In this paper we present a theoretical and algorithmic analysis on the normality of rational parametrizations of algebraic plane curves over arbitrary fields of characteristic zero. If the field is algebraically closed we give an algorithm to decide whether a parametrization is proper and, if not, a
Degrees of Parametrizations of Elliptic Curves by Shimura Curves
β Scribed by Shuzo Takahashi
- Publisher
- Elsevier Science
- Year
- 2001
- Tongue
- English
- Weight
- 146 KB
- Volume
- 90
- Category
- Article
- ISSN
- 0022-314X
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β¦ Synopsis
In this paper, we study some properties of parametrizations of elliptic curves by Shimura curves. Fix a square-free positive integer N and an isogeny class E of elliptic curves of conductor N defined over Q. Consider a pair (D, M ) such that N=DM and the number of prime factors of D is even. Let J be the Jacobian of Shimura curve X D 0 (M ) associated with an Eichler order of level M in an indefinite quaternion albebra of discriminant D defined over Q. There is a unique E in E and a homomorphism J Γ E having the connected kernel. For a prime r | N, we study the map on groups of connected components of Ne ron fibers at r induced from J Γ E. We show that if r divides D, then the map is surjective. Moreover, we study some relations among degrees of parametrizations X D 0 (M) Γ E when D and M vary. Also, we describe a method of computing the degree of X D 0 (M ) Γ E when D>1.
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