Feige's Random -SAT Refutation Hypothesis
OPENMajorConjectureProposed 2002 · Standard version
Canonical statement
For every sufficiently large constant , there is no randomized polynomial-time algorithm having both of the following properties. First, for every satisfiable -CNF formula , never outputs . Second, if is formed on variables by choosing clauses independently and uniformly, each clause using three distinct variables with independent uniformly random signs, then
where the probability includes the randomness of both the formula and .
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
\(A\).Notes
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 clauses.
This record fixes Feige's proper-refutation formulation: the algorithm may answer only or decline, and it must never falsely refute a satisfiable formula.
References (2)
- [Feige2002Random3SAT]
Relations between average case complexity and approximation complexity
Open ↗Uriel Feige · 2002 · misc
- [FeigeOfek2007Refutation]
Easily refutable subformulas of large random 3CNF formulas
Open ↗Uriel Feige and Eran Ofek · 2007 · misc
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.