Pseudocompact hyperspaces of Isbell-Mrówka spaces
J. Ginsburg has asked what is the relation between the pseudocompactness of the ω-th power of a topological space X and the pseudocompactness of its Vietoris Hyperspace, exp(X). M. Hrusak, I. Martínez-Ruiz and F. Hernandez-Hernandez studied this question restricted to Isbell-Mrówka spaces, that is, spaces of the form Ψ(A) where A is an almost disjoint family. Regarding these spaces, if exp(X) is pseudocompact, then Xω is also pseudocompact, and Xω is pseudocompact iff A is a MAD family. They showed that if the cardinal characteristic p is c, then for every MAD family A, exp(Ψ(A)) is pseudocompact, and if the cardinal characteristic h is less than c, there exists a MAD family A such that exp(Ψ(A)) is not pseudocompact. They asked if there exists a MAD family A (in ZFC) such that exp(Ψ(A)) is pseudocompact.
In this talk, we present some new results on the (consistent) existence of MAD families whose hyperspaces of their Isbell-Mrówka spaces are (or are not) pseudocompact by constructing new examples. Moreover, we give some combinatorial equivalences for every Isbell-Mrówka space from a MAD family having pseudocompact hyperspace. This is a joint work with, O. Guzman, M. Hrusak, S. Todorcevic and A. Tomita.