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Homotopy theory, homological algebra, algebraic treatments of manifolds.

11 votes

Are the higher homotopy groups of the Hawaiian earring trivial?

Here is a short natural argument that planar continua are aspherical, different from the technique of Cannon/Conner/Zastrow, and straight forwardly applied to the Hawaiian earring. The Hawaiian earr …
Paul Fabel's user avatar
  • 1,968
2 votes
0 answers
131 views

Topological dimension of quotient group determined by the inverse limit of discrete free mon...

Must the natural quotient group of the inverse limit of a sequence of nested discrete free monoids have topological dimension zero? The question might well be open, but I would be grateful for news t …
Paul Fabel's user avatar
  • 1,968
14 votes
Accepted

Existence of a non-null-homotopic simple closed curve

No. The harmonic archipelago is a compact $2$-dimensional counterexample, embedded in $\mathbb R^3$. Let $S_n$ denote the planar circle with center on the $x$-axis, and whose intersection with the $x …
Paul Fabel's user avatar
  • 1,968
10 votes
Accepted

Is the homeomorphism class of a connected open set of C determined by its fundamental group?

The answer is indeed no as David Cohen has pointed out, and more generally the answer is determined by the complements of the sets U and U'. The complete solution is effectively due to R.L. Moore (19 …
Paul Fabel's user avatar
  • 1,968
3 votes

Homotopy problem for infinite dimensional topological space II

The following does not settle the original question. The answer is `no' if we ignore the intrinsic metric requirement and merely demand metric. For a counterexample first observe that the inverse li …
Paul Fabel's user avatar
  • 1,968