arXiv subjects

Ankan Mukherjee

Publications and source records attributed to Ankan Mukherjee.

29 records · Page 2Linked to original sources

arXiv2018

Interacting dark energy with time varying equation of state and the $H_0$ tension

Almost in all interacting dark energy models present in the literature, the stability of the model becomes potentially sensitive to the dark energy equation of state parameter $w_x$, and a singularity arises at `$w_x = -1$'. Thus, it becomes mandatory to test the stability of the model into two separate regions, namely, for quintessence and phantom. This essentially brings in a discontinuity into the parameters space for $w_x$. Such discontinuity can be removed with some specific choices of the interaction or coupling function. In the present work we choose one particular coupling between dark matter and dark energy which can successfully remove such instability and we allow a dynamical dark energy equation of state parameter instead of the constant one. In particular, considering a dynamical dark energy equation of state with only one free parameter $w_0$, representing the current value of the dark energy equation of state, we confront the interacting scenario with several observational datasets. The results show that the present cosmological data allow an interaction in the dark sector, in agreement with some latest claims by several authors, and additionally, a phantom behaviour in the dark energy equation of state is suggested at present. Moreover, for this case the tension on $H_0$ is clearly released. As a final remark, we mention that according to the Bayesian analysis, $Λ$-cold dark matter ($Λ$CDM) is always favored over this interacting dark energy model.

astro-ph.CO↗

arXiv2018

Constraining the dark energy statefinder hierarchy in a kinematic approach

In the present work, we have adopted a kinematic approach for constraining the extended null diagnostic of concordance cosmology, known as the statefinder hierarchy. A Taylor series expansion of the Hubble parameter has been utilised for the reconstruction. The coefficients of the Taylor series expansion are related to the kinematical parameters like the deceleration parameter, cosmological jerk parameter etc. The present values of the kinematical parameters are constrained from the estimated values of those series coefficients. A Markov chain Monte Carlo analysis has been carried out using the observational measurements of Hubble parameter at different redshifts, the distance modulus data of type Ia supernovae and baryon acoustic oscillation data to estimate the coefficient of series expansion of the Hubble parameter. The parameters in the statefinder diagnostic are related to the kinematical parameters. The statefinder diagnostic can form sets of hierarchy according to the order of the kinematical parameters. The present values of statefinder parameters have been constrained. The first set in the statefinder hierarchy allows $Λ$CDM to be well within the 1$σ$ confidence region, whereas the second set is in disagreement with the corresponding $Λ$CDM values at more than 1$σ$ level. Another dark energy diagnostic, namely the $Om$-parameters, is found to be consistent with concordance cosmology.

astro-ph.CO↗

arXiv2018

Astronomical bounds on a cosmological model allowing a general interaction in the dark sector

Non-gravitational interaction between two barotropic dark fluids, namely the pressureless dust and the dark energy in a spatially flat Friedmann-Lemaître-Robertson-Walker model has been discussed. It is shown that for the interactions which are linear in terms the energy densities of the dark components and their first order derivatives, the net energy density is governed by a second order differential equation with constant coefficients. Taking a generalized interaction, which includes a number of already known interactions as special cases, the dynamics of the universe is described for three types of the dark energy equation of state, namely that of interacting quintessence, interacting vacuum energy density and interacting phantom. The models have been constrained using the standard cosmological probes, Supernovae type Ia data from joint light curve analysis and the observational Hubble parameter data. Two geometric tests, the cosmographic studies and the $Om$ diagnostic have been invoked so as to ascertain the behaviour of the present model vis-a-vis the $Λ$-cold dark matter model. We further discussed the interacting scenarios taking into account the thermodynamic considerations.

astro-ph.CO↗

arXiv2017

Reconstructing the dark energy potential

Dark energy equation of state can be effectively described by that of a barotropic fluid. The barotropic fluid model describes the background evolution and the functional form of the equation of state parameter is well constrained by the observations. Equally viable explanations of dark energy are via scalar field models, both canonical and non-canonical; these scalar field models being low energy descriptions of an underlying high energy theory. In this paper, we attempt to reconcile the two approaches to dark energy by way of reconstructing the evolution of the scalar field potential. For this analysis, we consider canonical quintessence scalar field and the phantom field for this reconstruction. We attempt to understand the analytical or semi-analytical forms of scalar field potentials corresponding to typical well behaved parameterisations of dark energy using the constraints from recent observations.

astro-ph.CO↗

arXiv2017

On the Reconstruction of Dark Energy Models

The present thesis is devoted to the reconstruction of the dark energy models using diverse observational data sets. The parametric approach has been adopted for the reconstruction of cosmological models. The reconstruction of kinematical quantities and the possibility of interaction between dark energy and dark matter has also been emphasised. In first chapter, a brief introduction to cosmology has been presented. In the second chapter, a reconstruction of the dark energy equation of state parameter for a quintessence scalar field model has been discussed. In the third chapter, a parametric reconstruction of the effective or total equation of state has been discussed. In the fourth chapter, a kinematic approach in the reconstruction of dark energy model through the parametrization of the cosmological jerk parameter has been discussed. The fifth chapter is also about a kinematic approach to the reconstruction of dark energy. The reconstruction has been done with an assumption that the jerk parameter is a very slowly varying function. The sixth chapter is devoted to the reconstruction of the interaction rate in holographic dark energy model. Finally, chapter seven contains the concluding remarks and relevant discussions regarding the overall work presented in the thesis.

