User Jens Reinhold

67 votes

Independent evidence for the classification of topological 4-manifolds?

answered May 26, 2021 at 17:44

39 votes

Non-homeomorphic spaces that have continuous bijections between them

answered Sep 29, 2016 at 17:56

21 votes

Accepted

Is there a concrete description of the nontorsion elements in the homotopy groups of spheres?

answered Aug 27, 2021 at 6:29

18 votes

Homotopy groups of Diff(X) and Homeo(X)

answered Oct 7, 2020 at 12:29

18 votes

Accepted

What is known about exotic spheres up to stable diffeomorphism?

answered Feb 26, 2021 at 16:20

16 votes

Finite CW complex with finite non-abelian fundamental group and higher homologies zero

answered Aug 4, 2021 at 15:01

14 votes

Accepted

Homotopy groups $\pi_{4n-1}(SO(4n))$

answered Mar 4, 2021 at 13:39

13 votes

Accepted

About the cohomology of $BG^\delta$. Making a Lie group discrete

answered Mar 27, 2020 at 14:12

12 votes

Accepted

Generalize Wu formula to integral cohomology classes

answered Apr 26, 2017 at 23:29

11 votes

SO(3) action on (simply connected) 6 manifold with discrete fixed point

answered Apr 14, 2017 at 15:27

8 votes

Accepted

3-sphere bundles over 4-sphere bound smooth disc bundles

answered Dec 3, 2015 at 20:19

8 votes

If two smooth manifolds are homeomorphic, then their stable tangent bundles are vector bundle isomorphic

answered Aug 7, 2020 at 7:04

8 votes

Accepted

Why is the mapping class group of a surface with nonempty boundary torsion-free?

answered Mar 15, 2021 at 15:09

8 votes

Accepted

Conditions under which the preimage of a submanifold in nontrivial in homology

answered Feb 12, 2021 at 14:00

7 votes

Accepted

Are all pointed maps of classifying spaces of abelian groups homotopy equivalent to homomorphisms?

answered Nov 25, 2019 at 21:46

6 votes

Normal invariants

answered Nov 2, 2020 at 14:25

6 votes

classifying space of orthogonal groups

answered Nov 18, 2015 at 3:51

6 votes

What does positivity of the first Pontryagin number of a vector bundle tell us?

answered Apr 12, 2017 at 20:46

6 votes

Accepted

comparing homology of a space and homology of the classifying space of its fundamental group

answered Mar 1, 2016 at 21:17

5 votes

Accepted

Oddness of intersection form of surface bundle

answered Jul 3, 2020 at 9:26

4 votes

Accepted

When given degrees generate the cohomology ring of a manifold?

answered Mar 30, 2021 at 9:21

4 votes

Vanishing of characteristic numbers vs vanishing of characteristic classes

answered Oct 31, 2016 at 13:08

4 votes

Can one calculate possible mapping degrees from a connected-sum to another manifold?

answered Apr 14, 2017 at 0:15

4 votes

"Economic" Eilenberg-MacLane topological abelian groups

answered Mar 3, 2017 at 1:16

4 votes

Accepted

cohomology module of unit tangent vector bundles over spheres

answered Jan 15, 2016 at 7:21

4 votes

Building a manifold from a CW complex inductively

answered Dec 13, 2021 at 17:15

4 votes

Accepted

References for properties which are invariant under partition of $\mathbb{Z}$ by a finite number of sets

answered Jan 17, 2022 at 16:19

3 votes

How much do characteristic classes fail to characterize bundles?

answered Nov 2, 2021 at 17:32

3 votes

Accepted

fiber sequence of principal bundles

answered Jan 13, 2015 at 4:47

3 votes

When are principal bundles preserved by colimits?

answered Apr 28, 2015 at 0:54

Stack Exchange Network

41 Answers

Independent evidence for the classification of topological 4-manifolds?

Non-homeomorphic spaces that have continuous bijections between them

Is there a concrete description of the nontorsion elements in the homotopy groups of spheres?

Homotopy groups of Diff(X) and Homeo(X)

What is known about exotic spheres up to stable diffeomorphism?

Finite CW complex with finite non-abelian fundamental group and higher homologies zero

Homotopy groups $\pi_{4n-1}(SO(4n))$

About the cohomology of $BG^\delta$. Making a Lie group discrete

Generalize Wu formula to integral cohomology classes

SO(3) action on (simply connected) 6 manifold with discrete fixed point

3-sphere bundles over 4-sphere bound smooth disc bundles

If two smooth manifolds are homeomorphic, then their stable tangent bundles are vector bundle isomorphic

Why is the mapping class group of a surface with nonempty boundary torsion-free?

Conditions under which the preimage of a submanifold in nontrivial in homology

Are all pointed maps of classifying spaces of abelian groups homotopy equivalent to homomorphisms?

Normal invariants

classifying space of orthogonal groups

What does positivity of the first Pontryagin number of a vector bundle tell us?

comparing homology of a space and homology of the classifying space of its fundamental group

Oddness of intersection form of surface bundle

When given degrees generate the cohomology ring of a manifold?

Vanishing of characteristic numbers vs vanishing of characteristic classes

Can one calculate possible mapping degrees from a connected-sum to another manifold?

"Economic" Eilenberg-MacLane topological abelian groups

cohomology module of unit tangent vector bundles over spheres

Building a manifold from a CW complex inductively

References for properties which are invariant under partition of $\mathbb{Z}$ by a finite number of sets

How much do characteristic classes fail to characterize bundles?

fiber sequence of principal bundles

When are principal bundles preserved by colimits?