scholarly journals The gravitational energy-momentum pseudo-tensor of higher-order theories of gravity

2017 ◽  
Vol 529 (5) ◽  
pp. 1600376 ◽  
Author(s):  
Salvatore Capozziello ◽  
Maurizio Capriolo ◽  
Maria Transirico
Keyword(s):  
Higher Order ◽  
Gravitational Energy ◽  
Theories Of Gravity

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 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.

On the evolution and stability of cosmological perturbations in higher order scalar–tensor theories of gravity

2019 ◽  
Vol 97 (4) ◽  
pp. 360-373
Author(s):  
Fateme Rajabi ◽  
Kourosh Nozari
Keyword(s):  
Scalar Field ◽  
Higher Order ◽  
De Sitter ◽  
Cosmological Perturbations ◽  
First Order ◽  
Higher Order Terms ◽  
General Scalar ◽  
New Type ◽  
Theories Of Gravity ◽  
The Stability

We study a new type of extended theory of gravity in the framework of general scalar–tensor theories in which the higher order terms of curvature are coupled with a scalar field and its derivatives. We analyze the stability and evolution of cosmological perturbations in this setup. For this purpose, we perturb the Hubble parameter, matter density, and scalar field to check stability and evolution of perturbations to first order. In this framework, we investigate stability conditions for de Sitter and power law solutions and we examine viability of cosmological evolution of these perturbations. We consider some specific f(R) models and show that the stability analysis gives some constraints on the parameters of these models.

POSITIVE ENERGY VIA THE TELEPARALLEL HAMILTONIAN

1989 ◽  
Vol 04 (07) ◽  
pp. 1755-1772 ◽  
Author(s):  
JAMES M. NESTER
Keyword(s):  
Total Energy ◽  
Gravitational Theory ◽  
Gauge Condition ◽  
Gravitational Energy ◽  
Positive Energy ◽  
Spatial Infinity ◽  
Schwarzschild Solution ◽  
Hamiltonian Density ◽  
Theories Of Gravity ◽  
Insight Into

The canonical analysis of the teleparallel form of Einstein’s gravitational theory is discussed. For teleparallel theories of gravity the Hamiltonian density is mostly quadratic and the flux integrand at spatial infinity for the conserved total energy-momentum is quite naturally fully 4-covariant. These features plus a rotational gauge condition allow us to obtain a new, strictly tensorial, proof of the positivity of total energy for Einstein gravity from its teleparallel formulation. The Schwarzschild solution is used to provide insight into the proof and its various allowed positive “localizations” of gravitational energy.

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