arXiv subjects

E. Karimkhani

Publications and source records attributed to E. Karimkhani.

4 recordsLinked to original sources

arXiv2019

D-class of dark energy against $Λ$CDM in Brans-Dicke cosmology

Three general models of dynamical interacting dark energy (D-class) are investigated in the context of Brans-Dicke cosmology. All cosmological quantities such as equation of state parameters, deceleration parameters, Hubble function, and the density ratio are calculated as a function of redshift parameter. The most important part of this paper is fitting of models to the observational data (SNIa+BAO$_A$+$Omh^{2}$). We obtain a table of best fit value of parameters and report $χ_{tot}^2/dof$ and Akaike Information Criterion (AIC) for each model. By these diagnostic tools, we find that some models have no chance against $Λ$CDM and some (e.g. $\mathcal{BD-D}C2$ and $\mathcal{BD-D}A^*$) render the best fit quality. Specially, the value of AIC analysis and figures show that the interacting $\mathcal{BD-D}C2$ model fit perfectly with overall data and reveals a strong evidence in favor of this model, against $Λ$CDM.

physics.gen-ph↗

arXiv2019

Hubble-rate-dependent Dark Energy in Brans-Dicke Cosmology

Three general cases of dynamical interacting dark energy models ($\mathcal{D}$-class) are investigated in the context of Brans-Dicke cosmology. Some of important cosmological quantities are calculated for every cases as a function of redshift parameter. The most important part of this paper deals with fitting models with two different expansion history: (SNIa+BAO$_A$+$Omh^{2}$ and SNIa+BAO$_A$+H(z)) and with two different sets of data for Hubble parameter. This provides a remarkable feature to could analytically see the effects of each analyzes and each data sets on final results. The best fitted values of parameters according to these analyzes and data points, $χ_{tot}^2/dof$, AIC and BIC are reported. By these diagnostic tools we found that some of these models have no chance against $Λ$CDM, even without need to study the structure formation, and could be ruled out. While some (e.g. $\mathcal{BD-D}C2$ and $\mathcal{BD-D}A^*$) render the best fit quality,i.e. the value of AIC and BIC and figures show that they fit perfectly with overall data and reveals a strong evidence in favor of these two models against $Λ$CDM.

astro-ph.CO↗

arXiv2016

Gauss Bonnet dark energy Chaplygin Gas Model

The correspondence of the Gauss-Bonnet (GB) and its modification (MGB) models of dark energy with the standard and generalized Chaplygin gas-scalar field models (SCG and GCG) have been studied in a °at universe. The exact solution of potentials and scalar fields, which describe the accelerated expansion of the universe, are reconstructed. According to the evolutionary behavior of the GB and MGB models, the same form of dynamics of scalar field and potential for different SCG and GCG models are derived. By calculating the squared sound speed of the MGB, GB model as well as the SCG, GCG, and investigating the GB-Chaplygin gas from the viewpoint of linear perturbation theory, we find that the best results which is consistent with the observation, may be appeared by considering the MGB-GCG. Also we find out some bounds for parameters.

gr-qc↗

arXiv2014

Best values of parameters for interacting HDE with GO IR-cutoff in Brans-Dicke cosmology

We investigate the interacting holographic dark energy (HDE) with Granda-Oliveros (GO) IR-cutoff in the framework of Brans-Dicke (BD) cosmology. We obtain the equation of state (EoS) parameter of HDE, $w_D$, the effective EoS parameter $w_{\mathrm{eff}}$, the deceleration parameter $q $ and the squared of sound speed $v_s^2$ in a flat FRW universe. We show that at late time the cosmic coincidence problem can be alleviated. Also we show that for non-interacting case, HDE can give a unified dark matter-dark energy profile in BD cosmology, except that it cannot solve the coincidence problem in the future. By studying the equation of state parameter, we see that the phantom divide may be crossed. Using the latest observational data, we calculate the best values of the parameters for interacting HDE in BD framework. Computing the deceleration parameter implies that the transition from deceleration to the acceleration phase occurred for redshift $z\geq 0.5$. Finally, we investigate the sound stability of the model, and find that HDE with GO cutoff in the framework of BD cosmology can lead to a stable DE-dominated universe favored by observations, provided we take $β=0.44$ and $b^2<0.35$. This is in contrast to HDE model in Einstein gravity which does not lead to a stable DE dominated universe.

gr-qc↗