Victor H. Cardenas

Cosmic slowing down of acceleration using fgas

We investigate the recent - low redshift - expansion history of the universe using the most recent observational data. Using only data from 42 measurements of

Cosmic slowing down of acceleration for several dark energy parametrizations

f_{gas}

Constraints on Holographic cosmologies from strong lensing systems

in clusters, we found that cosmic acceleration could have already peaked and we are witnessing now its slowing down. This effect, found previously by Shafieloo, Sahni and Starobinsky in 2010 using supernova data (at that time the Constitution SNIa sample) appears again using an independent observational probe. We also discuss the result using the most recent Union 2.1 data set.

The role of curvature in the slowing down acceleration scenario

We further investigate slowing down of acceleration of the universe scenario for five parametrizations of the equation of state of dark energy using four sets of Type Ia supernovae data. In a maximal probability analysis we also use the baryon acoustic oscillation and cosmic microwave background observations. We found the low redshift transition of the deceleration parameter appears, independently of the parametrization, using supernovae data alone except for the Union 2.1 sample. This feature disappears once we combine the Type Ia supernovae data with high redshift data. We conclude that the rapid variation of the deceleration parameter is independent of the parametrization. We also found more evidence for a tension among the supernovae samples, as well as for the low and high redshift data.

Testing a dissipative kinetic k-essence model

We use strongly gravitationally lensed (SGL) systems to put additional constraints on a set of holographic dark energy models. Data available in the literature (redshift and velocity dispersion) is used to obtain the Einstein radius and compare it with model predictions. We found that the ΛCDM is the best fit to the data. Although a preliminary statistical analysis seems to indicate that two of the holographic models studied show interesting agreement with observations, a stringent test lead us to the result that neither of the holographic models are competitive with the ΛCDM. These results highlight the importance of Strong Lensing measurements to provide additional observational constraints to alternative cosmological models, which are necessary to shed some light into the dark universe.

Asymmetry in the reconstructed deceleration parameter

Abstract We introduce the curvature Ω k as a new free parameter in the Bayesian analysis using SNIa, BAO and CMB data, in a model with variable equation of state parameter w ( z ) . We compare the results using both the Constitution and Union 2 data sets, and also study possible low redshift transitions in the deceleration parameter q ( z ) . We found that, incorporating Ω k in the analysis, it is possible to make all the three observational probes consistent using both SNIa data sets. Our results support dark energy evolution at small redshift, and show that the tension between small and large redshift probes is ameliorated. However, although the tension decreases, it is still not possible to find a consensus set of parameters that fit all the three data set using the Chevalier–Polarski–Linder CPL parametrization.

Exploring hints for dark energy density evolution in light of recent data

In this work, we present a study of a purely kinetic k-essence model, characterized basically by a parameter

Mimicking the LCDM model with stealths

\alpha