K-theory and localizing invariants of large categories

TL;DR

This paper develops the concept of continuous K-theory for large stable ∞-categories, extending localizing invariants, computing examples, and exploring dualizability properties, thereby advancing the understanding of K-theoretic invariants in higher category theory.

Contribution

It introduces continuous K-theory for dualizable presentable categories, extends localizing invariants, and provides new insights into dualizability and flatness in stable ∞-categories.

Findings

Continuous K-theory matches classical K-theory for compactly generated categories.

Proves K-theory commutes with infinite products in certain cases.

Establishes dualizability as equivalent to flatness in presentable stable categories.

Abstract

In this paper we introduce and study the so-called continuous $K$-theory for a certain class of "large" stable $\infty$-categories, more precisely, for dualizable presentable categories. For compactly generated categories, the continuous $K$-theory is simply the usual (non-connective) $K$-theory of the full subcategory of compact objects. More generally, we show that any localizing invariant of small stable $\infty$-categories can be uniquely extended to a localizing invariant of dualizable categories. We compute the continuous $K$-theory for categories of sheaves on locally compact Hausdorff spaces. Using the special case for sheaves on the real line, we give an alternative proof of the theorem of Kasprowski and Winges \cite{KW19} on the commutation of $K$-theory with infinite products for small stable $\infty$-categories. We also study the general theory of dualizable categories. In particular, we give an "explicit" proof of Ramzi's theorem \cite{Ram24a} on the $\omega_1$-presentability of the category of dualizable categories. Among other things, we prove that dualizability is equivalent to "flatness" in the category of presentable stable categories.