Effective Fluid Description of the Dark Universe

Abstract

We propose an effective anisotropic fluid description for a generic infrared-modified theory of gravity. In our framework, the additional component of the acceleration, commonly attributed to dark matter, is explained as a radial pressure generated by the reaction of the dark energy fluid to the presence of baryonic matter. Using quite general assumptions, and a microscopic description of the fluid in terms of a Bose-Einstein condensate of gravitons, we find the static, spherically symmetric solution for the metric in terms of the Misner-Sharp mass function and the fluid pressure. At galactic scales, we correctly reproduce the leading MOND-like $\log (r)$ and subleading $(1/r)\log (r)$ terms in the weak-field expansion of the potential. Our description also predicts a tiny (of order $10^{-6}$ for a typical spiral galaxy) Machian modification of the Newtonian potential at galactic scales, which is controlled by the cosmological acceleration.

13 pages, no figures. Replaced version: major revisions in the introduction, microscopic derivation of Tully-Fisher relation using Bose-Einstein condensate of gravitons. Some typos corrected

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• Too big to fail? The puzzling darkness of massive Milky Way subhaloes
• MOND theory
• Matter and gravitons in the gravitational collapse
• Two-fluid dark matter models
• Comments on "Modeling Galaxy Halos Using Dark Matter with Pressure"
• Perspective on MOND emergence from Verlinde's "emergent gravity" and its recent test by weak lensing
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Cited by in corpus (1)

• Galactic dynamics and long-range quantum gravity