Speaker: Robert Owen (University of Wisconsin-Madison)
Title: Outer models, class forcing, and weakly self-defining classes
Abstract: M.C. Stanley described [1] a notion of class forcing that allows
$0^\sharp$ to be realized from a ground model of $V=L$ assuming such
models exist in the universe. We consider the Definability Lemma for such
forcings and use this as a springboard to discuss set-theoretic complexity
classes lying between $\Sigma_n$/$\Pi_n$ and $\Delta_{n+1}$, and their
self-definability.
[1] M. C. Stanley: Outer models and genericity. J. Symb. Log. 68(2):
389-418 (2003)