Skip to main content
Search type Search syntax
Tags [tag]
Exact "words here"
Author user:1234
user:me (yours)
Score score:3 (3+)
score:0 (none)
Answers answers:3 (3+)
answers:0 (none)
isaccepted:yes
hasaccepted:no
inquestion:1234
Views views:250
Code code:"if (foo != bar)"
Sections title:apples
body:"apples oranges"
URL url:"*.example.com"
Saves in:saves
Status closed:yes
duplicate:no
migrated:no
wiki:no
Types is:question
is:answer
Exclude -[tag]
-apples
For more details on advanced search visit our help page
Results tagged with
Search options not deleted user 8824

Homotopy theory, homological algebra, algebraic treatments of manifolds.

11 votes

Intuition behind Thom class

The idea behind the Thom isomorphism $\beta:H^iX \rightarrow H^{n+i}(DE,SE)$ is implicit in the formula $$\int_{\sigma_{n+i}} \beta(\alpha_i) = \int_{X\cap \sigma_{n+i}} \alpha_i$$ Here $\sigma_{n+i} …
Christian Nassau's user avatar
3 votes

"The Z/2-cohomology functor from Top to GrVecSpaces factors through Unstable-A-Mod, and this...

My impression is that Haynes Miller uses the term "algebraic category" in the informal sense in his notes (but I may be wrong). So let me answer this informal version first: one could argue that there …
Christian Nassau's user avatar
4 votes
Accepted

Computing squaring operations in the Adams spectral sequence

I think for $k>0$ currently no-one knows an efficient algorithmic way to compute the $Sq^k$, e.g., from a minimal resolution. (The $Sq^0$ is easy since it is induced by the "Frobenius" map on $A_\ast$ …
Christian Nassau's user avatar
11 votes
Accepted

Adams-Novikov spectral sequence at p = 2

I don't think anybody knows how to compute this $E_2$-term efficiently (not just at the prime $2$). I would love to be proved wrong on this, of course. So far the only documented, algorithmic method …
Christian Nassau's user avatar
4 votes

Cohomology of the classifying space of $Ss(4m)$

I don't think the cohomology is known. As an indication of this I would refer to the 2007 paper "On the Stiefel–Whitney classes of the representations associated with Spin(15)" by Mamoru Mimura and Te …
Christian Nassau's user avatar
12 votes

Geometric interpretation of families in the stable homotopy groups of spheres

This has been a burning question for quite some time, but not much is known. Surely, people believe that the next layer (i.e. the $\beta$-family) should also admit a geometric description, although as …
Christian Nassau's user avatar
5 votes
Accepted

Morava's "Motives and cell bundles"?

Google knows about this preprint ("A theory of base motives") which seems related: http://folk.uio.no/rognes/yff/morava.pdf
Christian Nassau's user avatar
15 votes

What are the best known results for the stable homotopy groups of spheres?

Computing $\pi_\ast(S)$ is a tedious business that to this day can only be done "by hand", i.e. by humans. The $p=2$ computation up to dimension 64 was completed by Kochman (see his SLNM book) with la …
Christian Nassau's user avatar
5 votes

Realizing $\mathcal{A}(2)//\mathcal{A}(1)$ by a finite spectrum

As pointed out by John Rognes, this answer is not correct (it misses the $Sq^4$ from the bottom class to the class in dimension $4$). Sorry for the confusion. =========== previous answer ============ …
7 votes
Accepted

Image of J in the classical Adams Spectral Sequence

The image of $J$ is pretty easy to see in the Adams $E_2$ term: it consists of the elements along the vanishing line, plus, in dimensions 8k-1, of the towers that end near the vanishing line. This ide …
Christian Nassau's user avatar
7 votes
Accepted

Which sets of Stiefel-Whitney characteristic numbers can be realized as coming from a manifold?

The Steenrod operations on mod 2 cohomology imply the vanishing of some characteristic numbers. Specifically, if $p(w_1,w_2,\ldots)\in H^k(M^n;Z/2)$ for $k\lt n$ then $0=\langle \sum_{i+j=n-k}u_i{\rm …
Christian Nassau's user avatar