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Algebraic and topological K-theory, relations with topology, commutative algebra, and operator algebras

5 votes
1 answer
193 views

What is the most general notion of exactness for functors between triangulated categories?

For triangulated categories $T,T'$ I would like to define "weakly exact" functors as those that respect cones, that is, $F(Cone f)\cong Cone(F(f))$ for any $T$-morphism $f$, and I do not require any f …
3 votes
0 answers
163 views

Which "tensor" endofunctors on triangulated categories are essentially exact?

Assume that $T$ is a symmetric monoidal triangulated category, and $X$ is an object in it. Then the functors $X\otimes -$ and $-\otimes X: T\to T$ are not necessarily exact since they send distinguish …
5 votes
1 answer
369 views

Which complexes of coherent sheaves can be presented as countable homotopy limits of perfect...

Let $X$ be a noetherian scheme (actually, I need the case where $X$ is proper over an affine scheme), $C$ is an object of the derived category $D_{coh}(X)$ of coherent sheaves on $X$. Under which ass …
2 votes
0 answers
116 views

Did anybody study split homotopy cartesian squares in triangulated categories?

Let us call a commutative square $$ \require{AMScd} \begin{CD} A @>{g'}>> B \\ @V{f'}VV @VV{f}V \\ C @>>{g}> D \end{CD} $$ in a triangulated category split homotopy cartesian if the ("s …
1 vote
0 answers
151 views

"Interesting" examples of exact abelian subcategories of R-Mod

A somewhat vague question: for which rings there exist "interesting" exact abelian subcategories of $R-\operatorname{Mod}$ that are closed with respect to products? Actually, I would like the correspo …
1 vote

Which complexes of coherent sheaves can be presented as countable homotopy limits of perfect...

In the case where C is bounded above this statement was established in Neeman's https://arxiv.org/abs/1804.02240v4. Now I will try to extend his "approximation" statements to the case where $C$ is an …
Mikhail Bondarko's user avatar
2 votes
1 answer
259 views

Semi-orthogonal decompositions over singular schemes

Where can I find any more or less explicit semi-orthogonal decompositions of derived categories of perfect complexes or of bounded derived categories for singular schemes that are proper over a ring R …
2 votes
0 answers
125 views

When semi-simple subcategories "extend" to hearts of t-structures?

Let $A$ be a semi-simple abelian subcategory of a triangulated category $C$ that "generates" $A$ (that is, $C$ equals its own smallest triangulated subcategory that is closed under direct summands and …
1 vote
0 answers
120 views

On infinite global dimensions of "slightly non-commutative" rings

Assume $R$ is a commutative Noetherian ring of finite Krull dimension; $R'$ is a not commutative ring that contains $R$ in its center and also finitely generated as an $R$-module. If the (left) global …
3 votes
0 answers
149 views

Bounded derived categories of which smooth projectives possess bounded t-structures whose he...

I am interested in $P$ that is smooth and proper over a field and such that the derived category of coherent sheaves $D^b(P)$ possesses a $t$-structure whose heart is the category of finitely generate …
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 …
4 votes
0 answers
312 views

Which derived categories of coherent sheaves are equivalent (or "$t$-related") to derived ca...

As far as I understand, it was Beilinson who proved that the bounded derived category of coherent sheaves $D^b(\mathbb{P}^n)$ is equivalent to the bounded derived category of a certain (non-commutativ …
4 votes
Accepted

Motivation for Karoubi envelope/ idempotent completion

The "motivic motivation" is that by idempotent completing correspondences over a finite field one obtains a category of homological motives where Kunneth decompositions of diagonals are available. Mo …
Mikhail Bondarko's user avatar
5 votes
1 answer
318 views

Is the motivic homotopy spectrum of Hermitian K-theory $\eta$-complete?

Theorem 1.2 of the paper "The motivic Hopf map solves the homotopy limit problem for K-theory" (see https://elibm.org/article/10011880) says that (under certain assumptions on the base field) the homo …
4 votes
0 answers
205 views

When does the canonical $t$-structure restrict to perfect complexes?

I am interested in non-Noetherian(!) rings such that the canonical $t$-structure on $D(R)$ (the derived category of left $R$-modules) restricts to perfect complexes i.e. to the subcategory of complexe …

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