Statefinder: A New geometrical diagnostic of dark energy

Jan, 2002
6 pages
Published in:
  • JETP Lett. 77 (2003) 201-206,
  • Pisma Zh.Eksp.Teor.Fiz. 77 (2003) 249-253
e-Print:

Citations per year

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Abstract: (arXiv)
We introduce a new cosmological diagnostic pair {r,s}\lbrace r,s\rbrace called Statefinder. The Statefinder is dimensionless and, like the Hubble and deceleration parameters H(z)H(z) and q(z)q(z), is constructed from the scale factor of the Universe and its derivatives only. The parameter r(z)r(z) forms the next step in the hierarchy of geometrical cosmological parameters used to study the Universe after HH and qq, while the parameter s(z)s(z) is a linear combination of qq and rr chosen in such a way that it does not depend upon the dark energy density ΩX(z)\Omega_X(z). The Statefinder pair {r,s}\lbrace r,s\rbrace is algebraically related to the the dark energy pressure-to-energy ratio w=p/ϵw=p/\epsilon and its time derivative, and sheds light on the nature of dark energy/quintessence. Its properties allow to usefully differentiate between different forms of dark energy with constant and variable ww, including a cosmological constant (w=1w = -1). The Statefinder pair can be determined to very good accuracy from a SNAP type experiment.
Note:
  • 7 pages, 3 figures. Final version to be published in JETP Lett., presentation shortened, references added and updated, consideration of brane cosmological models included, conclusions unchanged