Simos, T. E.2022-06-202022-06-202011Demirci, M. vd. (2011). "Upper bounds for the level of normal subgroups of Hecke groups". ed. T. E. Simos. AIP Conference Proceedings, Numerical Analysis and Applied Mathematics Icnaam 2011: International Conference on Numerical Analysis and Applied Mathematics, 1389, 337-340.0094-243Xhttps://doi.org/10.1063/1.3636733https://aip.scitation.org/doi/10.1063/1.3636733http://hdl.handle.net/11452/27311Bu çalışma, 19-25 Eylül 2011 tarihleri arasında Halkidiki[Yunanistan]’da düzenlenen International Conference on Numerical Analysis and Applied Mathematics (ICNAAM)' da bildiri olarak sunulmuştur.In [4], Greenberg showed that n <= 6t(3) so that mu - nt <= 6t(4) for a normal subgroup N of level n and index mu having t parabolic classes in the modular group Gamma. Accola, [1], improved these to n <= 6t(2) always and n <= t(2) if Gamma/N is not abelian. In this work we generalise these results to Hecke groups. We get results between three parameters of a normal subgroup, i.e. the index mu, the level n and the parabolic class number t. We deal with the case q = 4, and then obtain the generalisation to other q. Two main problems here are the calculation of the number of normal subgroups and the determination of the bounds on the level n for a given t.eninfo:eu-repo/semantics/closedAccessMathematicsHecke groupsLevelParabolic class numberRiemann surfaceAutomorphismsNumberProceedings Paper0003022398000832-s2.0-818552001443373401389Mathematics, appliedKlein Surface; Automorphism Group; Belyi