scholarly journals Plane symmetric cosmological micro model in modified theory of Einstein’s general relativity

2003 ◽  
pp. 163-176 ◽  
Author(s):  
U.K. Panigrahi ◽  
R.C. Sahu
Keyword(s):  
General Relativity ◽  
Coupling Parameter ◽  
Massless Scalar ◽  
Massless Scalar Field ◽  
Quantum Level ◽  
Micro Model ◽  
Plane Symmetric ◽  
Homogeneous Plane ◽  
Modified Theory ◽  
Einstein’S General Relativity

In this paper, we have investigated an anisotropic homogeneous plane symmetric cosmological micro-model in the presence of massless scalar field in modified theory of Einstein's general relativity. Some interesting physical and geometrical aspects of the model together with singularity in the model are discussed. Further, it is shown that this theory is valid and leads to Ein?stein's theory as the coupling parameter ? ?>? 0 in micro (i.e. quantum) level in general.

Anisotropic plane symmetric model with massless scalar field

2020 ◽  
Author(s):  
D. D. Pawar ◽  
S. P. Shahare ◽  
Y. S. Solanke ◽  
V. J. Dagwal
Keyword(s):  
Scalar Field ◽  
Massless Scalar ◽  
Symmetric Model ◽  
Massless Scalar Field ◽  
Plane Symmetric

scholarly journals Cosmological bounce in Horndeski theory and beyond

2018 ◽  
Vol 191 ◽  
pp. 07013 ◽  
Author(s):  
R. Kolevatov ◽  
S. Mironov ◽  
V. Rubakov ◽  
N. Sukhov ◽  
V. Volkova
Keyword(s):  
General Relativity ◽  
Scalar Field ◽  
Massless Scalar ◽  
Massless Scalar Field ◽  
Cosmological Solutions ◽  
The Stability ◽  
The Way

We discuss the stability of the classical bouncing solutions in the general Horndeski theory and beyond Horndeski theory. We restate the no-go theorem, showing that in the general Horndeski theory there are no spatially flat non-singular cosmological solutions which are stable during entire evolution. We show the way to evade the no-go in beyond Horndeski theory and give two specific examples of bouncing solutions, whose asymptotic past and future or both are described by General Relativity (GR) with a conventional massless scalar field. Both solutions are free of any pathologies at all times.

scholarly journals WAVE EQUATION OF THE SCALAR FIELD AND SUPERFLUIDS

2009 ◽  
Vol 24 (40) ◽  
pp. 3249-3256 ◽  
Author(s):  
A. NADDEO ◽  
G. SCELZA
Keyword(s):  
General Relativity ◽  
Wave Equation ◽  
Scalar Field ◽  
Dimensional Space ◽  
Massless Scalar ◽  
Back Reaction ◽  
Massless Scalar Field ◽  
Sound Waves ◽  
Hydrodynamical Equation ◽  
Common Features

The new formal analogy between superfluid systems and cosmology, which emerges by taking into account the back-reaction of the vacuum to the quanta of sound waves,1 enables us to put forward some common features between these two different areas of physics. We find the condition that allows us to justify a General Relativity (GR) derivation of the hydrodynamical equation for the superfluid in a four-dimensional space whose metric is the Unruh one.2 Furthermore, we show how, in the particular case taken into account, our hydrodynamical equation can be deduced within a four-dimensional space from the wave equation of a massless scalar field.

On the Correspondence between Exact Solutions in Kaluza–Klein Theory and in Scalar–Tensor Theories

1997 ◽  
Vol 12 (28) ◽  
pp. 2121-2132 ◽  
Author(s):  
Andrew Billyard ◽  
Alan Coley
Keyword(s):  
General Relativity ◽  
Exact Solutions ◽  
The Other ◽  
Massless Scalar ◽  
Massless Scalar Field ◽  
Formal Equivalence ◽  
Higher Dimensional ◽  
Klein Theory ◽  
Dimensional Version ◽  
Kaluza Klein

Using the formal equivalences between Kaluza–Klein gravity, Brans–Dicke theory and general relativity coupled to a massless scalar field, exact solutions obtained in one theory will correspond to analogous solutions in the other two theories. Often exact solutions in one theory are "rediscovered" since theory are not recognized as analogs of the corresponding solutions in one of the other theories. We review here a number of exact solutions in each of the theories, with an emphasis on identifying and presenting the higher-dimensional version of the solutions. We also briefly comment upon the formal equivalence between Kaluza–Klein theory and scalar–tensor theories in general.

