The Cosmological Constant and Dark Energy

  title={The Cosmological Constant and Dark Energy},
  author={P J E Peebles and Bharat Ratra},
  journal={Reviews of Modern Physics},
Physics invites the idea that space contains energy whose gravitational effect approximates that of Einstein's cosmological constant, Lambda: nowadays the concept is termed dark energy or quintessence. Physics also suggests the dark energy could be dynamical, allowing the arguably appealing picture that the dark energy density is evolving to its natural value, zero, and is small now because the expanding universe is old. This alleviates the classical problem of the curious energy scale of order… 

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