arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 2005.00593cs.CCcs.LOmath.LOmath.RA
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强子代数与约束满足问题

Strong subalgebras and the Constraint Satisfaction Problem

Dmitriy Zhuk

摘要:

在2007年,它被证明,约束满足问题(CSP)的约束语言$Γ$是易处理的,当且仅当$Γ$是由一个弱近似(WNU)操作保持。经过多次努力和部分结果,该猜想于2017年由Andrei Bulatov和作者独立证明。在本文中,我们认为我的证明,即强子代数,使我们能够减少域的变量迭代的两个主要成分之一。为了解释这个想法是如何工作的,我们展示了强子代数的代数性质,并提供了关于CSP复杂性的两个重要事实的自包含证明。首先,我们证明,如果一个约束语言不被保存的WNU操作,那么相应的CSP是NP-难的。其次,我们描述了所有的约束语言,可以解决局部一致性检查。此外,我们刻画了所有幂等代数没有一个WNU项的具体arity $n$,没有一个WNU项,有WNU项的所有arity大于2。本文中提出的大多数结果都不是新的,但我相信本文可以帮助理解我对CSP的方法,并且对已知事实的新的自包含证明也将是有用的。

英文摘要:

In 2007 it was conjectured that the Constraint Satisfaction Problem (CSP) over a constraint language $Γ$ is tractable if and only if $Γ$ is preserved by a weak near-unanimity (WNU) operation. After many efforts and partial results, this conjecture was independently proved by Andrei Bulatov and the author in 2017. In this paper we consider one of two main ingredients of my proof, that is, strong subalgebras that allow us to reduce domains of the variables iteratively. To explain how this idea works we show the algebraic properties of strong subalgebras and provide self-contained proof of two important facts about the complexity of the CSP. First, we prove that if a constraint language is not preserved by a WNU operation then the corresponding CSP is NP-hard. Second, we characterize all constraint languages that can be solved by local consistency checking. Additionally, we characterize all idempotent algebras not having a WNU term of a concrete arity $n$, not having a WNU term, having WNU terms of all arities greater than 2. Most of the results presented in the paper are not new, but I believe this paper can help to understand my approach to CSP and the new self-contained proof of known facts will be also useful.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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