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Paper   IPM / Astronomy / 13922
School of Astronomy
  Title:   Comment on Ïnflation with a graceful exit and entrance driven by Hawking radiation"
  Author(s):  J.T. Firouzjaee
  Status:   Published
  Journal: Phys. Rev. D
  Vol.:  89
  Year:  2014
  Pages:   2
  Supported by:  IPM
Modak and Singleton [Phys. Rev. D 86, 123515 (2012), 10.1103/PhysRevD.86.123515] have presented Hawking-like radiation for cosmological inflation which has a natural "turn on" and a natural "turn off" mechanism. This Hawking-like radiation results in an effective negative pressure "fluid" which leads to a rapid period of expansion in the very early Universe. We discuss that the turn on mechanism cannot happen for the Friedmann-Robertson-Walker model in the early Universe because its horizon is an apparent horizon not an event horizon. Hence, we cannot apply geometric optic approximation which is a necessary condition for the tunneling method. It was shown that this model predicts a value for ρ/mpl4 which is bigger than the COBE normalization constraint in the cosmic microwave background at the horizon exit. The authors of the paper offer a Reply.

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