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Minkowski vs deSitter: hyperbolic vs spherical?

  1. Sep 3, 2009 #1

    nomadreid

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    I am a bit confused over the shape of matterless spacetime:confused:: on one side Minkowski space is described as hyperbolic, and deSitter space is (hyper)spherical. Both are used, yet how can you have spacetime being both hyperbolic and spherical?
     
  2. jcsd
  3. Sep 3, 2009 #2

    nomadreid

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    Wait. I just found the following from another thread:"de Sitter space is... a (3+1) 4-dimensional hypersurface in a 5-dimensional (4+1) Minkowski space." I think that answers my question, but this poses another, rather elementary question: in discussions of expanding spacetime, which one are we referring to?
     
  4. Sep 4, 2009 #3
    De Sitter space is not a physical model. It is a solution of the Einstein equations but doesn't make much sense.
    In discussions of expanding spacetime, we usually mean the Robertson-Walker-metric.
     
  5. Sep 4, 2009 #4

    nomadreid

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    Thanks for the tip about the Robertson-Walker-metric. That gives me something to work through.
    When you say that de Sitter space "doesn't make much sense", I presume you mean that its physical interpretation remains only useful on a cosmic scale.
     
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