On generic topological embeddings

Abstract

We show that an embedding of a fixed 0-dimensional compact space $K$ into the \v{C}ech--Stone remainder $\omega^*$ as a nowhere dense P-set is the unique generic limit, a special object in the category consisting of all continuous maps from $K$ to compact metric spaces. Using Fra\"iss\'e theory we get a few well know theorems about \v{C}ech--Stone remainder. We establish the following: -- an ultrametric space $K$ of weight $\kappa$ can be uniformly embedded into $\kappa^\kappa$ as a uniformly nowhere dense subset, -- every uniform homeomorphism of uniformly nowhere dense sets in $\kappa^\kappa$ can be extended to a uniform auto-homeomorphism of $\kappa^\kappa$, -- every uniformly nowhere dense set in $\kappa^\kappa$ is a uniform retract of $\kappa^\kappa$. If we assume that $\kappa$ is a weakly compact cardinal we get the counterpart of the above result without the uniformity assumption.