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Published September 16, 2020 | Version v112
Preprint Open

P versus NP

Creators

  • 1. CopSonic

Description

P versus NP is considered as one of the most important open problems in computer science. This consists in knowing the answer of the following question: Is P equal to NP? It was essentially mentioned in 1955 from a letter written by John Nash to the United States National Security Agency. However, a precise statement of the P versus NP problem was introduced independently by Stephen Cook and Leonid Levin. Since that date, all efforts to find a proof for this problem have failed. To attack the P versus NP question the concept of coNP-completeness has been very useful. A well-known coNP-complete problem is 3UNSAT. In 3UNSAT, it is asked whether a given Boolean formula ϕ in 3CNF is unsatisfiable.

In this paper, we consider the problem of computing the sum of the weighted densities of states of a Boolean formula in 3CNF. Given a Boolean formula ϕ, the density of states n(E) counts the number of truth assignments that leave exactly E clauses unsatisfied in ϕ. The weighted density of states m(E) is equal to E×n(E). The sum of the weighted densities of states of a Boolean formula in 3CNF with m clauses is equal to E=0mm(E). We prove that we can calculate the sum of the weighted densities of states in polynomial time. 

Diophantine equations of the form i=0mai×xi=c are solvable in polynomial time for arbitrary values of m. We can apply this Diophantine equation such that c is the value of the sum of the weighted densities of states from a Boolean formula ϕ in 3CNF, ai×xi is the value of each term E×n(E), where n(E) corresponds to the unknown value of xi. Hence, we only need to check that i=1mai×xi=c has all its solutions when  1im:xi>0 such that i=1mxi2n is always true, where n is the number of variables in ϕ. Certainly, if the Boolean formula ϕ has n variables, then ϕ has exactly 2n possible truth assignments. In this way, we are able to check whether the Boolean formula ϕ is unsatisfiable and obtain a solution for the problem 3UNSAT in polynomial time. If any coNP-complete problem is in P, then every NP problem can be decided by a polynomial time algorithm. Consequently, we show the complexity class P is equal to NP.

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