Reduced Power Operations in Motivic Cohomology

Karoubi’s Construction for Motivic Cohomology Operations

We use an analogue of Karoubi’s construction [4] in the motivic situation to give some cohomology operations in motivic cohomology. We prove many properties of these operations, and we show that they coincide, up to some nonzero constants, with the reduced power operations in motivic cohomology originally constructed by Voevodsky [12]. The relation of our construction to Voevodsky’s is, roughly...

1 Reduced power operations in motivic cohomology

Cohomology operations and algebraic geometry

This manuscript is based on a ten hours series of seminars I delivered in August of 2003 at the Nagoya Institute of Technology as part of the workshop on homotopy theory organized by Norihiko Minami and following the Kinosaki conference in honor of Goro Nishida. One of the most striking applications of homotopy theory in “exotic” contexes is Voevodsky’s proof of the Milnor Conjecture. This conj...

Cohomology Operations and Inverting the Motivic Bott Element

In this note we explore the relationships between the motivic cohomology operations and the (classical) cohomology operations defined on mod-l étale cohomology. More precisely we show that the cohomology operations on motivic cohomology transform to the (classical) cohomology operations on mod-l étale cohomology upon inverting the motivic Bott element.

The Motivic Cohomology of Stiefel Varieties

The main result of this paper is a computation of the motivic cohomology of varieties of n × m-matrices of of rank m, including both the ring structure and the action of the reduced power operations. The argument proceeds by a comparison of the general linear group-scheme with a Tate suspension of a space which is A1-equivalent to projective n− 1-space with a disjoint basepoint.