The dynamics of the Universe is analyzed using an exponential function for the dark energy equati... more The dynamics of the Universe is analyzed using an exponential function for the dark energy equation of state, known as Gong-Zhang parameterization. The phase space of the free parameters presented in the model is constrained using Cosmic Microwave Background radiation, Cosmic Chronometers, modulus distance from Hydrogen II Galaxies, Type Ia Supernovae and measurements from Baryon Acoustic Oscillations, together with a stronger bound from a Joint analysis. The cosmological model is confronted with ΛCDM, observing there is a strong evidence for ΛCDM in the Joint analysis although the exponential model is preferred when the data are separated. Based on the Joint analysis, a value of ω0 = −1.202 +0.027 −0.026 is found for the characteristic parameter presented in the equation of state. Additionally, the cosmographic parameters at current times are reported, having q0 = −0.789 +0.034 −0.036 , j0 = 1.779 +0.130 −0.119 , and a transition deceleration-acceleration redshift zT = 0.644 +0.011 −0.012. Furthermore, the age of the Universe is estimated as tU = 13.788 +0.019 −0.019 Gyrs. Finally, under the H0(z) diagnostic, we discuss this model could alleviate the H0 tension.
Fractional cosmology modifies the standard derivative to Caputo’s fractional derivative of order ... more Fractional cosmology modifies the standard derivative to Caputo’s fractional derivative of order μ, generating changes in General Relativity. Friedmann equations are modified, and the evolution of the species densities depends on μ and the age of the Universe tU. We estimate stringent constraints on μ using cosmic chronometers, Type Ia supernovae, and joint analysis. We obtain $\mu =2.839^{+0.117}_{-0.193}$ within the 1σ confidence level providing a non-standard cosmic acceleration at late times; consequently, the Universe would be older than the standard estimations. Additionally, we present a stability analysis for different μ values. This analysis identifies a late-time attractor corresponding to a power-law decelerated solution for μ < 2. Moreover, a non-relativistic critical point exists for μ > 1 and a sink for μ > 2. This solution is a decelerated power law if 1 < μ < 2 and an accelerated power-law solution if μ > 2, consistent with the mean values obtained ...
With the goal of studying the cosmological constant (CC) problem, we present an exhaustive analys... more With the goal of studying the cosmological constant (CC) problem, we present an exhaustive analysis of unimodular gravity as a possible candidate to resolve the CC origin and with this, the current Universe acceleration. In this theory, a correction constant (CC-like) in the field equations sources the late cosmic acceleration. This constant is related to a new parameter, zini, which is interpreted as the redshift of CC-like emergence. By comparing with the CC value obtained from Planck and Supernovaes measurements, it is possible to estimate zini = 11.15 +0.01 −0.02 and zini = 11.43 +0.03 −0.06 respectively, which is close to the reionization epoch. Moreover, we use the observational Hubble data (OHD), Type Ia Supernovae (SnIa), Baryon Acoustic Oscillations (BAO) and the Cosmic Microwave Background Radiation (CMB) distance data to constrain the UG cosmological parameters. A Joint analysis (OHD+SnIa+BAO+CMB), results in zini = 11.47 +0.074 −0.073 within 1σ confidence level consistent with our estimation from Planck and Supernovae measurements. We also include linear perturbations, starting with scalar and tensor perturbations and complementing with the perturbed Boltzmann equation for photons. We show that the 00 term in the UG field equations and the Boltzmann equation for photons contains corrections, meanwhile the other equations are similar as those obtained in standard cosmology.
arXiv Cosmology and Nongalactic Astrophysics, Oct 7, 2019
Inspired by a new compilation of strong lensing systems, which consist of 204 points in the redsh... more Inspired by a new compilation of strong lensing systems, which consist of 204 points in the redshift range 0.0625 < z l < 0.958 for the lens and 0.196 < z s < 3.595 for the source, we constrain three models that generate a late cosmic acceleration: the ω-cold dark matter model, the Chevallier-Polarski-Linder and the Jassal-Bagla-Padmanabhan parametrizations. Our compilation contains only those systems with early type galaxies acting as lenses, with spectroscopically measured stellar velocity dispersions, estimated Einstein radius, and both the lens and source redshifts. We assume an axially symmetric mass distribution in the lens equation, using a correction to alleviate differences between the measured velocity dispersion (σ) and the dark matter halo velocity dispersion (σ DM) as well as other systematic errors that may affect the measurements. We have considered different sub-samples to constrain the cosmological parameters of each model. Additionally, we generate a mock data of SLS to asses the impact of the chosen mass profile on the accuracy of Einstein radius estimation. Our results show that cosmological constraints are very sensitive to the selected data: some cases show convergence problems in the estimation of cosmological parameters (e.g. systems with observed distance ratio D obs < 0.5), others show high values for the chi-square function (e.g. systems with a lens equation D obs > 1 or high velocity dispersion σ > 276 km s −1). However, we obtained a fiduciary sample with 143 systems which improves the constraints on each tested cosmological model.
