arXiv subjects

G. K. Goswami

Publications and source records attributed to G. K. Goswami.

28 records · Page 2Linked to original sources

arXiv2019

Two Fluid Scenario in Bianchi Type-I Universe

In this paper, we study a Bianchi type -I model of universe filled with barotropic and dark energy(DE) type fluids. The present values of cosmological parameters such as Hubble constant $H_0$, barotropic, DE and anisotropy energy parameters $(Ω_{m})_0$, $(Ω_{de})_0$ and $(Ω_σ)_0 $ and Equation of State(EoS) parameter for DE ($ω_{de}$) are statistically estimated in two ways by taking 38 point data set of Hubble parameter H(z) and 581 point data set of distance modulus of supernovae in the range $0\leq z \leq 1.414$. It is found that the results agree with the Planck result [P.A.R. Ade, et al., Astron. Astrophys. 594 A14 (2016)] and more latest result obtained by Amirhashchi and Amirhashchi [H. Amirhashchi and S. Amirhashchi, arXiv:1811.05400v4 (2019)]. Various physical properties such as age of the universe, deceleration parameter etc have also been investigated.

gr-qc↗

arXiv2019

FRW dark energy cosmological model with hybrid expansion law

In this work, we study a cosmological model of spatially homogeneous and isotropic accelerating universe which exhibits a transition from deceleration to acceleration. For this, Friedmann Robertson Walker(FRW) metric is taken and Hybrid expansion law $a(t)=t^α \exp(βt )$ is proposed and derived. We consider the universe to be filled with two types of fluids barotropic and dark energy which have variable equations of state. The evolution of dark energy, Hubble, and deceleration parameters etc., have been described in the form of tables and figures. We consider $581$ data's of observed values of distance modulus of various SNe Ia type supernovae from union $2.1$ compilation to compare our theoretical results with observations and found that model satisfies current observational constraints. We have also calculated the time and redshift at which acceleration in the Universe had commenced.

gr-qc↗

arXiv2019

FLRW accelerating universe with interactive dark energy

We have developed an accelerating cosmological model for the present universe which is phantom for the period $ (0 \leq z \leq 1.99)$ and quintessence phase for $(1.99 \leq z \leq 2.0315)$. The universe is assumed to be filled with barotropic and dark energy(DE) perfect fluid in which DE interact with matter. For a deceleration parameter(DP) having decelerating-accelerating transition phase of universe, we assume hybrid expansion law for scale factor. The transition red shift for the model is obtained as $z_t = 0.956$. The model satisfies current observational constraints.

gr-qc↗

arXiv2017

Cosmological Parameters For Spatially Flat Dust Filled Universe In Brans-Dicke Theory

In this paper, we have investigated late time acceleration for a spatially flat dust filled Universe in Brans-Dicke theory in the presence of a positive cosmological constant $Λ$ . Expressions for Hubble's constant, luminosity distance and apparent magnitude have been obtained for our model. The theoretical results are compared with the observed values of the the latest 287 high red shift ($ .3 \leq z \leq 1.4$ ) SN Ia supernova data's taken from Union 2.1 compilation to estimate the present values of the matter and dark energy parameters $(Ω_{m})_0$ and $(Ω_Λ)_0$. We have also estimated the present value of Hubble's constant $H_0$ in the light of a updated sample of Hubble parameter measurements including 19 independent data points. The results are found to be in good agreement with recent astrophysical observations. We have also calculated various physical parameters such as the matter and dark energy densities, the present age of the universe and deceleration parameter. The value for BD-coupling constant $ω$ is set to be 40000 on the basis of accuracy of the solar system tests and recent experimental evidence.

gr-qc↗

arXiv2016

$Λ$-CDM type Heckmann - Suchuking model and union 2.1 compilation

In this paper, we have investigated $Λ$CDM type cosmological model in Heckmann-Schucking space-time, by using 287 high red shift ($ .3 \leq z \leq 1.4$ ) SN Ia data of observed absolute magnitude along with their possible error from Union 2.1 compilation. We have used $χ^{2}$ test to compare Union 2.1 compilation observed data and corresponding theoretical values of apparent magnitude $(m)$. It is found that the best fit value for $(Ω_{m})_0$, $(Ω_Λ)_0$ and $(Ω_σ)_0$ are $0.2940$, $0.7058$ and $0.0002$ respectively and the derived model represents the features of accelerating universe which is consistent with recent astrophysical observations.

