scholarly journals Critical Tidal Currents in General Relativity

Universe ◽  
2020 ◽  
Vol 6 (8) ◽  
pp. 104
Author(s):  
Bahram Mashhoon
Keyword(s):  
General Relativity ◽  
Rest Frame ◽  
Analytic Solutions ◽  
Tidal Currents ◽  
Free Motion ◽  
Kerr Spacetime ◽  
Acceleration Mechanism ◽  
Test Particles ◽  
Gravitational Source ◽  
Tidal Acceleration

Relativistic tidal equations are formulated with respect to the rest frame of a central gravitational source and their solutions are studied. The existence of certain relativistic critical tidal currents are thereby elucidated. Specifically, observers that are spatially at rest in the exterior Kerr spacetime are considered in detail; in effect, these fiducial observers define the rest frame of the Kerr source. The general tidal equations for the free motion of test particles are worked out with respect to the Kerr background. The analytic solutions of these equations are investigated and the existence of a tidal acceleration mechanism is emphasized.

scholarly journals WEYL GEOMETRY AS CHARACTERIZATION OF SPACE-TIME

2011 ◽  
Vol 03 ◽  
pp. 87-97 ◽  
Author(s):  
F. P. POULIS ◽  
J. M. SALIM
Keyword(s):  
General Relativity ◽  
Scalar Field ◽  
Riemannian Geometry ◽  
Axiomatic Approach ◽  
Space Time ◽  
Weyl Geometry ◽  
Test Particles ◽  
Variational Formalism ◽  
Physical Fields

Motivated by an axiomatic approach to characterize space-time it is investigated a reformulation of Einstein's gravity where the pseudo-riemannian geometry is substituted by a Weyl one. It is presented the main properties of the Weyl geometry and it is shown that it gives extra contributions to the trajectories of test particles, serving as one more motivation to study general relativity in Weyl geometry. It is introduced its variational formalism and it is established the coupling with other physical fields in such a way that the theory acquires a gauge symmetry for the geometrical fields. It is shown that this symmetry is still present for the red-shift and it is concluded that for cosmological models it opens the possibility that observations can be fully described by the new geometrical scalar field. It is concluded then that this reformulation, although representing a theoretical advance, still needs a complete description of their objects.

GEOMETRY OF SPACETIME AND FINSLER GEOMETRY

2009 ◽  
Vol 24 (08n09) ◽  
pp. 1678-1685 ◽  
Author(s):  
REZA TAVAKOL
Keyword(s):  
General Relativity ◽  
String Theory ◽  
Riemannian Geometry ◽  
Lorentz Invariance ◽  
Finsler Geometry ◽  
Spacetime Geometry ◽  
Test Particles ◽  
Light Rays ◽  
Recent Developments ◽  
Underlying Geometry

A central assumption in general relativity is that the underlying geometry of spacetime is pseudo-Riemannian. Given the recent attempts at generalizations of general relativity, motivated both by theoretical and observational considerations, an important question is whether the spacetime geometry can also be made more general and yet still remain compatible with observations? Here I briefly summarize some earlier results which demonstrate that there are special classes of Finsler geometry, which is a natural metrical generalization of the Riemannian geometry, that are strictly compatible with the observations regarding the motion of idealised test particles and light rays. I also briefly summarize some recent attempts at employing Finsler geometries motivated by more recent developments such as those in String theory, whereby Lorentz invariance is partially broken.

scholarly journals Modifications to Plane Gravitational Waves from Minimal Lorentz Violation

Symmetry ◽  
2019 ◽  
Vol 11 (10) ◽  
pp. 1318 ◽  
Author(s):  
Rui Xu
Keyword(s):  
General Relativity ◽  
Gravitational Wave ◽  
Gravitational Waves ◽  
Lorentz Invariance ◽  
Lorentz Violation ◽  
First Order ◽  
Test Particles ◽  
Violation Of Lorentz Invariance ◽  
Plane Gravitational Waves ◽  
Wave Modes

General Relativity predicts two modes for plane gravitational waves. When a tiny violation of Lorentz invariance occurs, the two gravitational wave modes are modified. We use perturbation theory to study the detailed form of the modifications to the two gravitational wave modes from the minimal Lorentz-violation coupling. The perturbation solution for the metric fluctuation up to the first order in Lorentz violation is discussed. Then, we investigate the motions of test particles under the influence of the plane gravitational waves with Lorentz violation. First-order deviations from the usual motions are found.

