Article ID Journal Published Year Pages File Type
6424727 Topology and its Applications 2013 7 Pages PDF
Abstract

Let G be a countably infinite group. A topology on G is left invariant if left translations are continuous. A left invariant topology is strongly complete if it is regular and for every partition {Un:n<ω} of G into open sets, there is a neighborhood V of 1 such that for every x∈G, {n<ω:(xV)∩Un≠∅} is finite. We show that assuming MA, for every n∈N, there is a strongly complete left invariant topology T on G with exactly n nonprincipal ultrafilters converging to 1, and in the case G=⨁ωZ2, T can be chosen to be a group topology. We also show that it is consistent with ZFC that if G can be embedded algebraically into a compact group, then there are no such topologies on G.

Related Topics
Physical Sciences and Engineering Mathematics Geometry and Topology
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