Almost maximal topologies on semigroups
Yevhen Zelenyuk · Proceedings of the American Mathematical Society · 2010
A topology on a semigroup is left invariant if left translations are continuous and open. We show that for every infinite cancellative semigroup S S and n ∈ N n\in \mathbb {N} , there is a zero-dimensional Hausdorff left invariant topology on S S with exactly n n nonprincipal ultrafilters converging to the same point, all of them being uniform.