591 research outputs found
Cosmic constraint on the unified model of dark sectors with or without a cosmic string fluid in the varying gravitational constant theory
Observations indicate that most of the universal matter are invisible and the
gravitational constant maybe depends on the time. A theory of the
variational (VG) is explored in this paper, with naturally producing the
useful dark components in universe. We utilize the 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 parameters with the covariance matrix, constraints on the
variation of are and , the small uncertainties
around constants. Limit on the equation of state of dark matter is
with assuming in unified
model, and dark energy is with assuming
at prior. Restriction on UM parameters are
and
with and
confidence level. In addition, the effect of a cosmic string fluid on 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 the larger errors are given:
(dimensionless energy
density of cosmic string), and .Comment: 17 pages,4 figure
Investigate the interaction between dark matter and dark energy
In this paper we investigate the interaction between dark matter and dark
energy by considering two different interacting scenarios, i.e. the cases of
constant interaction function and variable interaction function. By fitting the
current observational data to constrain the interacting models, it is found
that the interacting strength is non-vanishing, but weak for the case of
constant interaction function, and the interaction is not obvious for the case
of variable interaction function. In addition, for seeing the influence from
interaction we also investigate the evolutions of interaction function,
effective state parameter for dark energy and energy density of dark matter. At
last some geometrical quantities in the interacting scenarios are discussed.Comment: 14 pages, 6 figure
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