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A branch of algebraic topology concerning the study of cocycles and coboundaries. It is in some sense a dual theory to homology theory. This tag can be further specialized by using it in conjunction with the tags group-cohomology, etale-cohomology, sheaf-cohomology, galois-cohomology, lie-algebra-cohomology, motivic-cohomology, equivariant-cohomology, ...

2 votes
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Borel's transgression theorem for spectral sequences

Mimura and Toda's statement in The Topology of Lie Groups, Theorem VII.2.9 (p. 378), requires less severe degree constraints. They start with a Serre fibration $F \to E \to B$ with $B$ simply-connecte …
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9 votes
0 answers
258 views

Reference request: $H^* X$-module structure on the Mayer–Vietoris coboundary

Let $E^*$ a multiplicative cohomology theory. … \cap V) \wedge I\big) \cup V \simeq X.$ And this one is stated as Proposition 2.15 of Allen Hatcher's Vector Bundles and K-Theory (for complex topological K-theory): Let $E^*$ be a multiplicative cohomology
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4 votes
0 answers
93 views

A dimension condition on the cohomology of a homogeneous space

The rational cohomology of a homogeneous space $G/K$ admits a homomorphism from $H^*(BK)$ induced from the classifying map $G/K \to BK$ of the principal $K$-bundle $G \to G/K$. …
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2 votes

cohomology ring of homogenous manifold

The third arrow is a fixed but arbitrary choice of lifting of this module of generators to a subspace of the cohomology ring, and the last map is induced by the inclusion $H_0 \hookrightarrow G$. … One can compute the cohomology algebra then as $$\mathbb R[s] / (s^2) \otimes \Lambda [z],$$ where $z_3 - 2sz_2/3$ represents $z$. …
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7 votes
1 answer
529 views

Naive equivariant transfer

Given a group $G$, a $\mathbb Z$-graded cohomology theory $E^*_G$, and a $n$-sheeted covering $p\colon X \to Y$, I would like a transfer map $$p_! …
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5 votes
1 answer
145 views

Example request: seriously deficient homogeneous spaces

The quotient map $G \to G/K$ induces a ring map $H^*(G/K) \to H^*(G)$ in rational cohomology whose image is an exterior algebra $\Lambda \hat P$. …
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7 votes

Cohomology ring of mapping torus

Here are some more partial observations, overlapping some of the others. The result won't be completely explicit, as there are too many case distinctions for a clean answer, but hopefully at least the …
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9 votes

Is there any "deep" relation between the localization theorem of equivariant cohomology and ...

I have never checked this, but because $R(G)$ is Noetherian, I believe the localization theorem in equivariant cohomology at the level of $\mathbb Z/2$-graded rings then follows from the K-theoretic localization …
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