Yet another hierarchy theorem

Publisher: Cambridge University Press

E-ISSN: 1943-5886|65|2|627-640

ISSN: 0022-4812

Source: The Journal of Symbolic Logic, Vol.65, Iss.2, 2000-06, pp. : 627-640

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Abstract

n + 1 nested k-ary fixed point operators are more expressive than n. This holds on finite structures for all sublogics of partial fixed point logic PFP that can express conjunction, existential quantification and deterministic transitive closure of binary relations using at most k-ary fixed point operators and that are closed against subformulas. Among those are a lot of popular fixed point logics.