Games and full completeness for multiplicative linear logic
Journal of Symbolic Logic
The modal mu-calculus alternation hierarchy is strict
Theoretical Computer Science
A Calculus of Circular Proofs and Its Categorical Semantics
FoSSaCS '02 Proceedings of the 5th International Conference on Foundations of Software Science and Computation Structures
Ambiguous classes in µ-calculi hierarchies
Theoretical Computer Science - Foundations of software science and computation structures
The Variable Hierarchy of the μ-Calculus Is Strict
Theory of Computing Systems
Ambiguous classes in the games µ-calculus hierarchy
FOSSACS'03/ETAPS'03 Proceedings of the 6th International conference on Foundations of Software Science and Computation Structures and joint European conference on Theory and practice of software
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The variable hierarchy problem asks whether every μ -term t is equivalent to a μ -term t *** where the number of fixed-point variables in t *** is bounded by a constant. In this paper we prove that the variable hierarchy of the lattice μ -calculus --- whose standard interpretation is over the class of all complete lattices --- is infinite, meaning that such a constant does not exist if the μ -terms are built up using the basic lattice operations as well as the least and the greatest fixed point operators. The proof relies on the description of the lattice μ -calculus by means of games and strategies.