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arXiv · 2512.17378

When Symmetry Yields NP-Hardness: Affine ML-SAT on S5 Frames

Andreas Krebs·Arne Meier
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Abstract

Hemaspaandra~et~al.~[JCSS 2010] conjectured that satisfiability for multi-modal logic restricted to the connectives XOR and 1, over frame classes T, S4, and S5, is solvable in polynomial time. We refute this for S5 frames, by proving NP-hardness.

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Andreas Krebs, Arne Meier. 2025-12-19. When Symmetry Yields NP-Hardness: Affine ML-SAT on S5 Frames. https://arxiv.org/abs/2512.17378

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