Orador: Sérgio Mendes (ISCTE-IUL). Data, hora e local: 4 de Março de 2015, início às 14h30m na sala de reuniões do Departamento de Matemática.
Resumo: Let be a local function field of characteristic 2. Quadratic extensions in this case are Artin-Schreier extensions. The group is an infinite profinite group. As a consequence there are countable many quadratic and biquadratic extensions of . We show that these extensions lead to a parametrization of certain -packets – those with cardinality 2 and 4 – which play a fundamental role in the construction of the Langlands correspondence for the reductive group . Every quadratic character comes from the Artin-Schreier symbol. Explicit formulae for quadratic characters are computed. If time permits we will relate these results with a recent geometric conjecture. The talk will be elementary and as self-contained as possible. Joint work with Roger Plymen.