Einstein–Cartan and general relativity cosmologies with a nonminimally coupled ghost scalar field

2012 ◽  
Vol 45 (2) ◽  
pp. 275-303 ◽  
Author(s):  
A. M. Galiakhmetov
Keyword(s):  
General Relativity ◽  
Scalar Field ◽  
Ghost Scalar Field

SPATIALLY FLAT FRW MODELS WITH A NONMINIMALLY COUPLED GHOST SCALAR FIELD AND PERFECT FLUID IN EINSTEIN–CARTAN THEORY

2012 ◽  
Vol 21 (01) ◽  
pp. 1250001 ◽  
Author(s):  
A. M. GALIAKHMETOV
Keyword(s):  
General Relativity ◽  
Scalar Field ◽  
Perfect Fluid ◽  
Analogous Problem ◽  
General Solutions ◽  
Cartan Theory ◽  
Frw Models ◽  
Ghost Scalar Field

Exact general solutions to the Einstein–Cartan equations are obtained for spatially flat Friedmann cosmologies with a nonminimally coupled ghost scalar field and perfect fluid. It is shown that both singular and bouncing models are possible. An analogous problem is investigated in general relativity. Some effects of torsion are elucidated. The role of perfect fluid in the Einstein–Cartan cosmology is discussed.

scholarly journals WEYL GEOMETRY AS CHARACTERIZATION OF SPACE-TIME

2011 ◽  
Vol 03 ◽  
pp. 87-97 ◽  
Author(s):  
F. P. POULIS ◽  
J. M. SALIM
Keyword(s):  
General Relativity ◽  
Scalar Field ◽  
Riemannian Geometry ◽  
Axiomatic Approach ◽  
Space Time ◽  
Weyl Geometry ◽  
Test Particles ◽  
Variational Formalism ◽  
Physical Fields

Motivated by an axiomatic approach to characterize space-time it is investigated a reformulation of Einstein's gravity where the pseudo-riemannian geometry is substituted by a Weyl one. It is presented the main properties of the Weyl geometry and it is shown that it gives extra contributions to the trajectories of test particles, serving as one more motivation to study general relativity in Weyl geometry. It is introduced its variational formalism and it is established the coupling with other physical fields in such a way that the theory acquires a gauge symmetry for the geometrical fields. It is shown that this symmetry is still present for the red-shift and it is concluded that for cosmological models it opens the possibility that observations can be fully described by the new geometrical scalar field. It is concluded then that this reformulation, although representing a theoretical advance, still needs a complete description of their objects.

Brans–Dicke type teleparallel scalar–tensor theory

2017 ◽  
Vol 32 (34) ◽  
pp. 1750183 ◽  
Author(s):  
Mustafa Salti ◽  
Oktay Aydogdu ◽  
Hilmi Yanar ◽  
Figen Binbay
Keyword(s):  
General Relativity ◽  
Dark Energy ◽  
Scalar Field ◽  
Noether Symmetry ◽  
Scalar Tensor Theory ◽  
Minimal Coupling ◽  
Energy Effect ◽  
New Model ◽  
Symmetry Approach ◽  
Tensor Theory

The teleparallel alternative of general relativity which is based on torsion instead of curvature is considered as the gravitational sector to explore the dark universe. Inspired from the well-known Brans–Dicke gravity, here, we introduce a new proposal for the galactic dark energy effect. The new model includes a scalar field with self-interacting potential and a non-minimal coupling between the gravity and scalar field. Additionally, we analyze the idea via the Noether symmetry approach and thermodynamics.

scholarly journals QCD MODIFIED GHOST SCALAR FIELD DARK ENERGY MODELS

2013 ◽  
Vol 22 (05) ◽  
pp. 1350018 ◽  
Author(s):  
K. KARAMI ◽  
S. ASADZADEH ◽  
M. MOUSIVAND ◽  
Z. SAFARI
Keyword(s):  
Dark Energy ◽  
Scalar Field ◽  
Linear Perturbation ◽  
Density Parameter ◽  
Frw Cosmology ◽  
Frw Universe ◽  
Ghost Dark Energy ◽  
Energy Models ◽  
Scalar Field Models ◽  
Ghost Scalar Field

Within the framework of FRW cosmology, we study the QCD modified ghost scalar field models of dark energy (DE) in the presence of both interaction and viscosity. For a spatially nonflat FRW universe containing modified ghost dark energy (MGDE) and dark matter (DM), we obtain the equation of state of MGDE, the deceleration parameter as well as a differential equation governing the MGDE density parameter. We also investigate the growth of structure formation for our model in a linear perturbation regime. Furthermore, we reconstruct both the dynamics and potentials of the quintessence, tachyon, K-essence and dilaton scalar field DE models according to the evolution of the MGDE density.

