Motion of extended bodies in general relativity and gravitational radiation

1985 ◽  
Vol 28 (1) ◽  
pp. 9-12 ◽  
Author(s):  
I. V. Sandina
Keyword(s):  
General Relativity ◽  
Gravitational Radiation ◽  
Extended Bodies

scholarly journals Gravitational Radiation by Ultrarelativistic Bodies

1974 ◽  
Vol 64 ◽  
pp. 60-60
Author(s):  
Peter Jocelyn Westervelt
Keyword(s):  
General Relativity ◽  
Gravitational Waves ◽  
Direct Observation ◽  
Gravitational Radiation ◽  
Indirect Evidence ◽  
Forward Direction ◽  
Recent Analysis ◽  
Circular Orbits ◽  
Low Efficiency

I have shown (Westervelt, 1966) that ultrarelativistic bodies do not radiate gravitational waves in the forward direction. This work has been extended so as to apply to circular orbits. Even if low efficiency of generation precludes direct observation of gravitational waves, indirect evidence for their existence is available in a recent analysis (Westervelt, 1969) of Shapiro's fourth test of general relativity.

Spherical gravitational waves

1959 ◽  
Vol 251 (994) ◽  
pp. 233-271 ◽  
Keyword(s):  
General Relativity ◽  
Gravitational Waves ◽  
Large Class ◽  
Linear Approximation ◽  
Gravitational Radiation ◽  
Gravitational Mass ◽  
Field Equations ◽  
Spherical Waves ◽  
Non Linear ◽  
External Forces

The field of gravitational radiation emitted from two moving particles is investigated by means of general relativity. A method of approximation is used, and in the linear approximation retarded potentials corresponding to spherical gravitational waves are introduced. As is already known, the theory in this approximation predicts that energy is lost by the system. The field equations in the second, non-linear, approximation are then considered, and it is shown that the system loses an amount of gravitational mass precisely equal to the energy carried away by the spherical waves of the linear approximation. The result is established for a large class of particle motions, but it has not been possible to determine whether energy is lost in free gravitational motion under no external forces. The main conclusion of this work is that, contrary to opinions frequently expressed, gravitational radiation has a real physical existence, and in particular, carries energy away from the sources.

scholarly journals Rotation and Spin and Position Operators in Relativistic Gravity and Quantum Electrodynamics

2019 ◽  
Author(s):  
Robert F O'Connell
Keyword(s):  
Black Holes ◽  
General Relativity ◽  
Gravitational Radiation ◽  
Quantum Electrodynamics ◽  
Binary Systems ◽  
Center Of Mass ◽  
Position Operator ◽  
Spinning Particle ◽  
Classical Version ◽  
Relativistic Particles

First, we examine how spin is treated in special relativity and the necessity of introducing spin supplementary conditions (SSC) and how they are related to the choice of a center-of-mass of a spinning particle. Next, we discuss quantum electrodynamics and the Foldy-Wouthuysen transformation which we note is a position operator identical to the Pryce-Newton-Wigner position operator. The classical version of the operators are shown to be essential for the treatment of classical relativistic particles in general relativity, of special interest being the case of binary systems (black holes/neutron stars) which emit gravitational radiation.

scholarly journals Gravitational waves — A review on the theoretical foundations of gravitational radiation

2018 ◽  
Vol 33 (14n15) ◽  
pp. 1830013 ◽  
Author(s):  
Alain Dirkes
Keyword(s):  
General Relativity ◽  
Gravitational Wave ◽  
Gravitational Waves ◽  
Gravitational Radiation ◽  
Wave Zone ◽  
Einstein Field Equations ◽  
Field Equations ◽  
Radiative Losses ◽  
Zone Field ◽  
Theoretical Foundations

In this paper, we review the theoretical foundations of gravitational waves in the framework of Albert Einstein’s theory of general relativity. Following Einstein’s early efforts, we first derive the linearized Einstein field equations and work out the corresponding gravitational wave equation. Moreover, we present the gravitational potentials in the far away wave zone field point approximation obtained from the relaxed Einstein field equations. We close this review by taking a closer look on the radiative losses of gravitating [Formula: see text]-body systems and present some aspects of the current interferometric gravitational waves detectors. Each section has a separate appendix contribution where further computational details are displayed. To conclude, we summarize the main results and present a brief outlook in terms of current ongoing efforts to build a spaced-based gravitational wave observatory.

Detecting Blackholes through Gravitational Waves

2014 ◽  
Author(s):  
Charles D. Bailyn
Keyword(s):  
Black Holes ◽  
General Relativity ◽  
Electromagnetic Radiation ◽  
Gravitational Waves ◽  
Gravitational Radiation ◽  
Stellar Mass ◽  
Supermassive Black Holes ◽  
Current Technology

This chapter looks at the detection of black holes through gravitational waves. While further improvements can be expected in the ability to detect and measure electromagnetic radiation, it is possible that the next great advances in observational astrophysics will come from the detection of other kinds of information altogether. Currently, there is a great excitement about the possibility of directly detecting an entirely new “celestial messenger,” namely, gravitational radiation. The existence of gravitational waves is a prediction of general relativity, and current technology is very close to being able to detect them directly. The strongest sources of gravitational radiation are expected to be merging black holes. Since such mergers are expected to occur, both between stellar-mass and supermassive black holes, the detection of gravitational radiation would provide a new way not only to explore gravitational physics but also to look for and to study celestial black holes.

scholarly journals On the ergoregion instability

1978 ◽  
Vol 364 (1717) ◽  
pp. 211-226 ◽  
Keyword(s):  
General Relativity ◽  
Scalar Field ◽  
Angular Dependence ◽  
Gravitational Radiation ◽  
Compact Stars ◽  
Effective Potentials ◽  
Age Of The Universe ◽  
Photon Motion ◽  
The Universe

Rotating, ultra-compact stars in general relativity can have an ergo-region, in which all trajectories are dragged in the direction of the star’s rotation. The existence of the ergoregion leads to a classical instability to emission of scalar, electromagnetic and gravitational radiation from the star. In this paper we calculate eigenfrequencies (including e-folding times) for stable and unstable modes of a scalar field on a background metric which has an ergoregion. Within a W. K. B. J. approximation for modes with angular dependence exp (i mϕ ), we find that unstable modes exist for all | m | > m 0 ( m 0 depending upon the star), but that the e-folding time is asymptotically τ = τ 0 exp (2 βm ), where β is of order 1. Typically, τ 0 is several orders of magnitude longer than the age of the universe. However, the techniques evolved here should be applicable to other ‘rotational dragging’ instabilities in general relativity. Particularly useful should be the result that links the eigenfrequencies to resonances in the effective potentials governing photon motion in the metric; these potentials are rotationally ‘split’.

scholarly journals Gravitational Waves from Compact Bodies

1996 ◽  
Vol 165 ◽  
pp. 153-183
Author(s):  
Kip S. Thorne
Keyword(s):  
Black Holes ◽  
General Relativity ◽  
Neutron Stars ◽  
Gravitational Radiation ◽  
Relativity Theory ◽  
Energy Concentration ◽  
Speed Of Light ◽  
General Relativity Theory ◽  
Concentration Changes ◽  
The Universe

According to general relativity theory, compact concentrations of energy (e.g., neutron stars and black holes) should warp spacetime strongly, and whenever such an energy concentration changes shape, it should create a dynamically changing spacetime warpage that propagates out through the Universe at the speed of light. This propagating warpage is called gravitational radiation — a name that arises from general relativity's description of gravity as a consequence of spacetime warpage.

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