Cosmological consequences of a rolling homogeneous scalar field
Abstract
The cosmological consequences of a pervasive, rolling, selfinteracting, homogeneous scalar field are investigated. A number of models in which the energy density of the scalar field redshifts in a specific manner are studied. In these models the current epoch is chosen to be scalarfield dominated to agree with dynamical estimates of the density parameter, Ω_{dyn~0.2}, and zero spatial curvature. The required scalarfield potential is ``nonlinear'' and decreases in magnitude as the value of the scalar field increases. A special solution of the field equations which is an attractive, timedependent, fixed point is presented. These models are consistent with the classical tests of gravitation theory. The EötvösDicke measurements strongly constrain the coupling of the scalar field to light (nongravitational) fields. Nucleosynthesis proceeds as in the standard hot bigbang model. In linear perturbation theory the behavior of baryonic perturbations, in the baryondominated epoch, do not differ significantly from the canonical scenario, while the presence of a substantial amount of homogeneous scalarfield energy density at low redshifts inhibits the growth of perturbations in the baryonic fluid. The energy density in the scalar field is not appreciably perturbed by nonrelativistic gravitational fields, either in the radiationdominated, matterdominated, or scalarfielddominated epochs. On the basis of this effect, we argue that these models could reconcile the low dynamical estimates of the mean mass density with the negligibly small spatial curvature preferred by inflation.
 Publication:

Physical Review D
 Pub Date:
 June 1988
 DOI:
 10.1103/PhysRevD.37.3406
 Bibcode:
 1988PhRvD..37.3406R
 Keywords:

 98.80.Bp;
 11.10.Ef;
 12.25.+e;
 98.80.Dr;
 Origin and formation of the Universe;
 Lagrangian and Hamiltonian approach