group cohomology, nonabelian group cohomology, Lie group cohomology
cohomology with constant coefficients / with a local system of coefficients
differential cohomology
homotopy theory, (∞,1)-category theory, homotopy type theory
flavors: stable, equivariant, rational, p-adic, proper, geometric, cohesive, directed…
models: topological, simplicial, localic, …
see also algebraic topology
Introductions
Definitions
Paths and cylinders
Homotopy groups
Basic facts
Theorems
The generalized cohomology theory which is represented by the sphere spectrum is also called stable cohomotopy, as it is the stable homotopy theory version of cohomotopy.
Equivalenty, it is the cohomolgical dual concept to stable homotopy homology theory.
By the Pontryagin-Thom theorem this is equivalently framed cobordism cohomology theory.
The following is known as the Barratt-Priddy-Quillen theorem:
(stable cohomotopy is K-theory of FinSet)
Let $\mathcal{C} =$ FinSet be a skeleton of the category of finite sets, regarded as a permutative category. Then the K-theory of this permutative category
is represented by the sphere spectrum, hence is stable cohomotopy.
This is due to Barratt-Priddy 72 reproved in Segal 74, Prop. 3.5. See also Priddy 73, Glasman 13.
(stable cohomotopy as algebraic K-theory over the field with one element)
Notice that for $F$ a field, the K-theory of a permutative category of its category of modules $F Mod$ is its algebraic K-theory $K F$ (see this example)
Now (pointed) finite sets may be regarded as the modules over the “field with one element” $\mathbb{F}_1$ (see there):
If this is understood, example says that stable cohomotopy is the algebraic K-theory of the field with one element:
This perspective is highlighted for instance in (Deitmar 06, p. 2, Guillot 06, Mahanta 17, Dundas-Goodwillie-McCarthy 13, II 1.2, Morava, Connes-Consani 16).
The perspective that the K-theory $K \mathbb{F}_1$ over $\mathbb{F}_1$ should be stable Cohomotopy has been highlighted in (Deitmar 06, p. 2, Guillot 06, Mahanta 17, Dundas-Goodwillie-McCarthy 13, II 1.2, Morava, Connes-Consani 16). Generalized to equivariant stable homotopy theory, the statement that equivariant K-theory $K_G \mathbb{F}_1$ over $\mathbb{F}_1$ should be equivariant stable Cohomotopy is discussed in Chu-Lorscheid-Santhanam 10, 5.3.
(equivariant) cohomology | representing spectrum | equivariant cohomology of the point $\ast$ | cohomology of classifying space $B G$ |
---|---|---|---|
(equivariant) ordinary cohomology | HZ | Borel equivariance $H^\bullet_G(\ast) \simeq H^\bullet(B G, \mathbb{Z})$ | |
(equivariant) complex K-theory | KU | representation ring $KU_G(\ast) \simeq R_{\mathbb{C}}(G)$ | Atiyah-Segal completion theorem $R(G) \simeq KU_G(\ast) \overset{ \text{compl.} }{\longrightarrow} \widehat {KU_G(\ast)} \simeq KU(B G)$ |
(equivariant) complex cobordism cohomology | MU | $MU_G(\ast)$ | completion theorem for complex cobordism cohomology $MU_G(\ast) \overset{ \text{compl.} }{\longrightarrow} \widehat {MU_G(\ast)} \simeq MU(B G)$ |
(equivariant) algebraic K-theory | $K \mathbb{F}_p$ | representation ring $(K \mathbb{F}_p)_G(\ast) \simeq R_p(G)$ | Rector completion theorem $R_{\mathbb{F}_p}(G) \simeq K (\mathbb{F}_p)_G(\ast) \overset{ \text{compl.} }{\longrightarrow} \widehat {(K \mathbb{F}_p)_G(\ast)} \!\! \overset{\text{<a href="https://ncatlab.org/nlab/show/Rector+completion+theorem">Rector 73</a>}}{\simeq} \!\!\!\!\!\! K \mathbb{F}_p(B G)$ |
(equivariant) stable cohomotopy | $K \mathbb{F}_1 \overset{\text{<a href="stable cohomotopy#StableCohomotopyIsAlgebraicKTheoryOverFieldWithOneElement">Segal 74</a>}}{\simeq}$ S | Burnside ring $\mathbb{S}_G(\ast) \simeq A(G)$ | Segal-Carlsson completion theorem $A(G) \overset{\text{<a href="https://ncatlab.org/nlab/show/Burnside+ring+is+equivariant+stable+cohomotopy+of+the+point">Segal 71</a>}}{\simeq} \mathbb{S}_G(\ast) \overset{ \text{compl.} }{\longrightarrow} \widehat {\mathbb{S}_G(\ast)} \!\! \overset{\text{<a href="https://ncatlab.org/nlab/show/Segal-Carlsson+completion+theorem">Carlsson 84</a>}}{\simeq} \!\!\!\!\!\! \mathbb{S}(B G)$ |
The Kahn-Priddy theorem characterizes a comparison map between stable cohomotopy and cohomology with coefficients in the infinite real projective space $\mathbb{R}P^\infty \simeq B \mathbb{Z}/2$.
