63 research outputs found
Exploring the potentiality of standard sirens to probe cosmic opacity at high redshifts
In this work, using the Gaussian process, we explore the potentiality of
future gravitational wave (GW) measurements to probe cosmic opacity at high
redshifts through comparing its opacity-free luminosity distance (LD) with the
opacity-dependent one from the combination of Type Ia supernovae (SNIa) and
gamma-ray bursts (GRBs). The GW data, SNIa and GRB data are simulated from the
measurements of the future Einstein Telescope, the actual Pantheon compilation
and the latest observation of GRBs compiled by L. Amati {\it et al},
respectively. A nonparametric method is proposed to probe the spatial
homogeneity of cosmic transparency at high redshift by comparing the LD
reconstructed from the GW data with
that reconstructed from the Pantheon and GRB data. In addition, the cosmic
opacity is tested by using the parametrization for the optical depth, and the
results show that the constraints on cosmic opacity are more stringent than the
previous ones. It shows that the future GW measurements may be used as an
important tool to probe the cosmic opacity in the high redshift region.Comment: 21pages, 3 figures accepted by EPJC. arXiv admin note: text overlap
with arXiv:1912.0232
Testing the FLRW metric with the Hubble and transversal BAO measurements
The cosmological principle is one of the fundamental assumptions of the
standard model of Cosmology (SCM), and it allow us to describe cosmic distances
and clocks by using the Friedmann-Lema\rm{\hat{{\i}}}tre-Roberton-Walker
(FLRW) metric. Thus, it is essential to test the FLRW metric with cosmological
observations to verify the validity of the SCM. In this work, we perform tests
of the FLRW metric by comparing the observational comoving angles between the
Hubble and angular Baryon Acoustic Oscillation (BAO) measurements. The
Gaussian process is employed to reconstruct the Hubble measurements and
the angular diameter distance (ADD) from the transversal BAO data. A
non-parametric method is adopted to probe the possible deviations from the FLRW
metric at any redshift by comparing the comoving distances from the
reconstructed Hubble measurements with the ADD reconstructed from the
transversal BAO data. Then, we propose two types of parameterizations for the
deviations from the FLRW metric, and test the FLRW metric by using the priors
of specific sound horizon scales. To avoid the bias caused by the prior of a
specific sound horizon scale, we perform the consistency test with a flat prior
of the sound horizon scale. We find that there a concordance between the FLRW
metric and the observational data by using parametric and non-parametric
methods, and the parameterizations can be employed to test the FLRW metric in a
new way independent of the sound horizon scale.Comment: Submitted to PRD and received comments from referee
Cold quark matter in a quasiparticle model: thermodynamic consistency and stellar properties
The strong coupling in the effective quark mass was usually taken as a
constant in a quasiparticle model while it is, in fact, running with an energy
scale. With a running coupling, however, the thermodynamic inconsistency
problem appears in the conventional treatment. We show that the renormalization
subtraction point should be taken as a function of the summation of the
biquadratic chemical potentials if the quark's current masses vanish, in order
to ensure full thermodynamic consistency. Taking the simplest form, we study
the properties of up-down () quark matter, and confirm that the revised
quasiparticle model fulfills the quantitative criteria for thermodynamic
consistency. Moreover, we find that the maximum mass of an quark star can
be larger than two times the solar mass, reaching up to , for
reasonable model parameters. However, to further satisfy the upper limit of
tidal deformability observed in the event
GW170817, the maximum mass of an quark star can only be as large as
, namely . In other words,
our results indicate that the measured tidal deformability for event GW170817
places an upper bound on the maximum mass of quark stars, but which does
not rule out the possibility of the existence of quark stars composed of
quark matter, with a mass of about two times the solar mass.Comment: 10 pages, 8 figure
A parametrization for the growth index of linear matter perturbations
We propose a parametrization for the growth index of the linear matter
perturbations, . The growth factor of
the perturbations parameterized as is analyzed for both the
CDM model and the DGP model with our proposed form for . We find
that is negative for the CDM model but is positive for the DGP
model. Thus it provides another signature to discriminate them. We demonstrate
that with taking our proposed form approximates
the growth factor very well both at low and high redshfits for both kinds of
models. In fact, the error is below 0.03% for the CDM model and 0.18%
for the DGP model for all redshifts when . Therefore, our
parametrization may be robustly used to constrain the growth index of different
models with the observational data which include points for redshifts ranging
from 0.15 to 3.8, thus providing discriminative signatures for different
models.Comment: 14 pages, 6 figures; Added reference
Density pertubation of unparticle dark matter in the flat Universe
The unparticle has been suggested as a candidate of dark matter. We
investigated the growth rate of the density perturbation for the unparticle
dark matter in the flat Universe. First, we consider the model in which
unparticle is the sole dark matter and find that the growth factor can be
approximated well by , where is
the equation of state of unparticle. Our results show that the presence of
modifies the behavior of the growth factor . For the second model
where unparticle co-exists with cold dark matter, the growth factor has a new
approximation and
is a function of . Thus the growth factor of unparticle is quite
different from that of usual dark matter. These information can help us know
more about unparticle and the early evolution of the Universe.Comment: 6pages, 4 figures, accepted for publication in Eur. Phys. J.
The growth of linear perturbations in the DGP model
We study the linear growth of matter perturbations in the DGP model with the
growth index as a function of redshift. At the linear approximation:
, we find that, for
, takes the value from 0.658 to 0.671,
and ranges from 0.035 to 0.042. With three low redshift
observational data of the growth factor, we obtain the observational
constraints on and for the and DGP models
and find that the observations favor the model but at the
confidence level both the and DGP models are consistent
with the observations.Comment: 12 pages, 4 figuers, to appear in PL
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