Modified Chaplygin Gas Research Articles

Stability of thin shell wormholes with a modified Chaplygin gas in Einstein–Hoffman–Born–Infeld theory

In the framework of Darmois–Israel formalism, the dynamics of motion equations of spherically symmetric thin shell wormholes that are supported by a modified Chaplygin gas in Einstein–Hoffman–Born–Infeld theory are constructed. The stability analysis of a thin shell wormhole is also discussed using a linearized radial perturbation around static solutions at the wormhole throat. The existence of stable static solutions depends on the value of some parameters of dynamical shell.

Logarithmic-corrected Ricci and modified Chaplygin gas dark energy models in fractal framework

Making use of the quantum theory of gravity in fractal geometry (FG) and considering a flat Friedmann-Robertson-Walker (FRW)-type universe containing dark matter interacting with dark energy, we investigate how the quantum and fractal contributions affect the dynamics of logarithmic-corrected Ricci dark energy (LCRDE) and modified Chaplygin gas (MCG).

Erratum: Big brake singularity is accommodated as an exotic quintessence field [Phys. Rev. D 93 , 043524 (2016)

We describe a big brake singularity in terms of a modified Chaplygin gas equation of state $p=(\ga_{m}-1)\rho+\al\ga_{m}\rho^{-n}$, accommodate this late-time event as an exotic quintessence model obtained from an energy-momentum tensor, and focus on the cosmological behavior of the exotic field, its kinetic energy and the potential energy. At the background level, the exotic field does not blow up whereas its kinetic energy and potential both grow without limit near the future singularity. We evaluate the classical stability of this background solution by examining the scalar perturbations of the metric along with the inclusion of entropy perturbation in the perturbed pressure. Within the Newtonian gauge, the gravitational field approaches a constant near the singularity plus additional regular terms. When the perturbed exotic field is associated with $\al>0$ the perturbed pressure and contrast density both diverge, whereas the perturbed exotic field and the divergence of the exotic field's velocity go to zero exponentially. When the perturbed exotic field is associated with $\al<0$ the contrast density always blows up, but the perturbed pressure can remain bounded. In addition, the perturbed exotic field and the divergence of the exotic field's velocity vanish near the big brake singularity. We also briefly look at the behavior of the intrinsic entropy perturbation near the singular event.

The general class of Bianchi cosmological models with dark energy and variable Λ and G in viscous cosmology

The general class of Bianchi cosmological models with dark energy in the form of modified Chaplygin gas with variable Λ and G and bulk viscosity have been considered. We discuss three types of average scale factor by using a special law for deceleration parameter which is linear in time with negative slope. The exact solutions to the corresponding field equations are obtained. We obtain the solution of bulk viscosity (ξ), cosmological constant (Λ), gravitational parameter (G) and deceleration parameter (q) for different equations of state. The model describes an accelerating Universe for large value of time t, wherein the effective negative pressure induced by Chaplygin gas and bulk viscous pressure are driving the acceleration.

Thermodynamics of scale factor dual universes

The thermodynamical aspects of the conformal time scale factor duality (SFD) of cosmological models within Einstein Gravity are investigated. We derive the SFD transformations of the thermodynamical quantities describing the thermal evolution of the matter fluid and of the apparent horizon. The thermodynamical properties of the self-dual cosmological models with a modified Chaplygin gas are studied in detail. We deduce the restrictions on the equation of state parameters that allow to extend scale factor duality as a UV/IR symmetry of the cosmological models consistent with their thermodynamical behavior.

Dynamics of modified Chaplygin gas inflation on the Brane with bulk viscous pressure

We investigate the role of bulk viscous pressure on the warm inflationary modified Chaplygin gas (MCG) in braneworld framework in the presence of standard scalar field. We assume the intermediate inflationary scenario in strong dissipative regime and constructed the inflaton, potential, entropy density, slow-roll parameters, scalar and tensor power spectra, scalar spectral index and tensor-to-scalar ratio. We develop various trajectories such as [Formula: see text], [Formula: see text] and [Formula: see text] (where [Formula: see text] is the spectral index, [Formula: see text] is the running of spectral index, [Formula: see text] is the number of e-folds and [Formula: see text] is tensor-to-scalar ratio) for variable as well as constant dissipation and bulk viscous coefficients at high dissipative regime. It is interesting to remark here that our results of these parameters are compatible with recent observational data such as WMAP [Formula: see text], BICEP[Formula: see text] and Planck data.

