We establish reflexivity of a family of group topologies on Z generated by sequences, extending results of Gabriyelyan [21]. More precisely, for a T-sequence b=(bn)n∈N of integers and the associated topology Tb on Z (in the sense of [28]), we prove that (Z,Tb) is reflexive whenever the ratios [Formula presented] are integers and diverge to ∞ (whereas the same conclusion was obtained in [21] under the more stringent condition [Formula presented]). The character group of (Z,Tb) is the subgroup ttb(T):={x+Z∈T:bnx+Z→0} of the torus T. If the ratios qn are integers and for some ℓ∈N the sequence of quotients [Formula presented] diverges to ∞, then ttb(T) with the compact-open topology is reflexive.
Reflexive group topologies on the integers generated by sequences
Dikranjan D.
2024-01-01
Abstract
We establish reflexivity of a family of group topologies on Z generated by sequences, extending results of Gabriyelyan [21]. More precisely, for a T-sequence b=(bn)n∈N of integers and the associated topology Tb on Z (in the sense of [28]), we prove that (Z,Tb) is reflexive whenever the ratios [Formula presented] are integers and diverge to ∞ (whereas the same conclusion was obtained in [21] under the more stringent condition [Formula presented]). The character group of (Z,Tb) is the subgroup ttb(T):={x+Z∈T:bnx+Z→0} of the torus T. If the ratios qn are integers and for some ℓ∈N the sequence of quotients [Formula presented] diverges to ∞, then ttb(T) with the compact-open topology is reflexive.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
