Semilocal Milnor K-theory

TL;DR

This paper introduces semilocal Milnor K-theory for fields, constructs a spectral sequence linking it to motivic cohomology, and applies these results to key conjectures and computations in algebraic K-theory.

Contribution

It develops the theory of semilocal Milnor K-theory, establishes a spectral sequence relating it to motivic cohomology, and applies these tools to important conjectures and calculations.

Findings

Computed motivic cohomology groups in weight 2 as semilocal Milnor K-theory groups.

Provided criteria for the Beilinson-Soulé Vanishing Conjecture.

Showed the equivalence of the Beilinson conjecture for rational K-theory to vanishing of rational semilocal Milnor K-theory.

Abstract

In this paper, semilocal Milnor $K$-theory of fields is introduced and studied. A strongly convergent spectral sequence relating semilocal Milnor $K$-theory to semilocal motivic cohomology is constructed. In weight 2, the motivic cohomology groups $H^p_{Zar}(k,\mathbb Z(2))$, $p\leq 1$, are computed as semilocal Milnor $K$-theory groups $\widehat{K}^M_{2,3-p}(k)$. The following applications are given: (i) several criteria for the Beilinson-Soul\'e Vanishing Conjecture; (ii) computation of $K_4$ of a field; (iii) the Beilinson conjecture for rational $K$-theory of fields of prime characteristic is shown to be equivalent to vanishing of rational semilocal Milnor $K$-theory.