Probing the Lambda-DGP Braneworld model

In order to study the effect of the anti de Sitter/ conformal field theory correspondence (AdS/CFT) on the primordial inflationary era, we consider a universe filled with a tachyon field in a slow-roll regime. In this context, the background and perturbative parameters characterising the inflationary era are related to the standard one by correction terms. We show a clear agreement between the theoretical prediction and the observational data for the above mentioned model. The main results of our work are illustrated for an exponential potential. We show that, for a suitable conformal anomaly coefficient, AdS/CFT correspondence might leave its imprints on the spectrum of the gravitational waves amplitude with a tensor to scalar ratio, r, of the perturbations compatible with Planck data.

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“…(3.17), we obtain 19) which can be written in term of the standard slow roll parameter and the correction to standard general relativity as:…”

Section: Perturbationsmentioning

confidence: 99%

Constraints on tachyon inflationary models with an AdS/CFT correspondence

et al. 2016

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“…As shown in Ref. [12,13], the current Planck data used is best suited to the model in a non-planar ΛDGP. In [8][9][10][11]14], put forward the idea that if gravity is sufficiently weakened in the infrared, then vacuum energy could effectively decouple from gravity or degravitate over time.…”

mentioning

confidence: 99%

The Ambiguity in the Definition and Behavior of the Gravitational and Cosmological ‘Coupling Constants’ in the Theory of Induced Gravity

Zaripov¹

2019

Symmetry

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This work is the extension of author's research, where the modified theory of induced gravity (MTIG) is proposed. The theory describes two systems (stages): Einstein (ES) and "restructuring" (RS). We consider equations with quadratic potential that are symmetric with respect to scale transformations. The solutions of the equations obtained for the case of spaces defined by the Friedman-Robertson-Walker metric, as well as for a centrally symmetric space are investigated. In our model arise effective gravitational and cosmological "constants" , which are defined by the "mean square" of the scalar fields. In obtained solutions the values of such parameters as "Hubble parameter", gravitational and cosmological "constants" in the RS stage fluctuate near monotonically evolving mean values. These parameters are matched with observational data, described as phenomena of dark energy and dark matter. The MTIG equations for the case of a centrally symmetric gravitational field, in addition to the Schwarzschild-de Sitter solutions, contain solutions that lead to the new physical effects at large distances from the center. The Schwarzschild-Sitter solution becomes unstable and enters the oscillatory regime. For distances greater than a certain critical value, the following effects can appear: deviation from General relativity and Newton's law of gravitational interaction, antigravity. Telescope (HST) and Planck observatory [5]. The Hubble Space Telescope is tuned to measure the parallax Milky Way Cepheid variables and the distances are 1.7-3.6 kpc (the modern Universe). The measurements of the Planck spacecraft correspond to distant galaxies (the early Universe is about 375,000 years old). In 2018, the accuracy of the measurement of H 0 is increased to 2.3 percent, which gives H 0 = 73.48 ± 1.66 km · s −1 Mpc −1 . In the early Universe, based on the data received from the "Planck" spacecraft and ΛCDM theory, the predicted value is H 0 = 67.0 ± 1.2 km · s −1 Mpc −1 . The difference is about 9 percent. The accuracy of the measurements is about 4.5 percent. There is also a variance in the observations made at different times and different methods. For example, as indicated in the work [6], the local and direct definition of H 0 gives H 0 = 73.24 ± 1.74 km · s −1 Mpc −1 , and the most recent value from [7] in consent with ΛCDM is 66.93 ± 0.62 km · s −1 Mpc −1 . In our opinion, the problem can be reduced to a strong binding of calculations of the Hubble parameter H 0 to the ΛCDM model. In our work we present a model where, due to the oscillatory regime in the solutions of equations, the Hubble parameter also fluctuates with respect to the mean value-which is also a function of time.3. The problems of so-called "dark energy" (DE) and "dark matter" (DM). The first of them can be reduced to the problem of existence and smallness of the "cosmological constant" (par. 1). The challenge posed by the cosmological constant problem [1] has spurred many attempts at directly modifying Einstein's gravity at large distances [8]. As example of s...

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“…In an earlier work we tried to show the role of extra dimension in resolving this problem in a normal DGP scenario in the presence of Λ, as the DE component [42]. Here, we will represent the effect of normal DGP model with ADE, in ameliorating the coincidence problem.…”

Section: B Coincidence Problemmentioning

confidence: 99%

Stability Analysis of DGP Brane-world Model with Agegraphic Dark Energy

Ravanpak,

Fadakar

2018

Preprint

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The aim of this work is to apply the dynamical system approach to study the linear dynamics of normal DGP brane-world model with agegraphic dark energy as the dark energy component. The stability analysis of the model will be investigated and phase plane portrait will be shown. The nature of critical points will be analyzed by evaluating the eigenvalues of linearized Jacobi matrix. Also, statefinder diagnostic procedure will be applied to compare deviation from ΛCDM model.One of the most interesting results of this work is the great alleviation of the coincidence problem.

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Probing the Lambda-DGP Braneworld model

Cited by 8 publications

References 57 publications

Constraints on tachyon inflationary models with an AdS/CFT correspondence

Constraints on tachyon inflationary models with an AdS/CFT correspondence

The Ambiguity in the Definition and Behavior of the Gravitational and Cosmological ‘Coupling Constants’ in the Theory of Induced Gravity

Stability Analysis of DGP Brane-world Model with Agegraphic Dark Energy

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