scholarly journals Chaplygin-gas solutions of f(R) gravity

2016 ◽  
Vol 13 (10) ◽  
pp. 1650120 ◽  
Author(s):  
Maye Elmardi ◽  
Amare Abebe ◽  
Abiy Tekola
Keyword(s):  
Dark Energy ◽  
Scalar Field ◽  
Early Universe ◽  
Equations Of State ◽  
Initial Conditions ◽  
Exact Formula ◽  
Chaplygin Gas ◽  
Cosmic Acceleration ◽  
Late Time ◽  
Modified Chaplygin Gas

We explore exact [Formula: see text] gravity solutions that mimic Chaplygin-gas inspired [Formula: see text]CDM cosmology. Starting with the original, generalized and modified Chaplygin-gas (MCG) equations of state (EoS), we reconstruct the forms of [Formula: see text] Lagrangians. The resulting solutions are generally quadratic in the Ricci scalar, but have appropriate [Formula: see text]CDM solutions in limiting cases. These solutions, given appropriate initial conditions, can be potential candidates for scalar field-driven early universe expansion (inflation) and dark energy-driven late-time cosmic acceleration.

scholarly journals Interacting models of generalized Chaplygin gas and modified Chaplygin gas with barotropic fluid

2019 ◽  
Vol 34 (09) ◽  
pp. 1950064 ◽  
Author(s):  
Promila Biswas ◽  
Ritabrata Biswas
Keyword(s):  
Dark Energy ◽  
Energy Density ◽  
Cosmological Parameters ◽  
Chaplygin Gas ◽  
Cosmic Acceleration ◽  
Late Time ◽  
Modified Chaplygin Gas ◽  
Interaction Coefficients ◽  
Generalized Chaplygin Gas ◽  
Barotropic Fluid

In this paper, we consider two different models of our present universe. We choose the models which consist of different sets of two separate fluids. The first one of each set tries to justify the late time acceleration and the second one is barotropic fluid. The former model considers our present time universe to be homogeneously filled up by Generalized Chaplygin Gas which is interacting with barotropic fluid. On the other hand, the latter model considers that the cosmic acceleration is generated by Modified Chaplygin Gas which is interacting with matter depicted by barotropic equation of state (EoS). For both the models, we consider the interaction term to vary proportionally with Hubble’s parameter as well as with the exotic matter/dark energy’s energy density. We find an explicit function form of the energy density of the cosmos which is found to depend on different cosmological parameters like scale factor, dark energy and barotropic fluid’s EoS parameters and other constants, like interacting constants, etc. We draw curves of effective EoS-s, different cosmological parameters like deceleration parameter q, statefinder parameters r and s with respect to the redshift z (for different values of dark energy and barotropic fluid parameters) and study them thoroughly. We compare two models as well as the nature of dependencies on these models’ interaction coefficients. We point out the particular redshift for which the universe may transit from a deceleration to acceleration phase. We tally all these values with different observational data. Here, we also analyze how this value of particular redshift does change for different values of interaction coefficients and different dark energy models.

Bouncing scenario in Brans–Dicke theory

2020 ◽  
Vol 17 (04) ◽  
pp. 2050056
Author(s):  
Sunil Kumar Tripathy ◽  
Subingya Pandey ◽  
Alaka Priyadarsini Sendha ◽  
Dipanjali Behera
Keyword(s):  
Dark Energy ◽  
Scalar Field ◽  
Equation Of State ◽  
Linear Equation ◽  
Scale Factor ◽  
Cosmic Acceleration ◽  
Late Time ◽  
Dark Fluid

A bouncing scenario is studied in the framework of generalized Brans–Dicke theory. In order to have a dark energy (DE) driven late time cosmic acceleration, we have considered a unified dark fluid simulated by a linear equation of state (EoS). The evolutionary behavior of the DE equation of parameter derived from the unified dark fluid has been discussed. The effect of the bouncing scale factor on the Brans–Dicke parameter, self-interacting potential and the Brans–Dicke scalar field is investigated.

