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1.
Ujjal Debnath Subenoy Chakraborty 《International Journal of Theoretical Physics》2011,50(9):2892-2898
In this work, we have examined the emergent scenario in brane world model for phantom and tachyonic matter. For tachyonic
matter field we have obtained emergent scenario is possible for closed, open and flat model of the universe with some restriction
of potential. For normal scalar field the emergent scenario is possible only for closed model and the result is identical
with the work of Ellis et al. (Class. Quantum Gravity 21:223, 2004), but for phantom field the emergent scenario is possible for closed, open and flat model of the universe with some restriction
of potential. 相似文献
2.
Sudeshna Mukerji Nairwita Mazumder Ritabrata Biswas Subenoy Chakraborty 《International Journal of Theoretical Physics》2011,50(9):2708-2719
In this work, Emergent Universe scenario has been developed in general homogeneous anisotropic model and for the inhomogeneous
LTB model. In the first case, it is assumed that the matter in the universe has two components—one is perfect fluid with barotropic
equation of state p=ωρ (ω, a constant) and the other component is a real or phantom (or tachyonic) scalar field. In the second case, the universe is
only filled with a perfect fluid and possibilities for the existence of emergent scenario has been examined. 相似文献
3.
Shuvendu Chakraborty Ujjal Debnath 《International Journal of Theoretical Physics》2012,51(4):1224-1238
In this work, we have analyzed two scenarios namely, “intermediate” and “logamadiate” scenarios for closed, open and flat
anisotropic universe in presence of phantom field, normal tachyonic field and phantom tachyonic field. We have assumed that
there is no interaction between the above mentioned dark energy and dark matter. In these two types of the scenarios of the
Universe, the nature of the scalar fields and corresponding potentials have been investigated. In intermediate scenario, (i)
the potential for normal tachyonic field decreases, (ii) the potentials for phantom tachyonic field and phantom field increase
with the corresponding fields. Also in logamediate scenario, (i) the potential for normal tachyonic field increases, (ii)
the potentials for phantom tachyonic field and phantom field decrease with the corresponding fields. 相似文献
4.
Shuvendu Chakraborty Ujjal Debnath 《International Journal of Theoretical Physics》2010,49(8):1693-1698
We have considered N-dimensional Einstein field equations in which four-dimensional space-time is described by a FRW metric and that of extra
dimensions by an Euclidean metric. We have supposed that the higher dimensional anisotropic universe is filled with only normal
scalar field or tachyonic field. Here we have found the nature of potential of normal scalar field or tachyonic field. From
graphical representations, we have seen that the potential is always decreases with field φ increases. 相似文献
5.
In this paper, we have considered the curved universe which is filled by tachyonic field. We have found the exact solutions
for the field, pressure, density, and scale factor and some cosmological parameters. In such universe, we have investigated
the role of tachyonic field in different stages of k for the evolution of the universe. Finally we draw the graphs for the scale factor, Hubble’s parameter, energy density, pressure,
acceleration parameter, equation of state and potential for the different values of k. Also we obtained the exact form of field which shows that the tachyonic field has the kink form. 相似文献
6.
Sudeshna Mukerji Subenoy Chakraborty 《International Journal of Theoretical Physics》2010,49(10):2446-2455
In this work, Emergent Universe scenario has been developed in Einstein-Gauss-Bonnet (EGB) theory. The universe is chosen
as homogeneous and isotropic FRW model and the matter in the universe has two components—the first one is a perfect fluid
with barotropic equation of state p=ω
ρ (ω, a constant) and the other component is a real or phantom (or tachyonic) scalar field. Various possibilities for the existence
of emergent scenario has been discussed and the results are compared with those in Einstein gravity. 相似文献
7.
In this paper, we have considered a model for Brans-Dicke scalar field in presence of Chaplygin gas and interaction between
them. We have shown that the BD parameter ω is constant or not, the Chaplygin gas provides early deceleration and late time acceleration of the universe. The graphical
representation of statefinder parameters shows the total evolution of the universe starts from radiation era to phantom model. 相似文献
8.
In this study, we investigate the expansion of the FRLW universe in the open, closed, and flat geometries. The universe is dominated by a scalar field (spatially homogeneous) as a source of dark energy. We consider the three different classes of scalar fields – quintessence, tachyonic, and phantom field – for our analysis. A mathematical analysis is carried out by considering these three scalar fields with exponential and power-law potentials. Both potentials give exponential expansion in the open, closed, and flat FRLW universes. It is found that quintessence, tachyonic, and phantom scalar fields are indistinguishable under the slow roll approximation. 相似文献
9.
