The Consistency of the ${\mathbf{\Sigma }}_3^1$-Separation Property

Stefan Hoffelner

We generically construct a model in which the ${\mathbf{\Sigma }}_3^1$-separation property is true, i.e. every pair of disjoint ${\mathbf{\Sigma }}_3^1$-sets can be separated by a ${\mathbf{\Delta }}_3^1$-definable s…