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Homotopy theory, homological algebra, algebraic treatments of manifolds.
30
votes
Accepted
Is the $H$-space structure on $S^7$ associative up to homotopy?
It is not. See Theorem 1.4 of this paper by I.M. James (Trans. AMS 84 (1957), 545-558).
In particular, there exists no homotopy associative multiplication on $S^n$ unless $n=1$ or $n=3$.
1
vote
Accepted
Thom isomorphism's effect on module structure of n-oriented spectra
Okay, so maybe I'm being naive here, but I think this is probably a naive question. The answer might be a little complicated by the fact that I don't have any good way to drawcommutative diagrams on h …
3
votes
1
answer
292
views
Formal group laws arising from localizations of MU
This is sort of a two part question:
1) In one construction of $BP$, the Brown-Peterson spectrum, one uses this idempotent map of Quillen's, $g:MU_{(p)}\to MU_{(p)}$ and from what I can tell, the ima …
0
votes
Filtration on Smash Product of Cofibers
So it seems to me that, using Peter May's paper above, for two distinguished triangles $X\to Y\to Z$ and $X'\to Y'\to Z'$, we have a 'filtration':
$$Z\wedge Z'\overset{f_1}\leftarrow Y\wedge Y'\overs …
9
votes
1
answer
289
views
Essential maps of spectra which are null when localized at any prime
There are maps of spaces which are not null-homotopic, but when localized at any prime become null. I don't know explicit constructions of any, but an example is given in Section 6 of Chapter 25 of th …
4
votes
1
answer
864
views
A Model for the Moore Spectrum of $\mathbb{Z}_{(p)}$
Is it true that the Moore spectrum for the group $\mathbb{Z}_{(p)}$ can be constructed by smashing $\mathbb{S}$ with $q^{-1}\mathbb{S}$ for each $q\neq p$ (here both $q$ and $p$ are primes). It seems …
10
votes
2
answers
630
views
Geometric Interpretations of Homotopy Theoretical Constructions
In homotopy theory there are lots of nice constructions that seem designed to have some effect on the homotopy of a space, i.e. completing, localizing, and taking various homotopy (co)limits. It seems …
5
votes
2
answers
221
views
Filtration on Smash Product of Cofibers
I have seen some similar questions to this one on here recently, so I hope this isn't redundant. Basically, suppose I have two cofiber sequences of spectra (or perhaps just work in some general homot …
9
votes
1
answer
483
views
Thom isomorphism's effect on module structure of n-oriented spectra
This question is specifically related to the spectra $X(n)$ used in Devinatz, Hopkins and Smith's proof of the nilpotence conjectures, but any general answer in terms of the Thom isomorphism would als …
7
votes
1
answer
771
views
Thom isomorphism from the ABGHR perspective
In ABGHR Thom spectra are described in the following way: we start with a morphism of Kan complexes $X\to \mathbb{S}\text{-line}$, where $\mathbb{S}\text{-line}$ is an $\infty$-groupoid which is equiv …
4
votes
1
answer
316
views
Bar Construction Model of Ring Spectrum Quotient
Suppose I am given a morphism $f:BG\to BGL_1(R)$ for $R$ some at least $E_1$-ring spectrum and $G$ a loop space. Then This corresponds, I believe, to an action of $G$ on $R$, coming from a morphism $G …
1
vote
Accepted
Thom Spectra and Hopf-Galois Extensions of Ring Spectra
So this can definitely be done. It took me a while to figure out all the details, but in the end it's not so conceptually complex.
The basic idea is that if you've got a fibration $F\overset{i}\to E …
5
votes
0
answers
173
views
(Co)homology of a directed space with coefficients in a commutative monoid
This is essentially a reference request, or a request for an explanation of why this cannot be done in a useful or interesting way (i.e. an explanation of why no such reference exists!).
If I have a d …
6
votes
0
answers
91
views
Group structure on cohomology with coefficients in a spectral 2-type
Let $E$ be a spectrum having exactly two non-trivial homotopy groups, $\pi_k(E)=G$ and $\pi_j(E)=G'$ for $j>k\geq 0$, and having $k$-invariant $\alpha\colon\Sigma^{k}HG\to\Sigma^jHG'$. Also assume tha …
2
votes
0
answers
250
views
Invariant Ideals in Split Hopf Algebroids
Given a split Hopf algebroid $(S,\Sigma)=(S,S\otimes B)$ over $K$, Ravenel leaves as an exercise the proof of the following:
An ideal $J\subset S$ is invariant under the action of the group $\mathrm{ …