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  • “School of Astronomy”

     
    Paper   IPM / Astronomy / 13673
       School of Astronomy
      Title: Cosmological perturbations in inflationary models with anisotropic space-time scaling in a Lifshitz background
      Author(s):
    1 . M. Alishahiha
    2 . H. Firouzjahi
    3 . K. Koyama
    4 . M.H. Namjoo
      Status: Published
      Journal: Phys. Rev. D
      Year: 2013
      Supported by: IPM
      Abstract:
    Models of inflation in a gravitational background with an anisotropic space-time scaling are studied. The background is a higher-dimensional Lifshitz throat with the anisotropy scaling z�?�1. After the dimensional reduction, the four-dimensional general covariance is explicitly broken to a three-dimensional spatial diffeomorphism. As a result the cosmological perturbation theory in this set up with less symmetries have to be formulated. We present the consistent cosmological perturbation theory for this set up. We find that the effective four-dimensional gravitational wave perturbations propagate with a different speed than the higher dimensional gravitational excitations. Depending on the model parameters, for an observer inside the throat, the four-dimensional gravitational wave propagation can be superluminal. We also find that the Bardeen potential and the Newtonian potential are different. This can have interesting observational consequences for lensing and CMB fluctuations. Furthermore, we show that at the linearized level the inflaton field excitations vanish.

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