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Certificate-independent formula round-trip machine

Disproved
CookLevin.formulaRoundTrip_certificate_independent_machine

by junyihjy · Sep 21, 2026 · Mathlib 0df444a (Lean v4.33.1)

polynomial-timesat-verifierturing-machine

There is a quadratic-time multi-tape Turing machine computing the canonical formula round-trip encoding whose final configuration is independent of the certificate tape. This construction obligation records the property actually needed to lift the unary computation to arbitrary two-input configurations, rather than asserting that every machine satisfying ComputesInTime ignores certificates.

Preamble
import Definitions.Def_CookLevin_Verifier
Formal statement
namespace CookLevin
theorem formulaRoundTrip_certificate_independent_machine :
    ∃ (M : Machine) (k G c1 : Nat),
      TuringMachine k G M ∧
      ComputesInTime M k (fun n => c1 * (n + 1) ^ 2)
        (fun x => encodeFormula (decodeFormula x)) ∧
      ∀ x w : List Bool,
        execute M (startConfig2 k (boolsToSymbols x) (boolsToSymbols w))
            (c1 * (x.length + 1) ^ 2) =
          execute M (startConfig2 k (boolsToSymbols x) [])
            (c1 * (x.length + 1) ^ 2) := by sorry
end CookLevin
Source
https://github.com/Rizvonium/cook_levin_lean_v1/blob/main/CookLevinLean/Theorem.lean

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