TY - JOUR AU - Protasov, I.V. AU - Protasova, K. PY - 2020/03/17 Y2 - 2024/03/29 TI - Closeness and linkness in balleans JF - Matematychni Studii JA - Mat. Stud. VL - 53 IS - 1 SE - Articles DO - 10.30970/ms.53.1.100-108 UR - http://matstud.org.ua/ojs/index.php/matstud/article/view/9 SP - 100-108 AB - A set $X$ endowed with a coarse structure is called ballean or coarse space. For a ballean $(X, \mathcal{E})$, we say that two subsets $A$, $B$ of $X$ are close (linked) if there exists an entourage $E\in \mathcal{E}$ such that $A\subseteq E [B]$, $B\subseteq E[A]$ (either $A, B$ are bounded or contain unbounded close subsets). We explore the following general question: which information about a ballean is contained and can be extracted from the relations of closeness and linkness. ER -