6,276 research outputs found
Asymmetry in the reconstructed deceleration parameter
We study the orientation dependence of the reconstructed deceleration
parameter as a function of redshift. We use the Union 2 and Loss datasets, by
using the well known preferred axis discussed in the literature, finding the
best fit reconstructed deceleration parameter. We found that a low redshift
transition of the reconstructed is clearly absent in one direction and
amazingly sharp in the opposite one. We discuss the possibility that such a
behavior can be associated with large scale structures affecting the data.Comment: 9 pages, 12 figure
Testing cosmic acceleration for parameterizations using measurements in galaxy clusters
In this paper we study the cosmic acceleration for five dynamical dark energy
models whose equation of state varies with redshift. The cosmological
parameters of these models are constrained by performing a MCMC analysis using
mainly gas mass fraction, , measurements in two samples of galaxy
clusters: one reported by Allen et al. (2004), which consists of points
spanning the redshift range , and the other by Hasselfield et al.
(2013) from the Atacama Cosmology Telescope survey, which consists of data
points in the redshift range . In addition, we
perform a joint analysis with the measurements of the Hubble parameter ,
baryon acoustic oscillations and the cosmic microwave background radiation from
WMAP and Planck measurements to estimate the equation of state parameters. We
obtained that both samples provide consistent constraints on the
cosmological parameters. We found that the data is consistent at the
confidence level with a cosmic slowing down of the acceleration at
late times for most of the parameterizations. The constraints of the joint
analysis using WMAP and Planck measurements show that this trend disappears. We
have confirmed that the probe provides competitive constraints on the
dark energy parameters when a is assumed.Comment: 21 pages, 8 Tables, 11 Figures, accepted for publication in MNRA
Collaborative semantic web browsing with Magpie
Web browsing is often a collaborative activity. Users involved in a joint information gathering exercise will wish to share knowledge about the web pages visited and the contents found. Magpie is a suite of tools supporting the interpretation of web pages and semantically enriched web browsing. By automatically associating an ontology-based semantic layer to web resources, Magpie allows relevant services to be invoked as well as remotely triggered within a standard web browser. In this paper we describe how Magpie trigger services can provide semantic support to collaborative browsing activities
A magnified glance into the dark sector: probing cosmological models with strong lensing in A1689
In this paper we constrain four alternative models to the late cosmic
acceleration in the Universe: Chevallier-Polarski-Linder (CPL), interacting
dark energy (IDE), Ricci holographic dark energy (HDE), and modified polytropic
Cardassian (MPC). Strong lensing (SL) images of background galaxies produced by
the galaxy cluster Abell are used to test these models. To perform this
analysis we modify the LENSTOOL lens modeling code. The value added by this
probe is compared with other complementary probes: Type Ia supernovae (SNIa),
baryon acoustic oscillations (BAO), and cosmic microwave background (CMB). We
found that the CPL constraints obtained of the SL data are consistent with
those estimated using the other probes. The IDE constraints are consistent with
the complementary bounds only if large errors in the SL measurements are
considered. The Ricci HDE and MPC constraints are weak but they are similar to
the BAO, SNIa and CMB estimations. We also compute the figure-of-merit as a
tool to quantify the goodness of fit of the data. Our results suggest that the
SL method provides statistically significant constraints on the CPL parameters
but weak for those of the other models. Finally, we show that the use of the SL
measurements in galaxy clusters is a promising and powerful technique to
constrain cosmological models. The advantage of this method is that
cosmological parameters are estimated by modelling the SL features for each
underlying cosmology. These estimations could be further improved by SL
constraints coming from other galaxy clusters.Comment: 13 pages, 5 figures, accepted for publication in Ap
The value function of an asymptotic exit-time optimal control problem
We consider a class of exit--time control problems for nonlinear systems with
a nonnegative vanishing Lagrangian. In general, the associated PDE may have
multiple solutions, and known regularity and stability properties do not hold.
In this paper we obtain such properties and a uniqueness result under some
explicit sufficient conditions. We briefly investigate also the infinite
horizon problem
- …