Research-Stack/0-Core-Formalism/lean/external/OTOM/BraidCross.lean

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/-
BraidCross.lean - Braid Crossing and Strand Merge Operations
Crossing topology: strands interact, merge, and generate residuals.
The merge rule remains linear on phaseAcc; bracket is recomputed after.
zᵢⱼ = zᵢ + zⱼ (linear merge)
μᵢⱼ = X(μᵢ, μⱼ) (crossing slot operator)
Bᵢⱼ = C(zᵢⱼ, μᵢⱼ) (bracket from merged state)
Rᵢⱼ = Bᵢⱼ - (Bᵢ + Bⱼ) (interaction residual)
-/
import Semantics.DynamicCanal
import Semantics.BraidBracket
import Semantics.BraidStrand
namespace Semantics.BraidCross
open DynamicCanal
open Semantics.BraidBracket
open Semantics.BraidStrand
/-- Crossing slot operator X(μᵢ, μⱼ)
Combines transport slots from two strands into merged slot.
Default: bitwise XOR of slot indices (creates unique crossing ID).
-/
def crossSlot (μᵢ μⱼ : Fix16) : Fix16 :=
-- XOR the raw representations for unique crossing slot
Fix16.mk (μᵢ.raw.xor μⱼ.raw)
/-- BraidCross: merge two strands into a crossing
This is THE fundamental merge operation. It:
1. Linearly adds phase accumulations: zᵢⱼ = zᵢ + zⱼ
2. Computes crossed slot: μᵢⱼ = X(μᵢ, μⱼ)
3. Derives new bracket: Bᵢⱼ = C(zᵢⱼ, μᵢⱼ)
4. Calculates residual: Rᵢⱼ = Bᵢⱼ - (Bᵢ + Bⱼ)
Key: merge in linear space first, derive bracket afterward.
-/
def braidCross (sᵢ sⱼ : BraidStrand) : BraidStrand × BraidBracket :=
-- Linear merge of phase accumulations
let zᵢⱼ := PhaseVec.add sᵢ.phaseAcc sⱼ.phaseAcc
-- Crossing slot operator
let μᵢ := Fix16.mk sᵢ.slot
let μⱼ := Fix16.mk sⱼ.slot
let μᵢⱼ := crossSlot μᵢ μⱼ
-- Derive new bracket from merged state (NOT from merging brackets)
let Bᵢⱼ := BraidBracket.fromPhaseVec zᵢⱼ μᵢⱼ
-- Calculate crossing residual
let Rᵢⱼ := BraidBracket.crossingResidual Bᵢⱼ sᵢ.bracket sⱼ.bracket
-- Construct merged strand
let mergedStrand : BraidStrand :=
{ phaseAcc := zᵢⱼ
, parity := sᵢ.parity && sⱼ.parity
, slot := sᵢ.slot.xor sⱼ.slot -- unique crossing slot
, residue := Rᵢⱼ.kappa -- store residual magnitude
, jitter := Fix16.add sᵢ.jitter sⱼ.jitter
, bracket := Bᵢⱼ }
(mergedStrand, Rᵢⱼ)
/-- Concrete left-identity witness for the zero strand. -/
theorem braidCrossZeroLeftWitness :
(braidCross (BraidStrand.zero 0) (BraidStrand.zero 1)).1.phaseAcc = PhaseVec.zero := by
native_decide
/-- Concrete right-identity witness for the zero strand. -/
theorem braidCrossZeroRightWitness :
(braidCross (BraidStrand.zero 1) (BraidStrand.zero 0)).1.phaseAcc = PhaseVec.zero := by
native_decide
/-- Parallel crossing: merge multiple strands simultaneously
z = Σᵢ zᵢ (linear sum over all strands)
Then derive single bracket from total.
-/
def parallelCross (strands : List BraidStrand) : BraidStrand :=
let totalPhase := strands.foldl (fun acc s => PhaseVec.add acc s.phaseAcc) PhaseVec.zero
let totalSlot := strands.foldl (fun acc s => acc.xor s.slot) 0
let totalJitter := strands.foldl (fun acc s => Fix16.add acc s.jitter) Fix16.zero
let μ := Fix16.mk totalSlot
let B := BraidBracket.fromPhaseVec totalPhase μ
{ phaseAcc := totalPhase
, parity := strands.all (fun s => s.parity)
, slot := totalSlot
, residue := Fix16.zero -- parallel merge has no pairwise residual
, jitter := totalJitter
, bracket := B }
/-- Check if crossing is admissible (merged bracket valid) -/
def crossingAdmissible (sᵢ sⱼ : BraidStrand) : Bool :=
let (merged, residual) := braidCross sᵢ sⱼ
merged.isAdmissible && residual.admissible
/-- Total residual norm from a crossing -/
def crossingResidualNorm (sᵢ sⱼ : BraidStrand) : Fix16 :=
let (_, residual) := braidCross sᵢ sⱼ
residual.kappa
/-- Crossing history for AVMR audit trail -/
structure CrossingHistory where
leftSlot : UInt32
rightSlot : UInt32
mergedSlot : UInt32
residual : BraidBracket
timestamp : UInt64
deriving Repr, DecidableEq
namespace CrossingHistory
def fromCross (sᵢ sⱼ : BraidStrand) (ts : UInt64) : CrossingHistory :=
let (_, residual) := braidCross sᵢ sⱼ
{ leftSlot := sᵢ.slot
, rightSlot := sⱼ.slot
, mergedSlot := sᵢ.slot.xor sⱼ.slot
, residual := residual
, timestamp := ts }
end CrossingHistory
#eval let s1 := BraidStrand.zero 1
let s2 := BraidStrand.zero 2
let (m, _) := braidCross s1 s2
m.slot
end Semantics.BraidCross