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تسجيل مستخدم جديدCountably compact group topologies on the free Abelian group of size continuum (and a Wallace semigroup) from a selective ultrafilter
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We prove that the existence of a selective ultrafilter implies the existence of a countably compact Hausdorff group topology on the free Abelian group of size continuum. As a consequence, we show that the existence of a selective ultrafilter implies the existence of a Wallace semigroup (i.e., a countably compact both-sided cancellative topological semigroup which is not a topological group).
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