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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, ...
12
votes
1
answer
822
views
Stiefel-Whitney class of fibre bundles
Or even in terms of the cohomology ring
$$
H^*(B;\mathbb{Z}_2), H^*(F;\mathbb{Z}_2)
$$
And other factors? …
13
votes
2
answers
891
views
References for Stiefel-Whitney class of Stiefel manifolds and Grassmannians
Let $M$ be a manifold. The total Stiefel-Whitney class of $M$ is defined to be the Stiefel-Whitney class of the tangent bundle $TM$
$$
w(M)=1+w_1(TM)+w_2(TM)+\cdots
$$
I want to find references for
$$ …
9
votes
4
answers
1k
views
Examples of Stiefel-Whitney classes of manifolds
Let $M$ by an compact, connected $n$-dimensional manifold without boundary.
Are there any other computable examples of the Stiefel-Whitney class $w(M)$ except for $M=S^m, \mathbb{R}P^m,\mathbb{C}P^m, …
8
votes
2
answers
1k
views
rational cohomology of finite real grassmannian
Then according to Theorem 1.6, The Cohomology of BSO n and BO n with Integer Coefficients, Proceedings of the American Mathematical Society 1982 Vol 85-2, Edgar H.Brown JR.,
$H^*(G_n(\mathbb{R}^\infty …
7
votes
0
answers
192
views
mod $p$ homology module of unordered configuration spaces of the projective plane
Let $M$ be a manifold and $k$ be a positive integer. Let $F(M,k)$ be the $k$-th ordered configuration space over $M$, consisting of all ordered $k$-tuples of distinct points in $M$. Let $\Sigma_k$ be …
3
votes
1
answer
450
views
cohomology module of unit tangent vector bundles over spheres
Let $S^m$ be the $m$-sphere and $\tau (S^m)$ the sphere bundle consisting of unit tangent vectors in the tangent bundle $TS^m$. Then we have a fibration
$$
S^{m-1}\longrightarrow \tau(S^m)\longrightar …
4
votes
1
answer
250
views
Configuration spaces of positive and negative particles
.
$$
Question: Could the theorem 1.1 be strengthened to the statement that for some $k$,
$$
(\alpha_k)^*: H^*(\Gamma_k(M;S^0))\to H^*(F(M,k)/\Sigma_k)
$$
is a ring isomorphism of cohomology rings? …
2
votes
1
answer
148
views
positions of regular cubes in Euclidean space with all its vertices without distinction
What is the mod 2 cohomology ring
$$
H^*(O(3)/Sym(P);\mathbb{Z}/2)?
$$ …
3
votes
1
answer
453
views
geometric conditions on maps between manifolds inducing monomorphisms on cohomology
Let $M,N$ be manifolds whose dimensions may be different. Let $f: M\longrightarrow N$ be a smooth map. What geometric conditions on $f$ can we impose such that the induced homomorphism
$$
f^*: H^*(N; …
10
votes
1
answer
1k
views
positions of a methane molecule with carbon atom at the origin
Question: as a manifold, what is the cohomology ring (with cup product)
$$
H^*(G;\mathbb{Z}_2)
$$
and the Steenrod square $Sq$'s acting on the cohomology ring? …
3
votes
2
answers
595
views
mod p cohomology ring of alternating groups
What is the cohomology ring
$$
H^*(A_4;\mathbb{Z}/3)
$$
and its Steenrod operation $P^i$'s?
(2). … Are there general results about the cohomology ring
$$
H^*(A_{p+1};\mathbb{Z}/p)
$$
for general primes $p\geq 3$?
(3). …
5
votes
0
answers
148
views
configuration space of Riemannian manifolds with a parameter on the distance of distinct points
Question: are there any references for the cohomology ring
$$
H^*(B(M,k,\epsilon);\mathbb{Z}_2)?
$$ …
2
votes
1
answer
312
views
Kunneth formula of Cartesian product modulo orders of coordinates
Let $X$ be a topological space and $F$ a field. Let the $n$-th permutation group $\Sigma_n$ act on
$$
\prod_n X
$$
by
$$
\sigma(x_1,\cdots,x_n)=(x_{\sigma(1)},\cdots,x_{\sigma(n)}), \sigma\in \Sig …
0
votes
1
answer
189
views
cohomology ring of the fundamental group of unordered configuration space
From the lecture notes INTRODUCTION TO CONFIGURATION SPACES AND THEIR
APPLICATIONS, p. 18, I find:
Os it possible to derive the cohomology ring $H^*(Conf(S,k)/\Sigma_k;\mathbb{Z}_2)$ from the above theorem … $$
Question 2: Given a group $G=\pi_1(Conf(S,k)/\Sigma_k)$, I find
$
K(G,1)=BG.
$
Are there any methods to compute the cohomology ring (cup product structure)
$$
H^*(BG;\mathbb{Z}_2)?
$$ …
9
votes
1
answer
484
views
Steenrod operations on cohomology of grassmannians
Their cohomology rings are expressed in terms of universal Stiefel-Whitney classes
$$
H^*(G_k(\mathbb{R}^\infty);\mathbb{Z}_2)=\mathbb{Z}_2[w_1,w_2,\cdots,w_k],$$
$$
H^*(G_k(\mathbb{R}^n);\mathbb{Z}_2) … =\mathbb{Z}_2[w_1,w_2,\cdots,w_k]/(\bar w_{n-k+1},\bar w_{n-k+2}\cdots,\bar w_n).$$
What are the Steenrod operations $Sq^i$ on these cohomology rings? …