logo IMB
Retour

Séminaire de Théorie des Nombres

Self-Dual Normal Bases for the Square-Root of the Inverse Different

Erik Pickett

Salle de Conférences

le 06 février 2009 à 14:00

Let KK be a finite extension of Qp\mathbb{Q}_p, let L/KL/K be a finite abelian Galois extension of odd degree and let OLO_L be the valuation ring of LL. We define AL/KA_{L/K} to be the unique fractional OLO_L-ideal with square equal to the inverse different of L/KL/K. Combining a result of Erez with a result of Fainsilber and Morales we can see that AL/KA_{L/K} admits an integral normal basis that is self-dual with respect to the trace form if and only if L/KL/K is at most weakly ramified. For pp an odd prime and L/QpL/\mathbb{Q}_p contained in certain cyclotomic extensions, Erez has described such self-dual integral normal bases for AL/QpA_{L/\mathbb{Q}_p}. Assuming K/\QpK/\Q_p to be unramified we generate odd abelian weakly ramified extensions of KK using Lubin-Tate formal groups. We then use Dwork's exponential power series to explicitly construct self-dual integral normal bases for the square-root of the inverse different in these extensions. These constructions generalise Erez's results for cyclotomic extensions.