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 43054

For questions about simplicial sets, simplicial (co)algebras and simplicial objects in other categories; geometric realization, Dold-Kan correspondence, simplicial resolutions etc.

5 votes
Accepted

contracting homotopy on simplicial sets

It is easier to define the map you're looking for if you adjoint it over and define a map $Map(\Delta[1],X)\to Map(\Delta[1],Map(\Delta[1],X)) = Map (\Delta[1]\times \Delta[1],X)$ Then this comes fr …
Denis Nardin's user avatar
  • 16.5k
2 votes
Accepted

Transfer map of simplicial sets

In the more general version with compact (finitely dominated) fibers, this is called the Becker-Gottlieb transfer. You can find a long list of references on the nlab. Here are a few of them: Becker, …
Denis Nardin's user avatar
  • 16.5k
6 votes
Accepted

Topological realisation of a stack (explicit description)

Let $\mathrm{Ét}_\mathbb{C}$ be the étale $\infty$-topos of schemes over $\mathbb{C}$, that is the $\infty$-categories of étale sheaves of $\infty$-groupoids over $\mathbb{C}$. This contains necessari …
Denis Nardin's user avatar
  • 16.5k
3 votes
Accepted

Pullbacks and fibers in the $\infty$-category of spaces

Well, I guess I can write as an answer what I wrote as a comment. Any pullback square where $C$ is not discrete will yield a counterexample. For simplicity let $B=G=\ast$ and $C=S^1$. Then $E=H=\Omeg …
Denis Nardin's user avatar
  • 16.5k
9 votes

Example of a non-$\infty$-category whose homotopy category is a groupoid

Since the homotopy category depends only on the 2-skeleton of the simplicial set, the easiest thing to do is to take the 2-skeleton of an ∞-groupoid. For example, let $E$ be the nerve of the contracti …
Denis Nardin's user avatar
  • 16.5k
8 votes
Accepted

Homotopy function complex for quasi-categories

Yes, you can compute the mapping spaces in ∞-categories by taking the biggest Kan subcomplex of the internal hom. The trick is not to use the Joyal model structure, but instead the model structure on …
Denis Nardin's user avatar
  • 16.5k
16 votes
Accepted

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

It depends on what you mean by "all results". Of course results regarding manifolds or vector bundles do not admit statements completely internal to the world of simplicial sets (although most of them …
Denis Nardin's user avatar
  • 16.5k
3 votes
Accepted

Kan complexes and semigroups

(2) is true (and so (1) is false). To see it, note that every horn $\Lambda^n_i\to S$ to a constant simplicial set must be constant, and so it can be filled by the constant horn $\Delta^n\to S$. Equi …
Denis Nardin's user avatar
  • 16.5k