First countability, tightness, and other cardinal invariants in remainders of topological groups

Abstract

We consider the following natural questions: when a topological group G has a first countable remainder, when G has a remainder of countable tightness? This leads to some further questions on the properties of remainders of topological groups. Let G be a topological group. The following facts are established. 1. If G ω has a first countable remainder, then either G is metrizable, or G is locally compact. 2. If G has a countable network and a first countable remainder, then either G is separable and metrizable, or G is σ -compact. 3. Under ( MA + ¬ CH ) every topological group with a countable network and a first countable remainder is separable and metrizable. Some new open problems are formulated.