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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.

9 votes
Accepted

The Bousfield Class of the Infinite Wedge of Telescopes of Finite Spectra

The spectrum $H\mathbf{F}_p$ is an acyclic for both $\bigvee \langle T(n) \rangle$ and $\bigvee \langle K(n) \rangle$. Therefore neither of these wedges equals $\langle S \rangle$.
John Palmieri's user avatar
11 votes
1 answer
292 views

W H Lin's thesis and Hopf subalgebras of the Steenrod algebra

If $B$ is a subalgebra of $A$, you can ask whether the $B$-module structure on $B$ can be extended to give an $A$-module structure on $B$. W H Lin, in his 1973 PhD thesis at Northwestern, showed that …
John Palmieri's user avatar
11 votes
Accepted

W H Lin's thesis and Hopf subalgebras of the Steenrod algebra

Using @CarloBeenakker's answer, our librarian found an electronic version, produced from the microfilm copy of the original: https://search.proquest.com/docview/302701183 (full text may require access …
John Palmieri's user avatar
11 votes

What are some good examples of spectral sequences which degenerate after the first nontrivia...

The Serre spectral sequence for the path-loop fibration for an $n$-sphere is a positive answer to question 1, a negative answer to question 2. More generally, a fibration in which either the base or t …
8 votes

Simplicial model of Hopf map?

There is a small simplicial set description of the Hopf map in Clemens Berger's thesis, Exemple 1.19, pp. 45-47.
John Palmieri's user avatar
8 votes

What are some toy models for the stable homotopy groups of spheres?

As Dave Benson says, the Noetherian condition simplifies a lot of things. The derived category of a commutative ring satisfies many of the properties of the stable homotopy category. The derived categ …
John Palmieri's user avatar
8 votes

Algebraic topology and homotopy theory with simplicial sets instead of topological spaces

It certainly used to be the case that if you went to an algebraic topology research talk, when the speaker said, "Let $X$ be a space," then there was about a 50% chance that they really meant "Let $X$ …
John Palmieri's user avatar
4 votes

Derivations in the Steenrod algebra

I have a guess for question 1. Fix $n \geq 0$ and let $E(n)$ be the Hopf subalgebra dual to $\mathbb{F}_2 [\xi_{n+1}, \xi_{n+2}, \dots] / (\xi_i^{2^{n+1}})$. Every $x\in E(n)$ satisfies $x^2=0$, and m …
John Palmieri's user avatar
5 votes

Is there an additive model of the stable homotopy category?

In the category $Ho(C)$, say that every map is a fibration and a cofibration, and define the weak equivalences to be the isomorphisms. This makes $Ho(C)$ into a model category; its homotopy category i …
John Palmieri's user avatar
15 votes
Accepted

Is homology finitely generated as an algebra?

Another counterexample: let $A$ be the algebra $\mathbb{Q}[y,z]/(y^2) \otimes \bigwedge(x)$ with $x$ in degree 1, $y$ and $z$ in degree 2. Put a differential on this by $z \mapsto xy$. This is a commu …
John Palmieri's user avatar