Consider the unit morphism
from the sphere spectrum to the Eilenberg-MacLane spectrum of the integers. For any topological space/spectrum postcomposition with this morphism induces Boardman homomorphisms of cohomology groups (in fact of commutative rings)
from the stable cohomotopy of $X$ in degree $n$ to its ordinary cohomology in degree $n$.
(bounds on (co-)kernel of Boardman homomorphism from stable cohomotopy to integral cohomology)
If $X$ is a CW-spectrum which
is $(m-1)$-(m-1)-connected
of dimension $d \in \mathbb{N}$
then
the kernel of the Boardman homomorphism $b^n$ (1) for
is a $\overline{\rho}_{d-n}$-torsion group:
the cokernel of the Boardman homomorphism $b^n$ (1) for
is a $\overline{\rho}_{d-n-1}$-torsion group:
where
is the product of the exponents of the stable homotopy groups of spheres in positive degree $\leq i$.
flavours of Cohomotopy cohomology theory | cohomology (full or rational) | equivariant cohomology (full or rational) |
---|---|---|
non-abelian cohomology | Cohomotopy (full or rational) | equivariant Cohomotopy |
twisted cohomology (full or rational) | twisted Cohomotopy | twisted equivariant Cohomotopy |
stable cohomology (full or rational) | stable Cohomotopy | equivariant stable Cohomotopy |
The basic concept appears in
The identification of stable cohomotopy with the K-theory of the permutative category of finite set is due to
Michael Barratt, Stewart Priddy, On the homology of non-connected monoids and their associated groups, Commentarii Mathematici Helvetici, December 1972, Volume 47, Issue 1, pp 1–14 (doi:10.1007/BF02566785)
Graeme Segal, Categories and cohomology theories, Topology vol 13, pp. 293-312, 1974 (pdf)
see also
Stewart Priddy, Transfer, symmetric groups, and stable homotopy theory, in Higher K-Theories, Springer, Berlin, Heidelberg, 1973. 244-255 (pdf)
Saul Glasman, The multiplicative Barratt-Priddy-Quillen theorem and beyond, talk 2013 (pdf)
The resulting interpretation of stable cohomotopy as algebraic K-theory over the field with one element is amplified in the following texts:
Bjørn Dundas, Thomas Goodwillie, Randy McCarthy, chapter II, section 1.2 of The local structure of algebraic K-theory, Springer 2013 (pdf)
Anton Deitmar, Remarks on zeta functions and K-theory over $\mathbb{F}_1$ (arXiv:math/0605429)
Pierre Guillot, Adams operations in cohomotopy (arXiv:0612327)
Snigdhayan Mahanta, G-theory of $\mathbb{F}_1$-algebras I: the equivariant Nishida problem, J. Homotopy Relat. Struct. 12 (4), 901-930, 2017 (arXiv:1110.6001)
Chenghao Chu, Oliver Lorscheid, Rekha Santhanam, Sheaves and K-theory for $\mathbb{F}_1$-schemes, Advances in Mathematics, Volume 229, Issue 4, 1 March 2012, Pages 2239-2286 (arxiv:1010.2896)
see also
Jack Morava, Some background on Manin’s theorem $K(\mathbb{F}_1) \sim \mathbb{S}$ (pdf, MoravaSomeBackground.pdf)
Alain Connes, Caterina Consani, Absolute algebra and Segal’s Gamma sets, Journal of Number Theory 162 (2016): 518-551 (arXiv:1502.05585)
John D. Berman, p. 92 of Categorified algebra and equivariant homotopy theory, PhD thesis 2018 (pdf)
The Kahn-Priddy theorem is due to
The relation to β-rings is discussed in
E. Vallejo, Polynomial operations from Burnside rings to representation functors, J. Pure Appl. Algebra, 65 (1990), pp. 163–190.
E. Vallejo, Polynomial operations on stable cohomotopy, Manuscripta Math., 67 (1990), pp. 345–365
E. Vallejo, The free β-ring on one generator, J. Pure Appl. Algebra, 86 (1993), pp. 95–108.
see also
Discussion of Boardman homomorphisms from stable cohomotopy is in
A lift of Seiberg-Witten invariants to classes in circle group-equivariant stable cohomotopy is discussed in
A stable cohomotopy refinement of Seiberg-Witten invariants: I (arXiv:math/0204340)
A stable cohomotopy refinement of Seiberg-Witten invariants: II (arXiv:math/0204267)
Last revised on October 22, 2019 at 08:37:17. See the history of this page for a list of all contributions to it.