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Paper   IPM / P / 6685
School of Physics
  Title:   Tunneling in Λ Decaying Cosmologies and the Cosmological Constant Problem
1.  F. Darabi
2.  A. Rezaei-Aghdam
3.  A.R. Rastegar
4.  M.A. Jafarizadeh
  Status:   Published
  Journal: Phys. Rev. D
  No.:  50
  Vol.:  60
  Year:  1999
  Pages:   063514-1-8
  Supported by:  IPM
The tunneling rate, with exact prefactor, is calculated to first order in h for an empty closed Friedmann-Robertson-Walker (FRW) universe with decaying cosmological term Λ  ∼ Rm (R is the scale factor and m is a parameter 0 ≤ m ≤ 2). This model is equivalent to a cosmology with the equation of state pχ=(m/3−1)ρχ. The calculations are performed by applying the diluteinstanton approximation on the corresponding Duru-Kleinert path integral. It is shown that the highest tunneling rate occurs for m=2 corresponding to the cosmic string matter universe. The obtained most probable cosmological term, like one obtained by Strominger, accounts for a possible solution to the cosmological constant problem.

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