| DATE: | Thursday September 3, 2009 |
| TIME: | 4:30 - 5:30 PM |
| PLACE: | LN 2205 |
| SPEAKER: | Thomas Zink, Bielefeld University, Germany |
| TITLE: | Witt vectors cohomology of algebraic varieties in characteristic p>0. |
Let X be a smooth affine variety over the field C of complex numbers. By a theorem of Grothendieck the cohomology groups $H^i(X,C)$ may be computed by algebraic differential forms. Let now X be a smooth algebraic variety over an algebraically closed field k of characteristic p >0. Monsky and Washnitzer introduced a complex of differential forms which lead to the correct cohomology groups for affine varieties X. We globalize their approach using the de Rham-Witt complex of Deligne--Illusie. There is a comparison with the rigid cohomology of Berthelot.