gr-qc↗

arXiv2016

Anisotropic String Cosmological Models in Heckmann-Suchuking Space-Time

In the present work we have searched the existence of the late time acceleration of the universe with string fluid as source of matter in anisotropic Heckmann-Suchking space-time by using 287 high red shift $(0.3 \leq z\leq 1.4)$ SN Ia data of observed absolute magnitude along with their possible error from Union 2.1 compilation. It is found that the best fit values for $(Ω_{m})_{0}$, $(Ω_Λ)_{0}$, $(Ω_σ)_{0}$ and $(q)_{0}$ are 0.2820, 0.7177, 0.0002 $\&$ -0.5793 respectively. Several physical aspects and geometrical properties of the model are discussed in detail.

gr-qc↗

arXiv2014

$Λ$CDM-type cosmological model and observational constraints

In the present work, we have searched the existence of $Λ$CDM-type cosmological model in anisotropic Heckmann-Schucking space-time. The matter source that is responsible for the present acceleration of the universe consist of cosmic fluid with $p = ωρ$, where $ω$ is the equation of state parameter. The Einstein's field equations have been solved explicitly under some specific choice of parameters that isotropizes the model under consideration. It has been found that the derived model is in good agreement with recent SN Ia observations. Some physical aspects of the model has been discussed in detail.

gr-qc↗

arXiv2012

Magnetized dark energy and the late time acceleration

In the present work we have searched the existence of the late time acceleration of the Universe. The matter source that is responsible for the late time acceleration of the Universe consists of cosmic fluid with the equation of state parameter $ω=\frac{p}ρ$ and uniform magnetic field of energy density $ρ_{B}$. The study is done here under the framework of spatially homogeneous and anisotropic locally rotationally symmetric (LRS) Bianchi-I cosmological model in the presence of magnetized dark energy. To get the deterministic model of the Universe, we assume that the shear scalar $(σ)$ in the model is proportional to expansion scalar $(θ)$. This condition leads to $A=B^{n}$, where $A$ and $B$ are metric functions and $n$ is a positive constant giving the proportionality condition between shear and expansion scalar. It has been found that the isotropic distribution of magnetized dark energy leads to the present accelerated expansion of the Universe and the derived model is in good agreement with the recent astrophysical observations. The physical behavior of the Universe has been discussed in details.

physics.gen-ph↗

arXiv2012

A Cosmological Model of Thermodynamic Open Universe

In this paper we have given a generalisation of the earlier work by Prigogine et al. who have constructed a phenomenological model of entropy production via particle creation in the very early universe generated out of the vacuum rather than from a singularity, by including radiation also as the energy source and tried to develop an alternative cosmological model in which particle creation prevents the big bang. We developed Radiation dominated model of the universe which shows a general tendency that (i) it originates from instability of vacuum rather than from a singularity. (ii) Up to a characteristic time cosmological quantities like density, pressure, Hubble constant and expansion parameter vary rapidly with time. (iii) After the characteristic time these quantities settles down and the models are turned into de-sitter type model with uniform matter, radiation, creation densities and Hubble's constant H. The de-sitter regime survives during a decay time then connects continuously to a usual adiabatic matter radiation RW universe.The interesting thing in the paper is that we have related the phenomenological radiation dominated model to macroscopic model of quantum particle creation in the early universe giving rise to the present observed value of cosmic background radiation . It is also found that the dust filled model tallies exactly with that of the Prigogine's one, which justifies that our model is generalized Prigogine's model. Although the model originates from instability of vacuum rather than from a singularity, still there is a couple of unavoidable singularities in the model.

gr-qc↗

arXiv2011

A Non - Singular Cosmological Model with Shear and Rotation

We have investigated a non-static and rotating model of the universe with an imperfect fluid distribution. It is found that the model is free from singularity and represents an ever expanding universe with shear and rotation vanishing for large value of time.

gr-qc↗