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

Andreas Krebs, Arne Meier

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 poly…