Constraining the variable generalized Chaplygin gas model in matter creation cosmology

We explore the variable generalized Chaplygin gas(VGCG)model in the theory of matter creation cosmology within the framework of a spatially homogeneous and isotropic flat Friedmann—Lemai tre—Robertson—Walker space-time.Matter creation cosmology is based on reinterpretation of the energy–momentum tensor in Einstein's field equations.This creation corresponds to an irreversible energy flow from the gravitational field to the created matter constituents.The variable Chaplygin gas(VCG)is also studied as a particular solution.We use the Markov chain Monte Carlo method to constrain the free parameters of three models,namely,Lambda-Cold-Dark matter(ΛCDM),VGCG and VCG models with and without matter creation from the latest observational data from baryon acoustic oscillations,cosmic chronometer,type Ia supernovae(Pantheon)including gamma-ray bursts,quasars and the local measurement of H_(0) from R21 data.Two different combinations of dataset provide a fairly tight constraint on the parameters of theΛCDM,VGCG and VCG models.The present values of various cosmological parameters are obtained,which are very close to theΛCDM model.Furthermore,we perform stability analysis,Bayesian evidence analysis and information criteria analysis for these models through studying the sound speed,Bayes factor,and Akaike information criteria(AIC)and Bayesian information criteria(BIC)selection criteria.The values of sound speed for VGCG and VCG models shows that both the models are stable.According to AIC,it is observed that VGCG and VCG models with matter creation are supported considerably less by current observations,while BIC shows that these models are not favoured by observational data.

Viscous cosmology in holographic dark energy with Granda–Oliveros cut-off

We study the effect of bulk viscosity on holographic dark energy(HDE)with Granda–Oliveros infra-red cut-off.We focus on a generalized form of the bulk viscous coefficient which successfully describes the present-day evolution of the Universe.We observe that the model with bulk viscosity provides an elegant description of the early and late-time evolution of the Universe.We constrain the model through the combined observational data of the Strong Lensing System(SLS),measurements of Hubble parameter,Type Ia supernova data of Pantheon sample and local H_(0)measured by SH0ES.Using best-fit values obtained from two different combinations of data,we estimate the present value of Hubble’s constant H_(0)=71.567-0.848+1.448and H_(0)=69.197-1.924+1.563,the deceleration parameter q_(0)=-0.535-0.016+0.016and q_(0)=-0.536-0.016+0.016,and the equation of state w_(0)=-0.690-0.010+0.010and w_(0)=-0.691-0.011+0.011,respectively.The HDE model with bulk viscosity exhibits the phase transition from decelerated epoch to accelerated epoch.A comparison of the model with the standardΛCDM model is discussed with the statefinder and cosmographic parameters.