On the additivity of geometric invariants in Grothendieck categories

TL;DR

This paper proves the additivity of geometric invariants like the Chern character in Grothendieck categories by establishing a compatible triangulation of their derived categories without model categories, enabling new intersection theory insights.

Contribution

It demonstrates that derived categories of Grothendieck categories have a compatible triangulation using inherent properties, leading to proofs of additivity of traces and Chern characters.

Findings

Additivity of traces in derived categories established

Additivity of the Chern character proven in this context

Interprets results as a group homomorphism in intersection theory

Abstract

We study the additivity of various geometric invariants involved in Reimann-Roch type formulas and defined via the trace map. To do so in a general context we prove that given any Grothendieck category A, the derived category D(A) has a compatible triangulation in the sense of [May, J.P. :The Additivity of Traces in Triangulated Categories, Advances in Mathematics 163, (2001), 34-73], but not resorting to model categories. The result is proved just using the structural properties inherent to D(A). In the second part of the paper we apply compatibility to prove additivity of traces firstly and then additivity of the Chern character, interpreting this result in terms of a group homomorphism which plays the same role as the Chern character in intersection theory with the i-th Chow group replaced by the i-th Hodge cohomology group.