Rahul Ghosh Surajit Chattopadhyay Ujjal Debnath 《International Journal of Theoretical Physics》2012,51(2):589-603
This work is motivated by the work of Kim et al. (Mod. Phys. Lett. A 23:3049, 2008), which considered the equation of state parameter for the new agegraphic dark energy based on generalized uncertainty principle
coexisting with dark matter without interaction. In this work, we have considered the same dark energy interacting with dark
matter in emergent, intermediate and logamediate scenarios of the universe. Also, we have investigated the statefinder, kerk and lerk parameters in all three scenarios under
this interaction. The energy density and pressure for the new agegraphic dark energy based on generalized uncertainty principle
have been calculated and their behaviors have been investigated. The evolution of the equation of state parameter has been
analyzed in the interacting and non-interacting situations in all the three scenarios. The graphical analysis shows that the
dark energy behaves like quintessence era for logamediate expansion and phantom era for emergent and intermediate expansions
of the universe. 相似文献
10.
We have considered a model of two component mixture i.e., mixture of Chaplygin gas and barotropic fluid with tachyonic field.
In the case, when they have no interaction then both of them retain their own properties. Let us consider an energy flow between
barotropic and tachyonic fluids. In both the cases we find the exact solutions for the tachyonic field and the tachyonic potential
and show that the tachyonic potential follows the asymptotic behavior. We have considered an interaction between these two
fluids by introducing a coupling term. Finally, we have considered a model of three component mixture i.e., mixture of tachyonic
field, Chaplygin gas and barotropic fluid with or without interaction. The coupling functions decays with time indicating
a strong energy flow at the initial period and weak stable interaction at later stage. To keep the observational support of
recent acceleration we have considered two particular forms (i) Logamediate Scenario and (ii) Intermediate Scenario, of evolution
of the Universe. We have examined the natures of the recent developed statefinder parameters and slow-roll parameters in both
scenarios with and without interactions in whole evolution of the universe. 相似文献
11.
Jhumpa Bhadra Shuvendu Chakraborty Ujjal Debnath 《International Journal of Theoretical Physics》2013,52(9):3353-3365
In this work, we have studied the Brans-Dicke (BD) cosmology in anisotropic models. We present three dimensional dynamical system describing the evolution of anisotropic models containing perfect fluid and BD scalar field with self-interacting potential. The relevant equations have been transformed into the dynamical system. The critical points and the corresponding eigen values have been found in radiation, dust, dark energy, ΛCDM and phantom phases of the universe. The natures and the stability around the critical points have also been investigated. 相似文献
12.
We study an anisotropic Bianchi-I universe in the presence of a phantom field and a cosmological constant. Cosmological solutions
are obtained when the kinetic energy of the phantom field is of the order of anisotropy and dominates over the potential energy
of the field. The anisotropy of the universe decreases and the universe transits to an isotropic flat FRW universe accommodating
the present acceleration. A class of new cosmological solutions is obtained for an anisotropic universe in case an initial
anisotropy exists which is bigger than the value determined by the parameter of the kinetic part of the field. Later, an autonomous
system of equations for an axially symmetric Bianchi-I universe with phantom field in an exponential potential is studied.
We discuss the stability of the cosmological solutions.
相似文献
13.
Two cosmological models with non-phantom matter having the same expansion of the universe as phantom cosmologies are constructed in anisotropic Bianchi type-V universe. The exact solutions to the corresponding Einstein field equations have been obtained. The statefinder diagnostic pair i.e. {r,s} parameters have been obtained for disordered radiation i.e. γ=1/3. We have also discussed the well-known astrophysical phenomena, namely the look-back time, luminosity distance and event horizon with redshift. 相似文献
14.
We find that the expansion of the universe is accelerating by analyzing the recent observation data of type Ia supernova (SN-Ia). It indicates that the equation of state of the dark energy might be smaller than -1, which leads to the introduction of phantom models featured by its negative kinetic energy to account for the regime of equation of state parameter w < -1. In this paper the possibility of using a non-minimally coupled real scalar field as phantom to realize the equation of state parameter w < -1 is discussed. The main equations which govern the evolution of the universe are obtained. Then we rewrite them with the observable quantities. 相似文献
15.
