Universiteit Leiden Mathematisch Instituut
Geometry Seminar

Thursday, 12 June 2008

James Borger: Witt vectors, Lambda-rings, and absolute algebraic geometry

Abstract:

I will explain how the closely related concepts of Witt vector and Lambda-ring give rise to a kind of algebraic geometry that is, in a precise sense, over a deeper base than the ring of integers. I will show that it conforms to several predictions about absolute geometry. I will also say something brief about how it relates to other issues in arithmetic algebraic geometry, such as crystalline cohomology, Buium's theory of arithmetic jet spaces, and explicit class field theory.