Clarification of an extended theory of gravity and a reply to Gr�n and Soleng

1990 ◽  
Vol 22 (6) ◽  
pp. 707-713 ◽  
Author(s):  
Paul S. Wesson
Keyword(s):  
Extended Theory ◽  
Theory Of Gravity

scholarly journals Investigating $f(R)$ gravity and cosmologies

2021 ◽  
Author(s):  
Vaibhav Kalvakota
Keyword(s):  
General Relativity ◽  
Lagrangian Density ◽  
Ricci Scalar ◽  
Metric Tensor ◽  
Extended Theory ◽  
Theories Of Gravity ◽  
Theory Of Gravity ◽  
Hilbert Action ◽  
Geometric Nature

The f (R) theory of gravity is an extended theory of gravity that is based on general relativity in the simplest case of $f(R) = R$. This theory extends such a function of the Ricci scalar into arbitrary functions that are not necessarily linear, i.e. could be of the form $f(R) = \alpha R^{2}$. The action for such a theory would be $S_{EH} = \frac{1}{2k} \int f(R) + L^{m}\; d^{4}x\sqrt{−g}$, where $S_{EH}$ is the Einstein-Hilbert action for our theory, $g$ is the determinant of the metric tensor $g_{\mu \nu}$ and $L^{m}$ is the Lagrangian density for matter. In this paper, we will look at some of the physical implications of such a theory, and the importance of such a theory in cosmology and in understanding the geometric nature of such f (R) theories of gravity.

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.

Gravitational waves in an algebraically extended theory of gravity

1985 ◽  
Vol 31 (10) ◽  
pp. 2488-2496 ◽  
Author(s):  
R. B. Mann ◽  
J. W. Moffat
Keyword(s):  
Gravitational Waves ◽  
Extended Theory ◽  
Theory Of Gravity

scholarly journals Cosmological Models with Big Rip and Pseudo Rip Scenarios in Extended Theory of Gravity

2021 ◽  
pp. 2100086
Author(s):  
Pratik P Ray ◽  
Sankarsan Tarai ◽  
B. Mishra ◽  
S. K. Tripathy
Keyword(s):  
Cosmological Models ◽  
Extended Theory ◽  
Big Rip ◽  
Theory Of Gravity

An extended theory of gravity in a modified Riemann’s geometry

2019 ◽  
Vol 16 (05) ◽  
pp. 1950067 ◽  
Author(s):  
Hoavo Hova ◽  
Huanxiong Yang ◽  
Samuel Owusu
Keyword(s):  
Displacement Vector ◽  
Isotropic Universe ◽  
Extended Theory ◽  
Displacement Vector Field ◽  
Vectorial Function ◽  
State Formula ◽  
Normal Gauge ◽  
Theory Of Gravity ◽  
The Universe ◽  
Critical Scale

In this work, we study the evolution of an isotropic universe in an extended theory of gravity obtained geometrically by transforming the normal-gauge Lyra displacement vector field [Formula: see text] as a complex vectorial function depending on a dynamical scalar field [Formula: see text]. By using the latest observational data, we observe that for [Formula: see text] the universe starts accelerating at the critical scale factor [Formula: see text] which corresponds to a redshift of [Formula: see text]. We also find that the dark energy fluid considered in this model is a generalized fluid with equation of state [Formula: see text].

scholarly journals Phantom cosmology in an extended theory of gravity

2020 ◽  
Vol 63 ◽  
pp. 448-458 ◽  
Author(s):  
S.K. Tripathy ◽  
B. Mishra
Keyword(s):  
Extended Theory ◽  
Theory Of Gravity

scholarly journals Diagrammar in an extended theory of gravity

2017 ◽  
Vol 771 ◽  
pp. 230-234 ◽  
Author(s):  
David C. Dunbar ◽  
John H. Godwin ◽  
Guy R. Jehu ◽  
Warren B. Perkins
Keyword(s):  
Extended Theory ◽  
Theory Of Gravity

scholarly journals Bouncing cosmology in an extended theory of gravity

2019 ◽  
Vol 134 (10) ◽  
Author(s):  
Sunil Kumar Tripathy ◽  
Rakesh Kumar Khuntia ◽  
Priyabrata Parida
Keyword(s):  
Extended Theory ◽  
Bouncing Cosmology ◽  
Theory Of Gravity

scholarly journals Boson stars in f(T) extended theory of gravity

2020 ◽  
Vol 102 (8) ◽  
Author(s):  
S. Ilijić ◽  
M. Sossich
Keyword(s):  
Boson Stars ◽  
Extended Theory ◽  
Theory Of Gravity
Sign in / Sign up

Export Citation Format

Share Document