User Matthias Künzer

201

votes

66

answers

38k

views

Proofs that require fundamentally new ways of thinking

ho.history-overview big-list

Mar 1 '20 at 20:25 the L 984

113

votes

12

answers

9k

views

Spectral sequences: opening the black box slowly with an example

spectral-sequences homological-algebra at.algebraic-topology

Aug 15 '17 at 10:20 Julien Grivaux 500

69

votes

6

answers

5k

views

Rigidity of the category of schemes

ag.algebraic-geometry ct.category-theory

Dec 23 '19 at 21:10 Community♦ 1

65

votes

1

answer

6k

views

Derived Functors Versus Spectral Sequences

ag.algebraic-geometry ct.category-theory kt.k-theory-and-homology homological-algebra

Aug 24 '12 at 4:47 Sándor Kovács 39.5k

58

votes

9

answers

11k

views

Arguments against large cardinals

set-theory soft-question lo.logic mathematical-philosophy large-cardinals

Jan 12 '19 at 13:36 Martin Sleziak 4,267

52

votes

2

answers

7k

views

Grothendieck's manuscript on topology

big-picture gn.general-topology topos-theory

Jun 13 at 2:41 Community♦ 1

38

votes

4

answers

2k

views

Pre-triangulated category that isn't triangulated

ct.category-theory triangulated-categories reference-request

Mar 7 '17 at 0:50 motivique 57

36

votes

0

answers

981

views

Computer calculations in A_infinity categories?

ct.category-theory ag.algebraic-geometry computer-science mathematical-software

Jan 22 '13 at 19:29 Community♦ 1

31

votes

3

answers

4k

views

In which situations can one see that topological spaces are ill-behaved from the homotopical viewpoint?

big-list homotopy-theory at.algebraic-topology gt.geometric-topology ct.category-theory

Feb 7 '12 at 10:30 Community♦ 1

26

votes

5

answers

2k

views

“Lie algebra” for a general group ?

gr.group-theory ra.rings-and-algebras

Jun 22 '12 at 0:58 Adrien 6,415

24

votes

2

answers

5k

views

Large cardinal axioms and Grothendieck universes

ct.category-theory set-theory lo.logic large-cardinals

Jan 24 '10 at 6:20 François G. Dorais♦ 41.2k

22

votes

1

answer

2k

views

What is a self-dual category?

ct.category-theory reference-request

Mar 28 '12 at 9:04 Dan Petersen 33.5k

16

votes

2

answers

1k

views

Loop space of a category

at.algebraic-topology loop-spaces homotopy-theory

Dec 6 '12 at 7:16 Ilias A. 1,874

15

votes

2

answers

920

views

Does $\mathbb{K}[G]\simeq\mathbb{K}[H]$ for some field $\mathbb{K}$ of characteristic $p$, imply $\mathbb{F}_p[G]\simeq\mathbb{F}_p[H]$?

group-algebras gr.group-theory associative-algebras ra.rings-and-algebras finite-fields

Aug 24 '15 at 20:17 David E Speyer 128k

15

votes

5

answers

2k

views

Tate Cohomology via stable categories

gr.group-theory homological-algebra finite-groups group-cohomology triangulated-categories

Jun 17 at 13:54 YCor 42.5k

14

votes

1

answer

565

views

$A_\infty$ structure on Ext-algebras well defined?

reference-request homological-algebra

Mar 12 '12 at 22:47 David White 20.6k

11

votes

2

answers

2k

views

How would a motivic proof of the Riemann hypothesis over finite fields go?

ag.algebraic-geometry weil-conjectures motives nt.number-theory

Aug 14 '11 at 20:16 anon 431

11

votes

4

answers

3k

views

group of Yoneda extensions and the EXT groups defined via derived category

derived-categories homological-algebra

May 17 '11 at 15:27 Lux 116

11

votes

4

answers

1k

views

Localizing an arbitrary additive category

ct.category-theory localization

Jul 28 '13 at 10:55 Ricardo Andrade 5,998

10

votes

2

answers

538

views

Does a triangulated category that possesses a subcategory $B$ of generators with no extensions of non-zero degree between them have to be isomorphic to $K^b(B)$?

