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Is this a valid parametrization of the torus?

  1. Feb 28, 2015 #1
    I am reading "Differential Geometry of Curves and Surfaces" by Manfredo do Carmo and on page 156 he gives the following parameterization of the torus

    x(u,v) = ((a + r cos u )cos v, (a + r cos u)sin v, r sin u) 0 < u < 2*pi, 0 < v < 2*pi

    Doesnt this leave out some of the torus,? I know that he needs to map from an open set in R^2 and he therefore want to map from the product of two open intervals in R, but by not including either 0 or 2*pi I dont see how this is onto the torus. Am I missing something here?
     
  2. jcsd
  3. Feb 28, 2015 #2

    Ben Niehoff

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    Yes, strictly speaking it covers all of the torus except two intersecting circles.
     
  4. Feb 28, 2015 #3
    But then it's not covering it, why is this not a problem?
     
  5. Feb 28, 2015 #4

    Ben Niehoff

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    You can't cover the torus in a single chart.
     
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