Linear topologies on $\Z$ are not Mackey topologies
  In this article it is shown that to every non-discrete Hausdorff linear topology on $\Z$ other metrizable locally quasi-convex group topologies can be associated which are strictly finer than the linear topology and such that the character groups coincide. Applying this result to the $p$-adic topology on $\Z$, we give a negative answer to the question of Dikranjan, whether this topology is Mackey. 
Lydia Aussenhofer and Daniel de la Barrera Mayoral
math.GN math.GR