MG14 - Talk detail

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I will consider cosmology of the recently introduced "Mimetic Matter" with higher derivatives (HD): arXiv:1403.3961. Without HD and with shift-symmetry this system describes irrotational dust - Dark Matter (DM), as we see it on cosmologically large scales. Breaking of the shift-symmetry allows one to model Dark Energy (DE) using the same scalar field. In arXiv:1412.7136 we show that mimetic matter with HD and shift-symmetry corresponds to an imperfect DM which: i) renormalises the Newton's constant in the Friedmann equations, ii) has zero pressure when there is no extra matter in the universe, iii) survives the inflationary expansion which puts the system on a dynamical attractor with a vanishing shift-charge, iv) perfectly tracks any external matter on this attractor, v) can become the main (and possibly the only) source of DM, provided the shift-symmetry in the HD terms is broken during some small time interval in the radiation domination era. In this talk I will show how these properties change for the interesting novel models of DE. I will also discuss a hydrodynamical description of general anisotropic and inhomogeneous configurations of the system. This imperfect mimetic fluid has an energy flow in the field's rest frame. It is important that, in the Eckart and in the Landau-Lifshitz frames the mimetic fluid possesses nonvanishing vorticity appearing already at the first order in the HD. Thus, the structure formation and gravitational collapse should proceed in a rather different fashion from the simple irrotational DM models.

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