Precompact groups and convergence

Abstract

We consider precompact sequential and Fr\'echet group topologies and show that some natural constructions of such topologies always result in metrizable groups answering a question of D.~Dikranjan et al. We show that it is consistent that all sequential precompact topologies on countable groups are Fr\'echet (or even metrizable). For some classes of groups (for example boolean) extra set-theoretic assumptions may be omitted (although in this case such groups do not have to be metrizable). We also build (using $\diamondsuit$) an example of a countably compact Fr\'echet group that is not $\alpha_3$ and obtain a counterexample to a conjecture of D.~Shakhmatov as a corollary.