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Homework Help: Homotopy Classes

  1. Feb 13, 2013 #1
    The problem asks to show that if the space Y is path connected, then [I,Y], the set of homotopy classes of maps I into Y where I = [0,1], consists of a single element. What I tried to do is take two arbitrary continuous maps f,g: I -> Y and show that they are homotopic. For each s ε I, f(s) and g(s) are elements of Y. Thus, by our assumption, there exists some path, call it ps, such that ps(0)=f(s) and ps(1)=g(s). Define F: I X I -> Y by the equation
    for each s ε I.
    F(s,0)=ps(0) = f(s) and F(s,1)=ps(1)=g(s)​
    for each s.

    I have since learned that this is incorrect as the correct approach would be to take an arbitrary continous map and show that it is homotopic to a constant map. My question is regarding where my argument failed. Any help/guidance would be great! Thank you!
  2. jcsd
  3. Feb 13, 2013 #2


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    What's wrong with that is that I don't see how you can claim that F is continuous in the two variables s and t. You picked the ##p_s## independently for each s. How do you know they fit together to make a continuous map from IxI to Y?
  4. Feb 13, 2013 #3
    Thank you! :) I knew it didn't quite make sense, which is why I eventually gave up and searched for a solution.
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