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Meaning of cosmological constant ?

  1. Nov 1, 2007 #1
    Incredibly much has been written about the cosmological constant and all its implications on the evolution of the universe. I want to ask however a more basic question about it. The cosmological constant has the dimension of 1/R^2. So supposing this constant is non-zero, its value points to the existence of some characteristic distance or radius. The Schwarzschild radius for instance has a clear understandable meaning but what could be the meaning of the radius associated with the cosmological constant? The only thing which comes to (my) mind is the radius of the universe itself. What other opinions exist (or are described in literature - related to "radius")?

    Rudi Van Nieuwenhove
  2. jcsd
  3. Nov 1, 2007 #2


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    The cosmological constant has a value whose units are energy. I'm not sure what you mean by saying 'it has the dimensions of 1/R^2"?

    If you mean that the energy density of the cosmological constant evolves as 1/R^2 where R is the scale factor that is incorrect. Curvature evolves in that way (in the way it is represented in cosmology) but the cosmological constant, unsurprisingly, remains constant for all time.
  4. Nov 1, 2007 #3


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    The dimensions of 1/L2 for the cosmological constant are correct in the usual geometrized unit system of general relativity. To find a deeper meaning to such a length scale one should go beyond general relativity, see for example section 7 of Padmanabhan's Cosmological Constant - the Weight of the Vacuum.
  5. Nov 1, 2007 #4

    Chris Hillman

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    It might help to point out that in geometric units, energy density (and sectional curvatures, e.g. the components of the Riemann curvature tensor) have the units of reciprocal area. Since Lambda contributes a diagonal term to the stress-energy tensor of our spacetime models, with the entries proportional to Lambda (in any frame!), this represents an energy density and has the units of reciprocal area.
  6. Nov 5, 2007 #5

    Thanks for this interesting reference. This means a lot of reading (114 pages)!
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