Speaker: Anschel Schaffer-Cohen

Abstract: Halmos’s lovely Naive Set Theory, after spending three chapters developing the theory of ordinal numbers, admits that they don’t actually come up much in set theory. In his words, “it just turns out that their main use is elsewhere, in topology, for instance, as a source of illuminating examples and counterexamples”. Let’s “recall” what the ordinal numbers actually are, and investigate their topological properties a bit.