scholarly journals Spherical "Top-Hat" collapse in a modified Chaplygin gas dominated universe

2015 ◽  
Vol 24 (07) ◽  
pp. 1550050 ◽  
Author(s):  
S. Karbasi ◽  
H. Razmi
Keyword(s):  
Equation Of State ◽  
Structure Formation ◽  
Observational Data ◽  
Chaplygin Gas ◽  
Modified Chaplygin Gas ◽  
Time Rate ◽  
Generalized Chaplygin Gas ◽  
The Stability ◽  
Perturbation Growth ◽  
Good Agreement

Considering perturbation growth in spherical Top-Hat (STH) model of structure formation in a generalized Chaplygin gas (GCG) dominated universe, we want to study this scenario with modified Chaplygin gas (MCG) obeying an equation of state p = A - B/ρα model. Different parameters of this scenario for positive and negative values of A are computed. The evolution of background and collapsed region parameters are found for different cases. The stability of the model and the collapse time rate are considered in different cases. The turn-around redshifts for different values of α are computed; the results are in relatively good agreement with current observational data.

STABILITY ANALYSIS OF THIN SHELL WORMHOLES SUPPORTED BY THE MODIFIED CHAPLYGIN GAS

2009 ◽  
Vol 18 (13) ◽  
pp. 1977-1990 ◽  
Author(s):  
TANWI BANDYOPADHYAY ◽  
ANUSUA BAVEJA ◽  
SUBENOY CHAKRABORTY
Keyword(s):  
Stability Analysis ◽  
Equation Of State ◽  
Thin Shell ◽  
Chaplygin Gas ◽  
Modified Chaplygin Gas ◽  
De Sitter ◽  
Static Solutions ◽  
Thin Shell Wormholes ◽  
Stable Solutions ◽  
The Stability

In this work, the stability of static solutions of spherical thin shell wormholes is analyzed when a slight perturbation (which preserves the basic symmetry) is applied to them. The modified Chaplygin gas (with α = 1 in the equation of state) has been chosen as a candidate for exotic matter needed around the throat. Different cases for such thin shell wormhole construction have been studied, viz. wormholes constructed from Schwarzschild, Schwarzschild–de Sitter, Schwarzschild–anti-de Sitter and Reissner–Nordström metrics. Depending upon the values of the parameters and some restrictions obeyed by them, static stable solutions are seen to exist in some cases.

scholarly journals Dynamical system analysis of FLRW models with Modified Chaplygin gas

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Ali Osman Yılmaz ◽  
Ertan Güdekli
Keyword(s):  
Dynamical System ◽  
Equation Of State ◽  
Energy Density ◽  
System Analysis ◽  
Chaplygin Gas ◽  
Modified Chaplygin Gas ◽  
State Spaces ◽  
The Universe ◽  
Matter Energy ◽  
Far Future

AbstractWe investigate Friedmann–Lamaitre–Robertson–Walker (FLRW) models with modified Chaplygin gas and cosmological constant, using dynamical system methods. We assume $$p=(\gamma -1)\mu -\dfrac{A}{\mu ^\alpha }$$ p = ( γ - 1 ) μ - A μ α as equation of state where $$\mu$$ μ is the matter-energy density, p is the pressure, $$\alpha$$ α is a parameter which can take on values $$0<\alpha \le 1$$ 0 < α ≤ 1 as well as A and $$\gamma$$ γ are positive constants. We draw the state spaces and analyze the nature of the singularity at the beginning, as well as the fate of the universe in the far future. In particular, we address the question whether there is a solution which is stable for all the cases.

scholarly journals An Attempt for an Emergent Scenario with Modified Chaplygin Gas

2016 ◽  
Vol 2016 ◽  
pp. 1-5 ◽  
Author(s):  
Sourav Dutta ◽  
Sudeshna Mukerji ◽  
Subenoy Chakraborty
Keyword(s):  
Equation Of State ◽  
Chaplygin Gas ◽  
Space Time ◽  
Modified Chaplygin Gas ◽  
Emergent Universe ◽  
Emergent Scenario ◽  
The Universe

The present work is an attempt for emergent universe scenario with modified Chaplygin gas. The universe is chosen as spatially flat FRW space-time with modified Chaplygin gas as the only cosmic substratum. It is found that emergent scenario is possible for some specific (unrealistic) choice of the parameters in the equation of state for modified Chaplygin gas.

VISCOUS GENERALIZED CHAPLYGIN GAS

2006 ◽  
Vol 15 (08) ◽  
pp. 1151-1161 ◽  
Author(s):  
XIANG-HUA ZHAI ◽  
YOU-DONG XU ◽  
XIN-ZHOU LI
Keyword(s):  
Equation Of State ◽  
Bulk Viscosity ◽  
Critical Energy ◽  
State Equation ◽  
Chaplygin Gas ◽  
Point Of View ◽  
Dynamical Analysis ◽  
Density Parameter ◽  
Generalized Chaplygin Gas ◽  
Barotropic Fluid