Evolution of the Universe with two rotating fluids

2020 ◽  
Vol 35 (02n03) ◽  
pp. 2040042
Author(s):  
V. F. Panov ◽  
O. V. Sandakova ◽  
E. V. Kuvshinova ◽  
D. M. Yanishevsky
Keyword(s):  
General Relativity ◽  
Dark Energy ◽  
Scalar Field ◽  
Bianchi Type ◽  
Relativity Theory ◽  
Anisotropic Fluid ◽  
Rotating Fluids ◽  
General Relativity Theory ◽  
Exponential Expansion ◽  
The Universe

An anisotropic cosmological model with expansion and rotation and the Bianchi type IX metric has been constructed within the framework of general relativity theory. The first inflation stage of the Universe filled with a scalar field and an anisotropic fluid is considered. The model describes the Friedman stage of cosmological evolution with subsequent transition to accelerated exponential expansion observed in the present epoch. The model has two rotating fluids: the anisotropic fluid and dust-like fluid. In the approach realized in the model, the anisotropic fluid describes the rotating dark energy.

scholarly journals Cosmological bounce in Horndeski theory and beyond

2018 ◽  
Vol 191 ◽  
pp. 07013 ◽  
Author(s):  
R. Kolevatov ◽  
S. Mironov ◽  
V. Rubakov ◽  
N. Sukhov ◽  
V. Volkova
Keyword(s):  
General Relativity ◽  
Scalar Field ◽  
Massless Scalar ◽  
Massless Scalar Field ◽  
Cosmological Solutions ◽  
The Stability ◽  
The Way

We discuss the stability of the classical bouncing solutions in the general Horndeski theory and beyond Horndeski theory. We restate the no-go theorem, showing that in the general Horndeski theory there are no spatially flat non-singular cosmological solutions which are stable during entire evolution. We show the way to evade the no-go in beyond Horndeski theory and give two specific examples of bouncing solutions, whose asymptotic past and future or both are described by General Relativity (GR) with a conventional massless scalar field. Both solutions are free of any pathologies at all times.

Disappearance of Black Hole Criticality in Semiclassical General Relativity

1997 ◽  
Vol 12 (10) ◽  
pp. 709-718 ◽  
Author(s):  
Takeshi Chiba ◽  
Masaru Siino
Keyword(s):  
General Relativity ◽  
Black Hole ◽  
Scalar Field ◽  
Critical Phenomena ◽  
Equations Of Motion ◽  
Quantum Effects ◽  
Hole Formation ◽  
Trace Anomaly ◽  
Self Similar ◽  
Similar Solutions

We investigate the quantum effects on the so-called critical phenomena in black hole formation. Quantum effects of a scalar field are treated semiclassically via a trace anomaly method. It is found that the demand of regularity at the origin implies the disappearance of the echo. It is also found that semiclassical equations of motion do not admit continuously self-similar solutions. The quantum effects would change the critical solution from a discretely self-similar one to a solution without critical phenomena.

scholarly journals Reconstructing f(R) gravity from a Chaplygin scalar field in de Sitter spacetimes

2018 ◽  
Vol 15 (02) ◽  
pp. 1850027 ◽  
Author(s):  
Heba Sami ◽  
Neo Namane ◽  
Joseph Ntahompagaze ◽  
Maye Elmardi ◽  
Amare Abebe
Keyword(s):  
General Relativity ◽  
Scalar Field ◽  
Field Model ◽  
Exact Formula ◽  
Chaplygin Gas ◽  
Reconstruction Technique ◽  
Field Potentials ◽  
De Sitter ◽  
Cosmological Expansion ◽  
Lagrangian Densities

We present a reconstruction technique for models of [Formula: see text] gravity from the Chaplygin scalar field in flat de Sitter spacetimes. Exploiting the equivalence between [Formula: see text] gravity and scalar–tensor (ST) theories, and treating the Chaplygin gas (CG) as a scalar field model in a universe without conventional matter forms, the Lagrangian densities for the [Formula: see text] action are derived. Exact [Formula: see text] models and corresponding scalar field potentials are obtained for asymptotically de Sitter spacetimes in early and late cosmological expansion histories. It is shown that the reconstructed [Formula: see text] models all have General Relativity (GR) as a limiting solution.

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