Bull. Korean Math. Soc. 2012; 49(1): 57-61
Printed January 1, 2012
https://doi.org/10.4134/BKMS.2012.49.1.57
Copyright © The Korean Mathematical Society.
Liulan Li and Xi Fu
Hengyang Normal University, Hunan Normal University
It is well known that one could use a fixed loxodromic or parabolic element of a non-elementary group $G\subset M(\overline{\mathbb R}^n)$ as a test map to test the discreteness of $G$. In this paper, we show that a test map need not be in $G$. We also construct an example to show that the similar result using an elliptic element as a test map does not hold.
Keywords: discreteness, non-elementary M\"obius group, test map
MSC numbers: Primary 30F40; Secondary 20H10
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