Transition from accelerated to decelerated regimes in JT and CGHS cosmologies

Christmann, M. H.; Devecchi, F. P.; Kremer, Gilberto M.; Zanetti, C. M.

doi:10.1209/epl/i2004-10130-9

Cited by 7 publications

(40 citation statements)

References 15 publications

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“…This indicates that the nonlinear term is playing a role similar to the cosmological constant (see [6]) but in this case the responsible for that final accelerated era has a geometrical origin. The effect happens in a more drastic way as parameter ω increases.…”

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confidence: 94%

“…Another interesting result is that a three eras regime (a first strongly accelerated period followed by a decelerated one dominated by matter/radiation; and a final accelerated era) can be obtained when a cosmological constant Λ is included. Here this constant is playing the role of a dark energy density that must always have negative values ( a situation that occurs only in 2D [6]). …”

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confidence: 99%

“…The scalar curvature for the metric (2) in given by R = 2ä a [6]. Using these expressions in the field equation (4) (together with the energy-momentum tensor conservation law) we obtain the following system of equations…”

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confidence: 99%

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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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confidence: 94%

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confidence: 99%

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Non-linear terms in 2D cosmology

Devecchi¹,

Froehlich²

2005

Europhys. Lett.

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“…One such model is the exactly soluble two-dimensional gravity [4,5,6,7,8,9,10,11,12], which has attracted much attention in the study of cosmology in various aspects [13,14,15,16,17,18] (for a review of two or higher dimensional dilaton gravity, see Ref. [19]).…”

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confidence: 99%

Future-singularity-free accelerating expansion with modified Poisson brackets

Kim

Son

2007

Phys. Rev. D

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We show that the second accelerating expansion of the universe appears smoothly from the decelerating phase, which follows the initial inflation, in the two-dimensional soluble semi-classical dilaton gravity along with the modified Poisson brackets with noncommutativity between the relevant fields. This is contrast to the fact that the ordinary solution of the equations of motion following from the conventional Poisson algebra describes permanent accelerating universe without any phase change. In this modified model, it turns out that the noncommutative Poisson algebra is responsible for the remarkable phase transition to the second accelerating expansion.

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“…Introduction. -Cosmological models in lower dimensions have been under analysis in several works [1][2][3][4]. These theories offer interesting mathematical results that, if properly taken into account, can also be used in realistic models.…”

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Accelerated expansion in bosonic and fermionic 2D cosmologies with quantum effects

2009

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Cosmological models in lower dimensions.Abstract.-In this work we analyze the effects produced by bosonic and fermionic constituents, including quantum corrections, in two-dimensional (2D) cosmological models. We focus on a gravitational theory related to the Callan-Giddings-Harvey-Strominger model, to simulate the dynamics of a young, spatially-lineal, universe. The cosmic substratum is formed by an inflaton field plus a matter component, sources of the 2D gravitational field; the degrees of freedom also include the presence of a dilaton field. We show that this combination permits, among other scenarios, the simulation of a period of inflation, that would be followed by a (bosonic/fermionic) matter dominated era. We also analyse how quantum effects contribute to the destiny of the expansion, given the fact that in 2D we have a consistent (renormalizable) quantum theory of gravity. The dynamical behavior of the system follows from the solution of the gravitational field equations, the (Klein-Gordon and Dirac) equations for the sources and the dilaton field equation. Consistent (accelerated) regimes are present among the solutions of the 2D equations; the results depend strongly on the initial conditions used for the dilaton field. In the particular case where fermions are included as matter fields a transition to a decelerated expansion is possible, something that does not happen in the exclusively bosonic case.

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Transition from accelerated to decelerated regimes in JT and CGHS cosmologies

Cited by 7 publications

References 15 publications

Non-linear terms in 2D cosmology

Non-linear terms in 2D cosmology

Future-singularity-free accelerating expansion with modified Poisson brackets

Accelerated expansion in bosonic and fermionic 2D cosmologies with quantum effects

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