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arXiv 1802.09377cs.LO
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命题证明复杂性的有限模型论视角

A Finite-Model-Theoretic View on Propositional Proof Complexity

Erich Grädel, Martin Grohe, Benedikt Pago, Wied Pakusa

AI总结:

本文建立了命题证明系统(如Horn归结、有界宽度归结、有界次多项式演算)与有限模型论中不动点逻辑之间的紧密对应关系,并利用这些联系为多项式演算证明下界提供了新工具。

摘要:

我们在命题证明复杂性与有限模型论之间建立了新的、且令人惊讶地紧密的联系。具体而言,我们证明了若干命题证明系统(如Horn归结、有界宽度归结和有界次单项式演算)的能力,可以在精确意义上由描述复杂性理论中具有根本重要性的不动点逻辑变体来刻画。我们的主要结果是:Horn归结具有与最小不动点逻辑相同的表达能力;有界宽度归结捕获了存在性最小不动点逻辑;而有理数上的有界次多项式演算恰好解决可在带计数的不动点逻辑中定义的问题。我们还研究了有界次多项式演算。在有理数上,如果我们限制系数的比特复杂度,它捕获带计数的不动点逻辑。对于无限制的系数,我们只能说有界次多项式演算至多与有界变量无穷计数逻辑一样强大,但其能力的精确逻辑刻画仍然是一个开放问题。这些逻辑与证明系统之间的联系使我们能够建立有限模型论工具,用于证明有理数上以及有限域上的多项式演算的下界。这是论文(arXiv:1802.09377)的修正版,原版于2019年1月23日发布。

英文摘要:

We establish new, and surprisingly tight, connections between propositional proof complexity and finite model theory. Specifically, we show that the power of several propositional proof systems, such as Horn resolution, bounded-width resolution, and the monomial calculus of bounded degree, can be characterised in a precise sense by variants of fixed-point logics that are of fundamental importance in descriptive complexity theory. Our main results are that Horn resolution has the same expressive power as least fixed-point logic, that bounded-width resolution captures existential least fixed-point logic, and that the polynomial calculus with bounded degree over the rationals solves precisely the problems definable in fixed-point logic with counting. We also study the bounded-degree polynomial calculus. Over the rationals, it captures fixed-point logic with counting if we restrict the bit-complexity of the coefficients. For unrestricted coefficients, we can only say that the bounded-degree polynomial calculus is at most as powerful as bounded variable infinitary counting logic, but a precise logical characterisation of its power remains an open problem. These connections between logics and proof systems allow us to establish finite-model-theoretic tools for proving lower bounds for the polynomial calculus over the rationals and also over finite fields. This is a corrected version of the paper (arXiv:1802.09377) published originally on January 23, 2019.

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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