[Show abstract][Hide abstract] ABSTRACT: We present a family of spherically symmetric multihorizon spacetimes with a vacuum dark fluid, associated with a time-dependent and spatially inhomogeneous cosmological term. The vacuum dark fluid is defined in a model-independent way by the symmetry of its stress–energy tensor, i.e. its invariance under Lorentz boosts in a distinguished spatial direction (pr = −ρ for the spherically symmetric fluid), which makes dark fluid essentially anisotropic and allows its density to evolve. The related cosmological models belong to the Lemaître class of models with anisotropic fluids and describe evolution of a universe with several scales of vacuum energy related to phase transitions during its evolution. The typical behavior of solutions and the number of spacetime horizons are determined by the number of vacuum scales. We study in detail the model with three vacuum scales: GUT, QCD and that responsible for the present accelerated expansion. The model parameters are fixed by the observational data and by conditions of analyticity and causality. We find that our Universe has three horizons. During the first inflation, the Universe enters a T-region, which makes expansion irreversible. After second phase transition at the QCD scale, the Universe enters R-region, where for a long time its geometry remains almost pseudo-Euclidean. After crossing the third horizon related to the present vacuum density, the Universe should have to enter the next T-region with the inevitable expansion.
Classical and Quantum Gravity 05/2012; 29(9). · 3.10 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We outline the properties and possible observational signatures of gravitational vacuum solitons (G-lumps) which are spherically
symmetric, globally neutral, gravitationally bound compact vacuum objects without horizons, asymptotically de Sitter at the
center. Their existence is implied by the Einstein equations. Their masses are restricted by m < m
crit, where m
crit = αmp1 √ϱ0/ϱp1 with a coefficient α depending on the model. G-lumps can be considered as dark matter candidates which are generically related to vacuum dark
energy through the de Sitter vacuum trapped inside.
Gravitation and Cosmology 01/2011; 17(1):38-41. · 0.49 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: A unified description of dark ingredients is realized by a vacuum dark fluid defined by symmetry of its stress-energy tensor
and allowed by General Relativity. The symmetry is reduced compared with the maximally symmetric de Sitter vacuum, which makes
vacuum dark fluid essentially anisotropic and allows its density and pressure to evolve. It represents distributed vacuum
dark energy by a time-evolving and spatially inhomogeneous cosmological term, and vacuum dark matter by gravitational vacuum
solitons which are regular gravitationally bound structures without horizons (dark particles or dark stars), with the de Sitter
) in de Sitter space (λδ
Keywordsvacuum dark energy–dark matter
Central European Journal of Physics 06/2010; 9(3):644-653. · 1.08 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We address the question of unified description of dark ingredients in the Universe by a vacuum dark fluid with continuous density and pressures, which represents both distributed vacuum dark energy by a time evolving and spatially inhomogeneous cosmological term, and compact self-gravitating objects with de Sitter vacuum trapped inside. The existence of spherically symmetric globally neutral gravitationally bound vacuum objects without horizons (called G-lumps) asymptotically de Sitter at the center, is implied by the Einstein equations. Their masses are restricted by m<mcrit where with a coefficient α depending on the model. We introduce vacuum dark fluid and present the criterion of stability of G-lumps to external polar perturbations.
[Show abstract][Hide abstract] ABSTRACT: This is the first of series of papers in which we investigate stability of the spherically symmetric spacetime with de Sitter centre. Geometry, asymptotically Schwarzschild for large r and asymptotically de Sitter as r → 0, describes a vacuum non-singular black hole for m ≥ mcr and particle-like self-gravitating structure for m < mcr where a critical value mcr depends on the scale of the symmetry restoration to the de Sitter group in the origin. In this paper, we address the question of stability of a vacuum non-singular black hole with de Sitter centre to external perturbations. We specify first two types of geometries with and without changes of topology. Then we derive the general equations governing polar perturbations, specify criteria of stability for a regular black hole with de Sitter centre, and study in detail the case of the density profile where ρ0 is the density of de Sitter vacuum at the centre, is the de Sitter radius and rg is the Schwarzschild radius.
Classical and Quantum Gravity 05/2005; 22(12):2331. · 3.10 Impact Factor