scholarly journals Dynamics of classes of barotropic fluids in spatially curved FRW spacetimes

2020 ◽  
Vol 101 (4) ◽  
Author(s):  
Morteza Kerachian ◽  
Giovanni Acquaviva ◽  
Georgios Lukes-Gerakopoulos
Keyword(s):  
Barotropic Fluids

scholarly journals Applying He's variational iteration method to FRW cosmology

2019 ◽  
Vol 7 (2) ◽  
pp. 39
Author(s):  
V. K.Shchigolev
Keyword(s):  
Iteration Method ◽  
System Analysis ◽  
Variational Iteration Method ◽  
Cosmological Models ◽  
Frw Cosmology ◽  
Variational Iteration ◽  
Barotropic Fluids ◽  
He’S Variational Iteration Method ◽  
High Degree ◽  
The Universe

This work is devoted to the investigation of Friedmann-Robertson-Walker (FRW) cosmological models with the help of the so-called Variational Iteration Method (VIM). For this end, we briefly recall the main equations of the cosmological models and the basic idea of VIM. In order to approbate the VIM in FRW cosmology and demonstrate the main steps in solving by this method, we consider the test example of the universe with dust for which the exact solution of the model is known. Then, a solution for the spatially flat FRW model of the universe filled with the dust and quintessence is obtained when the exact analytic solution cannot be found. A comparison of our solution with the corresponding numerical solution shows that it is of a high degree of accuracy. Moreover, the Dynamical System Analysis to the dynamics of the homogeneous and isotropic FRW universes is used as a special case of generalized Lotka–Volterra system where the competitive species are the barotropic fluids filling the Universe. With the help of VIM, we have found the iterative formulae for the density parameters of the cosmological analog of the generalized Lotka–Volterra set of equations. All solutions illustrated graphically by means of Maple software.  

scholarly journals Nonlinear Schrödinger-type formulation of scalar field cosmology: Two barotropic fluids and exact solutions

2020 ◽  
Vol 35 (19) ◽  
pp. 2050157
Author(s):  
Chonticha Kritpetch ◽  
Jarunee Sanongkhun ◽  
Pichet Vanichchapongjaroen ◽  
Burin Gumjudpai
Keyword(s):  
Scalar Field ◽  
Exact Solutions ◽  
Time Dependent ◽  
Frw Cosmology ◽  
Dependent Case ◽  
Nonlinear Schrödinger ◽  
Barotropic Fluids ◽  
Scalar Field Cosmology ◽  
Formulation Variables ◽  
Canonical Scalar Field

Time-independent nonlinear Schrödinger-type (NLS) formulation of FRW cosmology with canonical scalar field is considered in the case of two barotropic fluids. We derived Friedmann formulation variables in terms of NLS variables. Seven exact solutions found by D’Ambroise [Ph.D. thesis, arXiv:1005.1410 ] and one new found solution are explored and tested in cosmology. The result suggests that time-independent NLS formulation of cosmology case should be upgraded to the time-dependent case.

scholarly journals Evolution of thin shells in D-dimensional general relativity

2019 ◽  
Vol 28 (04) ◽  
pp. 1950069 ◽  
Author(s):  
Marcos A. Ramirez ◽  
Daniel Aparicio
Keyword(s):  
Energy Condition ◽  
Cosmic Censorship ◽  
Einstein Equations ◽  
Thin Shells ◽  
Dominant Energy Condition ◽  
Spherically Symmetric ◽  
Barotropic Fluids ◽  
Large Shell ◽  
Asymptotic Dynamics ◽  
Electrovacuum Solution

In this paper, we consider singular timelike spherical hypersurfaces embedded in a [Formula: see text]-dimensional spherically symmetric bulk spacetime which is an electrovacuum solution of Einstein equations with cosmological constant. We analyze the different possibilities regarding the orientation of the gradient of the standard [Formula: see text] coordinate in relation to the shell. Then we study the dynamics according to Einstein equations for arbitrary matter satisfying the dominant energy condition. In particular, we thoroughly analyze the asymptotic dynamics for both the small and large-shell-radius limits. We also study the main qualitative aspects of the dynamics of shells made of linear barotropic fluids that satisfy the dominant energy condition. Finally, we prove weak cosmic censorship for this class of solutions.

Some vorticity theorems and conservation laws for non-barotropic fluids

1981 ◽  
Vol 108 ◽  
pp. 475-483 ◽  
Author(s):  
S. D. Mobbs
Keyword(s):  
Thermodynamic Properties ◽  
Conservation Laws ◽  
Potential Vorticity ◽  
Time Dependent ◽  
Dissipative Effects ◽  
Perfect Fluids ◽  
Barotropic Fluids ◽  
Complete Set ◽  
Circulation Theorem

Some theorems concerning the vorticity in barotropic flows of perfect fluids are generalized for non-barotropic flows. The generalization involves replacing the velocity in certain parts of the equations by a time-dependent quantity which is a function of the velocity and thermodynamic properties of the fluid. Results which are generalized include Kelvin's circulation theorem and conservation laws for potential vorticity and helicity. It is shown how the results can be further generalized to include dissipative effects. The possibility of using some of the results in deriving a complete set of Lagrangian conservation laws for perfect fluids is discussed.

scholarly journals Aetherizing Lambda: Barotropic fluids as dark energy

2009 ◽  
Vol 80 (2) ◽  
Author(s):  
Eric V. Linder ◽  
Robert J. Scherrer
Keyword(s):  
Dark Energy ◽  
Barotropic Fluids

ERRATA AND ADDENDA: DARBOUX CLASS OF COSMOLOGICAL FLUIDS WITH TIME-DEPENDENT ADIABATIC INDICES

2001 ◽  
Vol 16 (17) ◽  
pp. 1147-1150 ◽  
Author(s):  
H. C. Rosu
Keyword(s):  
Time Dependent ◽  
Barotropic Fluids ◽  
Supersymmetric Approach

A number of corrections to the work in which I introduced one-parameter Darboux supersymmetric barotropic fluids in cosmology are performed. As addenda, the flat FRW case, which was left apart, is presented in detail in the supersymmetric approach.

Sign in / Sign up

Export Citation Format

Share Document