On Goncharov's conjecture in next to Milnor degree
Vasily Bolbachan
TL;DR
The paper tackles Goncharov's conjecture in next to Milnor degree by proving a canonical isomorphism between the motivic cohomology $H^{m-1,m}(\mathrm{Spec}\mathbb{K},\mathbb{Q})$ and the cohomology $H^{m-1}(\Gamma(\mathbb{K},m))$ of the polylogarithmic complex for a field $\mathbb{K}$ of characteristic zero and $m\ge 2$. The authors build an auxiliary complex $\Lambda(\mathbb{K},m)$ and relate it to higher Chow groups via a map $\mathcal{W}$, while a Totaro-type map $\mathcal{T}$ connects the polylogarithmic side to the higher Chow side; a crucial step is proving that $\widetilde{\mathcal{W}}$ and $\mathcal{T}'$ are (quasi-)isomorphisms. A strong Suslin reciprocity law is developed to control reciprocity phenomena across valuations and field extensions, including a norm-map machinery to reduce to the algebraically closed case (Galois descent). The result provides a partial extension of Suslin's description of indecomposable $K_3$ and builds a robust framework to approach Goncharov's conjecture in characteristic zero, linking motivic cohomology with polylogarithmic and higher Chow constructions. Overall, the work advances the understanding of how motivic invariants align with explicit polylogarithmic complexes, enabling concrete computations and potential characteristic-generalizations.
Abstract
Let $\mathbb K$ be a field of characteristic zero. We prove that its motivic cohomology in degree $m-1$ and weight $m$ is rationally isomorphic to the cohomology of the polylogarithmic complex. This gives a partial extension of A. Suslin theorem describing the indecomposable $K_3$ of a field.
