We construct a special class of noncongruence modular subgroups and curves, analogous in some ways to the usual congruence ones. The subgroups are obtained via the Burau representation, and the associated quotient curves have a natural moduli space interpretation. In fact, they are reduced Hurwitz s
Singularities of the Modular Curve
โ Scribed by Alexander Klyachko; Orhun Kara
- Publisher
- Elsevier Science
- Year
- 2001
- Tongue
- English
- Weight
- 280 KB
- Volume
- 7
- Category
- Article
- ISSN
- 1071-5797
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โฆ Synopsis
Let X (l) be the modular curve, parameterizing cyclic isogenies of degree l, and Z (l) be its plane model, given by the classical modular equation l (X, >)"0. We prove that all singularities of Z (l), except two cusps, are intersections of smooth branches, and evaluate the order of contact of these branches.
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