Promise-gap hardness of Max Independent Set

Lax614640.IndependentSetGapHardness · concepts/Lax614640/IndependentSetGapHardness.lean · lax-614640

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    Natural Language Statement

    Theorem

    Håstad's general-graph inapproximability result supplies the hardness theorem used by the reduction. We use its rational promise-gap form. For every integer q>2q>2, a bounded-error polynomial-step algorithm distinguishing nn-vertex graphs HH with α(H)≤n1/q\alpha(H)\leq n^{1/q} from those with n1−1/q≤α(H)n^{1-1/q}\leq\alpha(H) would imply NP⊆BPPNP\subseteq BPP.

    This formulation is proved here from the registered PCP-to-clique reduction in lax-253009. The proof complements the graph, guards the relative threshold, handles graphs below the solver's cutoff by bounded exhaustive search, and certifies the encoding conversion and randomized composition in the finite Turing-machine models.

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    Proven claimDefinitionThis conceptRelated conceptA → B: B builds on A
    Evidence

    Lean source view on GitHub

    1import Lax614640.Gap
    2import Lax434930.NondeterministicPolynomialTime
    3import Lax666725.RandomizedPolynomialTime
    4
    5/-!
    6---
    7title: Promise-gap hardness of Max Independent Set
    8type: theorem
    9---
    10Håstad's general-graph inapproximability result supplies the hardness theorem
    11used by the reduction. We use its rational promise-gap form. For
    12every integer q>2q>2, a bounded-error polynomial-step algorithm distinguishing
    13nn-vertex graphs HH with α(H)≤n1/q\alpha(H)\leq n^{1/q} from those with
    14n1−1/q≤α(H)n^{1-1/q}\leq\alpha(H) would imply NP⊆BPPNP\subseteq BPP.
    15
    16This formulation is proved here from the registered PCP-to-clique reduction
    17in lax-253009. The proof complements the graph, guards the relative threshold,
    18handles graphs below the solver's cutoff by bounded exhaustive search, and
    19certifies the encoding conversion and randomized composition in the finite
    20Turing-machine models.
    21-/
    22
    23set_option autoImplicit false
    24
    25namespace Lax614640.IndependentSetGapHardness
    26
    27open Lax614640.Gap
    28open Lax434930.NondeterministicPolynomialTime
    29open Lax666725.RandomizedPolynomialTime
    30
    31/-- Håstad's general-graph promise-gap inapproximability theorem. -/
    32axiom gapSolver_implies_np_subset_bpp :
    33 ∀ q : ℕ, 3 ≤ q → MISGapSolver q → NP ⊆ BPP
    34
    35end Lax614640.IndependentSetGapHardness
    36
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