Analysis on modified Chaplygin gas as dark energy model

2015 ◽  
Vol 30 (01) ◽  
pp. 1550005 ◽  
Author(s):  
Ya-Bo Wu ◽  
Cheng-Yuan Zhang ◽  
Jian-Bo Lu ◽  
Jun-Wang Lu ◽  
Xue Zhang ◽  
...  
Keyword(s):  
Dark Energy ◽  
Scalar Field ◽  
Chaplygin Gas ◽  
Model Parameters ◽  
Modified Chaplygin Gas ◽  
Related Data ◽  
Om Diagnostic ◽  
Interaction Terms ◽  
Special Cases ◽  
Evolutionary Trajectories

In this paper, we will continue to study the modified Chaplygin gas (MCG) based on Ref. 25. Concretely, we not only discuss both the change rates of the energy densities and the Hubble parameter H(z) as a function of the model parameters, which is compared and consistent with the related data in Ref. 27, but also perform the Om diagnostic in order to geometrically differentiate the MCG model from the ΛCDM, GCG and CG models. Moreover, we plot the evolutionary trajectories of MCG model with different interaction terms in Om planes, and find that the coupling intensity b2 plays an important role in the MCG model. Furthermore, we also reconstruct the potential of MCG scalar field as well as the dynamics of the scalar field according to the evolution of the MCG dark energy. It is worth stressing that the results given by us can include the ones without interaction as the special cases.

RECENT STATUS OF DARK ENERGY

2010 ◽  
Vol 25 (11n12) ◽  
pp. 843-858 ◽  
Author(s):  
SHINJI TSUJIKAWA
Keyword(s):  
Dark Energy ◽  
Cosmological Constant ◽  
Chaplygin Gas ◽  
Cosmic Acceleration ◽  
Late Time ◽  
Energy Models ◽  
Local Gravity ◽  
Dynamical Dark Energy

We review a number of approaches that have been adopted to explain the origin of dark energy responsible for the late-time cosmic acceleration. This includes the cosmological constant and dynamical dark energy models such as quintessence, k -essence, Chaplygin gas, f(R) gravity, scalar-tensor theories, and braneworld models. We also discuss observational and local gravity constraints on those models and clarify which models are favored or ruled out in current observations.

scholarly journals Cosmological dynamics and bifurcation analysis of the general non-minimal coupled scalar field models

2021 ◽  
Vol 81 (8) ◽  
Author(s):  
Wompherdeiki Khyllep ◽  
Jibitesh Dutta
Keyword(s):  
Dark Energy ◽  
Scalar Field ◽  
Bifurcation Analysis ◽  
Bifurcation Theory ◽  
Initial Conditions ◽  
Fine Tuning ◽  
Inflationary Universe ◽  
Global Dynamics ◽  
Late Time ◽  
Scalar Field Models

AbstractNon-minimal coupled scalar field models are well-known for providing interesting cosmological features. These include a late-time dark energy behavior, a phantom dark energy evolution without singularity, an early-time inflationary Universe, scaling solutions, convergence to the standard $$\Lambda $$ Λ CDM, etc. While the usual stability analysis helps us determine the evolution of a model geometrically, bifurcation theory allows us to precisely locate the parameters’ values describing the global dynamics without a fine-tuning of initial conditions. Using the center manifold theory and bifurcation analysis, we show that the general model undergoes a transcritical bifurcation, predicting us to tune our models to have certain desired dynamics. We obtained a class of models and a range of parameters capable of describing a cosmic evolution from an early radiation era towards a late time dark energy era over a wide range of initial conditions. There is also a possible scenario of crossing the phantom divide line. We also find a class of models where the late time attractor mechanism is indistinguishable from a structurally stable general relativity-based model; thus, we can elude the big rip singularity generically. Therefore, bifurcation theory allows us to select models that are viable with cosmological observations.

scholarly journals Interacting F(R, T) gravity with modified Chaplygin gas

2015 ◽  
Vol 93 (12) ◽  
pp. 1453-1459 ◽  
Author(s):  
Ali R. Amani ◽  
S.L. Dehneshin
Keyword(s):  
Dark Energy ◽  
Sound Speed ◽  
Cosmological Parameters ◽  
Field Potential ◽  
Chaplygin Gas ◽  
Accelerated Expansion ◽  
Late Time ◽  
Modified Chaplygin Gas ◽  
Curvature And Torsion ◽  
The Universe

