Nonsingular solutions in multidimensional cosmology with a perfect fluid: acceleration and variation of G (original) (raw)

Multidimensional cosmology with anisotropic fluid: acceleration and variation of G

Gravitation and Cosmology

A multidimensional cosmological model describing the dynamics of n+1 Ricci-flat factor-spaces M_i in the presence of a one-component anisotropic fluid is considered. The pressures in all spaces are proportional to the density: p_i = w_i \rho, i = 0,...,n. Solutions with accelerated expansion of our 3-space M_0 and small enough variation of the gravitational constant G are found. These solutions exist for two branches of the parameter w_0. The first branch describes superstiff matter with w_0 > 1, the second one may contain phantom matter with w_0 < - 1, e.g., when G grows with time.

A multicomponent perfect fluid with variable parameters in n ricci-flat spaces

Journal of the Korean Physical Society, 2004

D-dimensional cosmological model describing the evolution of a multicomponent perfect fluid with variable barotropic parameters in n Ricci-flat spaces is investigated. The equations of motion are integrated for the case, when each component possesses an isotropic pressure with respect to all spaces. Exact solutions are presented in the Kasner-like form. Some explicit examples are given: 4-dimensional model with an isotropic accelerated expansion at late times and (4+d)-dimensional model describing a compactification of extra dimensions.

Multicomponent perfect fluid with variable parameters in n Ricci-flat spaces

2004

Multidimensional Cosmology with mmm-Component Perfect Fluid

Int J Mod Phys D, 1994

A cosmological model describing the evolution of n Einstein spaces (n>1) with m- component perfect-fluid matter is considered. When all spaces are Ricci-flat and for any α-th component the pressures in all spaces are proportional to the density: pi(α ) = (1- hi(α ))ρ (α ), hi(α ) = const., the Einstein and Wheeler-DeWitt equations are integrated in the cases: (i) m=1, for all hi(α ); (ii) m>1, for some special sets of hi(α ). For m=1 the quantum wormhole solutions are also obtained.

Integrable multicomponent perfect fluid multidimensional cosmology. I

General Relativity and Gravitation, 1996

We consider anisotropic cosmological models with an universe of dimension 4 or more, factorized into n ≥ 2 Ricci-flat spaces, containing an m-component perfect fluid of m noninteracting homogeneous minimally coupled scalar fields under special conditions. We describe the dynamics of the universe: It has a Kasner-like behaviour near the singularity and isotropizes during the expansion to infinity.

Multidimensional Classical and Quantum Cosmology with Perfect Fluid

Gravitation and Cosmology, 1995

A cosmological model describing the evolution of n Ricci-flat spaces (n>1) in the presence of 1-component perfect-fluid and minimally coupled scalar field is considered. When the pressures in all spaces are proportional to the density, the Einstein and Wheeler-DeWitt equations are integrated for a large variety of parameters. Classical and quantum wormhole solutions are obtained for negative density. Some special classes of solutions, e.g. solutions with spontaneous and dynamical compactification, exponential and power-law inflations, are singled out. For positive density a third quantized cosmological model is considered and the Planckian spectrum of ``created universes'' is obtained.

Exact solutions in multi-dimensional cosmology with shear and bulk viscosity

Classical and Quantum Gravity, 1997

Multidimensional cosmological model describing the evolution of a fluid with shear and bulk viscosity in n Ricci-flat spaces is investigated. The barotropic equation of state for the density and the pressure in each space is assumed. The second equation of state is chosen in the form when the bulk and the shear viscosity coefficients are inversely proportional to the volume of the Universe. The integrability of Einstein equations reads as a colinearity constraint between vectors which are related to constant parameters in the first and second equations of state. We give exact solutions in a Kasner-like form. The processes of dynamical compactification and the entropy production are discussed. The non-singular D-dimensional isotropic viscous solution is singled out.

Exact Solutions in Multidimensional Gravity and Cosmology III

Multidimensional gravitational models containing certain combinations of scalar fields, an-tisymmetric forms and multicomponent perfect fluid are considered. The manifold has the form M = M 0 × M 1 ×. .. × M n , where M i are Einstein (e.g. Ricci-flat) spaces (i ≥ 1). The exact solutions in the model are reviewed (e.g. cosmological, spherically-symmetric, black holes and branes etc) and billiard representation near the singular point is considered. The consideration is based on the sigma-model approach. Observational windows of p-branes and extra dimensions are discussed.

Perfect and viscous fluid cosmological models in presence of scalar fields for anisotropic metric

Astrophysics and Space Science, 1995

An exact solution of Einstein equations representing a perfect fluid model in the presence of a zero-mass scalar field is obtained for an anisotropic metric. The effect of dissipative processes on the model is also discussed. Different physically valid forms of the scale factors in the three spatial directions give rise to some distinct models. The physical behaviour of these models is discussed in detail. Some of the perfect fluid models exhibit the 'cigar' singularity.

Isotropic Cosmological Singularities: I. Polytropic Perfect Fluid Spacetimes

Annals of Physics, 1999

We consider the conformal Einstein equations for 1 ≤ γ ≤ 2 polytropic perfect fluid cosmologies which admit an isotropic singularity. For 1 < γ ≤ 2 it is shown that the Cauchy problem for these equations is well-posed, that is to say that solutions exist, are unique and depend smoothly on the data, with data consisting of simply the 3-metric of the singularity. The analogous result for γ = 1 (dust) is obtained when Bianchi type symmetry is assumed.

Nonsingular solutions in multidimensional cosmology with a perfect fluid: acceleration and variation of G (original) (raw)

Related papers