Tunneling in a Cosmological Model with Violation of Strong Energy   Condition
  The tunneling rate, with exact prefactor, is calculated to first order in \hbar for a closed FRW universe filled with perfect fluid violating the strong energy condition. The calculations are performed by applying the dilute-instanton approximation on the corresponding Duru-Kleinert path integral. It is shown that a closed FRW universe filled with a perfect fluid with small violation of strong energy condition is more probable to tunnel than the same universe with large violation of strong energy condition. 
M. A. Jafarizadeh, F. Darabi, A. Rezaei-Aghdam, A. R. Rastegar