scholarly journals Classification of Einstein equations with cosmological constant in warped product space-time

2018 ◽  
Vol 15 (03) ◽  
pp. 1850041 ◽  
Author(s):  
F. Gholami ◽  
A. Haji-Badali ◽  
F. Darabi
Keyword(s):  
Cosmological Constant ◽  
Product Space ◽  
Warped Product ◽  
Space Time ◽  
Einstein Equations ◽  
Twisted Product ◽  
Product Structures ◽  
Static Space

We classify all warped product space-times in three categories as (i) generalized twisted product structures, (ii) base conformal warped product structures and (iii) generalized static space-times and then we obtain the Einstein equations with the corresponding cosmological constant by which we can determine uniquely the warp functions in these warped product space-times.

scholarly journals The W2-curvature tensor on warped product manifolds and applications

2016 ◽  
Vol 13 (07) ◽  
pp. 1650099 ◽  
Author(s):  
Sameh Shenawy ◽  
Bülent Ünal
Keyword(s):  
Curvature Tensor ◽  
Product Space ◽  
Warped Product ◽  
Space Time ◽  
Product Manifold ◽  
Warped Product Manifold ◽  
Static Space

The purpose of this paper is to study the [Formula: see text]-curvature tensor on (singly) warped product manifolds as well as on generalized Robertson–Walker and standard static space-times. Some different expressions of the [Formula: see text]-curvature tensor on a warped product manifold in terms of its relation with [Formula: see text]-curvature tensor on the base and fiber manifolds are obtained. Furthermore, we investigate [Formula: see text]-curvature flat warped product manifolds. Many interesting results describing the geometry of the base and fiber manifolds of a [Formula: see text]-curvature flat warped product manifold are derived. Finally, we study the [Formula: see text]-curvature tensor on generalized Robertson–Walker and standard static space-times; we explore the geometry of the fiber of these warped product space-time models that are [Formula: see text]-curvature flat.

scholarly journals Cosmological model favored by the holographic principle

2016 ◽  
Vol 41 ◽  
pp. 1660127
Author(s):  
Irina Dymnikova ◽  
Anna Dobosz ◽  
Bożena Sołtysek
Keyword(s):  
Cosmological Model ◽  
Cosmological Constant ◽  
Space Time ◽  
Holographic Principle ◽  
Einstein Equations ◽  
Energy Tensor ◽  
De Sitter ◽  
Quantum Evaporation ◽  
Stress Energy ◽  
De Sitter Vacua

We present a regular spherically symmetric cosmological model of the Lemaitre class distinguished by the holographic principle as the thermodynamically stable end-point of quantum evaporation of the cosmological horizon. A source term in the Einstein equations connects smoothly two de Sitter vacua with different values of cosmological constant and corresponds to anisotropic vacuum dark fluid defined by symmetry of its stress-energy tensor which is invariant under the radial boosts. Global structure of space-time is the same as for the de Sitter space-time. Cosmological evolution goes from a big initial value of the cosmological constant towards its presently observed value.

scholarly journals Space-Time Second-Quantization Effects and the Quantum Origin of Cosmological Constant in Covariant Quantum Gravity

Symmetry ◽  
2018 ◽  
Vol 10 (7) ◽  
pp. 287 ◽  
Author(s):  
Claudio Cremaschini ◽  
Massimo Tessarotto
Keyword(s):  
Gravitational Field ◽  
Quantum Gravity ◽  
Cosmological Constant ◽  
Proper Time ◽  
Theoretical Background ◽  
Space Time ◽  
Einstein Equations ◽  
Field Equations ◽  
Metric Tensor ◽  
Covariant Quantum

