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近自由代数:从词问题到消去量词

Almost free algebras: from the word problem to elimination of quantifiers

University of Electronic Science and Technology of China(电子科技大学)

Yifan Jia, Heer Tern Koh, Bakh Khoussainov

AI总结:

本文研究近自由代数的多项式时间可解性,包括词问题、同余类基数计算及同构检查等,同时证明其可通过扩展语言实现量词消去。

摘要:

术语代数在计算机科学中非常重要,且已被广泛研究。一种自然的推广是通过对有限多个地面术语等式来商这些代数,从而得到我们称之为近自由代数的对象。近自由代数中的一个最早结果是其词问题可以在多项式时间内决定。在本文中,我们证明了其他自然问题:寻找标准代表;计算同余类的基数;检查所有同余类是否无限;检查代数是否有限;检查两个代数是否同构,都是多项式时间可决定的。术语代数的另一个著名结果是它们可以在适当扩展的语言中实现量词消除。遵循这一模式,我们还展示了近自由代数可以通过扩展语言加入标准测试谓词来实现量词消除。虽然这已被现有结果所暗示,但我们将本文的主要贡献视为提供了一种不同的方法,我们认为这种方法可以轻松扩展到一个更大的类别,而该类别并未被现有工作所覆盖。最后,我们提供了一个应用于量词消除过程的应用,构造了具有多项式时间词问题的任意签名非初始代数示例。

英文摘要:

Term algebras are important objects in computer science and are correspondingly well-studied. A natural generalization is to quotient these algebras by finitely many ground term equations, obtaining what we call almost free algebras. One of the earliest results on almost free algebras is that their word problem is polynomial time decidable. In this paper, we show that other natural problems: finding canonical representatives; computing the cardinality of a congruence class; checking if all congruence classes are infinite; checking if the algebra is finite; checking if two algebras are isomorphic, are all polynomial time decidable. Another famous result regarding term algebras is that they admit quantifier elimination in a suitably expanded language. Following this pattern, we also show that almost free algebras admit quantifier elimination by expanding the language with the standard tester predicates. While this is implied by existing results, we view our main contribution here as providing a different approach, which we posit can be easily extended to a larger class that is not covered by existing works. Finally, we provide an application to the quantifier elimination procedure, constructing examples of non-initial algebras over arbitrary signatures with a polynomial time word problem.

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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