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Search options not deleted user 12547

This tag is used if a reference is needed in a paper or textbook on a specific result.

3 votes
Accepted

Is $\text{Ind-}\bf C$ the category of models for a sketch?

As suggested I repost my comment as an answer. The paper Adámek, Borceux, Lack, Rosický, A classification of accessible categories addresses exactly these types of questions. In particular, Section 3 …
Karol Szumiło's user avatar
3 votes
Accepted

geometric realization on $\mathbf{sTop}$

The results on homotopy invariance of the geometric realization of simplicial spaces go back at least to May's The Geometry of Iterated Loop Spaces, although he doesn't explicitly mention model catego …
Karol Szumiło's user avatar
8 votes
0 answers
358 views

Tornehave's preprint "On BSG and the symmetric groups"

There are a few papers that cite Tornehave's preprint entitled On BSG and the symmetric groups apparently dating from early 70s or late 60s. Google search reveals very little. Does anyone have access …
Karol Szumiło's user avatar
15 votes
Accepted

Can homotopy pullbacks of spaces be checked on fibers?

$\require{AMScd}$I don't know a reference but the proof is easy enough. Form homotopy pullback squares \begin{CD} Fu @>>> Ff @>>> A \\ @VVV @VVV @V{u}VV \\ * @>>> Fg @>>> P @>>> B \\ @. @VVV @VVV @VV …
Karol Szumiło's user avatar
2 votes
Accepted

Defining degeneracies for semi-simplicial sets with inner Kan conditions

The short answer is no. If you take the semi-simplicial set $X$ with one $0$-simplex and no higher simplices, then it has fillers for all inner horns (because it has no inner horns) but clearly does n …
Karol Szumiło's user avatar
5 votes

Reedy model structures on oplax limits

You may be thinking of Johnson, Mark W. On modified Reedy and modified projective model structures. Theory Appl. Categ. 24 (2010), No. 8, 179–208. but his constructions (Definitions 3.3 and 5.2) hav …
Karol Szumiło's user avatar
12 votes
Accepted

Reference for "lax monoidal functors" = "monoids under Day convolution"

This observation appears already in Day's thesis as Example 3.2.2. For some reason it is only stated for commutative monoids and symmetric (pro)monoidal functors and only as a correspondence of object …
Karol Szumiło's user avatar
5 votes

Functors between simplicial sets and cubical sets with connections

I believe that the standard barycentric subdivision functor $\mathrm{Sd} \colon \mathsf{sSet} \to \mathsf{sSet}$ factors through cubical sets with connections. We define a functor $S \colon \Delta \to …
Karol Szumiło's user avatar
16 votes
Accepted

Cocontinuous product-preserving functor between Grothendieck toposes

For any small category $J$, the colimit functor $\mathsf{Set}^J \to \mathsf{Set}$ preserves colimits. It preserves finite limits if and only if $J$ is filtered and it preserves finite products if and …
Karol Szumiło's user avatar
10 votes

Enriched locally presentable categories

The theory is also developed further in two papers by Borceux, Quinteiro and Rosický: Enriched accessible categories MR1419612 and A theory of enriched sketches MR1624638. In the second one they say t …
Karol Szumiło's user avatar
3 votes
Accepted

Combinatorial proof that some model categories are monoidal/enriched?

This is far from a comprehensive answer, but since you ask for references, here are two. The result for simplicial sets is obtained by an explicit computation in Appendix H of Joyal's The Theory of Q …
Karol Szumiło's user avatar
2 votes

Ref request: making a homotopy equivalence fibrewise, in an abstract setting (eg fibration c...

I was quite sure that this was explicitly written down by Rădulescu-Banu or by Hirschhorn, but I cannot find this exact statement. However, this follows directly by combining Theorems 7.5.10 and 7.6. …
Karol Szumiło's user avatar
6 votes
Accepted

Different model structures on Top

No. Let $X$ be an uncountable set and consider $I^X$ with the product topology. Then the inclusion $\{ 0 \} \to I^X$ is a closed embedding between (strongly) contractible spaces which are therefore mi …
Karol Szumiło's user avatar