×

A note on generalized triangle groups. (English) Zbl 0633.20018

The generalized triangle groups are two generator groups with a presentation \(a^ n=b^ p=R^ m(a,b)=1\) where \(2\leq n\leq p\), \(m\geq 2\) and R(a,b) is a cyclically reduced word involving both a and b. For the usual triangle groups where \(R(a,b)=ab\) it is well-known for which triples of integers n, p, m the group is infinite. The authors show that these generalized triangle groups are infinite when \(m\geq 3\) and \(\frac{1}{m}+\frac{1}{n}+\frac{1}{p}\leq 1\) and also for most cases when \(m=2\). The method of proof is to choose elements A and B(z) in \(SL_ 2({\mathbb{C}})\) whose orders are n and p in \(PSL_ 2({\mathbb{C}})\) and then choose \(z\in {\mathbb{C}}\) such that tr R(a,b) is 2 cos(k\(\pi\) /m), \((k,m)=1\), thereby obtaining a representation of the group in \(PSL_ 2({\mathbb{C}})\). A more judicious choice of z shows that the image cannot be one of the (well-known) two generator finite groups in \(PSL_ 2({\mathbb{C}})\).
Reviewer: C.Maclachlan

MSC:

20F05 Generators, relations, and presentations of groups
20H05 Unimodular groups, congruence subgroups (group-theoretic aspects)
Full Text: DOI

References:

[1] G. Baumslag,J. Morgan,P. Shalen (Preprint).
[2] A. F. Beardon, The geometry of discrete groups. Graduate Texts in Math.91, Springer-Verlag 1983. · Zbl 0528.30001
[3] H. S. M. Coxeter,W. O. J. Moser, Generators and relations for discrete groups. Ergebnisse der Math, und ihrer Grenzgebiete 14, 3. Auflage, Springer-Verlag 1972. · Zbl 0239.20040
[4] B. Fine,J. Howie,G. Rosenberger, One-relator quotients and free prpducts of cyclics (Preprint). · Zbl 0653.20029
[5] H. Zieschang,?. Vogt,H.-D. Coldewey, Surfaces and planar discontinuous groups. Lecture Notes in Math. 835, Springer-Verlag 1980. · Zbl 0438.57001
This reference list is based on information provided by the publisher or from digital mathematics libraries. Its items are heuristically matched to zbMATH identifiers and may contain data conversion errors. In some cases that data have been complemented/enhanced by data from zbMATH Open. This attempts to reflect the references listed in the original paper as accurately as possible without claiming completeness or a perfect matching.