════════════════════════════════════════════════════════
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/-- The observations of two coprime sieve observers uniquely determine the
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semantic coordinate modulo ℓ₁·ℓ₂. This is the "depth-token coprime
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intersection": two independent sieve depths coincide at exactly one
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residue class of the product modulus. -/
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theorem depth_token_coprime_intersect
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(ℓ1 ℓ2 : SieveModulus) (x : Nat) (hc : CoprimeObservers ℓ1 ℓ2) :
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let r1 := observe ℓ1 x
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let r2 := observe ℓ2 x
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crtReconstruct ℓ1 ℓ2 r1 r2 hc % (ℓ1.val * ℓ2.val) = x % (ℓ1.val * ℓ2.val) := by
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intro r1 r2
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have h1 : crtReconstruct ℓ1 ℓ2 r1 r2 hc % ℓ1.val = x % ℓ1.val := by
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rw [crtReconstruct_mod_ℓ1 ℓ1 ℓ2 r1 r2 hc]
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simp [observe, r1]
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have h2 : crtReconstruct ℓ1 ℓ2 r1 r2 hc % ℓ2.val = x % ℓ2.val := by
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rw [crtReconstruct_mod_ℓ2 ℓ1 ℓ2 r1 r2 hc]
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simp [observe, r2]
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exact (modEq_and_modEq_iff_modEq_mul hc).mp ⟨h1, h2⟩
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-- ═══════════════════════════════════════════════════════════════════════════
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-- §4 Witness
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-- ═══════════════════════════════════════════════════════════════════════════
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/-- Human (ℓ=7) and dolphin (ℓ=11) reconstruct 61 mod 77. -/
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def humanℓ : SieveModulus := ⟨7, by decide⟩
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def dolphinℓ : SieveModulus := ⟨11, by decide⟩
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def shared : Nat := 61
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def humanShadow : Nat := observe humanℓ shared
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def dolphinShadow : Nat := observe dolphinℓ shared
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def reconciled : Nat :=
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crtReconstruct humanℓ dolphinℓ humanShadow dolphinShadow (by decide)
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#eval humanShadow -- 5
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#eval dolphinShadow -- 6
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#eval! reconciled -- 61
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end Semantics.SieveLemmas
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