Allen Hatcher's user avatar
Allen Hatcher's user avatar
Allen Hatcher's user avatar
Allen Hatcher
  • Member for 14 years, 4 months
  • Last seen this week
86 votes
Accepted

Why do finite homotopy groups imply finite homology groups?

81 votes

Learning Topology

80 votes
Accepted

Maps which induce the same homomorphism on homotopy and homology groups are homotopic

76 votes
Accepted

Definition of "simplicial complex"

76 votes

Periods and commas in mathematical writing

73 votes

Homotopy groups of Lie groups

56 votes
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Intuition behind Thom class

47 votes
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Triangulating surfaces

45 votes

Spectral sequences: opening the black box slowly with an example

43 votes
Accepted

nontrivial $\pi_2(\textrm{Diff}(M))$

41 votes

Parallelizability of the Milnor's exotic spheres in dimension 7

39 votes

Colloquial catchy statements encoding serious mathematics

35 votes

Why do wedges of spheres often appear in combinatorics?

35 votes

Why do the homology groups capture holes in a space better than the homotopy groups?

34 votes
Accepted

Are there pairs of highly connected finite CW-complexes with the same homotopy groups?

32 votes
Accepted

Survey articles on homotopy groups of spheres

32 votes
Accepted

What characteristic class information comes from the 2-torsion of $H^*(BSO(n);Z)$?

31 votes
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Fundamental group of the line with the double origin.

29 votes
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Fibers of fibrations of a 3-manifold over $S^1$

28 votes
Accepted

Is the space of diffeomorphisms homotopy equivalent to a CW-complex?

28 votes

How to compute $\pi_{3}$ of $L(p,q)\# L(p',q')$?

24 votes

Reference for a fact (?) on homeomorphic knot complements

24 votes
Accepted

Points on a sphere

23 votes
Accepted

Homology equivalence and isomorphism on $\pi_1$ not enough for homotopy equivalence?

23 votes
Accepted

how to visualize the class number of an imaginary quadratic field?

22 votes
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Detecting homotopy nontriviality of an element in a torsion homotopy group

22 votes

CW-structures and Morse functions: a reference request

19 votes
Accepted

An elementary proof that the degree of a map of spheres determines its homotopy type

19 votes
Accepted

The Wedge Sum of path connected topological spaces

19 votes

Closed manifold with non-vanishing homotopy groups and vanishing homology groups