We study the scenario of Kanadiakis horizon entropy cosmology which arises from the application o... more We study the scenario of Kanadiakis horizon entropy cosmology which arises from the application of the gravity-thermodynamics conjecture using the Kaniadakis modified entropy. The resulting modified Friedmann equations contain extra terms that constitute an effective dark energy sector. We use data from Cosmic chronometers, Supernova Type Ia, HII galaxies, Strong lensing systems, and Baryon acoustic oscillations observations and we apply a Bayesian Markov Chain Monte Carlo analysis to construct the likelihood contours for the model parameters. We find that the Kaniadakis parameter is constrained around 0, namely, around the value where the standard BekensteinHawking is recovered. Concerning the normalized Hubble parameter, we find h = 0.708 −0.011, a result that is independently verified by applying the H0(z) diagnostic and, thus, we conclude that the scenario at hand can alleviate the H0 tension problem. Regarding the transition redshift, the reconstruction of the cosmographic para...
Journal of Cosmology and Astroparticle Physics, 2021
In this work, we use an observational approach and dynamical system analysis to study the cosmolo... more In this work, we use an observational approach and dynamical system analysis to study the cosmological model recently proposed by Saridakis (2020), which is based on the modification of the entropy-area black hole relation proposed by Barrow (2020). The Friedmann equations governing the dynamics of the Universe under this entropy modification can be calculated through the gravity-thermodynamics conjecture. We investigate two models, one considering only a matter component and the other including matter and radiation, which have new terms compared to the standard model sourcing the late cosmic acceleration. A Bayesian analysis is performed in which using five cosmological observations (observational Hubble data, type Ia supernovae, HII galaxies, strong lensing systems, and baryon acoustic oscillations) to constrain the free parameters of both models. From a joint analysis, we obtain constraints that are consistent with the standard cosmological paradigm within 2σ confidence level. In...
In this paper we consider ϕ^2 scalar field potential as a candidate to dark matter. If it is an u... more In this paper we consider ϕ^2 scalar field potential as a candidate to dark matter. If it is an ultralight boson particle, it condensates like a Bose-Einstein system at very early times and forms the basic structure of the Universe. Real scalar fields collapse in equilibrium configurations that oscillate in space-time (oscillatons).The cosmological behavior of the field equations are solved using the dynamical system formalism. We use the current cosmological parameters as constraints for the present value of the scalar field. We reproduce the cosmological predictions of the standard ΛCDM model with this model. Therefore, scalar field dark matter seems to be a good alternative to cold dark matter nature.
Monthly Notices of the Royal Astronomical Society, 2022
We investigate Kaniadakis-holographic dark energy by confronting it with observations. We perform... more We investigate Kaniadakis-holographic dark energy by confronting it with observations. We perform a Markov Chain Monte Carlo analysis using cosmic chronometers, supernovae type Ia, and Baryon Acoustic Oscillations data. Concerning the Kaniadakis parameter, we find that it is constrained around zero, namely around the value in which Kaniadakis entropy recovers standard Bekenstein-Hawking one. Additionally, for the present matter density parameter $\Omega _m^{(0)}$, we obtain a value slightly smaller compared to ΛCDM scenario. Furthermore, we reconstruct the evolution of the Hubble, deceleration, and jerk parameters extracting the deceleration-acceleration transition redshift as $z_T = 0.86^{+0.21}_{-0.14}$. Finally, performing a detailed local and global dynamical system analysis, we find that the past attractor of the Universe is the matter-dominated solution, while the late-time stable solution is the dark-energy-dominated one.
Scalar fields are one of the most interesting and most mysterious fields in theoretical physics. ... more Scalar fields are one of the most interesting and most mysterious fields in theoretical physics. Fundamental scalar fields are needed in all unification’s theories, however, there are
In a recent work Zhang, Li and Noh [Phys. Lett. B 694, 177 (2010)] proposed a model for dark ener... more In a recent work Zhang, Li and Noh [Phys. Lett. B 694, 177 (2010)] proposed a model for dark energy assuming this component strictly obeys the holographic principle. They performed a dynamical system analysis, finding a scaling solution which is helpful to solve the coincidence problem. However they need explicitly a cosmological constant. In this paper we derive an explicit analytical solution, without Λ, that shows agreement with the Supernovae data. However this solution is not physical because violate all the energy conditions.
arXiv: Cosmology and Nongalactic Astrophysics, 2019
With the goal of studying the cosmological constant (CC) problem, we present an exhaustive analys... more With the goal of studying the cosmological constant (CC) problem, we present an exhaustive analysis of unimodular gravity as a possible candidate to resolve the CC origin and with this, the current Universe acceleration. An excess of radiation in epochs of reionization is the cause of the existence of a CC in the unimodular gravity scenario; tracing its birth at $z=11.27^{+0.05}_{-0.05}$ (Theoretical) which also coincides with epochs of the first complex structures in our Universe. In order to follow its dynamics, we propose to use the Hubble data from cosmic chronometers, Type Ia Supernovae, the brightness temperature and optical depth as a cosmological tests to follow the birth of the CC and constrain its free parameters. A Joint analysis from Hubble data and Supernovae results in a $z=11.761\pm0.14$ which is in good agreement with the theoretical value for the birth of the CC. The consequences of this result, open the possibility to understand the Universe acceleration and its re...
