4,618 research outputs found
A unification of RDE model and XCDM model
In this Letter, we propose a new generalized Ricci dark energy (NGR) model to
unify Ricci dark energy (RDE) and XCDM. Our model can distinguish between RDE
and XCDM by introducing a parameter called weight factor. When
, NGR model becomes the usual RDE model. The XCDM model is
corresponding to . Moreover, NGR model permits the situation where
neither nor . We then perform a statefinder analysis on NGR
model to see how effects the trajectory on the plane.
In order to know the value of , we constrain NGR model with latest
observations including type Ia supernovae (SNe Ia) from Union2 set (557 data),
baryonic acoustic oscillation (BAO) observation from the spectroscopic Sloan
Digital Sky Survey (SDSS) data release 7 (DR7) galaxy sample and cosmic
microwave background (CMB) observation from the 7-year Wilkinson Microwave
Anisotropy Probe (WMAP7) results. With Markov Chain Monte Carlo (MCMC) method,
the constraint result is
=, which
manifests the observations prefer a XCDM universe rather than RDE model. It
seems RDE model is ruled out in NGR scenario within regions.
Furthermore, we compare it with some of successful cosmological models using
AIC information criterion. NGR model seems to be a good choice for describing
the universe.Comment: 12 pages, 7 figures, 2 tables. Accepted for publication in PL
Constraints on f(R) cosmologies from strong gravitational lensing systems
f(R) gravity is thought to be an alternative to dark energy which can explain
the acceleration of the universe. It has been tested by different observations
including type Ia supernovae (SNIa), the cosmic microwave background (CMB), the
baryon acoustic oscillations (BAO) and so on. In this Letter, we use the Hubble
constant independent ratio between two angular diameter distances
to constrain f(R) model in Palatini approach . These data are from various large systematic
lensing surveys and lensing by galaxy clusters combined with X-ray
observations. We also combine the lensing data with CMB and BAO, which gives a
stringent constraint. The best-fit results are
or using lensing data only. When combined
with CMB and BAO, the best-fit results are or
. If we further fix (corresponding
to CDM), the best-fit value for is
= for the
lensing analysis and
= for the
combined data, respectively. Our results show that CDM model is within
1 range.Comment: 9 pages, 2 figures, 2 table
The wave nature of continuous gravitational waves from microlensing
Gravitational wave predicted by General Relativity is the transverse wave of
spatial strain. Several gravitational waveform signals from binary black holes
and from a binary neutron star system accompanied by electromagnetic
counterparts have been recorded by advanced LIGO and advanced Virgo. In analogy
to light, the spatial fringes of diffraction and interference should also exist
as the important features of gravitational waves. We propose that observational
detection of such fringes could be achieved through gravitational lensing of
continuous gravitational waves. The lenses would play the role of the
diffraction barriers. Considering peculiar motions of the observer, the lens
and the source, the spatial amplitude variation of diffraction or interference
fringes should be detectable as an amplitude modulation of monochromatic
gravitational signal.Comment: Accepted for publication in The Astrophysical Journa
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