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March 01, 2017
Wednesday, March 01
Algebra Seminar
Time: 14:30
Speaker: Adam Chapman (Tel-Hai Academic College)
Title: "Linked fields of characteristic 2 and their u-invariant"
Room: MC 107

Abstract: The u-invariant of a field is the maximal dimension of a nonsingular anisotropic quadratic form over that field, whose order in the Witt group of the field is finite. By a classical theorem of Elman and Lam, the u-invariant of a linked field of characteristic different from 2 can be either 0, 1, 2, 4 or 8. The analogous question in the case of characteristic 2 remained open for a long time. We will discuss the proof of the equivalent statement in characteristic 2, recently obtained in joint work by Andrew Dolphin and the speaker.