With the goal of studying the cosmological constant (CC) problem, we present an exhaustive analys... more With the goal of studying the cosmological constant (CC) problem, we present an exhaustive analysis of unimodular gravity as a possible candidate to resolve the CC origin and with this, the current Universe acceleration. In this theory, a correction constant (CC-like) in the field equations sources the late cosmic acceleration. This constant is related to a new parameter, zini, which is interpreted as the redshift of CC-like emergence. By comparing with the CC value obtained from Planck and Supernovaes measurements, it is possible to estimate zini = 11.15 +0.01 −0.02 and zini = 11.43 +0.03 −0.06 respectively, which is close to the reionization epoch. Moreover, we use the observational Hubble data (OHD), Type Ia Supernovae (SnIa), Baryon Acoustic Oscillations (BAO) and the Cosmic Microwave Background Radiation (CMB) distance data to constrain the UG cosmological parameters. A Joint analysis (OHD+SnIa+BAO+CMB), results in zini = 11.47 +0.074 −0.073 within 1σ confidence level consistent with our estimation from Planck and Supernovae measurements. We also include linear perturbations, starting with scalar and tensor perturbations and complementing with the perturbed Boltzmann equation for photons. We show that the 00 term in the UG field equations and the Boltzmann equation for photons contains corrections, meanwhile the other equations are similar as those obtained in standard cosmology.
The accelerated expansion of the Universe is one of the main discoveries of the past decades, ind... more The accelerated expansion of the Universe is one of the main discoveries of the past decades, indicating the presence of an unknown component: the dark energy. Evidence of its presence is being gathered by a succession of observational experiments with increasing precision in its measurements. However, the most accepted model for explaining the dynamic of our Universe, the so-called Lambda cold dark matter, faces several problems related to the nature of such energy component. This has led to a growing exploration of alternative models attempting to solve those drawbacks. In this review, we briefly summarize the characteristics of a (non-exhaustive) list of dark energy models as well as some of the most used cosmological samples. Next, we discuss how to constrain each model’s parameters using observational data. Finally, we summarize the status of dark energy modeling.
Monthly Notices of the Royal Astronomical Society, 2021
Using a new sub-sample of observed strong gravitational lens systems, for the first time, we pres... more Using a new sub-sample of observed strong gravitational lens systems, for the first time, we present the equation for the angular diameter distance in the y-redshift scenario for cosmography and use it to test the cosmographic parameters. In addition, we also use the observational Hubble data from cosmic chronometers and a joint analysis of both data are performed. Among the most important conclusions are that this new analysis for cosmography using strong-lensing systems (SLSs) is equally competitive to constrain the cosmographic parameters as others presented in literature. Additionally, we present the reconstruction of the effective equation of state inferred from our samples, showing that at z = 0 those reconstructions from SLSs and joint analysis are in concordance with the standard model of cosmology.
Monthly Notices of the Royal Astronomical Society, 2020
Recently, a phenomenologically emergent dark energy (PEDE) model was presented with a dark energy... more Recently, a phenomenologically emergent dark energy (PEDE) model was presented with a dark energy density evolving as $\widetilde{\Omega }_{\rm {DE}}(z) = \Omega _{\rm {DE,0}}[ 1 - {\rm {tanh}}({\log }_{10}(1+z))]$, i.e. with no degree of freedom. Later on, a generalized model was proposed by adding one degree of freedom to the PEDE model, encoded in the parameter Δ. Motivated by these proposals, we constrain the parameter space ($h,\Omega _m^{(0)}$) and ($h,\Omega _m^{(0)}, \Delta$) for PEDE and generalized emergent dark energy (GEDE), respectively, by employing the most recent observational (non-)homogeneous and differential age Hubble data. Additionally, we reconstruct the deceleration and jerk parameters and estimate yield values at z = 0 of $q_0 = -0.784^{+0.028}_{-0.027}$ and $j_0 = 1.241^{+0.164}_{-0.149}$ for PEDE and $q_0 = -0.730^{+0.059}_{-0.067}$ and $j_0 = 1.293^{+0.194}_{-0.187}$ for GEDE using the homogeneous sample. We report values on the deceleration–acceleration t...
