On the minimal ramification problem for -groups

Publisher: Cambridge University Press

E-ISSN: 1570-5846|146|3|599-606

ISSN: 0010-437x

Source: Compositio Mathematica, Vol.146, Iss.3, 2010-05, pp. : 599-606

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Abstract

Let be a prime number. It is not known whether every finite -group of rank n≥1 can be realized as a Galois group over ${\Bbb Q}$ with no more than n ramified primes. We prove that this can be done for the (minimal) family of finite -groups which contains all the cyclic groups of -power order and is closed under direct products, (regular) wreath products and rank-preserving homomorphic images. This family contains the Sylow -subgroups of the symmetric groups and of the classical groups over finite fields of characteristic not . On the other hand, it does not contain all finite -groups.