Characterized subgroups on the unit circle

Rafal Filipow, Adam kwela, Paolo Leonetti +1

Given an ideal $\mathcal{I}$ on $\omega$, a subgroup $H$ of the unit circle $\mathbb{T}$ is said to be $\mathcal{I}$-characterized if there exists an integer sequence $a=(a_n:n\in \omega )$…