Lévy hierarchy

短语

词形变化

the Lévy hierarchy

释义与例句

name
  1. 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.

    数学 哲学

词源

Introduced by Azriel Lévy in 1965.

来源：wiktionary