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Homotopy theory is an important sub-field of algebraic topology. It is mainly concerned with the properties and structures of spaces which are invariant under homotopy. Chief among these are the homotopy groups of spaces, specifically those of spheres. Homotopy theory includes a broad set of ideas and techniques, such as cohomology theories, spectra and stable homotopy theory, model categories, spectral sequences, and classifying spaces.

7 votes
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Computing Homotopy Fixed Point Spectral Sequences related to Morava E thories

In Ravenel's paper on the Arf invariant, he shows (p. 439) that there is a composite of maps $$ \mathrm{Ext}_{BP_*BP}(BP_*,BP_*) \to H^*_c(\mathbb{S}_n,E_*) \to H^*(C_p,E_*/\frak{m}), $$ under which t …
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10 votes

Does an H-space have at most one delooping?

The real projective spaces $\mathbb{R}P^3 \cong SO(3)$ and $\mathbb{R}P^7$ also give fun examples. Naylor proved that there exist 768 $H$-space structures on $SO(3)$, while Rees shows that there exist …
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5 votes

The cooperations algebras Johnson-Wilson theory and truncated BP-theory

Regarding $E(n)_*E(n)$, see "On the Structure of the Hopf Algebroid $E(n)_*E(n)$" by Keith Johnson. Johnson shows that $$E(n)_*E(n) \otimes \mathbb{Q} \simeq \mathbb{Q}[v_1,\cdots,v_{n-1},v_n^{\pm 1}, …
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9 votes

Multiplicative Structures on Moore Spectra

I think the answer to your question is essentially unknown. As far as I'm aware the best known results are: $M(p)$ admits an $A_{p-1}$ structure but never an $A_p$-structure. I learnt the following …
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12 votes
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Detecting the Brown-Comenetz dualizing spectrum

Your question appears to be equivalent to the 'dichotomy conjecture' of Hovey, which I believe is still open. First, note that any finite spectrum has a type, and all finite spectrum of type $n$ ha …
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9 votes
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$K_3(\mathbb{Z})$ and $\pi ^S_3$

We have $\pi_3(\mathbb{S}) \cong \mathbb{Z}/24\{ \nu\}$ and $\pi_3K(\mathbb{Z}) \cong \mathbb{Z}/48\{ \lambda \}$. As Achim suggested, the unit map $\mathbb{S} \to K(\mathbb{Z})$ induces on $\pi_3$ th …
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12 votes
1 answer
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Some calculations with the Adams spectral sequence and the cobar complex

I am trying to 'get my hands dirty', so to speak, with some of the calculations with the Adams spectral sequence in Ravenel's Complex Cobordism book, and I have a few questions (I hope it is OK to ask …
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10 votes
0 answers
487 views

Differentials in the Adams-Novikov spectral sequence and the geometric boundary theorem

$\newcommand\Ext{\mathrm{Ext}} \newcommand\Z{\mathbb{Z}} \newcommand\G{\mathbb{G}}$ The reference for this question will be the paper by Henn, Karamanov and Mahowald - "The homotopy of the $K(2)$-loca …
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9 votes
1 answer
467 views

Morava modules and completed $E$-homology

Let $E = E_n$ be the $n$-th Morava $E$-theory and let $\{ M_{I} \}$ be a tower of generalised Moore spectra. Then (see this previous question) there is a Milnor exact sequence $$0 \to \varprojlim_I { …
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6 votes
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Basic questions on spectra

Here is a slightly more fleshed out version of the comment above. First, the claim that the collection $\mathcal{C} = \{ \Sigma^{p,q} U \mid U \in Sm/S, p,q \in \mathbb{Z} \}$ is a collection of com …
Drew Heard's user avatar
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32 votes

Why should I care about topological modular forms?

TMF has been used to solve classical topological problems. For example Bruner, Davis and Mahowald obtained new results regarding nonimmersions of real projective spaces in Euclidean space (http://hopf …
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