Question

There does not exist a map $S^2\times S^2\to \mathbb{CP}^2$ with odd degree.

score 636 · Answer 1 · 2026-04-15 13:52:03

636

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There does not exist a map $S^2\times S^2\to \mathbb{CP}^2$ with odd degree.

Published on 15 Apr 2026 - 13:52

score 215 · Answer 2 · 2026-04-15 15:36:44

215

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Another differential topology lemma

Published on 15 Apr 2026 - 15:36

score 1.8k · Answer 3 · 2026-04-14 01:14:33

1.8k

Views

Product of CW complexes question

Published on 14 Apr 2026 - 1:14

score 1.4k · Answer 4 · 2026-04-12 06:29:31

1.4k

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The First Homology Group Obtained by Attaching a Möbius Strip to a Torus in a Certain Way.

Published on 12 Apr 2026 - 6:29

score 461 · Answer 5 · 2026-04-10 12:15:47

461

Views

The fundamental group of a scheme / variety

Published on 10 Apr 2026 - 12:15

score 605 · Answer 6 · 2026-04-16 09:11:37

605

Views

Commutative Diagrams and their relationship to induced homomorphisms

Published on 16 Apr 2026 - 9:11

score 254 · Answer 7 · 2026-04-15 13:00:49

254

Views

Show a particular $f:S^{2n}\to S^{2n}$ must be antipodal map.

Published on 15 Apr 2026 - 13:00

score 827 · Answer 8 · 2026-04-11 18:51:14

827

Views

Proof that homotopy equivalent maps induce equivalent homomorphisms on homology groups....

Published on 11 Apr 2026 - 18:51

score 139 · Answer 9 · 2026-04-14 03:57:28

139

Views

Calculating fundamental group and homology group to prove not homeomorphic to each other

Published on 14 Apr 2026 - 3:57

score 103 · Answer 10 · 2026-04-15 09:45:53

103

Views

Unit or non-zero octonions form an $A_\infty$-space?

Published on 15 Apr 2026 - 9:45

score 286 · Answer 11 · 2026-04-14 14:15:34

286

Views

Do $\pi_1$-surjective maps of degree $0$ exist?

Published on 14 Apr 2026 - 14:15

score 68 · Answer 12 · 2026-04-17 12:45:57

68

Views

Does ''homology vanishes eventually'' imply ''homotopy vanishes eventually''?

Published on 17 Apr 2026 - 12:45

score 69 · Answer 13 · 2026-04-19 09:13:26

69

Views

How to show $\frac{X\sqcup_{S^1}D^2}{D^2}\simeq \frac{X}{S^1}$

Published on 19 Apr 2026 - 9:13

score 56 · Answer 14 · 2026-04-10 17:06:42

56

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Can a factor map be a Serre fibration?

Published on 10 Apr 2026 - 17:06

score 1k · Answer 15 · 2026-04-11 17:18:45

1k

Views

How to compute the fundamental group of $S^2 / A$, where $A$ is a finite set of points?

Published on 11 Apr 2026 - 17:18

List Question

There does not exist a map $S^2\times S^2\to \mathbb{CP}^2$ with odd degree.

Another differential topology lemma

Product of CW complexes question

The First Homology Group Obtained by Attaching a Möbius Strip to a Torus in a Certain Way.

The fundamental group of a scheme / variety

Commutative Diagrams and their relationship to induced homomorphisms

Show a particular $f:S^{2n}\to S^{2n}$ must be antipodal map.

Proof that homotopy equivalent maps induce equivalent homomorphisms on homology groups....

Calculating fundamental group and homology group to prove not homeomorphic to each other

Unit or non-zero octonions form an $A_\infty$-space?

Do $\pi_1$-surjective maps of degree $0$ exist?

Does ''homology vanishes eventually'' imply ''homotopy vanishes eventually''?

How to show $\frac{X\sqcup_{S^1}D^2}{D^2}\simeq \frac{X}{S^1}$

Can a factor map be a Serre fibration?

How to compute the fundamental group of $S^2 / A$, where $A$ is a finite set of points?

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