A Simplest Undecidable Modal Logic
Edith Hemaspaandra, Henning Schnoor
Abstract
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Edith Hemaspaandra, Henning Schnoor
Abstract
Open-access reader
Modal logics are widely used in computer science. The complexity of their satisfiability problems has been an active field of research since the 1970s. We prove that even very "simple" modal logics can be undecidable: We show that there is an undecidable modal logic that can be obtained by restricting the allowed models with a first-order formula in which only universal quantifiers appear.
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Modal logics are widely used in computer science. The complexity of their satisfiability problems has been an active field of research since the 1970s. We prove that even very "simple" modal logics can be undecidable: We show that there is an undecidable modal logic that can be obtained by restricting the allowed models with a first-order formula in which only universal quantifiers appear.
Key concepts: Undecidable problem, Modal logic, Normal modal logic, Modal μ-calculus, Accessibility relation, Dynamic logic (digital electronics), Satisfiability, Modal