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Paper   IPM / Astronomy / 14764
School of Astronomy
  Title:   Instabilities in Mimetic Matter Perturbations
1.  H. Firouzjahi
2.  M A. Gorji
3.  A. Hosseini Mansoori
  Status:   Submitted
  Journal: JCAP
  Vol.:  2017
  Year:  2017
  Supported by:            ipm IPM
We study cosmological perturbations in mimetic matter scenario with a general higher derivative function. We show that the model suffers from the ghost and the gradient instabilities. We perform the analysis in both comoving and Newtonian gauges and confirm that the Hamiltonians and the associated instabilities are consistent with each other in both gauges. The existence of instabilities is independent of the specific form of higher derivative function which generates gradients for mimetic field perturbations. It is verified that these instabilities are not associated with the higher derivative instabilities such as the Ostrogradsky ghost.

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