Feige's Random 33-SAT Refutation Hypothesis

OPENMajorConjectureProposed 2002 · Standard version

Canonical statement

For every sufficiently large constant Δ>0\Delta>0, there is no randomized polynomial-time algorithm AA having both of the following properties. First, for every satisfiable 33-CNF formula FF, A(F)A(F) never outputs UNSAT\mathsf{UNSAT}. Second, if Fn,ΔF_{n,\Delta} is formed on variables x1,,xnx_1,\ldots,x_n by choosing m=Δnm=\lfloor\Delta n\rfloor clauses independently and uniformly, each clause using three distinct variables with independent uniformly random signs, then
Pr[A(Fn,Δ)=UNSAT]1as n, \Pr[A(F_{n,\Delta})=\mathsf{UNSAT}]\longrightarrow1 \quad\text{as }n\to\infty,
where the probability includes the randomness of both the formula and AA.
View source LaTeX
For every sufficiently large constant \(\Delta>0\),
there is no randomized polynomial-time algorithm \(A\) having both of
the following properties. First, for every satisfiable \(3\)-CNF
formula \(F\), \(A(F)\) never outputs \(\mathsf{UNSAT}\). Second, if
\(F_{n,\Delta}\) is formed on variables \(x_1,\ldots,x_n\) by choosing
\(m=\lfloor\Delta n\rfloor\) clauses independently and uniformly, each
clause using three distinct variables with independent uniformly random
signs, then
\[
  \Pr[A(F_{n,\Delta})=\mathsf{UNSAT}]\longrightarrow1
  \quad\text{as }n\to\infty,
\]
where the probability includes the randomness of both the formula and
\(A\).
At every sufficiently large constant density the random formula is unsatisfiable with probability tending to one, but no proper polynomial-time refuter is known there. Polynomial-time refutation is known at much higher densities, including order n3/2n^{3/2} clauses.
This record fixes Feige's proper-refutation formulation: the algorithm may answer only UNSAT\mathsf{UNSAT} or decline, and it must never falsely refute a satisfiable formula.

The boxed statement is the canonical open formulation — not a stronger variant or a related research program. The status reflects the catalog's last review; do your own literature search before investing serious effort.