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arXiv math/0407445math.AG
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P^1的自映射在特征p中具有指定的分支

Self maps of P^1 with prescribed ramification in characteristic p

Brian Osserman

摘要:

利用极限线性级数和一个控制可分映射退化为不可分映射的结果,给出了在所有ei都小于特征的情况下,在一般点Pi上具有e_i阶分支的射影线的自映射个数的计算公式.与特征为0的情形不同,Schubert演算不能给出这个问题的答案,而且对于不同的P_i,映射的个数也不总是有限的,即使在平凡分歧的情形下也是如此。然而,一般P_i的有限性,利用分支覆盖的关系,是一个关键的部分的论点。

英文摘要:

Using limit linear series and a result controlling degeneration from separable maps to inseparable maps, we give a formula for the number of self-maps of the projective line with ramification to order e_i at general points P_i, in the case that all e_i are less than the characteristic. Unlike the case of characteristic 0, the answer is not given by Schubert calculus, nor is the number of maps always finite for distinct P_i, even in the tamely ramified case. However, finiteness for general P_i, obtained by exploiting the relationship to branched covers, is a key part of the argument.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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