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

15 votes
1 answer
521 views

What are the advantages of various "models" for the motivic stable homotopy category

People use several distinct models for the motivic stable homotopy category (so, there are some choices for the underlying category and a collection of available model structures). I would like to ask …
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
13 votes
4 answers
2k views

Localizing an arbitrary additive category

Under which conditions localizing an additive category by some class S of morphisms yields and additive category? It seems easy to define certain addition on morphisms if we fix their representatives …
Mikhail Bondarko's user avatar
12 votes
1 answer
403 views

Which statements and arguments of Hovey's "Model categories" fail without functorial factori...

I would like to study the homotopy theory of the category of pro-objects over a proper model category $M$. $Pro-M$ is endowed with the strict model structure; it seems that functorial functorizations …
Mikhail Bondarko's user avatar
11 votes
Accepted

Does the Grothendieck group depend on the embedding?

I think that the Grothendieck group DOES depend on A. Indeed, any additive category C could be embedded (by the Yoneda embedding) into the abelian category of contravariant additive functors from C to …
Mikhail Bondarko's user avatar
9 votes
1 answer
649 views

Objects of which Grothendieck abelian categories have elements?

The Freyd-Mitchell embedding theorem is a very useful tool for dealing with small abelian categories. However, it does not allow to use "elements" of objects of an abelian category $A$ in those statem …
Mikhail Bondarko's user avatar
8 votes
Accepted

When does a triangulated category have a heart?

A silly remark is that "trivial" $t$-structures always exist. You should probably say that you want a bounded or a non-degenerate $t$-structure. As far as I remember, non-zero negative $K$-groups of $ …
Mikhail Bondarko's user avatar
7 votes
2 answers
400 views

Properness of the category of modules over a spectrum (that represents algebraic cobordism o...

The abstract form of the question: let $C$ be a closed proper stable model category, $R$ is a ring object in it. Which conditions ensure that the category $R-mod$ is also proper? Since weak equivalen …
Mikhail Bondarko's user avatar
7 votes

A toy example of a tensor triangulated category?

I think that the simplest example is $K(B)$ (the homotopy category of complexes; you can also consider $K^b(B)$) where $B$ is any tensor additive category. Certainly, this example is not independent f …
Mikhail Bondarko's user avatar
6 votes
0 answers
230 views

Nice references for injective model structures and Quillen functors between motivic homotopy...

It seems that for the injective model structures for the categories simplicial presheaves and simplicial Nisnevich sheaves (on the category of smooth varieties over a perfect field $k$) there exist co …
Mikhail Bondarko's user avatar
6 votes
1 answer
927 views

Does there exist a definition of equivalence of functors?

I have two functors $F_1,F_2$ from a category $C$ into two distinct categories $D_1,D_2$. I would like to say that $F_1$ and $F_2$ are equivalent if there exists a commutative square $\require{AMScd}$ …
Mikhail Bondarko's user avatar
6 votes
0 answers
71 views

How would you say that transformations are isomorphic in the arrow category?

For functors $E,F,E',F':X\to Y$ I would like to say that transformations $\tau:E\to F$ and $\tau':E'\to F'$ are isomorphic if they are isomorpic in the arrow category of functors $X\to Y$, that is, t …
Mikhail Bondarko's user avatar
5 votes
1 answer
349 views

Which abelian categories possess an exact faithful functor into abelian groups that respects...

Let $A$ be an abelian category closed with respect to small coproducts (that is, and AB3 category). Which assumptions are sufficient to ensure the existence of an exact faithful functor from $A^{op}$ …
Mikhail Bondarko's user avatar
5 votes
0 answers
186 views

Which t-structure extend from subcategories of compact objects uniquely?

Let $T$ be a compactly generated triangulated category, that is, $T$ is closed with respect to small coproducts and equals its own smallest triangulated subcategory closed with respect to coproducts a …
Mikhail Bondarko's user avatar
5 votes
Accepted

Clarification on Hanamura's work on $t$ structure of triangulated category of mixed motives

1) I believe that the (Murre's) vanishing needed for Hanamura's argument is stronger than the BS conjecture. 2) There are certain standard conditions ensuring that a triangulated category is equivale …
Mikhail Bondarko's user avatar

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