Stefan Hoffelner

activity

20162026

Σ_{3}^{1}

-Separation Property

5 citations · 13 across the 22 of their papers we have counts for

collaborators

Showing 2023 · math.LOShow all

2 papers · 2 filters

math.LO2023

A Failure of $Π_{n + 3}^{1}$ -Reduction in the Presence of $Σ_{n + 3}^{1}$ -Separation

Stefan Hoffelner

We show that one can force over $L$ that $Σ_{3}^{1}$ -separation holds, while $Π_{3}^{1}$ -reduction fails, thus separating these two principles for the first time. The construction can be l…

math.LO2023

PFA and the definability of the nonstationary ideal

Stefan Hoffelner, Paul Larson, Ralf Schindler +1

We produce, relative to a $ZFC$ model with a supercompact cardinal, a $ZFC$ model of the Proper Forcing Axiom in which the nonstationary ideal on $ω_{1}$ is $Π_{1}$ -definab…

A Failure of Πn+31​-Reduction in the Presence of Σn+31​-Separation

PFA and the definability of the nonstationary ideal

A Failure of $Π_{n + 3}^{1}$ -Reduction in the Presence of $Σ_{n + 3}^{1}$ -Separation