1. A classification of $\mathbb{C}$-Fuchsian subgroups of Picard modular groups
- Author
-
Frédéric Paulin and Jouni Parkkonen
- Subjects
Quaternion algebra ,General Mathematics ,Hyperbolic geometry ,010102 general mathematics ,Picard group ,01 natural sciences ,Combinatorics ,Picard modular group ,Discriminant ,Chain (algebraic topology) ,0103 physical sciences ,Complex geodesic ,Heisenberg group ,010307 mathematical physics ,0101 mathematics ,Mathematics - Abstract
Given an imaginary quadratic extension $K$ of $\mathbb{Q}$, we give a classification of the maximal nonelementary subgroups of the Picard modular group $\operatorname{PSU}_{1,2}(\mathcal{O}_K)$ preserving a complex geodesic in the complex hyperbolic plane $\mathbb{H}^2_\mathbb{C}$. Complementing work of Holzapfel, Chinburg-Stover and M\"oller-Toledo, we show that these maximal $\mathbb{C}$-Fuchsian subgroups are arithmetic, arising from a quaternion algebra $\Big(\!\begin{array}{c} D\,,D_K\\\hline\mathbb{Q}\end{array} \!\Big)$ for some explicit $D\in\mathbb{N}-\{0\}$ and $D_K$ the discriminant of $K$. We thus prove the existence of infinitely many orbits of $K$-arithmetic chains in the hypersphere of $\mathbb{P}_2(\mathbb{C})$.
- Published
- 2017
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