Subgroups of categorically closed semigroups

Taras Banakh, Serhii Bardyla

Let $\mathcal{C}$ be a class of topological semigroups. A semigroup $X$ is called (1) $\mathcal{C}$-$closed$ if $X$ is closed in every topological semigroup $Y\in \mathcal{C}$ containi…