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(Co)chain complexes, abelian Categories, (pre)sheaves, (co)homology in various (possibly highly generalized) settings, spectra, derived functors, resolutions, spectral sequences, homotopy categories. Chain complexes in an abelian category form the heart of homological algebra.

1 vote
0 answers
47 views

Any examples known of $K^b(B)$ localized by a set of morphisms (i.e. of complexes of length 1)?

I would like to understand the following setting: for an additive $B$ localize $K^b(B)$ by a set of $B$-morphisms (i.e. by a thick triangulated subcategory generated by some set of two-term complexes) …
Mikhail Bondarko's user avatar
10 votes
2 answers
566 views

Does a triangulated category that possesses a subcategory $B$ of generators with no extensio...

Suppose that a triangulated category $C$ contains a full additive subcategory $B$ of (strong) generators (i.e. there does not exist a proper strict triangulated subcategory $C'\subset C$ that contains …
Mikhail Bondarko's user avatar
9 votes

Chain homotopy: Why du+ud and not du+vd?

Amusingly, I have considered the category of complexes where maps of the form du+vd are killed in: Weight structures vs. $t$-structures; weight filtrations, spectral sequences, and complexes (for mo …
Mikhail Bondarko's user avatar
1 vote

A conservative, non faithful functor between triangulated categories

You can start with the derived category of graded polarizable Hodge structures or with the category of Hodge modules (over a complex variety $X$). These categories possess natural weight structures (a …
Mikhail Bondarko's user avatar
11 votes
1 answer
263 views

What are the projective dimensions of big fraction fields?

Let $A$ be an integral domain, $B$ is its fraction field. Can the projective dimension of the $A$-module $B$ be greater than $1$? This surely cannot happen if the spectrum of $A$ is countable (since t …
Mikhail Bondarko's user avatar
1 vote

Recollement of multiple $t$-structures

I didn't check that thoroughfully, but it seems that in the ("abstract") setting you are interested in there exist (exact) "projections" $j^{i*}:D\to D^i$ and $j^{i!}:D\to D^i$ ($D$ is the "big" trian …
Mikhail Bondarko's user avatar
4 votes
3 answers
531 views

When an exact embedding of abelian categories induces a full embedding of their derived cate...

Let $F:A\to A'$ be a (full) exact embedding of abelian categories. When $D(F):D(A)\to D(A')$ (or its bounded version) is a full embedding also? I would be interested in any necessary or sufficient c …
Mikhail Bondarko's user avatar
3 votes

distinguished triangles and cohomology

You might be interested in the paper: Vaknin A., Virtual Triangles// K-Theory, 22 (2001), no. 2, 161--197.
Mikhail Bondarko's user avatar
3 votes
3 answers
2k views

Homology or cohomology?

How do people call an additive functor from a triangulated category $C$ to an abelian one that converts distinguished triangles into long exact sequences. Does one usually call a covariant functor o …
Mikhail Bondarko's user avatar
6 votes
1 answer
535 views

Exceptional collections of objects in topological triangulated categories?

People often consider exceptional sets of objects (i.e. collections of objects satisfying certain strong orthogonality conditions: $Ext^{l}(P_i,P_j)$ should be zero for $l\neq 0$ + something else) in …
Mikhail Bondarko's user avatar
15 votes
1 answer
2k views

What is the purpose of section 3 of BBD?

I am not quite sure that this question is appropriate for Mathoverflow, yet I would be deeply grateful for any hint: what happens in section 3 of Beilinson A., Bernstein J., Deligne P., Faisceaux perv …
Mikhail Bondarko's user avatar
2 votes
Accepted

Is the dual of a compact generator also a compact generator of the derived category of a var...

Let me try to sketch an argument (though I am not quite sure in details). A theorem of Neeman implies that a compact object $M$ in a compactly generated triangulated category $T$ is a generator if an …
Mikhail Bondarko's user avatar
13 votes

Is there an additive functor between abelian categories which isn't exact in the middle?

As far as I remember, there is an important example of a functor that transforms mono- and epimorphisms into mono- and epimorphisms, respectively, but is not half-exact; this is the functor of interm …
Mikhail Bondarko's user avatar
6 votes
1 answer
240 views

For which exact couples do associated spectral sequences degenerate at $E_1$?

It is well known that a bigraded exact couple of objects of an abelian category yields a spectral sequence (cf. https://ncatlab.org/nlab/show/exact+couple#SpectralSequencesFromExactCouples). My questi …
Mikhail Bondarko's user avatar
2 votes

DG enhancements of $\ell$-adic derived categories

Q1. So, I suggest you the following plan of the proof. Note that any Verdier localization of a triangulated category possessing a differential graded enhancement possesses a differential graded enha …
Mikhail Bondarko's user avatar

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