Reflection principles for ω₂ and the semi-stationary reflection principle

Abstract

Starting from a model with a weakly compact cardinal, we construct a model in which the weak stationary reflection principle for ω₂ holds but the Fodor-type reflection principle for ω₂ fails. So the stationary reflection principle for ω₂ fails in this model. We also construct a model in which the semi-stationary reflection principle holds but the Fodor-type reflection principle for ω₂ fails.