Weakly Corson compact trees

Abstract

We introduce and study a new topology on trees, that we call the countably coarse wedge topology. Such a topology is strictly finer than the coarse wedge topology and it turns every chain complete, rooted tree into a Fréchet-Urysohn, countably compact topological space. We show the rôle of such topology in the theory of weakly Corson and weakly Valdivia compacta. In particular, we give the first example of a compact space T whose every closed subspace is weakly Valdivia, yet T is not weakly Corson. This answers a question due to Ondřej Kalenda.