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Homework Help: Topology Problem

  1. Apr 10, 2010 #1
    1. The problem statement, all variables and given/known data

    Find two spaces A,B compact where A and B are nonhomeomorphic but AX[0,1][tex]\cong[/tex]BX[0,1]

    2. Relevant equations

    Definitions of homeomorphism, cardinality possiby, I have no idea where to start.

    3. The attempt at a solution
    My idea Is [0,1] and S^1, but im not sure if the unit square is homeo to the cylinder.
  2. jcsd
  3. Apr 10, 2010 #2


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    It's not. The cylinder has a loop in it that can't be shrunk to a point (one going around it) and the unit square doesn't have anything like that.

    A hint: If f(x,t) is the homeomorphism from Ax[0,1] to Bx[0,1], it must be that if f(x,t)=(y,s) that t is not equal to s in general, otherwise restricting yourself to a single value of t would give a homeomorphism from A to B
  4. Apr 10, 2010 #3
    That's actually a really useful idea. For some reason I look at your hint and think homotopy. Is that a step in the right direction?
  5. Apr 11, 2010 #4
    How about A= space between two concentric circles, with a smaller circle glued to the inside of the smaller circle, and a circle of the same size glued to the outside, and B= the same concentric circle space, but two circles are on the outside?
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