Locally quasi-convex topologies on the group of the integers

Abstract

\noindent The most natural group topology on $\Z$ is the discrete one. There are other well-known group topologies on $\Z$, like the $p$-adic, defined for any prime number $p$. It is also an important group topology the weak topology with respect to the group of homomorphisms from $\Z$ to the unit circle of the complex plane; that is, the one defined by the characters and which is known as "the Bohr topology" on $\Z$. \noindent In \cite{tesislorenzo}, it is proved that taking as a neighbourhood basis at 0 the subsets $\{W_n\mid n\in\N\}$, defined by $W_n:=\{k\in\Z\mid\forall x\in S$, $ k\cdot x\in[-\frac{1}{4n},\frac{1}{4n}]+\Z\}$, where $S$ is a quasi-convex sequence in $\T$, a group topology on $\Z$ is obtained, $\tau_S$. We know that the topology $\tau_S$ is metrizable and locally quasi-convex. \noindent In this monograph we characterize convergent sequences in $\tau_S$, for some $S\subset\T$. We give sufficient conditions on the elements of $\Z$ in order that they belong to a neighbourhood $W_n$. For a fixed sequence $(b_n)$ of natural numbers, restricted to mild conditions, we have considered the "linear topology associated" whose neighbourhood basis at 0 is $\{b_n\Z\mid n\in\N\}$ and the "topology of uniform convergence" on $S=\{\frac{1}{b_n}+\Z\mid n\in\N\}\subset\T$. We make a comparative study between both classes of topologies.