Galois module structure in weakly ramified 3-extensions
For a prime number l and for a finite Galois l-extension of function fields L / K over an algebraically closed field of characteristic p <> l, it is obtained the Galois module structure of the generalized Jacobian associated to L, l and the ramified prime divisors. In the cyclic case an implicit integral representation of the Jacobian is obtained and this representation is compared with the explicit representation.
For , any totally ramified cyclic extension of degree of local fields which are finite extensions of the field of -adic numbers, we describe the -module structure of each fractional ideal of explicitly in terms of the indecomposable -modules classified by Heller and Reiner. The exponents are determined only by the invariants of ramification.
Let be a Galois extension of number fields with Gal and with property that the divisors of are non-ramified in . We denote the ring of integers of by and we study as a -module. In particular we show that the fourth power of the (locally free) class of is the trivial class. To obtain this result we use Fröhlich’s description of class groups of modules and his representative for the class of , together with new determinantal congruences for cyclic group rings and corresponding congruences...
The main results of this paper may be loosely stated as follows.Theorem.— Let and be sums of Galois algebras with group over algebraic number fields. Suppose that and have the same dimension and that they are identical at their wildly ramified primes. Then (writing for the maximal order in )In many cases The role played by the root numbers of and at the symplectic characters of in determining the relationship between the -modules and is described. The theorem includes...
We overview a unified approach to the André-Oort and Manin-Mumford conjectures based on a combination of Galois-theoretic and ergodic techniques. This paper is based on recent work of Klingler, Ullmo and Yafaev on the André-Oort conjecture, and of Ratazzi and Ullmo on the Manin-Mumford conjecture.
To an odd irreducible 2-dimensional complex linear representation of the absolute Galois group of the field Q of rational numbers, a modular form of weight 1 is associated (modulo Artin's conjecture on the L-series of the representation in the icosahedral case). In addition, linear liftings of 2-dimensional projective Galois representations are related to solutions of certain Galois embedding problems. In this paper we present some recent results on the existence of liftings of projective representations...