astro-ph.CO↗

arXiv2017

In search of the dark matter dark energy interaction: a kinematic approach

The present work deals with a kinematic approach to the modelling the late time dynamics of the universe. This approach is based upon the assumption of constant value of cosmological jerk parameter, which is the dimensionless representation of the 3rd order time derivative of the scale factor. For the $Λ$CDM model, the value of jerk parameter is -1 throughout the evolution history. Now any model dependent estimation of the value of the jerk parameter would indicate the deviation of the model from the cosmological constant. In the present work, it has also been shown that for a constant jerk parameter model, any deviation of its value from -1 would not allow the dark matter to have an independent conservation, thus indicating towards an interaction between dark matter and dark energy. Statistical analysis with different observational data sets (namely the observational Hubble parameter data (OHD), the type Ia supernova data (SNe), and the baryon acoustic oscillation data (BAO)) lead to a well constrained values of the jerk parameter and the model remains at a very close proximity of the $Λ$CDM. The possibility of interaction is found to be more likely at high redshift rather than at present epoch.

astro-ph.CO↗

arXiv2016

Reconstruction of interaction rate in Holographic dark energy

The present work is based on the holographic dark energy model with Hubble horizon as the infrared cut-off. The interaction rate between dark energy and dark matter has been reconstructed for three different parameterizations of the deceleration parameter. Observational constraints on the model parameters have been obtained by maximum likelihood analysis using the observational Hubble parameter data (OHD), type Ia supernovab data (SNe), baryon acoustic oscillation data (BAO) and the distance prior of cosmic microwave background (CMB) namely the CMB shift parameter data (CMBShift). The interaction rate obtained in the present work remains always positive and increases with expansion. It is very similar to the result obtained in previous findings where the interaction rate has been reconstructed for a parametrization of the dark energy equation of state. Tighter constraints on the interaction rate have been obtained in the present work as it is based on larger data sets. The nature of the dark energy equation of state parameter has also been studied for the present models. Though the reconstruction is done from different parametrizations, the overall nature of the interaction rate is very similar in all the cases. Different information criteria and the Bayesian evidence, which have been invoked in the context of model selection, show that the these models are at close proximity of each other.

astro-ph.CO↗

arXiv2016

Acceleration of the universe: a reconstruction of the effective equation of state

The present work is based upon a parametric reconstruction of the effective or total equation of state in a model for the universe with accelerated expansion. The constraints on the model parameters are obtained by maximum likelihood analysis using the supernova distance modulus data, observational Hubble data, baryon acoustic oscillation data and cosmic microwave background shift parameter data. For statistical comparison, the same analysis has also been carried out for the wCDM dark energy model. Different model selection criteria (Akaike information criterion (AIC)) and (Bayesian Information Criterion (BIC)) give the clear indication that the reconstructed model is well consistent with the wCDM model. Then both the models (w_{eff}(z) model and wCDM model) have also been presented through (q_0 ,j_0 ) parameter space. Tighter constraint on the present values of dark energy equation of state parameter (w_{DE}(z = 0)) and cosmological jerk (j_0) have been achieved for the reconstructed model.

astro-ph.CO↗

arXiv2016

A parametric reconstruction of the cosmological jerk from diverse observational data sets

A parametric reconstruction of the jerk parameter, the third order derivative of the scale factor expressed in a dimensionless way, has been discussed. Observational constraints on the model parameters have been obtained by Maximum Likelihood Analysis of the models using Supernova Distance Modulus data (SNe), Observational Hubble Data (OHD), Baryon Acoustic Oscillation (BAO) data and CMB shift parameter data (CMBShift). The present value of the jerk parameter has been kept open to start with, but the plots of various cosmological parameter like deceleration parameter $q(z)$, jerk parameter $j(z)$, dark energy equation of state parameter $w_{DE}(z)$ indicate that the reconstructed models are very close to a $Λ$CDM model with a slight inclination towards a non-phantom behaviour of the evolution.

gr-qc↗

arXiv2016

A Reconstruction of Quintessence Dark Energy

With a parametric form of the equation of state parameter of dark energy, a quintessence potential has been reconstructed. The potential is found to be a generalization of a double exponential potential. The constraints on the parameters are obtained by maximum likelihood analysis using observational Hubble data, type Ia supernova data, baryon acoustic oscillation data and the CMB shift parameter data. Th emodel shows preference towards the phantom behaviour of dark energy.

gr-qc↗

arXiv2014

Acceleration of the Universe in f(R) Gravity Models

A general formalism for the investigation of the late time dynamics of the universe for any analytic f(R) gravity model, along with a cold dark matter, has been discussed in the present work. The formalism is then elucidated with two examples. The values of the parameters of the models are chosen in such a way that they are consistent with the basic observational requirement.

gr-qc↗