group cohomology, nonabelian group cohomology, Lie group cohomology
cohomology with constant coefficients / with a local system of coefficients
differential cohomology
Background
Basic concepts
equivalences in/of $(\infty,1)$-categories
Universal constructions
Local presentation
Theorems
Extra stuff, structure, properties
Models
The algebraic K-theory $\mathcal{K}(\mathcal{C})$ of a symmetric monoidal (∞,1)-category $\mathcal{C}$ is the generalized (Eilenberg-Steenrod) cohomology theory represented by the ∞-group completion of the commutative ∞-monoid which is the core of $\mathcal{C}$.
This construction subsumes various other construction in algebraic K-theory. Specifically when restricted to 1-categories it reproduces the classical construction by (Segal 74) described at K-theory of a permutative category, see below.
Write
for the composite of
the core functor from symmetric monoidal (∞,1)-categories to E-∞ spaces;
their ∞-group completion to abelian ∞-groups;
the inclusion of “abelian ∞-groups”, hence connective spectra into all spectra.
This $\mathcal{K}$ is the algebraic K-theory of symmetric monoidal (∞,1)-categories. (Nikolaus 13, below remark 5.3, Bunke-Nikolaus-Völkl 13, def.6.1)
More generally, one may start with construction with other objects that map to Picard ∞-groups, such as (∞,1)-operads (Nikolaus 13). Also, instead of just group-completing one may “ring complete” to produce K-theory spectra equipped with the structure of E-∞ rings (Bunke-Tamme 13, section 2.4).
For $R$ a commutative ring, and $R$Mod its category of modules (projective modules), then $\mathcal{K}(R Mod)$ is Quillen’s algebraic K-theory of $R$. More generally this reproduces the K-theory of a permutative category etc. (Nikolaus 13, section 6).
In particular, applied to the stack of algebraic vector bundles this produces the sheaf of spectra of algebraic K-theory of schemes (Bunke-Tamme 12, section 3.3), see at differential algebraic K-theory – Algebraic K-theory sheaf of spectra.
Algebraic K-theory is traditionally applied to single symmetric monoidal/stable (∞,1)-categories, but to the extent that it is functorial it may just as well be applied to (∞,1)-sheaves with values in these.
Notably, applied to the monoidal stack of vector bundles (with connection) on the site of smooth manifolds, the K-theory of a monoidal category-functor produces a sheaf of spectra which is a form of differential K-theory and whose geometric realization is the topological K-theory spectrum. For more on this see at differential cohomology hexagon – Differential K-theory.
The functor from symmetric monoidal categories to connective spectra was originally given in
See also
1982.
The following article showed that this construction produces all connective spectra, up to equivalence
and a new proof of that is in
The natural generalization of the construction to symmetric monoidal (∞,1)-categories appears in
Ulrich Bunke, Georg Tamme, section 2.1 of Regulators and cycle maps in higher-dimensional differential algebraic K-theory (arXiv:1209.6451)
Thomas NikolausAlgebraic K-Theory of $\infty$-Operads (arXiv:1303.2198)
Ulrich Bunke, Thomas Nikolaus, Michael Völkl, def. 6.1 in Differential cohomology theories as sheaves of spectra (arXiv:1311.3188)
David Gepner, Moritz Groth, Thomas Nikolaus, Universality of multiplicative infinite loop space machines, arXiv:1305.4550.
Ulrich Bunke, Georg Tamme, Multiplicative differential algebraic K-theory and applications (arXiv:1311.1421)
Last revised on January 28, 2015 at 12:04:38. See the history of this page for a list of all contributions to it.