Ideals of the semigroup of ultrafilters of a topological group

Abstract

We construct two new series of closed left ideals of the semigroup \(\bar \tau \) of ultrafilters of a topological group (G, τ). The first series gives a disjunctive decomposition of τ-absorbing ultrafilters. Under certain restrictions on the topology of the group (G, τ), the second series gives a disjunctive decomposition of the semigroup of free ultrafilters. For a nondiscrete metrizable topological group (G, τ), we construct a large free subsemigroup of the semigroup \(\bar \tau \) .