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Part of higher category theory that for instance in Algebraic Topology enables us to capture finer homotopic distinctions. As in say Eilenberg-Maclane spaces.

7 votes
5 answers
2k views

Lecture notes, videos and other learning materials about $\infty$-category theory

I've heard several times (and realized myself) that Lurie's tomes (extraordinary as they are) are not so ideal for self study. I think it's a good idea to have some kind of compiled list of learning …
Saal Hardali's user avatar
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5 votes
0 answers
201 views

The notion of $\infty$-Cooperads for which Bar-Cobar duality is an equivalence

In the paper Bar-Cobar Duality by Michael Ching, he proves that the category of operads in spectra is equivalent via the Bar-Cobar adjunction to some model category of co-operads defined in the paper. …
Saal Hardali's user avatar
  • 7,789
30 votes
3 answers
4k views

DG categories in algebraic geometry - guide to the literature?

Although my experience with DG categories is pretty basic I find them to be a very neat tool for organizing (co-)homological techniques in algebraic geometry. For someone who has algebro-geometric app …
Saal Hardali's user avatar
  • 7,789
5 votes
1 answer
548 views

Defining hom spaces in the derived category as limits of hom spaces in the homotopy category

Let $C$ be an abelian category and $K(C)$ the homotopy category of complexes in $C$. I've seen the following claimed in several sources (without proof): A. The following isomorphisms hold: $$\li …
Saal Hardali's user avatar
  • 7,789
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
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8 votes
2 answers
533 views

A map of spaces implementing the Pontryagin Thom collapse map? (collapse maps in families)

Let $M$ be an $n$ dimensional smooth manifold and let $j: M \to \mathbb{R}^{m}$ be an embedding. Associated to this embedding we can form the "collapse map" which is a pointed map from a sphere to the …
Saal Hardali's user avatar
  • 7,789
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
502 views

Categorification of definitions in the context of the derived category of quasi-coherent she...

Let $SpecA=X$ be an affine noetherian scheme. Let $QCoh(X)$ denote the derived (stable $\infty$-)category of quasi-coherent sheaves on $X$. There are the following special full subcategories spanned b …
Saal Hardali's user avatar
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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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2 votes
0 answers
267 views

Interesting examples of large, accessible, non-presentable $\infty$-categories?

What are some interesting examples of accessible $\infty$-categories which are not presentable and not small? By interesting I mean a category which comes up naturally in a certain context and …
Saal Hardali's user avatar
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5 votes
1 answer
686 views

Closed symmetric monoidal structure on the derived category of modules whose unit is a duali...

Let $A$ be non-positively graded commutative DG-algebra almost of finite type over a field $k$ of characteristic $0$. Most of these assumptions (affine, commutative, characteristic, bound) are only to …
Saal Hardali's user avatar
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7 votes
0 answers
404 views

Generalities on sheaves - Where can I find the technology that can make this "proof" of Atiy...

Fix $R$ an $E_{\infty}$ ring spectrum which admits a "six functor formalism" over a suitable class of spaces (by which I mean a context in which what I'm about to say can be made correct). Let $X$ b …
Saal Hardali's user avatar
  • 7,789
8 votes
1 answer
610 views

Functorial construction of ("pre"-)spectral sequences? (Or - what is the "higher structure" ...

Let $\mathcal{C}$ be a stable $\infty$-category. Let $Fun(\mathbb{Z},\mathcal{C})$ be the category of sequences of objects in $\mathcal{C}$. Where the category $\mathbb{Z}$ stands for the nerve of the …
Saal Hardali's user avatar
  • 7,789
8 votes
1 answer
950 views

Homotopy theoretic description of homotopy fixed points (and obstructions) for an action of ...

There are several scattered statements about fixed points and obstructions which I'd very much like to see unified in some framework. To state them let $G$ be a group acting on a connected (1-truncat …
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