We present a parametric strong lensing modeling of the galaxy cluster MS 0440.5+0204 (located at ... more We present a parametric strong lensing modeling of the galaxy cluster MS 0440.5+0204 (located at z = 0.19). We have performed a strong lensing mass reconstruction of the cluster using three different models. The first model uses the image positions of four multiple imaged systems (providing 26 constraints). The second one combines strong lensing constraints with dynamical information (velocity dispersion) of the cluster. The third one uses the mass calculated from weak lensing as an additional constraint. Our three models reproduce equally well the image positions of the arcs, with a root-mean-square image equal to ≈0.5 ′′. However, in the third model, the inclusion of the velocity dispersion and the weak-lensing mass allows us to obtain better constraints in the scale radius and the line-of-sight velocity dispersion of the mass profile. For this model, we obtain r s = 132 +30 −32 kpc, σ s = 1203 +46 −47 km s −1 , M 200 = 3.1 +0.6 −0.6 ×10 14 M ⊙ , and a high concentration, c 200 = 9.9 +2.2 −1.4. Finally, we used our derived mass profile to calculate the mass up to 1.5 Mpc. We compare it with X-ray estimates previously reported, finding a good agreement.
Monthly Notices of the Royal Astronomical Society, 2020
Inspired by a new compilation of strong-lensing systems, which consist of 204 points in the redsh... more Inspired by a new compilation of strong-lensing systems, which consist of 204 points in the redshift range 0.0625 < zl < 0.958 for the lens and 0.196 < zs < 3.595 for the source, we constrain three models that generate a late cosmic acceleration: the ω-cold dark matter model, the Chevallier–Polarski–Linder, and the Jassal–Bagla–Padmanabhan parametrizations. Our compilation contains only those systems with early-type galaxies acting as lenses, with spectroscopically measured stellar velocity dispersions, estimated Einstein radius, and both the lens and source redshifts. We assume an axially symmetric mass distribution in the lens equation, using a correction to alleviate differences between the measured velocity dispersion (σ) and the dark matter halo velocity dispersion (σDM) as well as other systematic errors that may affect the measurements. We have considered different subsamples to constrain the cosmological parameters of each model. Additionally, we generate a mock ...
In this paper, we propose a new phenomenological two parameter parameterization of q(z) to constr... more In this paper, we propose a new phenomenological two parameter parameterization of q(z) to constrain barotropic dark energy models by considering a spatially flat Universe, neglecting the radiation component, and reconstructing the effective equation of state (EoS). This two free-parameter EoS reconstruction shows a non-monotonic behavior, pointing to a more general fitting for the scalar field models, like thawing and freezing models. We constrain the q(z) free parameters using the observational data of the Hubble parameter obtained from cosmic chronometers, the joint-light-analysis Type Ia Supernovae (SNIa) sample, the Pantheon (SNIa) sample, and a joint analysis from these data. We obtain, for the joint analysis with the Pantheon (SNIa) sample a value of q(z) today, $$q_0=-0.51\begin{array}{c} +0.09 \\ -0.10 \end{array}$$q0=-0.51+0.09-0.10, and a transition redshift, $$z_t=0.65\begin{array}{c} +0.19 \\ -0.17 \end{array}$$zt=0.65+0.19-0.17 (when the Universe change from an deceler...
In this paper we probe five cosmological models for which the dark energy equation of state param... more In this paper we probe five cosmological models for which the dark energy equation of state parameter, w(z), is parameterized as a function of redshift using strong lensing data in the galaxy cluster Abell 1689. We constrain the parameters of the w(z) functions by reconstructing the lens model under each one of these cosmologies with strong lensing measurements from two galaxy clusters, Abell 1689 and a mock cluster, Ares, from the Hubble Frontier Fields Comparison Challenge, to validate our methodology. To quantify how the cosmological constraints are biased due to systematic effects in the strong lensing modeling, we carry out three runs considering the following uncertainties for the multiple image positions: 0 25, 0 5, and 1 0. With Ares, we find that larger errors decrease the systematic bias on the estimated cosmological parameters. With real data, our strong-lensing constraints on w(z) are consistent with those derived from other cosmological probes. We confirm that strong lensing cosmography with galaxy clusters is a promising method to constrain w(z) parameterizations. A better understanding of galaxy clusters and their environment is needed, however, to improve the SL modeling and hence to estimate stringent cosmological parameters in alternative cosmologies.
We study unimodular gravity in the context of cosmology, particularly some interesting consequenc... more We study unimodular gravity in the context of cosmology, particularly some interesting consequences that might be able to describe the background cosmology and the late cosmic acceleration. We focus our attention on the hypothesis of non conservation of the energy momentum tensor. This characteristic has an interesting outcome: we can obtain a modified Friedmann equation along with the acceleration equation and also new fluid equations related to a third order derivative of the scale factor, known in cosmography as the jerk parameter. As a consequence of this theory, it seems that radiation and the cosmological constant are intimately related, in agreement with what some authors have called the third coincidence problem. Their connection is the parameter zini, which has a value of 11.29 and coincide with the reionization epoch. As a result, we are able to explain the late acceleration as a natural consequence of the equations, associating the new fluid to radiation and, thus, eliminating the need for another component (i.e. dark energy). Finally, we interpret the results and discuss the pros and cons of using the cosmological constant under the hypothesis of non conservation of the energy momentum tensor in the unimodular gravity scenario.
