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Enriched categories, topoi, abelian categories, monoidal categories, homological algebra.

10 votes

Complexity of coherence diagrams in an $n$-category

This is not a full answer to the question but it was too long for a comment. Depending on your conventions, "weak $n$-categories" might mean "$(n,n)$-categories" which are a special case of $(\infty,n …
Saal Hardali's user avatar
  • 7,799
4 votes
Accepted

Reference request: levelwise detection of a morphism of $\infty$-functors being an isomorphism

Making my comment an answer to remove it from the unanswered list: This is in Rezk's Stuff about quasicategories (pdf), Proposition 29.10.
Saal Hardali's user avatar
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21 votes
1 answer
2k views

Are all formal schemes *really* Ind-schemes?

$\newcommand\LRS{\mathsf{LRS}}\newcommand\FormalSch{\mathsf{FormalSch}}\DeclareMathOperator\Spf{Spf}\newcommand\IndSch{\mathsf{IndSch}}\newcommand\ALRS{\mathsf{ALRS}}\newcommand\FSch{\mathsf{FSch}}$I' …
Saal Hardali's user avatar
  • 7,799
11 votes
2 answers
869 views

From Weyl groups to Weyl groupoids?

I'm trying to find a framework where the choices in the classical construction of a root system of a semi-simple lie algebra are not needed. Let $\mathfrak{g}$ be a semisimple lie algebra. Defin …
Saal Hardali's user avatar
  • 7,799
24 votes
1 answer
1k views

About the abelian category of endofunctors of $\mathsf{Vect}$

Let $k$ be a field, $\mathsf{Vect}$ the category of finite dimensional vector spaces, and $\mathsf{C} = Fun(\mathsf{Vect},\mathsf{Vect})$ the abelian category of pointed endofunctors (sending $0$ to $ …
Saal Hardali's user avatar
  • 7,799
6 votes
1 answer
341 views

Compact objects in the $\infty$-category presented by a simplicial model category

Let $\mathsf{M}$ be a simplicial model category presenting an $\infty$-category $\mathcal{M}$. I'm interested in a general statement relating compact objects in $\mathcal{M}$ (in the $\infty$-categori …
Saal Hardali's user avatar
  • 7,799
7 votes
1 answer
383 views

The naive approach to deriving profunctors - What's wrong with it?

Let $(\mathcal{C,W})$ be relative category (equipped with a wide subcategory of weak equivalences satisfying 2 out of 3 property). Consider a profunctor $F: \mathcal{C \times D^{op}} \to \mathsf{Set}$ …
Saal Hardali's user avatar
  • 7,799
5 votes
0 answers
335 views

A compendium of weak factorization systems on $sSet$

A (weak) factorization system on a category $\mathcal{C}$ consists of a pair of classes of morphisms in the category $(L,R)$ satisfying Every morphism $f:x \to y \in \mathcal{C}$ can be factored (n …
12 votes
0 answers
403 views

The $\infty$-category of $n$-manifolds and open embeddings determined homotopically from tha...

Let $\mathrm{Diff}_n$, $\mathrm{PL}_n$, $\mathrm{Top}_n$ denote the $\infty$-categories of $n$-manifolds which are respectively smooth/PL/topological, and open embeddings (for instance by taking the h …
Saal Hardali's user avatar
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6 votes
0 answers
245 views

Uniqueness of the $(2,2)$-category theory of $(\infty,1)$-categories?

The question, as in the title, may be very simply stated as follows: Main Question: Can the homotopy $(2,2)$-category of $(\infty,1)$-categories be characterized as the unique $2$-category upto eq …
Saal Hardali's user avatar
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6 votes
0 answers
308 views

An adjunction between monads on $\mathcal{C}$ and presentable categories under $\mathcal{C}$

Fix a regular cardinal $\kappa$ and let $\mathcal{C}$ be a $\kappa$-presentable $\infty$-category (comments about the 1-categorical case are welcome as well!). I'm looking for a reference for the fol …
Saal Hardali's user avatar
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9 votes
0 answers
376 views

Is there any notion of "smoothification" from $\mathbb{R}$-schemes to generalized smooth spa...

I will write $\operatorname{Diff}$ to denote a category of generalized smooth spaces e.g. $Sh(\mathsf{CartSp})$. Is there a version of $\operatorname{Diff}$ for which there exists a functor $\mathcal{ …
Saal Hardali's user avatar
  • 7,799
6 votes
2 answers
626 views

Monomorphisms, epimorphisms, (co-)images and factorizations in $\infty$-categories

Several of the many notions that don't work the same way when passing to $\infty$-categories are the ones mentioned in the title. I'm trying to understand the conceptual picture around these notions i …
Saal Hardali's user avatar
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11 votes
0 answers
551 views

The intrinsic meaning of abelian sheaf cohomology of a category

Basically my question is: Suppose I meet an alien mathematician which understands everything through category theory and category theory alone. How would I convince said mathematician that certain …
Saal Hardali's user avatar
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