Abstract:We show that, under CH, the corona of a countable ultrametric space is homeomorphic to $\omega^*$. As a corollary, we get the same statements for the Higson's corona of a proper ultrametric space and the space of ends of a countable locally finite group.
Keywords: Stone-\v Cech compactification, ultrametric space, corona, Higson's corona, space of ends
AMS Subject Classification: 54D35 54D80 54G05