The dynamics of the Universe is analyzed using an exponential function for the dark energy equati... more The dynamics of the Universe is analyzed using an exponential function for the dark energy equation of state, known as Gong-Zhang parameterization. The phase space of the free parameters presented in the model is constrained using Cosmic Microwave Background radiation, Cosmic Chronometers, modulus distance from Hydrogen II Galaxies, Type Ia Supernovae and measurements from Baryon Acoustic Oscillations, together with a stronger bound from a Joint analysis. The cosmological model is confronted with ΛCDM, observing there is a strong evidence for ΛCDM in the Joint analysis although the exponential model is preferred when the data are separated. Based on the Joint analysis, a value of ω0 = −1.202 +0.027 −0.026 is found for the characteristic parameter presented in the equation of state. Additionally, the cosmographic parameters at current times are reported, having q0 = −0.789 +0.034 −0.036 , j0 = 1.779 +0.130 −0.119 , and a transition deceleration-acceleration redshift zT = 0.644 +0.011 −0.012. Furthermore, the age of the Universe is estimated as tU = 13.788 +0.019 −0.019 Gyrs. Finally, under the H0(z) diagnostic, we discuss this model could alleviate the H0 tension.
Fractional cosmology modifies the standard derivative to Caputo’s fractional derivative of order ... more Fractional cosmology modifies the standard derivative to Caputo’s fractional derivative of order μ, generating changes in General Relativity. Friedmann equations are modified, and the evolution of the species densities depends on μ and the age of the Universe tU. We estimate stringent constraints on μ using cosmic chronometers, Type Ia supernovae, and joint analysis. We obtain $\mu =2.839^{+0.117}_{-0.193}$ within the 1σ confidence level providing a non-standard cosmic acceleration at late times; consequently, the Universe would be older than the standard estimations. Additionally, we present a stability analysis for different μ values. This analysis identifies a late-time attractor corresponding to a power-law decelerated solution for μ < 2. Moreover, a non-relativistic critical point exists for μ > 1 and a sink for μ > 2. This solution is a decelerated power law if 1 < μ < 2 and an accelerated power-law solution if μ > 2, consistent with the mean values obtained ...
With the goal of studying the cosmological constant (CC) problem, we present an exhaustive analys... more With the goal of studying the cosmological constant (CC) problem, we present an exhaustive analysis of unimodular gravity as a possible candidate to resolve the CC origin and with this, the current Universe acceleration. In this theory, a correction constant (CC-like) in the field equations sources the late cosmic acceleration. This constant is related to a new parameter, zini, which is interpreted as the redshift of CC-like emergence. By comparing with the CC value obtained from Planck and Supernovaes measurements, it is possible to estimate zini = 11.15 +0.01 −0.02 and zini = 11.43 +0.03 −0.06 respectively, which is close to the reionization epoch. Moreover, we use the observational Hubble data (OHD), Type Ia Supernovae (SnIa), Baryon Acoustic Oscillations (BAO) and the Cosmic Microwave Background Radiation (CMB) distance data to constrain the UG cosmological parameters. A Joint analysis (OHD+SnIa+BAO+CMB), results in zini = 11.47 +0.074 −0.073 within 1σ confidence level consistent with our estimation from Planck and Supernovae measurements. We also include linear perturbations, starting with scalar and tensor perturbations and complementing with the perturbed Boltzmann equation for photons. We show that the 00 term in the UG field equations and the Boltzmann equation for photons contains corrections, meanwhile the other equations are similar as those obtained in standard cosmology.
arXiv Cosmology and Nongalactic Astrophysics, Oct 7, 2019
Inspired by a new compilation of strong lensing systems, which consist of 204 points in the redsh... more Inspired by a new compilation of strong lensing systems, which consist of 204 points in the redshift range 0.0625 < z l < 0.958 for the lens and 0.196 < z s < 3.595 for the source, we constrain three models that generate a late cosmic acceleration: the ω-cold dark matter model, the Chevallier-Polarski-Linder and the Jassal-Bagla-Padmanabhan parametrizations. Our compilation contains only those systems with early type galaxies acting as lenses, with spectroscopically measured stellar velocity dispersions, estimated Einstein radius, and both the lens and source redshifts. We assume an axially symmetric mass distribution in the lens equation, using a correction to alleviate differences between the measured velocity dispersion (σ) and the dark matter halo velocity dispersion (σ DM) as well as other systematic errors that may affect the measurements. We have considered different sub-samples to constrain the cosmological parameters of each model. Additionally, we generate a mock data of SLS to asses the impact of the chosen mass profile on the accuracy of Einstein radius estimation. Our results show that cosmological constraints are very sensitive to the selected data: some cases show convergence problems in the estimation of cosmological parameters (e.g. systems with observed distance ratio D obs < 0.5), others show high values for the chi-square function (e.g. systems with a lens equation D obs > 1 or high velocity dispersion σ > 276 km s −1). However, we obtained a fiduciary sample with 143 systems which improves the constraints on each tested cosmological model.
