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For questions about the derived categories of various abelian categories and questions regarding the derived category construction itself.

0 votes
1 answer
482 views

Understanding a lemma in "Loop Spaces and Langlands Parameters" article

First, some background. I was trying to read the article Loop Spaces and Langlands Parameters but I get immediately stuck at Theorem 2.1 in the introduction. This was actually forward-referring to C …
Ilya Nikokoshev's user avatar
6 votes

Heuristic behind the Fourier-Mukai transform

The following answers might be useful: Fourier-Mukai transform - a first example Intuition for Integral Transforms Fourier transform for dummies The last one has my sketch of an answer which I'll …
Ilya Nikokoshev's user avatar
5 votes
4 answers
819 views

$E_\infty$ spectrum corresponding to $\Bbb Z_p$

First of the questions about derived algebraic geometry from a noobie. The way I understand it, every discrete ring $R$ corresponds to some ring spectrum whose $\pi_0$ is $R$. Now consider $p$-adic nu …
Ilya Nikokoshev's user avatar
1 vote

What does a projective resolution mean geometrically?

Ah, great question! I'm not a big expert, but one thing it obviously does is constructing the sheaf M from the locally free bundles (locally free = projective). For example, consider a skyscraper she …
Ilya Nikokoshev's user avatar
22 votes
4 answers
5k views

Examples for Decomposition Theorem

There's an important piece of geometric knowledge usually quoted as Beilinson-Bernstein-Deligne. Here's a refresher: by $IC$ one means the intersection complex, which is just $\mathbb Q$ for a smooth …
Ilya Nikokoshev's user avatar
13 votes
1 answer
1k views

When do six operations work?

This question comes (heavily edited) from my notes, thus slightly unusual structure. We know that algebraic maps have very strict structure, and in many settings the operations f_*, f_!, their adjo …
Ilya Nikokoshev's user avatar
1 vote

Is the Fukaya category "defined"?

Yes, it's defined at least sometimes. See Constructible Sheaves and the Fukaya Category by Nadler and Zaslow, math/0604379
Ilya Nikokoshev's user avatar
0 votes

Is the Fukaya category "defined"?

This is a completely different answer. If my intuition is correct, in the case of noncompact Calabi-Yau, the Fukaya category is (1) expected to be defined (2) for a good physical reason (3) but not …
Ilya Nikokoshev's user avatar
5 votes
2 answers
942 views

Singular K3 -- mathematical meaning?

There's a very interesting text by Cumrun Vafa called Geometric Physics. Here I'm particularly interested in Chapter 4, where we take a Calabi-Yau manifold presented as a degenerating fibration: …
Ilya Nikokoshev's user avatar
36 votes
6 answers
5k views

How to think about model categories?

I've read about model categories from an Appendix to one of Lurie's papers. What are the examples of model categories? What should be my intuition about them? E.g. I understand the typical examples …
Ilya Nikokoshev's user avatar