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Algebraic varieties, stacks, sheaves, schemes, moduli spaces, complex geometry, quantum cohomology.

83 votes
Accepted

Derived algebraic geometry: how to reach research level math?

I propose the following plan, assuming a basic background in scheme theory and algebraic topology. I assume that you are interested in derived algebraic geometry from the point of view of application …
41 votes

A bestiary of topologies on Sch

I have just discovered a chart comparing topologies on Sch/S, made by Pieter Belmans. It includes all the topologies discussed above, and some more I haven't even heard of. It's even interactive and …
AAK's user avatar
  • 5,901
37 votes
3 answers
6k views

Conjectures in Grothendieck's "Pursuing stacks"

I read on the nLab that in "Pursuing stacks" Grothendieck made several interesting conjectures, some of which have been proved since then. For example, as David Roberts wrote in answer to this questi …
AAK's user avatar
  • 5,901
25 votes

Algebraic K-theory and Homotopy Sheaves

The question already has good answers but I think there is still more to be said. References As already mentioned, algebraic K-theory satisfies Zariski descent. For regular noetherian schemes this …
AAK's user avatar
  • 5,901
24 votes

Why do we need model categories?

This answer is an elaboration on Dylan's comments. 1) Let us define a homotopy theory to be a pair $(C, W)$, where $C$ is a category and $W$ is some class of morphisms called weak equivalences. (Let' …
AAK's user avatar
  • 5,901
23 votes
Accepted

Mysterious quotes (at least for me)

Here is a guess about the remark of Orlov. Suppose that one wants to define a good notion of noncommutative scheme, given that an affine noncommutative scheme is an associative algebra. Trying to de …
AAK's user avatar
  • 5,901
23 votes
Accepted

Motivation and potential applications of spectral algebraic geometry

This is not really an answer to your question, just an attempt to address your question from the comments. There are various flavours of homotopical or higher algebraic geometry that are commonly con …
AAK's user avatar
  • 5,901
22 votes
Accepted

Why is "naive" definition of non-commutative spectrum bad?

I have also wondered about this question and recently came across some papers that seem to answer it. First of all, the paper Manuel L. Reyes, Obstructing extensions of the functor Spec to noncommu …
AAK's user avatar
  • 5,901
17 votes

Why is the motivic category defined over the site of smooth schemes only?

It makes sense to consider larger versions of the (unstable and stable) motivic homotopy categories built out of the site $Sch_S$ of all schemes over $S$ (say of finite type to avoid dealing with size …
AAK's user avatar
  • 5,901
16 votes

DG categories in algebraic geometry - guide to the literature?

There are plenty of interesting dg-categories one can associate to a scheme. From the point of view of six functor yoga, these should be viewed as "categories of coefficients" for cohomology theories …
AAK's user avatar
  • 5,901
15 votes
Accepted

What is the applications of the dg-enhancements of derived categories of sheaves

It is hard to know where to begin! A general principle is that as long as you are only concerned with the derived category of a single variety, it is generally sufficient to consider it as a triangul …
AAK's user avatar
  • 5,901
12 votes
Accepted

A question on Voevodsky´s categories

One could say that the story begins with Beilinson's conjectures on the existence of a theory of motivic cohomology. In accordance with the insights of the Grothendieck school that cohomology theorie …
AAK's user avatar
  • 5,901
9 votes
Accepted

K theory long exact sequence

Regarding the first question: If $X$ is quasi-compact quasi-separated and $U \to X$ is a quasi-compact open immersion, then Thomason-Trobaugh showed that there is a "proto-localization sequence", i.e …
AAK's user avatar
  • 5,901
9 votes

References for the "nerve of an algebraic variety"

One way to understand your question is in the framework of $\mathbf{A}^1$-homotopy theory. This is because your nerve functor is better understood when defined on a cocomplete category like the categ …
AAK's user avatar
  • 5,901
9 votes

Basic questions about stacks 2

Regarding 3), Andrew Kresch just told me that they gave up on the project.
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  • 5,901

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