https://doi.org/10.1140/epjc/s10052-015-3691-3
Regular Article - Theoretical Physics
Cosmic constraint on the unified model of dark sectors with or without a cosmic string fluid in the varying gravitational constant theory
Department of Physics, Liaoning Normal University, Dalian, 116029, People’s Republic of China
* e-mail: lvjianbo819@163.com
Received:
10
March
2015
Accepted:
21
September
2015
Published online:
5
October
2015
Observations indicate that most of the universal matter is invisible and the gravitational constant G(t) maybe depends on time. A theory of the variational G (VG) is explored in this paper, naturally producing the useful dark components in the universe. We utilize the following observational data: lookback time data, model-independent gamma ray bursts, growth function of matter linear perturbations, type Ia supernovae data with systematic errors, CMB, and BAO, to restrict the unified model (UM) of dark components in VG theory. Using the best-fit values of the parameters with the covariance matrix, constraints on the variation of G are 
and 
, with small uncertainties around the constants. The limit on the equation of state of dark matter is 
, assuming 
in the unified model, and the dark energy is 
, assuming 
a priori. The restrictions on the UM parameters are 
and 
with 
and 
confidence level. In addition, the effects of a cosmic string fluid on the unified model in VG theory are investigated. In this case it is found that the 
CDM (
, 
, and 
) is included in this VG-UM model at confidence level, and larger errors are given: 
(dimensionless energy density of cosmic string), 
, and 
.
© SIF and Springer-Verlag Berlin Heidelberg, 2015
