A Nonuniform Dark Energy Fluid: Perturbation Equations
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 photonlike 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), EinsteinAether, MOND, TeVeS, BSTV, VΛ 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 K_{4} 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 VΛ 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:
 10.1086/587744
 arXiv:
 arXiv:0711.0958
 Bibcode:
 2008ApJS..177....1H
 Keywords:

 cosmology: theory;
 dark matter;
 gravitation;
 Astrophysics;
 General Relativity and Quantum Cosmology;
 High Energy Physics  Phenomenology;
 High Energy Physics  Theory
 EPrint:
 typos corrected and expanded to 25p, added DMDE coupling effects in f(K4) model. ApJ Supplement accepted