Abstract
Let \(\mathcal {\scriptstyle {O}}_K\) be the ring of integers of an imaginary quadratic number field K. In this paper we give a new description of the maximal discrete extension of the group \(SL_2(\mathcal {\scriptstyle {O}}_K)\) inside \(SL_2(\mathbb {C})\), which uses generalized Atkin–Lehner involutions. Moreover we find a natural characterization of this group in SO(1, 3).
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Krieg, A., Rodriguez, J. & Wernz, A. The maximal discrete extension of \(SL_2(\mathcal {\scriptstyle {O}}_K)\) for an imaginary quadratic number field K. Arch. Math. 113, 37–41 (2019). https://doi.org/10.1007/s00013-019-01312-x
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DOI: https://doi.org/10.1007/s00013-019-01312-x