Noncommutative stable homotopy and stable infinity categories

TL;DR

This paper develops a new infinity categorical framework for noncommutative stable homotopy theory, unifying and extending existing theories like KK-theory and E-theory within a topological and homotopical context.

Contribution

It constructs a stable presentable infinity category of noncommutative spectra and demonstrates that the noncommutative stable homotopy category is topological, providing a foundation for new noncommutative (co)homology theories.

Findings

The noncommutative stable homotopy category is topological.

The paper introduces a presentable infinity category of noncommutative pointed spaces.

It models classical bivariant homology theories like KK-theory and E-theory within the infinity categorical framework.

Abstract

The noncommutative stable homotopy category $\mathtt{NSH}$ is a triangulated category that is the universal receptacle for triangulated homology theories on separable $C^*$-algebras. We show that the triangulated category $\mathtt{NSH}$ is topological as defined by Schwede using the formalism of (stable) infinity categories. More precisely, we construct a stable presentable infinity category of noncommutative spectra and show that $\mathtt{NSH}^{op}$ sits inside its homotopy category as a full triangulated subcategory, from which the above result can be deduced. We also introduce a presentable infinity category of noncommutative pointed spaces that subsumes $C^*$-algebras and define the noncommutative stable (co)homotopy groups of such noncommutative spaces generalizing earlier definitions for separable $C^*$-algebras. The triangulated homotopy category of noncommutative spectra admits (co)products and satisfies Brown representability. These properties enable us to analyse neatly the behaviour of the noncommutative stable (co)homotopy groups with respect to certain (co)limits. Along the way we obtain infinity categorical models for some well-known bivariant homology theories like $\mathrm{KK}$-theory, $\mathrm{E}$-theory, and connective $\mathrm{E}$-theory via suitable (co)localizations. The stable infinity category of noncommutative spectra can also be used to produce new examples of generalized (co)homology theories for noncommutative spaces.