Fields of moduli of three-point G-covers with cyclic p-Sylow, I

Andrew Obus

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arXiv · 0911.1103

Fields of moduli of three-point G-covers with cyclic p-Sylow, I

Andrew Obus

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Abstract

We examine in detail the stable reduction of Galois covers of the projective line over a complete discrete valuation field of mixed characteristic (0, p), where G has a cyclic p-Sylow subgroup of order p^n. If G is further assumed to be p-solvable (i.e., G has no nonabelian simple composition factors with order divisible by p), we obtain the following consequence: Suppose f: Y --> P^1 is a three-point G-Galois cover defined over the complex numbers. Then the nth higher ramification groups above p for the upper numbering of the (Galois closure of the) extension K/Q vanish, where K is the field of moduli of f. This extends work of Beckmann and Wewers. Additionally, we completely describe the stable model of a general three-point Z/p^n-cover, where p > 2.

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Andrew Obus. 2011-09-26. Fields of moduli of three-point G-covers with cyclic p-Sylow, I. https://arxiv.org/abs/0911.1103

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