Viscous generalized Chaplygin gas (GCG) cosmology is discussed, assuming that there is bulk viscosity in the linear barotropic fluid and GCG. wγ = γ - 1 and wg represent the state equation parameters for barotropic fluid and GCG, respectively, in which γ = 1 or [Formula: see text] corresponds to ordinary matter or radiation. The dynamical analysis indicates that the phase [Formula: see text] is a dynamical attractor and the equation of state of GCG approaches it from either wg > -1 or wg < -1 depending on the choice of its initial cosmic density parameter and the ratio of pressure to critical energy density, where τg and τγ are viscosity parameters. Therefore, the equation of state wg will cross the boundary wg = -1 if we choose initial value wg < -1. Furthermore, we show that bulk viscosity coefficients should satisfy inequalities from the point of view of dynamics.

scholarly journals GEOMETRICAL DIAGNOSTIC FOR THE GENERALIZED CHAPLYGIN GAS MODEL

2009 ◽  
Vol 18 (11) ◽  
pp. 1741-1748 ◽  
Author(s):  
JIANBO LU ◽  
LIXIN XU
Keyword(s):  
Dark Matter ◽  
Dark Energy ◽  
Equation Of State ◽  
Diagnostic Method ◽  
Chaplygin Gas ◽  
Shift Parameter ◽  
Generalized Chaplygin Gas ◽  
Λcdm Model ◽  
Current Equation

A new diagnostic method, Om, is applied to the generalized Chaplygin gas (GCG) model as the unification of dark matter and dark energy. On the basis of the recently observed data — the Union supernovae, the observational Hubble data, the SDSS baryon acoustic peak and the five-year WMAP shift parameter — we show the discriminations between the GCG model and the ΛCDM model. Furthermore, it is calculated that the current equation of state of dark energy w 0de = -0.964, according to the GCG model.

scholarly journals Scalar models for the generalized Chaplygin gas and the structure formation constraints

2011 ◽  
Vol 17 (3) ◽  
pp. 259-271 ◽  
Author(s):  
Júlio C. Fabris ◽  
Thaisa C. da C. Guio ◽  
Mahamadou Hamani Daouda ◽  
Oliver F. Piattella
Keyword(s):  
Structure Formation ◽  
Chaplygin Gas ◽  
Generalized Chaplygin Gas

scholarly journals RASTALL COSMOLOGY

2012 ◽  
Vol 18 ◽  
pp. 67-76 ◽  
Author(s):  
JÚLIO C. FABRIS ◽  
OLIVER F. PIATTELLA ◽  
DAVI C. RODRIGUES ◽  
CARLOS E. M. BATISTA ◽  
MAHAMADOU H. DAOUDA
Keyword(s):  
Scalar Field ◽  
Observational Data ◽  
Canonical Form ◽  
Conservation Law ◽  
Chaplygin Gas ◽  
Cosmological Models ◽  
The Self ◽  
Generalized Chaplygin Gas ◽  
Field Representation ◽  
Theory Of Gravity

We review the difficulties of the generalized Chaplygin gas model to fit observational data, due to the tension between background and perturbative tests. We argue that such issues may be circumvented by means of a self-interacting scalar field representation of the model. However, this proposal seems to be successful only if the self-interacting scalar field has a non-canonical form. The latter can be implemented in Rastall's theory of gravity, which is based on a modification of the usual matter conservation law. We show that, besides its application to the generalized Chaplygin gas model, other cosmological models based on Rastall's theory have many interesting and unexpected new features.

Stability of a charged rotating BTZ thin shell with a different variable equation of state

2021 ◽  
pp. 2150086
Author(s):  
A. Eid
Keyword(s):  
Black Holes ◽  
Equation Of State ◽  
Thin Shell ◽  
Mechanical Stability ◽  
Chaplygin Gas ◽  
Throat Radius ◽  
Generalized Chaplygin Gas ◽  
Radial Perturbation ◽  
Btz Black Holes ◽  
Variable Equation

Dynamics of charged rotating BTZ black holes in 2 + 1 dimensions by using the cut and paste approach is discussed. Due to the mechanical stability of rotating charged BTZ thin shell, the radial perturbation about the equilibrium throat radius and three variable equation of state (EoS) is analyzed. Several examples are displayed satisfying it, such as variable Phantom-like, variable Chaplygin gas and variable modified generalized Chaplygin gas.

scholarly journals FRW TYPE OF COSMOLOGY WITH A CHAPLYGIN GAS

2012 ◽  
Vol 21 (10) ◽  
pp. 1250079 ◽  
Author(s):  
D. PANIGRAHI ◽  
S. CHATTERJEE
Keyword(s):  
Cosmological Constant ◽  
Structure Formation ◽  
Chaplygin Gas ◽  
Matter Field ◽  
Raychaudhuri Equation ◽  
Velocity Of Sound ◽  
Generalized Chaplygin Gas ◽  
Ordinary Matter

The evolution of a universe modeled as a mixture of generalized Chaplygin gas (GCG) and ordinary matter field is studied for a Robertson–Walker type of spacetime. This model could interpolate periods of radiation-dominated, matter-dominated and cosmological constant-dominated universes. Depending on the arbitrary constants appearing in our theory, the instant of flip changes. Interestingly, we also get a bouncing model when the signature of one of the constants changes. The velocity of sound may become imaginary under certain situations pointing to a perturbative state and consequently the possibility of structure formation. We also discuss the whole situation in the backdrop of the well-known Raychaudhuri equation and a comparison is made with the previous results.

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