A Finite-Model-Theoretic View on Propositional Proof Complexity

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 ch...

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Main Authors: Erich Grädel, Martin Grohe, Benedikt Pago, Wied Pakusa
Format: Article
Language:English
Published: Logical Methods in Computer Science e.V. 2022-06-01
Series:Logical Methods in Computer Science
Subjects:
Online Access:https://lmcs.episciences.org/4320/pdf
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author Erich Grädel
Martin Grohe
Benedikt Pago
Wied Pakusa
author_facet Erich Grädel
Martin Grohe
Benedikt Pago
Wied Pakusa
author_sort Erich Grädel
collection DOAJ
description 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.
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spelling doaj.art-6370b35ceda74a2cacae93fff84901012024-03-08T10:27:56ZengLogical Methods in Computer Science e.V.Logical Methods in Computer Science1860-59742022-06-01Volume 15, Issue 110.23638/LMCS-15(1:4)20194320A Finite-Model-Theoretic View on Propositional Proof ComplexityErich GrädelMartin GroheBenedikt PagoWied PakusaWe 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.https://lmcs.episciences.org/4320/pdfcomputer science - logic in computer sciencef.4.1
spellingShingle Erich Grädel
Martin Grohe
Benedikt Pago
Wied Pakusa
A Finite-Model-Theoretic View on Propositional Proof Complexity
Logical Methods in Computer Science
computer science - logic in computer science
f.4.1
title A Finite-Model-Theoretic View on Propositional Proof Complexity
title_full A Finite-Model-Theoretic View on Propositional Proof Complexity
title_fullStr A Finite-Model-Theoretic View on Propositional Proof Complexity
title_full_unstemmed A Finite-Model-Theoretic View on Propositional Proof Complexity
title_short A Finite-Model-Theoretic View on Propositional Proof Complexity
title_sort finite model theoretic view on propositional proof complexity
topic computer science - logic in computer science
f.4.1
url https://lmcs.episciences.org/4320/pdf
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