Abstract
In this paper, we show that the extended modular group \({\hat{\Gamma}}\) acts on \({\hat{\mathbb{Q}}}\) transitively and imprimitively. Then the number of orbits of \({\hat{\Gamma} _{0}(N)}\) on \({\hat{\mathbb{Q}}}\) is calculated and compared with the number of orbits of \({\Gamma _{0}(N)}\) on \({\hat{\mathbb{Q}}}\). Especially, we obtain the graphs \({\hat{G}_{u, N}}\) of \({\hat{\Gamma}_{0}(N)}\) on \({\hat{\mathbb{Q}}}\), for each \({N\in\mathbb{N}}\) and each unit \({u \in U_{N} }\), then we determine the suborbital graph \({\hat{F}_{u,N}}\). We also give the edge conditions in \({\hat{G}_{u, N}}\) and the necessary and sufficient conditions for a circuit to be triangle in \({\hat{F}_{u, N}.}\)
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Kader, S., Güler, B.Ö. On Suborbital Graphs for the Extended Modular Group \({\hat{\Gamma}}\) . Graphs and Combinatorics 29, 1813–1825 (2013). https://doi.org/10.1007/s00373-012-1226-3
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DOI: https://doi.org/10.1007/s00373-012-1226-3