scholarly journals Analytic treatment of near-extremal charged black holes supporting non-minimally coupled massless scalar clouds

2020 ◽  
Vol 80 (12) ◽  
Author(s):  
Shahar Hod
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Coupling Parameter ◽  
Analytical Formula ◽  
Scalar Fields ◽  
Massless Scalar ◽  
Massless Scalar Field ◽  
Charged Black Holes ◽  
Black Hole Spacetimes ◽  
Electromagnetic Tensor

AbstractIt has recently been revealed that massless scalar fields which are non-minimally coupled to the Maxwell electromagnetic tensor can be supported in the exterior spacetime regions of spherically symmetric charged black holes. The boundary between scalarized charged black-hole spacetimes and bald (scalarless) Reissner–Nordström black holes is determined by the presence of a critical existence-line which describes spatially regular linearized scalar ‘clouds’ that are supported in the black-hole spacetime. In the present paper we use analytical techniques in order to solve the Klein–Gordon wave equation for the non-minimally coupled linearized scalar fields in the spacetimes of near-extremal supporting black holes. In particular, we derive a remarkably compact analytical formula for the discrete resonant spectrum $$\{\alpha (l,Q/M;n)\}^{n=\infty }_{n=1}$$ { α ( l , Q / M ; n ) } n = 1 n = ∞ which characterizes the dimensionless coupling parameter of the composed Reissner–Nordström-black-hole-nonminimally-coupled-massless-scalar-field configurations along the critical existence-line of the Einstein–Maxwell-scalar theory (here Q/M is the dimensionless charge-to-mass ratio of the central supporting black hole and l is the angular harmonic index of the supported scalar configurations).

ON STABILITY OF SIMPLEST NONSINGULAR INFLATIONARY COSMOLOGICAL MODELS WITHIN GENERAL RELATIVITY AND GAUGE THEORIES OF GRAVITY

2004 ◽  
Vol 13 (04) ◽  
pp. 695-707 ◽  
Author(s):  
G. V. VERESHCHAGIN
Keyword(s):  
General Relativity ◽  
Scalar Field ◽  
Gauge Theories ◽  
Initial Conditions ◽  
Solvable Model ◽  
Cosmological Models ◽  
Massless Scalar ◽  
Massless Scalar Field ◽  
Theories Of Gravity ◽  
Analysis Of Stability

In this paper we provide approximate analytical analysis of stability of nonsingular inflationary chaotic-type cosmological models. Initial conditions for nonsingular solutions at the bounce correspond to dominance of potential part of the energy density of the scalar field over its kinetic part both within general relativity and gauge theories of gravity. Moreover, scalar field at the bounce exceeds the Planckian value and on expansion stage these models correspond to chaotic inflation. Such solutions can be well approximated by explicitly solvable model with constant effective potential (cosmological term) and massless scalar field during the bounce and on stages of quasi-exponential contraction and expansion. Perturbative analysis shows that nonsingular inflationary solutions are exponentially unstable during contraction stage. This result is compared with numerical calculations.

Metric and connections in theories of gravity. The role of equivalence principle

2016 ◽  
Vol 13 (08) ◽  
pp. 1640007 ◽  
Author(s):  
Salvatore Capozziello ◽  
Mariafelicia De Laurentis
Keyword(s):  
General Relativity ◽  
Equivalence Principle ◽  
Causal Structure ◽  
Quantum Level ◽  
Space Experiments ◽  
Theories Of Gravity ◽  
Geodesic Structure ◽  
Einstein’S General Relativity

Fundamental issues underlying gravitational physics and some of the shortcomings of Einstein’s general relativity (GR) are discussed. In particular, after taking into account the role of the two main objects of relativistic theories of gravity, i.e. the metric and the connection fields, we consider the possibility that they are not trivially related so that the geodesic structure and the causal structure of the spacetime could be disentangled, as supposed in the Palatini formulation of gravity. In this perspective, the equivalence principle (EP), in its weak and strong formulations, can play a fundamental role in discriminating among competing theories. The possibility of its violation at quantum level could open new perspectives in gravitational physics and in unification with other interactions. We shortly debate the possibility of EP measurements by ground-based and space experiments.

Sign in / Sign up

Export Citation Format

Share Document