Interacting modified Chaplygin gas in f(T) gravity framework and analysis of its stability against gravitational perturbation

In this work, we investigate the cosmological application of modified Chaplygin gas (MCG) interacting with pressureless dark matter (DM) in the [Formula: see text] modified gravity framework, where [Formula: see text] is the torsion scalar in teleparallelism. The interaction term has been chosen proportional to the MCG density with positive coupling constant. In the Einstein general relativity (GR) framework, the interacting MCG has been found to have equation of state (EoS) parameter behaving like quintessence. However, the [Formula: see text] gravity reconstructed via the interacting MCG has been found to have EoS crossing the phantom boundary of [Formula: see text]. Thus, one can generate a quintom-like EoS from an interacting MCG model in flat universe in the modified gravity cosmology framework. The reconstructed [Formula: see text] model has been found to interpolate between dust and [Formula: see text]CDM. Stability of the reconstructed [Formula: see text] has been investigated and it has been observed that the model is stable against gravitational perturbation. Cosmological evolution of primordial perturbations has also been investigated and the self-interacting potential has been found to increase with cosmic time and the squared speed of sound has been found to be non-negative.

Warm modified Chaplygin gas shaft inflation

In this paper, we examine the possible realization of a new inflation family called “shaft inflation” by assuming the modified Chaplygin gas model and a tachyon scalar field. We also consider the special form of the dissipative coefficient Gamma ={a_0}frac{T^{3}}{phi ^{2 }} and calculate the various inflationary parameters in the scenario of strong and weak dissipative regimes. In order to examine the behavior of inflationary parameters, the n_s – phi ,, n_s –r, and n_s – alpha _s planes (where n_s,, alpha _s,, r, and phi represent the spectral index, its running, tensor-to-scalar ratio, and scalar field, respectively) are being developed, which lead to the constraints r< 0.11, n_s=0.96 pm 0.025, and alpha _s =-0.019 pm 0.025. It is quite interesting that these results of the inflationary parameters are compatible with BICEP2, WMAP (7+9) and recent Planck data.

Bulk Viscous Cosmological Model in Brans-Dicke Theory with New Form of Time Varying Deceleration Parameter

We have presented FRW cosmological model in the framework of Brans-Dicke theory. This paper deals with a new proposed form of deceleration parameter and cosmological constant Λ. The effect of bulk viscosity is also studied in the presence of modified Chaplygin gas equation of state (p=Aρ-B/ρn). Furthermore, we have discussed the physical behaviours of the models.

Concentration in vanishing pressure limit of solutions to the modified Chaplygin gas equations

Two kinds of occurrence mechanism on the phenomenon of concentration and the formation of delta shock wave in vanishing pressure limit of solutions to the modified Chaplygin gas equations are analyzed and identified. The Riemann problem of the modified Chaplygin gas equations is first solved. Then it is shown that, as the pressure vanishes, any two-shock Riemann solution tends to a delta-shock solution to the transport equations, and the intermediate density between the two shocks tends to a weighted δ-measure which forms a delta shock wave; any two-rarefaction-wave Riemann solution tends to a two-contact-discontinuity solution to the transport equations, and the nonvacuum intermediate state in between tends to a vacuum state. It is also shown that, as the pressure approaches the generalized Chaplygin gas pressure, any two-shock Riemann solution tends to a delta-shock solution to the generalized Chaplygin gas equations. Some numerical results are presented to show the formation process of delta shock waves and vacuum states.

Chaplygin-gas solutions of f(R) gravity

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.

