In this article, we show that for a quasicompact scheme X and n > 0, the n-th K-group K n (X) is a λ-module over a λ-ring K 0 (X) in the sense of Hesselholt.
introductionIn [4], L. Hesselholt introduced the notion of module over λ-rings, i.e., λ-module. Let us first recall the definition from [4].such that the following axioms hold:(1) λ M,1 = id M ;(2) λ M,n λ M,m = λ M,nm for all m, n ≥ 1;(3) λ M,n (ax) = ψ n (a)λ M,n (x) for all a ∈ R and x ∈ M. Here ψ n is the n-th Adams operation associated to (R, λ R ).If we set M = R and λ M,n = ψ n , where ψ n are the Adams operations associated to (R, λ R ), then (R, ψ n ) is a (R, λ R )-module. For a quasicompact scheme X, K 0 (X) is a λ-ring with λ-operations defined by the usual exterior power on vector bundles. These exterior power operations have been extended to higher K-groups by several authors using homotopy theory (see [3], [6], [7] and [8]). Recently, a purely algebraic construction of the exterior power operations on higher K-groups of any quasicompact scheme is given in [2] using Grayson's description of higher K-groups in terms of binary complexes. In this article, we use the exterior power operations constructed in [2] to give a λ-module structure on K n (X) over K 0 (X) for n > 0 and any quasicompact scheme X.Here is our precise result: Theorem 1.2. For any quasicompact scheme X and n > 0, each K n (X) is a λ-module over K 0 (X).