We study the scenario of Kanadiakis horizon entropy cosmology which arises from the application o... more We study the scenario of Kanadiakis horizon entropy cosmology which arises from the application of the gravity-thermodynamics conjecture using the Kaniadakis modified entropy. The resulting modified Friedmann equations contain extra terms that constitute an effective dark energy sector. We use data from Cosmic chronometers, Supernova Type Ia, HII galaxies, Strong lensing systems, and Baryon acoustic oscillations observations and we apply a Bayesian Markov Chain Monte Carlo analysis to construct the likelihood contours for the model parameters. We find that the Kaniadakis parameter is constrained around 0, namely, around the value where the standard BekensteinHawking is recovered. Concerning the normalized Hubble parameter, we find h = 0.708 −0.011, a result that is independently verified by applying the H0(z) diagnostic and, thus, we conclude that the scenario at hand can alleviate the H0 tension problem. Regarding the transition redshift, the reconstruction of the cosmographic para...
Journal of Cosmology and Astroparticle Physics, 2021
In this work, we use an observational approach and dynamical system analysis to study the cosmolo... more In this work, we use an observational approach and dynamical system analysis to study the cosmological model recently proposed by Saridakis (2020), which is based on the modification of the entropy-area black hole relation proposed by Barrow (2020). The Friedmann equations governing the dynamics of the Universe under this entropy modification can be calculated through the gravity-thermodynamics conjecture. We investigate two models, one considering only a matter component and the other including matter and radiation, which have new terms compared to the standard model sourcing the late cosmic acceleration. A Bayesian analysis is performed in which using five cosmological observations (observational Hubble data, type Ia supernovae, HII galaxies, strong lensing systems, and baryon acoustic oscillations) to constrain the free parameters of both models. From a joint analysis, we obtain constraints that are consistent with the standard cosmological paradigm within 2σ confidence level. In...
In this paper we consider ϕ^2 scalar field potential as a candidate to dark matter. If it is an u... more In this paper we consider ϕ^2 scalar field potential as a candidate to dark matter. If it is an ultralight boson particle, it condensates like a Bose-Einstein system at very early times and forms the basic structure of the Universe. Real scalar fields collapse in equilibrium configurations that oscillate in space-time (oscillatons).The cosmological behavior of the field equations are solved using the dynamical system formalism. We use the current cosmological parameters as constraints for the present value of the scalar field. We reproduce the cosmological predictions of the standard ΛCDM model with this model. Therefore, scalar field dark matter seems to be a good alternative to cold dark matter nature.
Monthly Notices of the Royal Astronomical Society, 2022
We investigate Kaniadakis-holographic dark energy by confronting it with observations. We perform... more We investigate Kaniadakis-holographic dark energy by confronting it with observations. We perform a Markov Chain Monte Carlo analysis using cosmic chronometers, supernovae type Ia, and Baryon Acoustic Oscillations data. Concerning the Kaniadakis parameter, we find that it is constrained around zero, namely around the value in which Kaniadakis entropy recovers standard Bekenstein-Hawking one. Additionally, for the present matter density parameter $\Omega _m^{(0)}$, we obtain a value slightly smaller compared to ΛCDM scenario. Furthermore, we reconstruct the evolution of the Hubble, deceleration, and jerk parameters extracting the deceleration-acceleration transition redshift as $z_T = 0.86^{+0.21}_{-0.14}$. Finally, performing a detailed local and global dynamical system analysis, we find that the past attractor of the Universe is the matter-dominated solution, while the late-time stable solution is the dark-energy-dominated one.
Scalar fields are one of the most interesting and most mysterious fields in theoretical physics. ... more Scalar fields are one of the most interesting and most mysterious fields in theoretical physics. Fundamental scalar fields are needed in all unification’s theories, however, there are
In a recent work Zhang, Li and Noh [Phys. Lett. B 694, 177 (2010)] proposed a model for dark ener... more In a recent work Zhang, Li and Noh [Phys. Lett. B 694, 177 (2010)] proposed a model for dark energy assuming this component strictly obeys the holographic principle. They performed a dynamical system analysis, finding a scaling solution which is helpful to solve the coincidence problem. However they need explicitly a cosmological constant. In this paper we derive an explicit analytical solution, without Λ, that shows agreement with the Supernovae data. However this solution is not physical because violate all the energy conditions.
arXiv: Cosmology and Nongalactic Astrophysics, 2019
With the goal of studying the cosmological constant (CC) problem, we present an exhaustive analys... more With the goal of studying the cosmological constant (CC) problem, we present an exhaustive analysis of unimodular gravity as a possible candidate to resolve the CC origin and with this, the current Universe acceleration. An excess of radiation in epochs of reionization is the cause of the existence of a CC in the unimodular gravity scenario; tracing its birth at $z=11.27^{+0.05}_{-0.05}$ (Theoretical) which also coincides with epochs of the first complex structures in our Universe. In order to follow its dynamics, we propose to use the Hubble data from cosmic chronometers, Type Ia Supernovae, the brightness temperature and optical depth as a cosmological tests to follow the birth of the CC and constrain its free parameters. A Joint analysis from Hubble data and Supernovae results in a $z=11.761\pm0.14$ which is in good agreement with the theoretical value for the birth of the CC. The consequences of this result, open the possibility to understand the Universe acceleration and its re...
