A Note On The Natural Range Of Unambiguous-SAT

Abstract: We discuss the natural range of the Unambiguous-SAT problem with respect to the number of clauses. We prove that for a given Boolean formula in precise conjunctive normal form with n variables, there exist functions f(n) and g(n) such that if the number of clauses is greater than f(n) then the formula does not have a satisfying truth assignment and if the number of clauses is greater than g(n) then the formula either has a unique satisfying truth assignment or no satisfying truth assignment. The interval between functions f(n) and g(n) is the natural range of the Unambiguous-SAT problem. We also provide several counting rules and an algorithm that determine the unsatisfiability of some formulas in polynomial time.