Let G be a closed subgroup of S∞ and X be a Polish G-space. To each x ∈ X we associate an admissible set Ax and show how questions about X which involve Baire category, can be formalized in Ax.

6 Since (Q, <, f ) is not ω-categorical, we cannot apply [12] at this place c Majcher-Iwanow: Polish group actions, nice topologies and admissible sets

B Majcher-Iwanow

Math. Log. Quarterly

2003

Complexity of conjugacy classes of A(Q). Topology Appl

B Majcher-Iwanow

Complexity of conjugacy classes of A(Q). Topology…

2003

On quasiresolvent models and B-models. Algebra and Logic