Characterizing sequences for precompact group topologies
  A precompact group topology $\tau$ on an abelian group $G$ is called {\em single sequence characterized} (for short, {\em ss-characterized}) if there is a sequence $\mathbf{u}= (u_n)$ in $G$ such that $\tau$ is the finest precompact group topology on $G$ making $\mathbf{u}=(u_n)$ converge to zero. It is proved that a metrizable precompact abelian group $(G,\tau)$ is $ss$-characterized iff it is countable. For every metrizable precompact group topology $\tau$ on a countably infinite abelian group $G$ there exists a group topology $\eta$ such that $\eta$ is strictly finer than $\tau$ and the groups $(G,\tau)$ and $(G,\eta)$ have the equal Pontryagin dual groups. We give a complete description of all $ss$-characterized precompact abelian groups modulo countable $ss$-characterized groups from which we derive:   (1) No infinite pseudocompact abelian group is $ss$-characterized.   (2) An $ss$-characterized precompact abelian group is hereditarily disconnected. 
D. Dikranjan, S. S. Gabriyelyan, V. Tarieladze
math.GR