scholarly journals THE CAUCHY PROBLEM FOR f(R)-GRAVITY: AN OVERVIEW

2012 ◽  
Vol 09 (01) ◽  
pp. 1250006 ◽  
Author(s):  
S. CAPOZZIELLO ◽  
S. VIGNOLO
Keyword(s):  
Cauchy Problem ◽  
General Relativity ◽  
Scalar Fields ◽  
Conformal Transformations ◽  
Field Equations ◽  
The Cauchy Problem ◽  
Theories Of Gravity ◽  
Matter Fields

We review the Cauchy problem for f(R) theories of gravity, in metric and metric-affine formulations, pointing out analogies and differences with respect to General Relativity. The role of conformal transformations, effective scalar fields and sources in the field equations is discussed in view of the well-formulation and the well-position of the problem. Finally, criteria of viability of the f(R)-models are considered according to the various matter fields acting as sources.

scholarly journals Kerr–Schild–Kundt metrics in generic gravity theories with modified Horndeski couplings

2021 ◽  
Vol 81 (12) ◽  
Author(s):  
Metin Gürses ◽  
Yaghoub Heydarzade ◽  
Çetin Şentürk
Keyword(s):  
General Relativity ◽  
Plane Waves ◽  
Scalar Fields ◽  
Vacuum Field ◽  
Field Equations ◽  
Complete Proof ◽  
Universality Theorem ◽  
Covariant Derivatives ◽  
Matter Fields ◽  
Insight Into

AbstractThe Kerr–Schild–Kundt (KSK) metrics are known to be one of the universal metrics in general relativity, which means that they solve the vacuum field equations of any gravity theory constructed from the curvature tensor and its higher-order covariant derivatives. There is yet no complete proof that these metrics are universal in the presence of matter fields such as electromagnetic and/or scalar fields. In order to get some insight into what happens when we extend the “universality theorem” to the case in which the electromagnetic field is present, as a first step, we study the KSK class of metrics in the context of modified Horndeski theories with Maxwell’s field. We obtain exact solutions of these theories representing the pp-waves and AdS-plane waves in arbitrary D dimensions.

scholarly journals Plane Symmetric Solutions of a Scalar-Tensor Theory of Gravitation

1977 ◽  
Vol 30 (1) ◽  
pp. 109 ◽  
Author(s):  
DRK Reddy
Keyword(s):  
General Relativity ◽  
Empty Space ◽  
Scalar Fields ◽  
Scalar Tensor Theory ◽  
Field Equations ◽  
Plane Symmetric ◽  
Zero Mass ◽  
Tensor Theory ◽  
Special Cases ◽  
Theory Of Gravitation

Plane symmetric solutions of a scalar-tensor theory proposed by Dunn have been obtained. These solutions are observed to be similar to the plane symmetric solutions of the field equations corresponding to zero mass scalar fields obtained by Patel. It is found that the empty space-times of general relativity discussed by Taub and by Bera are obtained as special cases.

Role of gravity in particle physics: A unified approach

2020 ◽  
Vol 29 (11) ◽  
pp. 2041012
Author(s):  
Pedro D. Alvarez ◽  
Mauricio Valenzuela ◽  
Jorge Zanelli
Keyword(s):  
General Relativity ◽  
Standard Model ◽  
Particle Physics ◽  
Laws Of Nature ◽  
Lorentz Transformations ◽  
Unified Approach ◽  
The Standard Model ◽  
Matter Fields

General Relativity (GR) and the Standard Model (SM) of particle physics are two enormously successful frameworks for our understanding the fundamental laws of nature. However, these theoretical schemes are widely disconnected, logically independent and unrelated in scope. Yet, GR and SM at some point must intersect, producing claims about phenomena that should be reconciled. Be it as it may, both schemes share a common basic ground: symmetry under local Lorentz transformations. Here, we will focus on the consequences of assuming this feature from the beginning to combine geometry, matter fields and gauge interactions. We give a rough description of how this could be instrumental for the construction of a unified scheme of gravitation and particle physics.

Berichte: Mach's Principle - A Critical Review

1973 ◽  
Vol 28 (3-4) ◽  
pp. 529-537 ◽  
Author(s):  
Michael Reinhardt
Keyword(s):  
General Relativity ◽  
Selection Rule ◽  
Inertial Mass ◽  
Physical Principle ◽  
Mach's Principle ◽  
Mach’S Principle ◽  
Field Equations ◽  
Basic Physical Principle ◽  
Theories Of Gravitation

AbstractAfter a short historical introduction it is discussed how far Mach's principle is incorporated into general relativity. The possible role of Mach's principle as a selection rule for the solutions of Einstein's field equations is summarized. Then follows a discussion of Math's principle in theories of gravitation other than Einstein's, mainly the Brans-Dicke theory. Finally the experiments on the isotropy of inertial mass and their consequence for Mach's principle are described. The conclusion is that Mach's principle, though an extremely stimulating thought, has at present little claim to be a basic physical principle.

scholarly journals Some Mathematical Aspects of f(R)-Gravity with Torsion: Cauchy Problem and Junction Conditions

Universe ◽  
2019 ◽  
Vol 5 (12) ◽  
pp. 224 ◽  
Author(s):  
Stefano Vignolo
Keyword(s):  
Cauchy Problem ◽  
Initial Value Problem ◽  
Sufficient Conditions ◽  
Well Posedness ◽  
Junction Conditions ◽  
Field Equations ◽  
Initial Value ◽  
The Cauchy Problem ◽  
General Conditions

We discuss the Cauchy problem and the junction conditions within the framework of f ( R ) -gravity with torsion. We derive sufficient conditions to ensure the well-posedness of the initial value problem, as well as general conditions to join together on a given hypersurface two different solutions of the field equations. The stated results can be useful to distinguish viable from nonviable f ( R ) -models with torsion.

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