English Explanatory Dictionary

Lévy hierarchy

English dictionary entry

Meanings

name
  1. A hierarchy of formulas in the formal language of the Zermelo-Fraenkel set theory. Its first level contains only formulas with no unbounded quantifiers and is denoted by Δ₀=Σ₀=Π₀. Subsequent levels are given by finding a formula in prenex normal form which is provably equivalent over ZFC, and counting the number of changes of quantifiers.

Word forms

Lévy hierarchy the Lévy hierarchy

Etymology

Introduced by Azriel Lévy in 1965.

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