scholarly journals Ghost-free higher-order theories of gravity with torsion

2021 ◽  
Vol 81 (3) ◽  
Author(s):  
Álvaro de la Cruz-Dombriz ◽  
Francisco José Maldonado Torralba ◽  
Anupam Mazumdar
Keyword(s):  
Torsion Tensor ◽  
Theoretical Framework ◽  
Higher Order ◽  
Field Equations ◽  
Symmetric Connection ◽  
Theories Of Gravity ◽  
Theory Of Gravity ◽  
Infinite Derivative

AbstractIn this manuscript we will present the theoretical framework of the recently proposed infinite derivative theory of gravity with a non-symmetric connection. We will explicitly derive the field equations at the linear level and obtain new solutions with a non-trivial form of the torsion tensor in the presence of a fermionic source, and show that these solutions are both ghost and singularity-free.

scholarly journals Charged wormholes in f(R,T)-extended theory of gravity

2019 ◽  
Vol 28 (08) ◽  
pp. 1950098 ◽  
Author(s):  
P. H. R. S. Moraes ◽  
W. de Paula ◽  
R. A. C. Correa
Keyword(s):  
Degrees Of Freedom ◽  
Matter Content ◽  
Nonlinear Electrodynamics ◽  
Energy Conditions ◽  
Field Equations ◽  
Extended Theory ◽  
Extended Theories Of Gravity ◽  
Theories Of Gravity ◽  
Theory Of Gravity ◽  
Physical Quantities

Wormholes (WHs) are a solution for General Relativity field equations which characterize a passage or tunnel that connects two different regions of spacetime and is filled by some sort of exotic matter that does not satisfy the energy conditions. On the other hand, it is known that in extended theories of gravity, the extra degrees of freedom once provided may allow the energy conditions to be obeyed and, consequently, the matter content of the WH to be nonexotic. In this work, we obtain, as a novelty in the literature, solutions for charged WHs in the [Formula: see text]-extended theory of gravity. We show that the presence of charge in these objects may be a possibility to respect some stability conditions for their metric. Also, remarkably, the energy conditions are respected in the present approach. In addition, we argue that our framework can be very useful to study the possibility of evolving [Formula: see text] and [Formula: see text]-dimensional WH spacetime within the context of nonlinear electrodynamics, which open a new window to probe the physical quantities in a WH-type solution.

scholarly journals GRAVITATIONAL CHERENKOV RADIATION FROM EXTENDED THEORIES OF GRAVITY

2012 ◽  
Vol 27 (23) ◽  
pp. 1250136 ◽  
Author(s):  
M. DE LAURENTIS ◽  
S. CAPOZZIELLO ◽  
G. BASINI
Keyword(s):  
Cherenkov Radiation ◽  
Higher Order ◽  
Ricci Scalar ◽  
Field Equations ◽  
Massless Spin ◽  
Extended Theories Of Gravity ◽  
Theories Of Gravity ◽  
Scalar Invariants ◽  
Extended Theories

We linearize the field equations for higher order theories of gravity that contain scalar invariants other than the Ricci scalar. We find that besides a massless spin-2 field (the standard graviton), the theory contains also spin-0 and spin-2 massive modes with the latter being, in general, ghost modes. The rate at which such particles would emit gravitational Cherenkov radiation is calculated for some interesting physical cases.

scholarly journals f(R) View of Lyttleton-Bondi Cosmological Model in Peres Spacetime

2014 ◽  
Vol 8 ◽  
pp. 23-29
Author(s):  
S.N. Pandey ◽  
Sacheendra Shukla
Keyword(s):  
Cosmological Model ◽  
Gravitational Waves ◽  
Field Equations ◽  
Einstein Theory ◽  
Conformally Invariant ◽  
Theories Of Gravity ◽  
Theory Of Gravity

Over the last few years, among various alternatives to the Einstein theory of gravity, especially f(R) theories of gravity have received more importance due to number of interesting results in cosmology and astrophysics. Pandey [10] gave an f(R) theory of gravity to obtain conformally invariant gravitational waves in which field equations have the form given by (3). In this paper we have investigated Lyttleton Bondi Cosmological model in view of field equations of f(R) theory of gravity for Generalized Peres spacetime and finally a wave like solution is obtained.

scholarly journals TENSOR–SCALAR TORSION

2001 ◽  
Vol 16 (03) ◽  
pp. 113-119 ◽  
Author(s):  
CHARRO GRUVER ◽  
RICHARD HAMMOND ◽  
P. F. KELLY
Keyword(s):  
Angular Momentum ◽  
Scalar Field ◽  
Conservation Law ◽  
Torsion Tensor ◽  
Equations Of Motion ◽  
Exterior Derivative ◽  
Field Equations ◽  
Theory Of Gravity ◽  
Rotational Angular Momentum

A theory of gravity with torsion is examined in which the torsion tensor is constructed from the exterior derivative of an antisymmetric rank-two potential plus the dual of the gradient of a scalar field. Field equations for the theory are derived by demanding that the action be stationary under variations with respect to the metric, the antisymmetric potential, and the scalar field. A material action is introduced and the equations of motion are derived. The correct conservation law for rotational angular momentum plus spin is observed to hold in this theory.