With the goal of studying the cosmological constant (CC) problem, we present an exhaustive analys... more With the goal of studying the cosmological constant (CC) problem, we present an exhaustive analysis of unimodular gravity as a possible candidate to resolve the CC origin and with this, the current Universe acceleration. In this theory, a correction constant (CC-like) in the field equations sources the late cosmic acceleration. This constant is related to a new parameter, zini, which is interpreted as the redshift of CC-like emergence. By comparing with the CC value obtained from Planck and Supernovaes measurements, it is possible to estimate zini = 11.15 +0.01 −0.02 and zini = 11.43 +0.03 −0.06 respectively, which is close to the reionization epoch. Moreover, we use the observational Hubble data (OHD), Type Ia Supernovae (SnIa), Baryon Acoustic Oscillations (BAO) and the Cosmic Microwave Background Radiation (CMB) distance data to constrain the UG cosmological parameters. A Joint analysis (OHD+SnIa+BAO+CMB), results in zini = 11.47 +0.074 −0.073 within 1σ confidence level consistent with our estimation from Planck and Supernovae measurements. We also include linear perturbations, starting with scalar and tensor perturbations and complementing with the perturbed Boltzmann equation for photons. We show that the 00 term in the UG field equations and the Boltzmann equation for photons contains corrections, meanwhile the other equations are similar as those obtained in standard cosmology.
The accelerated expansion of the Universe is one of the main discoveries of the past decades, ind... more The accelerated expansion of the Universe is one of the main discoveries of the past decades, indicating the presence of an unknown component: the dark energy. Evidence of its presence is being gathered by a succession of observational experiments with increasing precision in its measurements. However, the most accepted model for explaining the dynamic of our Universe, the so-called Lambda cold dark matter, faces several problems related to the nature of such energy component. This has led to a growing exploration of alternative models attempting to solve those drawbacks. In this review, we briefly summarize the characteristics of a (non-exhaustive) list of dark energy models as well as some of the most used cosmological samples. Next, we discuss how to constrain each model’s parameters using observational data. Finally, we summarize the status of dark energy modeling.
Monthly Notices of the Royal Astronomical Society, 2021
Using a new sub-sample of observed strong gravitational lens systems, for the first time, we pres... more Using a new sub-sample of observed strong gravitational lens systems, for the first time, we present the equation for the angular diameter distance in the y-redshift scenario for cosmography and use it to test the cosmographic parameters. In addition, we also use the observational Hubble data from cosmic chronometers and a joint analysis of both data are performed. Among the most important conclusions are that this new analysis for cosmography using strong-lensing systems (SLSs) is equally competitive to constrain the cosmographic parameters as others presented in literature. Additionally, we present the reconstruction of the effective equation of state inferred from our samples, showing that at z = 0 those reconstructions from SLSs and joint analysis are in concordance with the standard model of cosmology.
Monthly Notices of the Royal Astronomical Society, 2020
Recently, a phenomenologically emergent dark energy (PEDE) model was presented with a dark energy... more Recently, a phenomenologically emergent dark energy (PEDE) model was presented with a dark energy density evolving as $\widetilde{\Omega }_{\rm {DE}}(z) = \Omega _{\rm {DE,0}}[ 1 - {\rm {tanh}}({\log }_{10}(1+z))]$, i.e. with no degree of freedom. Later on, a generalized model was proposed by adding one degree of freedom to the PEDE model, encoded in the parameter Δ. Motivated by these proposals, we constrain the parameter space ($h,\Omega _m^{(0)}$) and ($h,\Omega _m^{(0)}, \Delta$) for PEDE and generalized emergent dark energy (GEDE), respectively, by employing the most recent observational (non-)homogeneous and differential age Hubble data. Additionally, we reconstruct the deceleration and jerk parameters and estimate yield values at z = 0 of $q_0 = -0.784^{+0.028}_{-0.027}$ and $j_0 = 1.241^{+0.164}_{-0.149}$ for PEDE and $q_0 = -0.730^{+0.059}_{-0.067}$ and $j_0 = 1.293^{+0.194}_{-0.187}$ for GEDE using the homogeneous sample. We report values on the deceleration–acceleration t...
