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De Sitter space

  1. May 20, 2009 #1
    Hey all - I'm trying to get a better qualitative understanding of de Sitter space, and I'm a bit confused about the de Sitter universe. I've always seen it mathematically as a hyperboloid embedded in a higher-dimensional Minkowski space (with some annoying metric I've forgotten) but I've read (alright, fine, on Wikipedia :P) that a patch of de Sitter universe can be expressed as an FRW cosmology with a(t) = exp(Ht) - So... under that description, why is the de Sitter metric not just an FRW metric with that scale factor?
  2. jcsd
  3. May 21, 2009 #2

    George Jones

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  4. May 21, 2009 #3
    I always did understand de Sitter space through its cosmological description - a flat, vacuum filled universe that undergoes exponential expansion (equivalently, constant Hubble paramater). What about this description is unsatisfactory?
  5. May 22, 2009 #4
    Thanks George! Don't have my Wald or Carroll with me so I couldn't look it up....

    The problem was that I was used to seeing the de Sitter metric in a form similar to eqn 1.94 in George's link, so I was a bit confused by the description of it as a FRW cosmology with a=exp(Ht). The coordinate transformation makes sense (or will, when I think about it some more :)).
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