Black hole solutions and thermodynamics in the infinite derivative theory of gravity

2021 ◽  
Vol 103 (4) ◽  
Author(s):  
Yong Xiao ◽  
Yong Chen ◽  
Haiyuan Feng ◽  
Chenrui Zhu
Keyword(s):  
Black Hole ◽  
Theory Of Gravity ◽  
Infinite Derivative ◽  
Black Hole Solutions

scholarly journals Improved gravitational-wave constraints on higher-order curvature theories of gravity

2021 ◽  
Vol 104 (2) ◽  
Author(s):  
Scott E. Perkins ◽  
Remya Nair ◽  
Hector O. Silva ◽  
Nicolás Yunes
Keyword(s):  
Gravitational Wave ◽  
Higher Order ◽  
Theories Of Gravity

scholarly journals HIGHER-ORDER CURVATURE TERMS IN BORN–INFELD TYPE BRANE THEORIES

2011 ◽  
Vol 20 (01) ◽  
pp. 59-75 ◽  
Author(s):  
EFRAIN ROJAS
Keyword(s):  
Ricci Tensor ◽  
General Structure ◽  
Extrinsic Curvature ◽  
Higher Order ◽  
Square Root ◽  
Auxiliary Variables ◽  
Field Equations ◽  
Alternative Description ◽  
Brane Models ◽  
Combined Matrix

The field equations associated to Born–Infeld type brane theories are studied by using auxiliary variables. This approach hinges on the fact, that the expressions defining the physical and geometrical quantities describing the worldvolume are varied independently. The general structure of the Born–Infeld type theories for branes contains the square root of a determinant of a combined matrix between the induced metric on the worldvolume swept out by the brane and a symmetric/antisymmetric tensor depending on gauge, matter or extrinsic curvature terms taking place on the worldvolume. The higher-order curvature terms appearing in the determinant form come to play in competition with other effective brane models. Additionally, we suggest a Born–Infeld–Einstein type action for branes where the higher-order curvature content is provided by the worldvolume Ricci tensor. This action provides an alternative description of the dynamics of braneworld scenarios.

scholarly journals Field Independent Cosmic Evolution

2013 ◽  
Vol 2013 ◽  
pp. 1-12 ◽  
Author(s):  
Nayem Sk ◽  
Abhik Kumar Sanyal
Keyword(s):  
Higher Order ◽  
Noether Symmetry ◽  
Scalar Tensor Theory ◽  
Anisotropic Model ◽  
Tachyonic Field ◽  
Tensor Theory ◽  
Cosmic Evolution ◽  
Field Independent ◽  
Conserved Current ◽  
Theory Of Gravity

It has been shown earlier that Noether symmetry does not admit a form of corresponding to an action in which is coupled to scalar-tensor theory of gravity or even for pure theory of gravity taking anisotropic model into account. Here, we prove that theory of gravity does not admit Noether symmetry even if it is coupled to tachyonic field and considering a gauge in addition. To handle such a theory, a general conserved current has been constructed under a condition which decouples higher-order curvature part from the field part. This condition, in principle, solves for the scale-factor independently. Thus, cosmological evolution remains independent of the form of the chosen field, whether it is a scalar or a tachyon.

scholarly journals A NON-GEODESIC MOTION IN THE R-1 THEORY OF GRAVITY TUNED WITH OBSERVATIONS

2008 ◽  
Vol 23 (02) ◽  
pp. 109-114 ◽  
Author(s):  
CHRISTIAN CORDA
Keyword(s):  
Dark Matter ◽  
High Order ◽  
Ricci Scalar ◽  
Geodesic Motion ◽  
General Picture ◽  
Test Particles ◽  
Pioneer Anomaly ◽  
Theories Of Gravity ◽  
Theory Of Gravity

In the general picture of high order theories of gravity, recently, the R-1 theory has been analyzed in two different frameworks. In this letter a third context is added, considering an explicit coupling between the R-1 function of the Ricci scalar and the matter Lagrangian. The result is a non-geodesic motion of test particles which, in principle, could be connected with Dark Matter and Pioneer anomaly problems.

Phase space correspondence between Jordan and Einstein frames

2021 ◽  
pp. 2150087
Author(s):  
Amin Salehi
Keyword(s):  
Phase Space ◽  
Critical Point ◽  
Critical Points ◽  
Dynamical Behavior ◽  
Cosmological Parameters ◽  
Jordan Frame ◽  
Field Equations ◽  
Theories Of Gravity ◽  
The Stability ◽  
Jordan And Einstein Frames

Scalar–tensor theories of gravity can be formulated in the Einstein frame or in the Jordan frame (JF) which are related with each other by conformal transformations. Although the two frames describe the same physics and are equivalent, the stability of the field equations in the two frames is not the same. Here, we implement dynamical system and phase space approach as a robustness tool to investigate this issue. We concentrate on the Brans–Dicke theory in a Friedmann–Lemaitre–Robertson–Walker universe, but the results can easily be generalized. Our analysis shows that while there is a one-to-one correspondence between critical points in two frames and each critical point in one frame is mapped to its corresponds in another frame, however, stability of a critical point in one frame does not guarantee the stability in another frame. Hence, an unstable point in one frame may be mapped to a stable point in another frame. All trajectories between two critical points in phase space in one frame are different from their corresponding in other ones. This indicates that the dynamical behavior of variables and cosmological parameters is different in two frames. Hence, for those features of the study, which focus on observational measurements, we must use the JF where experimental data have their usual interpretation.

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