We present a parametric strong lensing modeling of the galaxy cluster MS 0440.5+0204 (located at ... more We present a parametric strong lensing modeling of the galaxy cluster MS 0440.5+0204 (located at z = 0.19). We have performed a strong lensing mass reconstruction of the cluster using three different models. The first model uses the image positions of four multiple imaged systems (providing 26 constraints). The second one combines strong lensing constraints with dynamical information (velocity dispersion) of the cluster. The third one uses the mass calculated from weak lensing as an additional constraint. Our three models reproduce equally well the image positions of the arcs, with a root-mean-square image equal to ≈0.5 ′′. However, in the third model, the inclusion of the velocity dispersion and the weak-lensing mass allows us to obtain better constraints in the scale radius and the line-of-sight velocity dispersion of the mass profile. For this model, we obtain r s = 132 +30 −32 kpc, σ s = 1203 +46 −47 km s −1 , M 200 = 3.1 +0.6 −0.6 ×10 14 M ⊙ , and a high concentration, c 200 = 9.9 +2.2 −1.4. Finally, we used our derived mass profile to calculate the mass up to 1.5 Mpc. We compare it with X-ray estimates previously reported, finding a good agreement.
Monthly Notices of the Royal Astronomical Society, 2020
Inspired by a new compilation of strong-lensing systems, which consist of 204 points in the redsh... more Inspired by a new compilation of strong-lensing systems, which consist of 204 points in the redshift range 0.0625 < zl < 0.958 for the lens and 0.196 < zs < 3.595 for the source, we constrain three models that generate a late cosmic acceleration: the ω-cold dark matter model, the Chevallier–Polarski–Linder, and the Jassal–Bagla–Padmanabhan parametrizations. Our compilation contains only those systems with early-type galaxies acting as lenses, with spectroscopically measured stellar velocity dispersions, estimated Einstein radius, and both the lens and source redshifts. We assume an axially symmetric mass distribution in the lens equation, using a correction to alleviate differences between the measured velocity dispersion (σ) and the dark matter halo velocity dispersion (σDM) as well as other systematic errors that may affect the measurements. We have considered different subsamples to constrain the cosmological parameters of each model. Additionally, we generate a mock ...
In this paper, we propose a new phenomenological two parameter parameterization of q(z) to constr... more In this paper, we propose a new phenomenological two parameter parameterization of q(z) to constrain barotropic dark energy models by considering a spatially flat Universe, neglecting the radiation component, and reconstructing the effective equation of state (EoS). This two free-parameter EoS reconstruction shows a non-monotonic behavior, pointing to a more general fitting for the scalar field models, like thawing and freezing models. We constrain the q(z) free parameters using the observational data of the Hubble parameter obtained from cosmic chronometers, the joint-light-analysis Type Ia Supernovae (SNIa) sample, the Pantheon (SNIa) sample, and a joint analysis from these data. We obtain, for the joint analysis with the Pantheon (SNIa) sample a value of q(z) today, $$q_0=-0.51\begin{array}{c} +0.09 \\ -0.10 \end{array}$$q0=-0.51+0.09-0.10, and a transition redshift, $$z_t=0.65\begin{array}{c} +0.19 \\ -0.17 \end{array}$$zt=0.65+0.19-0.17 (when the Universe change from an deceler...
In this paper we probe five cosmological models for which the dark energy equation of state param... more In this paper we probe five cosmological models for which the dark energy equation of state parameter, w(z), is parameterized as a function of redshift using strong lensing data in the galaxy cluster Abell 1689. We constrain the parameters of the w(z) functions by reconstructing the lens model under each one of these cosmologies with strong lensing measurements from two galaxy clusters, Abell 1689 and a mock cluster, Ares, from the Hubble Frontier Fields Comparison Challenge, to validate our methodology. To quantify how the cosmological constraints are biased due to systematic effects in the strong lensing modeling, we carry out three runs considering the following uncertainties for the multiple image positions: 0 25, 0 5, and 1 0. With Ares, we find that larger errors decrease the systematic bias on the estimated cosmological parameters. With real data, our strong-lensing constraints on w(z) are consistent with those derived from other cosmological probes. We confirm that strong lensing cosmography with galaxy clusters is a promising method to constrain w(z) parameterizations. A better understanding of galaxy clusters and their environment is needed, however, to improve the SL modeling and hence to estimate stringent cosmological parameters in alternative cosmologies.
We study unimodular gravity in the context of cosmology, particularly some interesting consequenc... more We study unimodular gravity in the context of cosmology, particularly some interesting consequences that might be able to describe the background cosmology and the late cosmic acceleration. We focus our attention on the hypothesis of non conservation of the energy momentum tensor. This characteristic has an interesting outcome: we can obtain a modified Friedmann equation along with the acceleration equation and also new fluid equations related to a third order derivative of the scale factor, known in cosmography as the jerk parameter. As a consequence of this theory, it seems that radiation and the cosmological constant are intimately related, in agreement with what some authors have called the third coincidence problem. Their connection is the parameter zini, which has a value of 11.29 and coincide with the reionization epoch. As a result, we are able to explain the late acceleration as a natural consequence of the equations, associating the new fluid to radiation and, thus, eliminating the need for another component (i.e. dark energy). Finally, we interpret the results and discuss the pros and cons of using the cosmological constant under the hypothesis of non conservation of the energy momentum tensor in the unimodular gravity scenario.
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Papers by juan magaña