Gravitational focusing of Imperfect Dark Matter

Abstract

Motivated by the projectable Horava--Lifshitz model/mimetic matter scenario, we consider a particular modification of standard gravity, which manifests as an imperfect low pressure fluid. While practically indistinguishable from a collection of non-relativistic weakly interacting particles on cosmological scales, it leaves drastically different signatures in the Solar system. The main effect stems from gravitational focusing of the flow of Imperfect Dark Matter passing near the Sun. This entails strong amplification of Imperfect Dark Matter energy density compared to its average value in the surrounding halo. The enhancement is many orders of magnitude larger than in the case of Cold Dark Matter, provoking deviations of the metric in the second order in the Newtonian potential. Effects of gravitational focusing are prominent enough to substantially affect the planetary dynamics. Using the existing bound on the PPN parameter ${\beta }_{PPN}$, we deduce a stringent constraint on the unique constant of the model.

34 pages, 1 figure. Clarifications and references added. Matches published version

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• Higher Derivative Mimetic Gravity
• Thick branes with inner structure in mimetic $f(R)$ gravity
• Disforming to Conformal Symmetry
• Mimetic Inflation
• Direct couplings of mimetic dark matter and their cosmological effects
• Emergent scenario in mimetic gravity
• Multi-field Mimetic Gravity
• Isotropic stellar model in mimetic theory
• Extensions of two-field mimetic gravity