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Thomas Kragh

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Name	Thomas Kragh
Member for	3 years
Seen	21 hours ago
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Location	MIT, Boston
Age	33

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23

54

votes

1

answer

3k

views

Nontrivial finite group with trivial group homologies?

gr.group-theory group-cohomology open-problem

feb 10 at 22:44 Dennis Sullivan 121●1●2

20

48

votes

1

answer

1k

views

Stiefel–Whitney classes in the spirit of Chern-Weil

characteristic-classes dg.differential-geometry

mar 12 at 16:22 MathOverflow♦ 1●2●3

14

35

votes

4

answers

2k

views

Torsion in homology or fundamental group of subsets of Euclidean 3-space

homology at.algebraic-topology gn.general-topology gt.geometric-topology

nov 19 10 at 19:51 Sergey Melikhov 3,722●12●19

16

30

votes

2

answers

1k

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Moving one family of commuting self-adjoint operators to another without losing commutativity on the way

fa.functional-analysis oa.operator-algebras missing-lemma

may 24 at 16:09 Sean Lawton 521●3●10

22

25

votes

5

answers

4k

views

Is there a complex structure on the 6-sphere?

dg.differential-geometry complex-geometry open-problem

jun 27 11 at 17:53 Al-burcas 101●1●3

11

25

votes

5

answers

1k

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How are the classifying space of $E_8$ and $K(\mathbb{Z},4)$ related?

at.algebraic-topology classifying-spaces principal-bundles

feb 5 12 at 16:32 Urs Schreiber 6,735●14●22

9

22

votes

0

answers

1k

views

Example of a compact set that isn’t the spectrum of an operator

fa.functional-analysis banach-spaces

may 29 11 at 9:42 Theo Buehler 3,696●1●11●25

7

17

votes

0

answers

970

views

Ricci flat metric on $n$-sphere?

dg.differential-geometry riemannian-geometry

jun 20 11 at 3:39 Viktor Bundle 999●2●8

6

17

votes

0

answers

328

views

Is there a (discrete) monoid M injecting into its group completion G for which BM is not homotopy equivalent to BG?

homotopy-theory at.algebraic-topology monoids classifying-spaces

feb 18 at 22:22 Omar Antolín-Camarena 1,517●7●16

8

15

votes

3

answers

857

views

Are there topological restrictions to the existence of almost quaternionic structures on compact manifolds?

dg.differential-geometry topology quaternionic-geometry

jun 5 12 at 17:21 Oldřich Spáčil 155●1●5

8

15

votes

2

answers

874

views

Proof of Bott Periodicity in twisted K-theory

at.algebraic-topology kt.k-theory-homology reference-request homotopy-theory

apr 10 at 20:58 Max Karoubi 91●1●1

5

13

votes

2

answers

631

views

Why Donaldson’s Four-Six Conjecture?

sg.symplectic-geometry dg.differential-geometry open-problem

nov 15 at 20:55 Chris Gerig 5,656●1●12●40

8

11

votes

2

answers

994

views

How to relate equivariant symplectic cohomology, Contact Homology, Cyclic Homology and String Topology?

fukaya-category sg.symplectic-geometry at.algebraic-topology

jul 5 11 at 0:19 Tim Perutz 8,673●1●16●42

5

10

votes

1

answer

401

views

Hamiltonian displaceability of tori in symplectic balls

symplectic-topology sg.symplectic-geometry

may 21 10 at 19:48 Chris Woodward 41●2

6

10

votes

0

answers

335

views

When does a representation admit a spin structure?

rt.representation-theory

jan 20 11 at 16:10 Charles Rezk 13.1k●1●31●67