Bijan Saha 《Physics of Particles and Nuclei》2014,45(2):349-396
In this review we discuss the evolution of the universe filled with dark energy with or without perfect fluid. In doing so we consider a number of cosmological models, namely Bianchi type I, III, V, VI0, VI and FRW ones. For the anisotropic cosmological models we have used proportionality condition as an additional constrain. The exact solutions to the field equations in quadrature are found in case of a BVI model. It was found that the proportionality condition used here imposed severe restriction on the energy-momentum tensor, namely it leads to isotropic distribution of matter. Anisotropic BVI0, BV, BIII and BIDE models with variable EoS parameter ω have been investigated by using a law of variation for the Hubble parameter. In this case the matter distribution remains anisotropic, though depending on the concrete model there appear different restrictions on the components of energy-momentum tensor. That is why we need an extra assumption such as variational a law for the Hubble parameter. It is observed that, at the early stage, the EoS parameter v is positive i.e. the universe was matter dominated at the early stage but at later time, the universe is evolving with negative values, i.e., the present epoch. DE model presents the dynamics of EoS parameter ω whose range is in good agreement with the acceptable range by the recent observations. A spatially homogeneous and anisotropic locally rotationally symmetric Bianchi-I space time filled with perfect fluid and anisotropic DE possessing dynamical energy density is studied. In the derived model, the EoS parameter of DE (ω(de)) is obtained as time varying and it is evolving with negative sign which may be attributed to the current accelerated expansion of Universe. The distance modulus curve of derived model is in good agreement with SNLS type Ia supernovae for high redshift value which in turn implies that the derived model is physically realistic. A system of two fluids within the scope of a spatially flat and isotropic FRW model is studied. The role of the two fluids, either minimally or directly coupled in the evolution of the dark energy parameter, has been investigated. In doing so we have used three different ansatzs regarding the scale factor that gives rise to a variable decelerating parameter. It is observed that, in the non-interacting case, both the open and flat universes can cross the phantom region whereas in the interacting case only the open universe can cross the phantom region. The stability and acceptability of the obtained solution are also investigated. 相似文献
16.
Samarpita Bhattacharya Ujjal Debnath 《International Journal of Theoretical Physics》2012,51(2):565-576
Here we generalize the results of the work of Myung () in modified Chaplygin gas model and tachyonic field model. Here we have studied the thermodynamical behavior and the equation
of state in terms of volume and temperature for both models. We have used the solution and the corresponding equation of state
of our previous work (Chattopadhyay et al., Astrophys. Space Sci. 314:41, 2008). for tachyonic field model. We have also studied the thermodynamical stability using thermal equation of state for the tachyonic
field model and have shown that there is no critical points during thermodynamical expansion. The determination of T
∗ due to expansion for the tachyonic field have been discussed by assuming some initial conditions. Here, the thermal quantities
have been investigated using some reduced parameters. 相似文献
17.
In the present paper we investigate tachyonic chameleon scalar field and present the phase space analysis for four different combinations of the tachyonic potential \(V(\phi )\) and the coupling function \(f(\phi )\) of the chameleon field with matter. We find some stable solution in which accelerated expansion of the universe is satisfied. In one case where both \(f(\phi )\) and \(V(\phi )\) are exponential a scaling attractor was found that can give rise to the late-time acceleration of the universe and alleviate the coincidence problem. 相似文献
18.
Surajit Chattopadhyay Ujjal Debnath 《International Journal of Theoretical Physics》2011,50(10):3166-3175
In this work, we have considered that the universe is filled with tachyon and hessence (or hantom) dark energies. Subsequently
we have investigated the interactions between tachyon and hessence (hantom) dark energies and calculated the potentials considering
the power law form of the scale factor. It has been revealed that the tachyonic potential always decreases and hessence (or
hantom) potential increases with corresponding fields. Furthermore, we have considered a correspondence between the hessence
(or hantom) dark energy density and variable modified Chaplygin gas energy density. From this, we have found the expressions
of the arbitrary positive constants B
0 and C of variable modified Chaplygin gas. 相似文献
19.
20.
Ahmad Rami El-Nabulsi 《General Relativity and Gravitation》2010,42(6):1381-1398
We consider the flat anisotropic Bianchi I braneworld model of the universe within the framework of low energy effective string
action in four-dimensions including the leading order α′ terms, two-scalar fields, their interaction, non-minimal coupling of the dark-energy scalar field to the scalar curvature
and effective cosmological constant. Backward (high energy limit) and forward (low energy limit) in time analytic solutions
are derived and late-time accelerated expansion was found. It is shown that during the transition from high energy limit to
the low energy limit, the topology of the universe is changing in time: we have a transition from a (1 + 3) FRW homogenous
and isotropic spacetime dominated by radiation to a (1 + 2) spacetime sheet dominated by phantom energy while the third spatial
dimension is contracted in time. We have also found that dark matter and dark energy may be unified at early epoch in the
form of radiation fluids while the late-time dynamics is governed by phantom energy and dark energy. Many interesting features
are revealed. 相似文献