We consider the spaces called $Seq(u_t)$, constructed on the set $Seq$ of all finite sequences of natural numbers using ultrafilters $u_t$ to define the topology. For such spaces, we discuss continuity, homogeneity, and rigidity. We prove that $S(u_t)$ is homogeneous if and only if all the ultrafilters $u_t$ have the same Rudin-Keisler type. We proved that a space of Louveau, and in certain cases, a space of Sirota, are homeomorphic to $Seq(p)$ (i.e., $u_t = p$ for all $t\in Seq$). It follows that for a Ramsey ultrafilter $p$, $Seq(p)$ is a topological group.
@article{119236, author = {Jerry E. Vaughan}, title = {Two spaces homeomorphic to $Seq(p)$}, journal = {Commentationes Mathematicae Universitatis Carolinae}, volume = {42}, year = {2001}, pages = {209-218}, zbl = {1053.54033}, mrnumber = {1825385}, language = {en}, url = {http://dml.mathdoc.fr/item/119236} }
Vaughan, Jerry E. Two spaces homeomorphic to $Seq(p)$. Commentationes Mathematicae Universitatis Carolinae, Tome 42 (2001) pp. 209-218. http://gdmltest.u-ga.fr/item/119236/
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