A Nonuniform Dark Energy Fluid: Perturbation Equations (original) (raw)
ADS
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Abstract
We propose that galactic dark matter can be described by a nonuniform dark energy fluid. The underlying field is a decaying vector field, which might corresponds to a photon-like but massive particle of 4 degrees of dynamical freedom. We propose a very general Lagrangian for this vector field. The model includes a continuous spectrum of plausible gravity theories, for example, quintessence, f(R), Einstein-Aether, MOND, TeVeS, BSTV, V-Λ theories, and the inflaton scalar field as special cases. We study in detail a special class of models with a fixed norm of the timelike vector field in the physical metric, which includes a nonlinear K4 term and a Ricci scalar term. We derive the Einstein equations in the perturbed form, which are needed for simulating structure growth in an FRW universe to test such theories. A special case of the model V-Λ shows promise of resembling the ΛCDM cosmology. We show that the vector field has the effect of a nonuniform dark fluid, which resembles dark matter in galaxies and dark energy in the late universe.
Publication:
The Astrophysical Journal Supplement Series
Pub Date:
July 2008
DOI:
arXiv:
Bibcode:
Keywords:
- cosmology: theory;
- dark matter;
- gravitation;
- Astrophysics;
- General Relativity and Quantum Cosmology;
- High Energy Physics - Phenomenology;
- High Energy Physics - Theory
E-Print:
typos corrected and expanded to 25p, added DM-DE coupling effects in f(K4) model. ApJ Supplement accepted