Spinning test-particles in general relativity. II

2003 ◽  
pp. 404-413
Author(s):  
E. CORINALDESI ◽  
A. PAPAPETROU
Keyword(s):  
General Relativity ◽  
Test Particles

The relativistic clock problem

1952 ◽  
Vol 48 (4) ◽  
pp. 608-615
Author(s):  
F. I. Mikhail
Keyword(s):  
General Relativity ◽  
Special Relativity ◽  
Relative Motion ◽  
Circular Orbit ◽  
The Other ◽  
Time Interval ◽  
Time Intervals ◽  
Test Particles ◽  
Clock Paradox ◽  
The Difference

AbstractThe so-called ‘clock paradox’ is concerned with the difference in the time-intervals reckoned by two observers in relative motion for the lapse of time between two encounters. In this paper the problem is treated purely by general relativity by considering a particular example in which the two observers are attached to two test-particles moving freely in the field of a gravitating mass; one of these makes complete revolutions in a circular orbit while the other moves radially outwards and inwards. The time-interval between two successive encounters is shorter in the reckoning of the former than in that of the latter. The difference is found to agree qualitatively with a naïve application of special relativity.

scholarly journals ABELIAN DECOMPOSITION OF GENERAL RELATIVITY

2009 ◽  
Vol 24 (18n19) ◽  
pp. 3327-3341 ◽  
Author(s):  
Y. M. CHO
Keyword(s):  
General Relativity ◽  
Gauge Theory ◽  
Quantum Gravity ◽  
Lorentz Group ◽  
Lorentz Invariance ◽  
Gauge Potential ◽  
Abelian Decomposition ◽  
Gravitational Source ◽  
Einstein’S General Relativity ◽  
Local Lorentz Invariance

We present an Abelian decomposition of Einstein's general relativity, viewing Einstein's theory as a gauge theory of Lorentz group and identifying the gravitational connection as the gauge potential of Lorentz group. The decomposition confirms the existence of the restricted gravity which is much simpler than Einstein's theory but which has the full local Lorentz invariance (and thus the full general invariance). Moreover, it tells that Einstein's theory can be viewed as the restricted gravity which has the Lorentz covariant valence connection as the gravitational source. With the Abelian decomposition we show how to construct all possible vacuum gravitational connections, which can be classified by the knot topology π3(S3) = π3(S2). We discuss the physical implications of our result in quantum gravity.

scholarly journals Geodesics in the field of a rotating deformed gravitational source

2016 ◽  
Vol 31 (02n03) ◽  
pp. 1641006 ◽  
Author(s):  
K. A. Boshkayev ◽  
H. Quevedo ◽  
M. S. Abutalip ◽  
Zh. A. Kalymova ◽  
Sh. S. Suleymanova
Keyword(s):  
Angular Momentum ◽  
Gravitational Field ◽  
Angular Velocity ◽  
Circular Orbits ◽  
Frame Dragging ◽  
Test Particles ◽  
Gravitational Source ◽  
Massive Particles ◽  
Analytic Expressions

We investigate equatorial geodesics in the gravitational field of a rotating and deformed source described by the approximate Hartle-Thorne metric. In the case of massive particles, we derive within the same approximation analytic expressions for the orbital angular velocity, the specific angular momentum and energy, and the radii of marginally stable and marginally bound circular orbits. Moreover, we calculate the orbital angular velocity and the radius of lightlike circular geodesics. We study numerically the frame dragging effect and the influence of the quadrupolar deformation of the source on the motion of test particles. We show that the effects originating from the rotation can be balanced by the effects due to the oblateness of the source.

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