October 26, Leiden, Room 411

Hendrik Lenstra

11:00-12:00: Construction of the Witt ring
16:00-17:00: Witt rings and zeta functions

These lectures are devoted to the `universal' Witt ring and one of its
applications. In the first lecture, which is of a tutorial nature, the
Witt ring is constructed in a manner that is relatively free of formulas,
and the Adams operations are introduced. The second lecture makes
a connection with Grothendieck rings of group representations and gives
an application to zeta functions.