Accelerating Universes with Scaling Dark Matter
Abstract
FriedmannRobertsonWalker universes with a presently large fraction of the energy density stored in an Xcomponent with w_{X}<1/3, are considered. We find all the critical points of the system for constant equations of state in that range. We consider further several background quantities that can distinguish the models with different w_{X} values. Using a simple toy model with a varying equation of state, we show that even a large variation of w_{X} at small redshifts is very difficult to observe with d_{L}(z) measurements up to z~1. Therefore, it will require accurate measurements in the range 1<z<2 and independent accurate knowledge of Ω_{m,0} (and/or Ω_{X,0}) in order to resolve a variable w_{X} from a constant w_{X}.
 Publication:

International Journal of Modern Physics D
 Pub Date:
 DOI:
 10.1142/S0218271801000822
 arXiv:
 arXiv:grqc/0009008
 Bibcode:
 2001IJMPD..10..213C
 Keywords:

 General Relativity and Quantum Cosmology;
 Astrophysics
 EPrint:
 submitted to IJMPD (uses Latex, 12 pages, 6 Figures) Minor corrections, Figures 4, 6 revised. Conclusions unchanged