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Paul Fabel's user avatar
Paul Fabel's user avatar
Paul Fabel
  • Member for 13 years, 4 months
  • Last seen this week
  • Mississippi State University
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Homotopy problem for infinite dimensional topological space II
The line x=1 in the (x,y) plane. The line (1,y,0) in (x,y,z) space.
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Homotopy problem for infinite dimensional topological space II
No, the spin I describe yields a compactification of the open unit disk by attaching a cylinder.
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Homotopy problem for infinite dimensional topological space II
No, the 0th homotopy group of a non path connected space is nontrivial. If this doesn't count, spin the original graph about the line x=1 in (x,y,z) space. Then X will have nontrivial fundamental group/
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Is the homeomorphism class of a connected open set of C determined by its fundamental group?
David's counterexample is correct. Every open subset of the plane has free fundamental group with at most countably many generators.
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Is the homeomorphism class of a connected open set of C determined by its fundamental group?
To fill in a few details in the above, suppose K and K' are nonempty compact totally disconnected subsets of the 2-sphere, with respective complements U and U'. Then any homeomorphism between U and U' extends to a homeomorphism of the 2-sphere, and any homeomorphism between K and K' extends to a homeomorphism of the 2-sphere. For the latter direction, see the pf. in Van Mill's book on infinitely dimensional topology that the Cantor set cannot be wildly embedded in the plane. For the former direction apply the Schoenflies theorem repeatedly.
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Is every connected metrizable locally path connected space a length space?
Thanks Sergei! My obtuse (and likely incorrect) definition should be ignored. The reader should use any standard definition of length space. For example, for all x and y in X and all e>0, there exists a rectifiable path from x to y whose length is less then d(x,y)+e.
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revised
Sufficient conditions for Hausdorffness
Improved notation for deleting a point from a set
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