We show that there is a model of ZF in which the Borel hierarchy on the reals has length 2. This implies that 1 has countable cofinality, so the axiom of choice fails very badly i...
We first consider infinite two-player games on pushdown graphs. In previous work, Cachat, Duparc and Thomas [4] have presented a winning decidable condition that is Σ3-complete ...
We analyze the degree-structure induced by large reducibilities under the Axiom of Determinacy. This generalizes the analysis of Borel reducibilities given in [1], [6] and [5] e.g...
We investigate diagonal actions of Polish groups and the related intersection operator on closed subgroups of the acting group. The Borelness of the diagonal orbit equivalence rela...
This paper is a continuation of the study of topological properties of omega context free languages (-CFL). We proved in [Topological Properties of Omega Context Free Languages, T...