triangulated-categories homological-algebra

Feb 6 '11 at 19:35 Fernando Muro 13.9k

8

votes

2

answers

1k

views

The composition of derived functors - commutation fails hazardly?

abelian-categories derived-categories derived-functors ct.category-theory homological-algebra

Dec 21 '11 at 21:31 Leonid Positselski 13.5k

7

votes

2

answers

523

views

Ostensibly different products on Ext-groups

homological-algebra ra.rings-and-algebras

Aug 7 at 21:02 Robert Bruner 3,198

7

votes

1

answer

626

views

Is every balanced pre-abelian category abelian?

homological-algebra

Oct 11 '10 at 0:56 Community♦ 1

6

votes

1

answer

788

views

Is it possible to make an autoequivalence of categories an automorphism?

ct.category-theory

Mar 22 '12 at 13:14 Martin Brandenburg 53.2k

6

votes

1

answer

889

views

Transporting model structures via adjunctions

ct.category-theory at.algebraic-topology model-categories

Mar 29 '12 at 10:07 Ittay Weiss 388

6

votes

1

answer

330

views

Making additive envelopes of monoidal categories monoidal

reference-request ct.category-theory monoidal-categories

Apr 4 '14 at 12:16 Dimitri Chikhladze 2,172

5

votes

1

answer

520

views

Perverse vs real formality?

homological-algebra a-infinity-algebras

May 18 '12 at 9:32 Jan Weidner 11.6k

4

votes

2

answers

424

views

Number of Subgroups of p-Groups

gr.group-theory

Sep 9 '11 at 15:07 Matthias Künzer 1,217

3

votes

1

answer

450

views

Center of the category of $R$-algebras

ct.category-theory ac.commutative-algebra

Apr 11 '11 at 11:57 Community♦ 1

3

votes

1

answer

326

views

Given an exact category, viewed as a site, do there exist non-additive sheaves?

ct.category-theory sheaf-theory exact-categories

Aug 1 '17 at 14:47 jeq 1,220

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Proofs that require fundamentally new ways of thinking

Spectral sequences: opening the black box slowly with an example

Rigidity of the category of schemes

Derived Functors Versus Spectral Sequences

Arguments against large cardinals

Grothendieck's manuscript on topology

Pre-triangulated category that isn't triangulated

Computer calculations in A_infinity categories?

In which situations can one see that topological spaces are ill-behaved from the homotopical viewpoint?

“Lie algebra” for a general group ?

Large cardinal axioms and Grothendieck universes

What is a self-dual category?

Loop space of a category

Does $\mathbb{K}[G]\simeq\mathbb{K}[H]$ for some field $\mathbb{K}$ of characteristic $p$, imply $\mathbb{F}_p[G]\simeq\mathbb{F}_p[H]$?

Tate Cohomology via stable categories

$A_\infty$ structure on Ext-algebras well defined?

How would a motivic proof of the Riemann hypothesis over finite fields go?

group of Yoneda extensions and the EXT groups defined via derived category

Localizing an arbitrary additive category

Does a triangulated category that possesses a subcategory $B$ of generators with no extensions of non-zero degree between them have to be isomorphic to $K^b(B)$?

The composition of derived functors - commutation fails hazardly?

Ostensibly different products on Ext-groups

Is every balanced pre-abelian category abelian?

Is it possible to make an autoequivalence of categories an automorphism?

Transporting model structures via adjunctions

Making additive envelopes of monoidal categories monoidal

Perverse vs real formality?

Number of Subgroups of p-Groups

Center of the category of $R$-algebras

Given an exact category, viewed as a site, do there exist non-additive sheaves?