# Recent and upcoming talks by Stefan Hoffelner

## Stefan Hoffelner: NS saturated and Delta_1-definable

Monday, June 19, 2017, 16.30 Seminar room 0.011, Mathematical Institute, University of Bonn Speaker: Stefan Hoffelner (University of Vienna) Title: NS saturated and Delta_1-definable Abstract: Questions which investigate the interplay of the saturation of the nonstationary ideal on $omega_1$, NS, and definability properties of the surrounding universe can yield surprising and deep results. continue reading…

## Stefan Hoffelner: $\text{NS}_{\omega_1}$ saturated and a $\Sigma^{1}_{4}$-definable wellorder on the reals

KGRC Research Seminar – 2017‑05‑11 at 4pm. Speaker: Stefan Hoffelner (KGRC) Abstract: The investigation of the saturation of the nonstationary ideal $\text{NS}_{\omega_1}$ has a long tradition in set theory. In the early 1970’s K. continue reading…