In this paper, we have studied F(R, T) gravity as an arbitrary function of curvature and torsion scalars in Friedmann–Lemaître–Robertson–Walker background. Then, we have considered interacting model between F(R, T) gravity and modified Chaplygin gas. The novelty of this model is that the Universe includes both curvature and torsion cases, and one dominated by a Chaplygin gas. To calculate cosmological solutions, we obtained the Friedmann equations and also equation of state parameter of dark energy. By employing the interacting model we considered the total energy density and the total pressure of the Universe as the combination of components of dark energy and Chaplygin gas. Subsequently, we reconstructed the model by an origin of a scalar field entitled quintessence model with a field potential. The field potential has been calculated in terms of free parameters of F(R, T) gravity and modified Chaplygin gas. In what follows, we used a parametrization, and the cosmological parameters have been written in terms of redshift z. Next, we plotted cosmological parameters with respect to three variables: cosmic time, redshift z, and e-folding number N = ln(a), and the figures showed us an accelerated expansion of the Universe. Also, we have described the scenario in three statuses: early time, late time, and future time, by e-folding number. Finally, the stability of the scenario has been investigated using sound speed, and the graph of sound speed versus e-folding number has shown us that there is stability in late time.

scholarly journals Late Time Attractors of Some Varying Chaplygin Gas Cosmological Models

Symmetry ◽  
2021 ◽  
Vol 13 (5) ◽  
pp. 769
Author(s):  
Martiros Khurshudyan ◽  
Ratbay Myrzakulov
Keyword(s):  
Dark Energy ◽  
Gravitational Interaction ◽  
Chaplygin Gas ◽  
Cosmological Models ◽  
Late Time ◽  
Time Behavior ◽  
Coincidence Problem ◽  
Energy Models ◽  
Non Linear ◽  
Bayesian Machine Learning

The goal of this paper is to study new cosmological models where the dark energy is a varying Chaplygin gas. This specific dark energy model with non-linear EoS had been often discussed in modern cosmology. Contrary to previous studies, we consider new forms of non-linear non-gravitational interaction between dark matter and assumed dark energy models. We applied the phase space analysis allowing understanding the late time behavior of the models. It allows demonstrating that considered non-gravitational interactions can solve the cosmological coincidence problem. On the other hand, we applied Bayesian Machine Learning technique to learn the constraints on the free parameters. In this way, we gained a better understanding of the models providing a hint which of them can be ruled out. Moreover, the learning based on the simulated expansion rate data shows that the models cannot solve the H0 tension problem.

scholarly journals NEW HOLOGRAPHIC CHAPLYGIN GAS MODEL OF DARK ENERGY

2011 ◽  
Vol 20 (03) ◽  
pp. 281-297 ◽  
Author(s):  
M. MALEKJANI ◽  
A. KHODAM-MOHAMMADI
Keyword(s):  
Dark Energy ◽  
Scalar Field ◽  
Chaplygin Gas ◽  
Accelerated Expansion ◽  
Linear Perturbation ◽  
Generalized Chaplygin Gas ◽  
Infrared Cutoff ◽  
Scalar Field Models ◽  
Linear Perturbation Theory ◽  
Limiting Case

In this work, we investigate the holographic dark energy model with a new infrared cutoff (new HDE model), proposed by Granda and Oliveros. Using this new definition for the infrared cutoff, we establish the correspondence between the new HDE model and the standard Chaplygin gas (SCG), generalized Chaplygin gas (GCG) and modified Chaplygin gas (MCG) scalar field models in a nonflat universe. The potential and dynamics for these scalar field models, which describe the accelerated expansion of the universe, are reconstructed. According to the evolutionary behavior of the new HDE model, we derive the same form of dynamics and potential for the different SCG, GCG and MCG models. We also calculate the squared sound speed of the new HDE model as well as the SCG, GCG and MCG models, and investigate the new HDE Chaplygin gas models from the viewpoint of linear perturbation theory. In addition, all results in the nonflat universe are discussed in the limiting case of the flat universe, i.e. k = 0.

scholarly journals MODIFIED GRAVITATIONAL THEORIES AND COSMIC ACCELERATION

2004 ◽  
Vol 19 (31) ◽  
pp. 5343-5350 ◽  
Author(s):  
DAMIEN A. EASSON
Keyword(s):  
Dark Energy ◽  
Cosmic Acceleration ◽  
Late Time ◽  
De Sitter ◽  
Gravitational Theories ◽  
Hilbert Action

Modified gravitational theories can provide alternatives to dark energy as an explaination for the observed late-time cosmic acceleration. Several examples of low-curvature corrections to the Einstein-Hilbert action are studied. These models generically contain unstable de Sitter solutions and, depending on the parameters of the theory, can exhibit late time accelerating attractor solutions.

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