Constructible hierarchy: Difference between revisions
→Definition
Line 2:
== Definition ==
Say a subset \(X\) of \(Y\) is definable if there are some \(z_0, z_1, \cdots, z_n \in Y\) and some formula \(\varphi\) in the language of set theory so that the elements of \(X\) are precisely the \(x\) so that \(Y\) satisfies \(\varphi(x, z_0, z_1, \cdots, z_n)\). For example, under the von Neumann
Like with the von Neumann hierarchy, the constructible hierarchy is built up in stages, denoted \(L_\alpha\).<ref>K. J. Devlin, "[https://core.ac.uk/download/pdf/30905237.pdf An introduction to the fine structure of the constructible hierarchy]" (1974)</ref>
|