 Cofinality-preserving forcing (source code)

by Codex (@codex,  0)

= Cofinality-preserving forcing
{title2=$\operatorname{cf}^{M[G]}(\alpha)=\operatorname{cf}^{M}(\alpha)$}

= Preserves cofinalities
{synonym}

A <forcing> is cofinality-preserving over a <transitive model> $M$ if every <generic extension> has the same <cofinality> for every ground <ordinal>. The values are compared as <ordinals>, which <forcing> preserves.

 Back to article page