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arXiv math/9911043math.AG
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极大曲线在Hermite簇中的嵌入

Embedding of a maximal curve in a Hermitian variety

Gabor Korchmaros, Fernando Torres

摘要:

设X是定义在$q^2$阶有限域F上的射影几何不可约非奇异代数曲线。若X的F-有理点的个数满足Hasse-Weil上界,则称X是F-极大的.对于点P_0 \in X(F),设π是由线性级数D:|(q+1)P_0|,并且令N:=dim(D)。已知N \ge 2,且当X是F-极大时,π与P_0无关。定理0.1:若X是F-极大的,则π:X \to π(X)是F-同构。非奇异模型π(X)的次数为q+1,位于P^N(\bar F)的F上的厄米特簇上;定理0.2:如果X是F-极大的,则它F-同构于P^M(\bar F)中的曲线Y,其中2 \le M \le N,使得Y的次数为q+1,位于\bar F)的F上的非退化厄米特簇上。定理0.3:如果X是F-双有理的,且Y嵌入P^M(\bar F)的曲线Y,使得Y的次数q+1,且位于P ^M(\bar F)的F上的非退化厄米簇上,则X是F-极大的,X与Y是F-同构的。

英文摘要:

Let X be a projective geometrically irreducible non-singular algebraic curve defined over a finite field F of order $q^2$. If the number of F-rational points of X satisfies the Hasse-Weil upper bound, then X is said to be F-maximal. For a point P_0\in X(F), let πbe the morphism arising from the linear series D:=|(q+1)P_0|, and let N:=dim(D). It is known that N\ge 2 and that πis independent of P_0 whenever X is F-maximal. The following theorems will be proved: Theorem 0.1: If X is F-maximal, then π:X\to π(X) is a F-isomorphism. The non-singular model π(X) has degree q+1 and lies on a Hermitian variety defined over F of P^N(\bar F); Theorem 0.2: If X is F-maximal, then it is F-isomorphic to a curve Y in P^M(\bar F), with 2\le M\le N, such that Y has degree q+1 and lies on a non-degenerate Hermitian variety defined over F of ¶^M(\bar F). Furthermore, Aut_F(X) is isomorphic to a subgroup of the projective unitary group PGU(M+1,q^2); Theorem 0.3: If X is F-birational to a curve Y embedded in P^M(\bar F) such that Y has degree q+1 and lies on a non-degenerate Hermitian variety defined over F of P^M(\bar F), then X is F-maximal and X is F-isomorphic to Y.

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