Van der Waals quintessence

Capozziello, Salvatore; Martino, Salvatore; Falanga, M.

doi:10.1016/s0375-9601(02)00753-3

Cited by 54 publications

(65 citation statements)

References 26 publications

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“…We show that a consistent formulation is possible when the usual barotropic equation of state is replaced by the van der Waals equation (VDW), as was proposed by Capozziello et al [9] in 4D models and explored by one of these authors [10]. We show that an inflationary scenario is possible in the JT model, with a compatible behavior of the physical quantities.…”

Section: Introductionmentioning

confidence: 52%

“…We have also investigated the accelerated regimes that follow from the CGHS model by considering again the VDW equation of state. We have solved numerically the system of differential equations (6), (9) and (10) for the energy density, the cosmic scale factor and the dilaton, respectively. The initial conditions chosen were: ρ(0) = 1, a(0) = 1,ȧ(0) = 1, φ(0) = 0,φ(0) = d were d is a constant that determine the transition from the different regimes obtained, as we discuss bellow.…”

Section: Inflation In Jt and Cghs Modelsmentioning

confidence: 99%

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Transition from accelerated to decelerated regimes in JT and CGHS cosmologies

et al. 2004

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In this work we discuss the possibility of positive-acceleration regimes, and their transition to decelerated regimes, in two-dimensional (2D) cosmological models. We use general relativity and the thermodynamics in a 2D space-time, where the gas is seen as the sources of the gravitational field. An early-Universe model is analyzed where the state equation of van der Waals is used, replacing the usual barotropic equation. We show that this substitution permits the simulation of a period of inflation, followed by a negative-acceleration era. The dynamical behavior of the system follows from the solution of the Jackiw-Teitelboim equations (JT equations) and the energymomentum conservation laws. In a second stage we focus the Callan-Giddings-Harvey-Strominger model (CGHS model); here the transition from the inflationary period to the decelerated period is also present between the solutions, although this result depend strongly on the initial conditions used for the dilaton field. The temporal evolution of the cosmic scale function, its acceleration, the energy density and the hydrostatic pressure are the physical quantities obtained in through the analysis.

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Section: Introductionmentioning

confidence: 52%

Section: Inflation In Jt and Cghs Modelsmentioning

confidence: 99%

Transition from accelerated to decelerated regimes in JT and CGHS cosmologies

et al. 2004

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“…Only for later times the presence of the non-linear term in R promotes a sensitive increasing in the expansion rate of this 2D universe. The behavior of the acceleration is the most interesting result, as we display in figure (7).…”

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confidence: 78%

Non-linear terms in 2D cosmology

Devecchi¹,

Froehlich²

2005

Europhys. Lett.

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Abstract. -In this work we investigate the behavior of two-dimensional (2D) cosmological models, starting with the Jackiw-Teitelboim (JT) theory of gravitation. A geometrical term, non-linear in the scalar curvature R, is added to the JT dynamics to test if it could play the role of dark energy in a 2D expanding universe. This formulation makes possible, first, the description of an early (inflationary) 2D universe, when the van der Waals (vdW) equation of state is used to construct the energymomentum tensor of the gravitational sources. Second, it is found that for later times the non-linear term in R can generate an old 2D universe in accelerated expansion, where an ordinary matter dominated era evolves into a decelerated/accelerated transition, giving to the dark energy effects a geometrical origin. The results emerge through numerical analysis, following the evolution in time of the scale factor, its acceleration, and the energy densities of constituents.Introduction. -The study of theories of gravity in lower dimensions has received extensive consideration in the literature [1]. Taking the particular case of two-dimensional (2D) theories, the gravity formulation proposed by Teitelboim and Jackiw [2] (JT model) provided consistent results at the classical and quantum levels [1]. This model is the most imediate substitute of general relativity in 2D field formulations, since the Einstein theory furnish no dynamics in 2D [1]. The JT model was under investigation also in a cosmological context [3,6]. The results obtained include the description of a Universe filled with ordinary matter or/and electromagnetic radiation, an inflationary 2D universe and a three-eras universe where a cosmological constant was responsible for a final accelerated period, that could de associated to the effects of dark energy [3].

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“…An immediate generalization can be achieved by taking into account the Van der Waals equation of state which describes a two phase fluid. Also in this case, we have an approximation, but the consequences on dynamics are interesting [10,13]. Hence we assume that the equation of state is :…”

Section: The Van Der Waals Equation Of Statementioning

confidence: 99%

Constraining Van der Waals quintessence with observations

Capozziello

Cardone

Carloni

et al. 2005

J. Cosmol. Astropart. Phys.

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Abstract. We discuss an alternative approach to quintessence modifying the usual equation of state of the cosmological fluid in order to see if going further than the approximation of perfect fluid allows to better reproduce the available data. We consider a cosmological model comprising only two fluids, namely baryons (modelled as dust) and dark matter with a Van der Waals equation of state. First, the general features of the model are presented and then the evolution of the energy density, the Hubble parameter and the scale factor are determined showing that it is possible to obtain accelerated expansion choosing suitably the model parameters. We use the the data on the dimensionless coordinate distances to Type Ia supernovae and distant radio galaxies to see whether Van der Waals quintessence is viable to explain dark energy and to constrain its parameters. We then compare the model predictions with the estimated age of the universe and the position of the first three peaks of the anisotropy spectrum of the cosmic microwave background radiation. IntroductionIn the last few years an increasing bulk of data have been accumulated favouring the scenario of a spatially flat universe dominated by some form of dark energy. A first strong evidence came from the Hubble diagram of type Ia supernovae (hereafter SNeIa) that turned out to be best fitted by spatially flat accelerating cosmological models † Present address :

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Van der Waals quintessence

Cited by 54 publications

References 26 publications

Transition from accelerated to decelerated regimes in JT and CGHS cosmologies

Transition from accelerated to decelerated regimes in JT and CGHS cosmologies

Non-linear terms in 2D cosmology

Constraining Van der Waals quintessence with observations

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