Modified Chaplygin gas equation of state on viscous dissipative extended holographic Ricci dark energy and the cosmological consequences

The present paper reports a study on modified Chaplygin gas (MCG)-based reconstruction scheme for extended holographic Ricci dark energy (EHRDE) in the presence of viscous type dissipative term. The dissipative effect has been described by using Eckart approach. Under the assumption that the universe is filled with MCG–EHRDE under the influence of bulk viscosity we have studied the cosmological dynamics, where the bulk viscosity coefficient has been chosen in a particular time varying form [Formula: see text], where [Formula: see text] and [Formula: see text] are constant coefficients and [Formula: see text] is the Hubble parameter. Furthermore, we have reconstructed the potential and dynamics of viscous MCG–EHRDE as scalar field. Thereafter we have studied the statefinder trajectories to discern its departure from [Formula: see text] cold dark matter ([Formula: see text]CDM) and finally investigated validity of the generalized second law (GSL) of thermodynamics considering event horizon as the enveloping horizon of the universe.

Constraints on modified Chaplygin gas from large scale structure

We study cosmological models with modified Chaplygin gas (MCG) to determine observational constraints on its EoS parameters using the background and the growth tests data. The background test data consists of \(H(z)-z\) data, Baryonic Acoustic Oscillations peak parameter, CMB shift parameter, SN Ia data and the growth test data consists of the linear growth function for the large scale structures of the universe are considered to study MCG in favor of dark energy. For a given range of redshift, the Wiggle-Z measurements and rms mass fluctuations from Ly-\(\alpha \) data, employed for analyzing cosmological models numerically to constrain the MCG parameters. The Wang-Steinhardt ansatz for the growth index (\(\gamma \)) and growth function (\(f\)) are also considered for numerical analysis. The best-fit values of EoS parameters determined here are used to study the variation of \(f\), growth index (\(\gamma \)), EoS parameter, squared sound speed and deceleration parameter with redshift. The constraints on the MCG parameters found here are compared with that of GCG (generalized Chaplygin gas) model for viable cosmology. Cosmologies with MCG satisfactorily describe late acceleration followed by a matter dominated phase. The range of values of EoS parameters, the associated parameters (\(f\), \(\gamma \), \(\omega \), \(\varOmega \), \(c^{2}_{s}\), \(q\)) are also determined from observational data in order to understand the suitability of the MCG model.

Chaplygin gas inspired scalar fields inflation via well-known potentials

Brane inflationary universe models in the context of modified Chaplygin gas and generalized cosmic Chaplygin gas are being studied. We develop these models in view of standard scalar and tachyon fields. In both models, the implemented inflationary parameters such as scalar and tensor power spectra, scalar spectral index and tensor to scalar ratio are derived under slow roll approximations. We also use chaotic and exponential potential in high energy limits and discuss the characteristics of inflationary parameters for both potentials. These models are compatible with recent astronomical observations provided by \(\mbox{WMAP}7{+}9\) and Planck data, i.e., \(\eta_{s}=1.027\pm0.051, 1.009\pm0.049, 0.096\pm0.025\) and \(r<0.38, 0.36, 0.11\).

Observational constraints on cosmological models with Chaplygingas and quadratic equation of state

Observational manifestations of accelerated expansion of the universe, in particular, recent data for Type Ia supernovae, baryon acoustic oscillations, for the Hubble parameter H(z) and cosmic microwave background constraints are described with different cosmological models. We compare the ΛCDM, the models with generalized and modified Chaplygin gas and the model with quadratic equation of state. For these models we estimate optimal model parameters and their permissible errors with different approaches to calculation of sound horizon scale rs(zd). Among the considered models the best value of χ2 is achieved for the model with quadratic equation of state, but it has 2 additional parameters in comparison with the ΛCDM and therefore is not favored by the Akaike information criterion.

LRS Bianchi type-V universe with variable modified Chaplygin gas in a scalar–tensor theory of gravitation

The spatially homogeneous and anisotropic LRS Bianchi type-V Universe filled with variable modified Chaplygin gas in the framework of the Brans–Dicke (Brans and Dicke. Phys. Rev. 124, 925 (1961). doi:10.1103/PhysRev.124.925) scalar–tensor theory of gravitation has been studied. To obtain a determinate solution of the field equations we have used the condition that scalar field ([Formula: see text]) is a function of average scale factor. Some physical and kinematical properties of the model are discussed. We have also analyzed the stability of the solution.

