Additivity and Fiber Sequences for Combinatorial K-Theory
Abstract
The (A)CGW categories of Campbell and Zakharevich show how finite sets and varieties behave like the objects of an exact category for the purpose of algebraic -theory. These structures admit a well-behaved Q-construction akin to Quillen's, and satisfy analogues of the D\'evissage and Localization theorems. In this work, we modify Campbell and Zakharevich's axioms to obtain a framework called ECGW categories that allows for an -construction akin to Waldhausen's, and show how it produces a K-theory spectrum which satisfies an analogue of the Additivity Theorem. We also define a notion of ``relative ECGW categories'' which have weak equivalences determined by a subcategory of acyclic objects satisfying minimal conditions; these satisfy analogues of the Fibration and Localization Theorems that generalize previous versions in the literature. We illustrate these results with examples including exact categories, extensive categories, algebraic varieties, and polytopes up to scissors congruence.
Cite
@article{arxiv.2107.07701,
title = {Additivity and Fiber Sequences for Combinatorial K-Theory},
author = {Maru Sarazola and Brandon T. Shapiro},
journal= {arXiv preprint arXiv:2107.07701},
year = {2025}
}
Comments
47 pages + 17 page technical appendix. This paper previously titled "A Gillet--Waldhausen Theorem for Chain Complexes of Finite Sets" is being split into two: this one with new examples and applications, and another with the previous title covering the Gillet--Waldhausen Theorem for finite sets and more general extensive categories, content which can still be found in v2