Space-time quantum contributions to the classical Einstein equations of General Relativity are determined. The theoretical background is provided by the non-perturbative theory of manifestly-covariant quantum gravity and the trajectory-based representation of the related quantum wave equation in terms of the Generalized Lagrangian path formalism. To reach the target an extended functional setting is introduced, permitting the treatment of a non-stationary background metric tensor allowed to depend on both space-time coordinates and a suitably-defined invariant proper-time parameter. Based on the Hamiltonian representation of the corresponding quantum hydrodynamic equations occurring in such a context, the quantum-modified Einstein field equations are obtained. As an application, the quantum origin of the cosmological constant is investigated. This is shown to be ascribed to the non-linear Bohm quantum interaction of the gravitational field with itself in vacuum and to depend generally also on the realization of the quantum probability density for the quantum gravitational field tensor. The emerging physical picture predicts a generally non-stationary quantum cosmological constant which originates from fluctuations (i.e., gradients) of vacuum quantum gravitational energy density and is consistent with the existence of quantum massive gravitons.

scholarly journals Multiply-warped product metrics and reduction of Einstein equations

2017 ◽  
Vol 14 (02) ◽  
pp. 1750021 ◽  
Author(s):  
Fateme Gholami ◽  
Farhad Darabi ◽  
Ali Haji-Badali
Keyword(s):  
Cosmological Constant ◽  
Warped Product ◽  
Einstein Equations ◽  
Product Form ◽  
Product Metrics ◽  
Cosmological Constants

It is shown that for every multidimensional metric in the multiply-warped product form [Formula: see text] with warp functions [Formula: see text], [Formula: see text], associated to the submanifolds [Formula: see text], [Formula: see text] of dimensions [Formula: see text], [Formula: see text] respectively, one can find the corresponding Einstein equations [Formula: see text], with cosmological constant [Formula: see text], which are reducible to the Einstein equations [Formula: see text] and [Formula: see text] on the submanifolds [Formula: see text], [Formula: see text], with cosmological constants [Formula: see text] and [Formula: see text], respectively, where [Formula: see text], [Formula: see text] and [Formula: see text] are functions of [Formula: see text], [Formula: see text] and [Formula: see text], [Formula: see text].

Compact Einstein multiply warped product space with nonpositive scalar curvature

2019 ◽  
Vol 16 (10) ◽  
pp. 1950162 ◽  
Author(s):  
Buddhadev Pal ◽  
Pankaj Kumar
Keyword(s):  
Riemannian Manifold ◽  
Scalar Curvature ◽  
Product Space ◽  
Warped Product ◽  
Space Time ◽  
Product Spaces ◽  
Warped Product Spaces ◽  
Friedmann Robertson Walker

In this paper, we characterize the Einstein multiply warped product space with nonpositive scalar curvature. As a result, it is shown that, if [Formula: see text] is Einstein multiple-warped product spaces with compact base and nonpositive scalar curvature, then [Formula: see text] is simply a Riemannian manifold. Next, we apply our result on Generalized Robertson–Walker space-time and Generalized Friedmann–Robertson–Walker space-time.

scholarly journals CPTM Discrete Symmetry, Quantum Wormholes and Cosmological Constant Problem

Universe ◽  
2020 ◽  
Vol 6 (8) ◽  
pp. 121
Author(s):  
Sergey Bondarenko
Keyword(s):  
Cosmological Constant ◽  
Discrete Symmetry ◽  
Space Time ◽  
Einstein Equations ◽  
Vacuum Energy Density ◽  
Extended Space ◽  
Classical Geometry ◽  
Proposed Model ◽  
Charge Parity ◽  
Non Local

We discuss the consequences of the charge, parity, time, and mass (CPTM) extended reversal symmetry for the problems of the vacuum energy density and value of the cosmological constant. The results obtained are based on the framework with the separation of extended space-time of the interest on the different regions connected by this symmetry with the action of the theory valid for the full space-time and symmetrical with respect to the extended CPTM transformations. The cosmological constant is arising in the model due the gravitational interactions between the different parts of the space-time trough the quantum non-local vertices. It is proposed that the constant’s value depends on the form and geometry of the vertices that glue the separated parts of the extended solution of Einstein equations determining, in turn, its classical geometry. The similarity of the proposed model to the bimetric theories of gravitation is also discussed.

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