Schaefer’s dichotomy theorem states that a Boolean constraint satisfaction problem (CSP) is polynomial-time solvable if one of four given conditions holds for every type of constraint allowed in its instances. Otherwise, it is NP-complete. In this paper, we analyze Boolean CSPs in terms of their topological complexity, instead of their computational complexity. Motivated by complexity and topological universality results in computational geometry, we attach a natural topological space to the set of solutions of a Boolean CSP and introduce the notion of projection-universality. We prove that a Boolean CSP is projection-universal if and only if it is categorized as NP-complete by Schaefer’s dichotomy theorem, showing that the dichotomy translates exactly from computational to topological complexity. We show a similar dichotomy for SAT variants and homotopy-universality.
@InProceedings{schnider_et_al:LIPIcs.SoCG.2024.77, author = {Schnider, Patrick and Weber, Simon}, title = {{A Topological Version of Schaefer’s Dichotomy Theorem}}, booktitle = {40th International Symposium on Computational Geometry (SoCG 2024)}, pages = {77:1--77:16}, series = {Leibniz International Proceedings in Informatics (LIPIcs)}, ISBN = {978-3-95977-316-4}, ISSN = {1868-8969}, year = {2024}, volume = {293}, editor = {Mulzer, Wolfgang and Phillips, Jeff M.}, publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik}, address = {Dagstuhl, Germany}, URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.SoCG.2024.77}, URN = {urn:nbn:de:0030-drops-200220}, doi = {10.4230/LIPIcs.SoCG.2024.77}, annote = {Keywords: Computational topology, Boolean CSP, satisfiability, computational complexity, solution space, homotopy universality, homological connectivity} }
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