# GEOMETRIC CHARACTERIZATIONS OF CONCENTRATION POINTS FOR M$\"{O}$BIUS GROUPS

• Sung Bok Hong (Department of Mathematics, Pusan Women's University, Pusan 616-060, Korea) ;
• Jung Sook Sakong (Department of Mathematics Education, Korea University, Seoul 136-701, Korea)
• Published : 1994.10.01
• 44 2

#### Abstract

Although the study of the limit points of discrete groups of M$\ddot{o}$bius transformations has been a fertile area for many decades, there are some very natural topological properties of the limit points which appear not to have been previously examined. Let $\Gamma$ be a nonelementary discrete group of hyperbolic isometries acting on the Poincare disc $B^m, m \geq 2$, and let $p \in \partial B^m$ be a limit point of $\Gamma$. By a neighborhood of p, we will always mean an open neighborhood of p in $\partial B^m$.