Dynamics of bulk viscous pressure effected inflation in braneworld scenario

The main goal of the present work is to examine the possible realization of warm chaotic inflation and logamediate inflation within the framework of a modified Chaplygin gas brane-world model. In this respect, the slow-roll parameters, number of e-folds, scalar-tensor power spectra, spectral indices, tensor–scalar ratio and running of scalar spectral index is being evaluated. These parameters are being analyzed for variable as well as constant dissipation and bulk viscous coefficients. Further, the trajectories among the inflationary parameters such as ns−ϕ,ns−r,αs−ϕ and ns−αs are also developed to examine their behavior as well as physical cosmology. Some of results of inflationary parameters in all cases are: r < 0.11, ns=0.96±0.025 and αs=−0.019±0.025. It is interesting to mention here that the results of inflationary parameters are consistent with BICEP2, WMAP (7+9) and Planck data.

Dynamics of warm Chaplygin gas inflationary models with quartic potential

Warm inflationary universe models in the context of generalized chaplygin gas, modified chaplygin gas, generalized cosmic chaplygin gas are being studied. The dissipative coefficient of the form $\Gamma\propto T$, weak and strong dissipative regimes are being considered. We use quartic potential $\frac{\lambda_{*}\phi^{4}}{4}$, which is ruled out by current data in cold inflation but in our models it is analyzed that it is in agreement with the WMAP$9$ and latest Planck data. In these scenarios, the power spectrum, spectral index, and tensor to scalar ratio are being examined under the slow roll approximation. We show the dependence of tensor scalar ratio $r$ on spectral index $n_{s}$ and observe that the range of tensor scalar ratio is $r<0.05$ in generalized chaplygin gas, $r<0.15$ in modified chaplygin gas, and $r<0.12$ in generalized cosmic chaplygin gas models. Our results are in agreement with recent observational data like WMAP$9$ and latest Planck data.

Thermodynamics of the variable modified Chaplygin gas

A cosmological model with a new variant of Chaplygin gas obeying an equation of state(EoS), P = Aρ − B/ρα where B= B0an is investigated in the context of its thermodynamical behaviour. Here B0 and n are constants and a is the scale factor. We show that the equation of state of this `Variable Modified Chaplygin gas' (VMCG) can describe the current accelerated expansion of the universe. Following standard thermodynamical criteria we mainly discuss the classical thermodynamical stability of the model and find that the new parameter, n introduced in VMCG plays a crucial role in determining the stability considerations and should always be negative. We further observe that although the earlier model of Lu explains many of the current observational findings of different probes it fails the desirable tests of thermodynamical stability. We also note that for 0n < our model points to a phantom type of expansion which, however, is found to be compatible with current SNe Ia observations and CMB anisotropy measurements. Further the third law of thermodynamics is obeyed in our case. Our model is very general in the sense that many of earlier works in this field may be obtained as a special case of our solution. An interesting point to note is that the model also apparently suggests a smooth transition from the big bang to the big rip in its whole evaluation process.

Modified Chaplygin gas inspired inflationary model in braneworld scenario

We investigate the modified Chaplygin gas inspired inflationary regime in the brane-world framework in the presence of standard and tachyon scalar fields. We consider the intermediate inflationary scenario and construct the slow-roll parameters, e-folding numbers, spectral index, scalar and tensor power spectra, tensor to scalar ratio for both scalar field models. We develop the $n_{s} - \mathcal{N}$ and $r - \mathcal{N}$ planes and concluded that $n_{s}\simeq96^{+0.5}_{-0.5}$ and $r\leq0.0016$ for $\mathcal{N}\simeq60^{+5}_{-5}$ in both cases of scalar field models as well as for all values of $m$ . These constraints are consistent with observational data such as WMAP7, WMAP9 and Planck data.