Formalized Homotopy Theory (Rev #2)

Here are some links to proofs about homotopy theory, formalized in homotopy type theory. Please add!

Maybe we could figure out a way not to duplicate stuff between this page and homotopy groups of spheres?

Cast of characters so far: Jeremy Avigad, Guillaume Brunerie, Favonia, Eric Finster, Chris Kapulkin, Dan Licata, Peter Lumsdaine, Mike Shulman.

- Guillaume proved that there is some n such that π4(S3) is Z_n. With a computational interpretation, we could run this proof and check that it’s 2.

- Peter’s construction of the Hopf fibration as a dependent type. Lots of people around know the construction, but I don’t know anywhere it’s written up. Here’s some Agda code with it in it.
- Guillaume’s proof that the total space of the Hopf fibration is S3, together with π_n(Sn), imply this by a long-exact-sequence argument, but this hasn’t been formalized.

- Prove that K(G,n) is a spectrum (Eric?).
- To do cohomology with finite coefficients, all we need is the boring work of defining Z/pZ as an explicit group.
- Calculate some cohomology groups.

- Dan’s proof for n-types.

- Dan’s construction.

Implies π_k(Sn) = π_k+1(Sn+1) whenever k <= 2n - 2

- Peter’s encode/decode-style proof, formalized by Dan, using a clever lemma about maps out of 2 n-connected types. This is the “95%” version, which shows that the relevant map is an equivalence on truncations.
- The full “100%” version, formalized by Dan, which shows that the relevant map is 2n-connected.

- Dan and Guillaume’s encode/decode-style proof using iterated loop spaces (for single-loop presentation).
- Guillaume’s proof (for suspension definition).
- Dan’s proof from Freudenthal suspension theorem (for suspension definition).

- Guillaume’s proof (see the book).
- Dan’s encode/decode-style proof for pi^1(S^2) only.
- Dan’s encode/decode-style proof for all k < n.
- Dan’s proof from Freudenthal suspension theorem (for suspension definition).

- Guillaume’s proof.
- Dan’s encode/decode-style proof.

- Mike’s proof by contractibility of total space of universal cover (HoTT blog).
- Dan’s encode/decode-style proof (HoTT blog). A paper mostly about the encode/decode-style proof, but also describing the relationship between the two.
- Guillaume’s proof using the flattening lemma.

- Chris/Peter/Jeremy’s development (link?).

- Mike’s proofs are in the book and Favonia formalized it.

- Favonia’s proofs (link in flux due to library rewrite).

- Favonia/Peter/Guillaume/Dan’s formalization of Peter/Eric/Dan’s proof (link in flux due to library rewrite).

Revision on March 3, 2014 at 14:11:53 by Mike Shulman. See the history of this page for a list of all contributions to it.