scholarly journals Viscous dark energy accretion activities : sonic speed, angular momentum and Mach number studies

2021 ◽  
Vol 81 (4) ◽  
Author(s):  
Sandip Dutta ◽  
Promila Biswas ◽  
Ritabrata Biswas
Keyword(s):  
Angular Momentum ◽  
Dark Energy ◽  
Mach Number ◽  
Average Rate ◽  
Radial Distance ◽  
Chaplygin Gas ◽  
Black Hole Accretion ◽  
Feeding Process ◽  
Sonic Speed ◽  
Inner Region

AbstractIn this present article, we study different accretion properties regarding viscous accretion of dark energy. Modified Chaplygin gas is chosen as the dark energy candidate. Viscosity is encountered with the help of Shakura–Sunyaev viscosity parameter. We study sonic speed vs radial distance curves. We compare between adiabatic and dark energy dominated cases and follow that sonic speed falls as we go nearer to the central gravitating object. As viscosity is imposed, a threshold drop in accretion sonic speed is followed. Average rate of fall in accretion sonic speed is increased with black hole’s spin. This is signifying that this kind of accretion is weakening the overall matter/energy infall. Specific angular momentum to Keplerian angular momentum ratio is found to fall as we go far from the black hole. Accretion Mach number turns high as we go towards the inner region and high wind Mach number is not allowed as we are going out. Combining, we conclude that the system weakens the feeding process of accretion.

ACCRETION PROBLEM IN A KERR BLACK HOLE GEOMETRY VIEWED AS FLOWS IN CONVERGING–DIVERGING DUCTS

2010 ◽  
Vol 19 (13) ◽  
pp. 2059-2069
Author(s):  
K. CHAKRABARTI ◽  
M. M. MAJUMDAR ◽  
SANDIP K. CHAKRABARTI
Keyword(s):  
Black Hole ◽  
Angular Momentum ◽  
Mach Number ◽  
Cross Sections ◽  
Kerr Black Hole ◽  
Flat Space ◽  
Accretion Flow ◽  
Black Hole Accretion ◽  
Hole Geometry ◽  
Hole Accretion

Accretion flow on a horizon is supersonic, no matter what the flow angular momentum or the spin of the black hole is. This means that a black hole accretion can always be viewed as a flow in a flat space–time through one or more convergent–divergent ducts. In this paper, we study how the area of cross-sections must vary in order that the flow has the same properties in both systems. We show that the accretion flow experiencing a shock is equivalent to having two ducts connected back-to-back, both with a neck where the flow becomes supersonic. We study the pressure and Mach number variations for corotating, contrarotating flows and flows around a black hole with evolving spin.

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 Nonlinear evolution of dark matter and dark energy in the Chaplygin-gas cosmology

2004 ◽  
Vol 2004 (11) ◽  
pp. 008-008 ◽  
Author(s):  
Neven Bili ◽  
Robert J Lindebaum ◽  
Gary B Tupper ◽  
Raoul D Viollier
Keyword(s):  
Dark Matter ◽  
Dark Energy ◽  
Nonlinear Evolution ◽  
Chaplygin Gas

scholarly journals OBSERVATIONAL CONSTRAINTS ON THE GENERALIZED CHAPLYGIN GAS

2009 ◽  
Vol 18 (13) ◽  
pp. 2007-2022 ◽  
Author(s):  
SERGIO DEL CAMPO ◽  
J. R. VILLANUEVA
Keyword(s):  
Dark Energy ◽  
Cosmological Model ◽  
Chaplygin Gas ◽  
Observational Constraints ◽  
Energy Component ◽  
Generalized Chaplygin Gas ◽  
Astronomical Data ◽  
Astronomical Observations ◽  
Dark Energy Component ◽  
Two Parameters

In this paper we study a quintessence cosmological model in which the dark energy component is considered to be the generalized Chaplygin gas and the curvature of the three-geometry is taken into account. Two parameters characterize this sort of fluid: ν and α. We use different astronomical data for restricting these parameters. It is shown that the constraint ν ≲ α agrees well enough with the astronomical observations.

scholarly journals Unification of dark matter and dark energy: the inhomogeneous Chaplygin gas

2002 ◽  
Vol 535 (1-4) ◽  
pp. 17-21 ◽  
Author(s):  
Neven Bilić ◽  
Gary B Tupper ◽  
Raoul D Viollier
Keyword(s):  
Dark Matter ◽  
Dark Energy ◽  
Chaplygin Gas

scholarly journals DARK MATTER TO DARK ENERGY TRANSITION IN k-ESSENCE COSMOLOGIES

2005 ◽  
Vol 20 (27) ◽  
pp. 2075-2082 ◽  
Author(s):  
L. P. CHIMENTO ◽  
MÓNICA FORTE ◽  
RUTH LAZKOZ
Keyword(s):  
Dark Matter ◽  
Dark Energy ◽  
Kinetic Energy ◽  
Speed Of Sound ◽  
Energy Transition ◽  
Chaplygin Gas ◽  
Large Set ◽  
Generalized Chaplygin Gas ◽  
General Terms ◽  
Transient Models

We implement the transition from dark matter to dark energy in k-essence cosmologies for a very large set of kinetic functions F, in a way alternative to recent proposals which use generalized Chaplygin gas and transient models. Here we require that the pressure admits a power-law expansion around some value of the kinetic energy where the pressure vanishes. In addition, for suitable values of the parameters of the model, the speed of sound of the dark matter will be low. We first present the discussion in fairly general terms, and later consider for illustration two examples.

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