Noncommutative stable homotopy and stable infinity categories

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.

26 pages; v2 major revision with some improved results, a mistake in matrix homotopy computation removed, title slightly changed (extended); v3 discussion of semigroup C*-algebras removed and made a part of arXiv:1403.4130, Section 3 rewritten accordingly and the title shortened to reflect the changes; v4 final revision incorporating the referee's corrections; v5 added/updated appendix/references