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Victor H. Cardenas

Publications and source records attributed to Victor H. Cardenas.

At least 19 recordsLinked to original sources
arXiv2021

Studies on dark energy evolution

In this work we explore signatures of evolution for the dark energy density $X(z)=ρ_{de}(z)/ρ_{de}(0)$ using latest observations on SNIa and H(z). The models consist of parametrizations of the dark energy density and consequently a reconstruction for the EoS parameter w(z) as a function of redshift. Both parametrization methods using the SH0Es prior results in a small deviation from LCDM at 1$σ$ for $X(z)$. Extending the analysis up to 2$σ$, the evidence for evolution of $X(z)$ dilute in both cases. We have also studied an interacting dark model where this trend is also found.

astro-ph.CO↗
arXiv2020

Interacting dark matter and cosmic acceleration

We study the effect of an explicit interaction between two scalar fields components describing dark matter in the context of a recent proposal framework for interaction. We find that, even assuming a very small coupling, it is sufficient to explain the observational effects of a cosmological constant, and also overcome the problems of the $Λ$CDM model without assuming an exotic dark energy.

astro-ph.CO↗
arXiv2018

Exploring evidence of interaction between dark energy and dark matter

In this work we use the latest observations on SNIa, $H(z)$, BAO, $f_{gas}$ in clusters and CMBR, to constrain three models showing an explicit interaction between dark matter and dark energy. In particular, we use the BOSS BAO measurements at $z \simeq 0.32$, $0.57$ and $2.34$, using the full 2-dimensional constraints on the angular and line of sight BAO scale. We find that using all five observational probes together, two of the interaction models show positive evidence at more than 3 $ σ$. Although significant, further study is needed to establish this statement firmly.

astro-ph.CO↗
arXiv2017

Testing cosmic acceleration for $w(z)$ parameterizations using $f_{gas}$ 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, $f_{gas}$, measurements in two samples of galaxy clusters: one reported by Allen et al. (2004), which consists of $42$ points spanning the redshift range $0.05<z<1.1$, and the other by Hasselfield et al. (2013) from the Atacama Cosmology Telescope survey, which consists of $91$ data points in the redshift range $0.118 < \mathrm{z} < 1.36$. In addition, we perform a joint analysis with the measurements of the Hubble parameter $H(z)$, 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 $f_{gas}$ samples provide consistent constraints on the cosmological parameters. We found that the $f_{gas}$ data is consistent at the $2σ$ 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 $f_{gas}$ probe provides competitive constraints on the dark energy parameters when a $w(z)$ is assumed.

astro-ph.CO↗
arXiv2016

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 $q(z)$ 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.

astro-ph.CO↗
arXiv2015

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 $1689$ 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.

astro-ph.CO↗
arXiv2015

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

Considering a quadratic parametrization of the dark energy density, we explore signatures of evolution using data from gas mass fraction in clusters, type Ia supernova, BAO and CMB. We find -- excluding CMB data -- a preference for a evolution of $ρ_{de}(z)$ towards smaller values as redshift increases, a result consistent with a recent study using the BAO DR11 data by Delubac et al. (2015).

astro-ph.CO↗
arXiv2013

Constraints on Holographic cosmologies from strong lensing systems

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 LCDM 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 LCDM. 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.

astro-ph.CO↗
arXiv2013

Cosmic slowing down of acceleration using $f_{gas}$

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

astro-ph.CO↗
arXiv2012

Step potentials for Dark Energy

We consider a reconstructing scheme using observational data from SNIa, BAO and CMB, based on a model of dark unification using a single non-minimally coupled scalar field. We investigate through a reconstruction program, the main features the current observational data imposes to the scalar field potential. We found that the form suggested by observations implies a step feature in the potential, where the kinetic and potential energy becomes of the same order of magnitude.

astro-ph.CO↗
arXiv2012

Dark energy, matter creation and curvature

The most studied way to explain the current accelerated expansion of the universe is to assume the existence of dark energy; a new component that fill the universe, does not clumps, currently dominates the evolution, and has a negative pressure. In this work I study an alternative model proposed by Lima et al. \cite{lima96}, which does not need an exotic equation of state, but assumes instead the existence of gravitational particle creation. Because this model fits the supernova observations as well as the $Λ$CDM model, I perform in this work a thorough study of this model considering an explicit spatial curvature. I found that in this scenario we can alleviate the cosmic coincidence problem, basically showing that these two components, dark matter and dark energy, are of the same nature, but they act at different scales. I also shown the inadequacy of some particle creation models, and also I study a previously propose new model that overcome these difficulties.

astro-ph.CO↗
arXiv2012

The role of curvature in the slowing down acceleration scenario

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.

astro-ph.CO↗
arXiv2010

The effect of curvature in thawing models

We study the evolution of spatial curvature for thawing class of dark energy models. We examine the evolution of the equation of state parameter, $w_ϕ$, as a function of the scale factor $a$, for the case in which the scalar field $ϕ$ evolve in nearly flat scalar potential. We show that all such models provide the corresponding approximate analytical expressions for $w_ϕ(Ω_ϕ,Ω_k)$ and $w_ϕ(a)$. We present observational constraints on these models.

astro-ph.CO↗
arXiv2010

Holographic Dark Energy with Curvature

In this paper we consider an holographic model of dark energy, where the length scale is the Hubble radius, in a non flat geometry. The model contains the possibility to alleviate the cosmic coincidence problem, and also incorporate a mechanism to obtain the transition from decelerated to an accelerated expansion regime. We derive an analytic form for the Hubble parameter in a non flat universe, and using it, we perform a Bayesian analysis of this model using SNIa, BAO and CMB data. We find from this analysis that the data favored a small value for $Ω_k$, however high enough to still produce cosmological consequences.

astro-ph.CO↗
arXiv2009

Inflation as a response to protect the Holographic Principle

A model where the inflationary phase emerges as a response to protect the Fischler-Susskind holographic bound is described. A two fluid model in a closed universe inflation picture is assumed, and a discussion on conditions under which is possible to obtain an additional exponential expansion phase as those currently observed is given.

gr-qc↗
arXiv2008

Accelerated expansion and matter creation

A set of cosmological models that takes into account the variation of the particle number is presented. In this context both dark matter and dark energy can be explained using a single component, without assuming any exotic equation of state, solving directly the cosmic coincidence problem.

astro-ph↗
arXiv2008

A chilean seismic regionalization through a Kohonen neural network

A study of seismic regionalization for central Chile based on a neural network is presented. A scenario with six seismic regions is obtained, independently of the size of the neighborhood or the reach of the correlation between the cells of the grid. The high correlation between the spatial distribution of the seismic zones and geographical data confirm our election of the training vectors of the neural network.

physics.geo-ph↗