The modal mu-calculus alternation hierarchy is strict

J.C. Bradfield
1998 Theoretical Computer Science  
One of the open questions about the modal mu-calculus is whether the alternation hierarchy collapses; that is, whether all modal fixpoint properties can be expressed with only a few alternations of least and greatest fixpoints. In this paper, we resolve this question by showing that the hierarchy does not collapse. @ 1998 -Elsevier Science B.V. All rights reserved
doi:10.1016/s0304-3975(97)00217-x fatcat:5s5cbfkq3ncdngny4qtoyqcl3e