Orbital dynamics of the gravitational field of stringy black holes

2014 ◽  
Vol 29 (29) ◽  
pp. 1450144 ◽  
Author(s):  
Yu Zhang ◽  
Jin-Ling Geng ◽  
En-Kun Li
Keyword(s):  
Black Holes ◽  
Angular Momentum ◽  
Gravitational Field ◽  
Phase Plane ◽  
Equations Of Motion ◽  
Orbital Dynamics ◽  
Phase Plane Analysis ◽  
Test Particles ◽  
Stable Circular Orbit ◽  
The Stability

In this paper, we study the orbital dynamics of the gravitational field of stringy black holes by analyzing the effective potential and the phase plane diagram. By solving the equation of Lagrangian, the general relativistic equations of motion in the gravitational field of stringy black holes are given. It is easy to find that the motion of test particles depends on the energy and angular momentum of the test particles. Using the phase plane analysis method and combining the conditions of the stability, we discuss different types of the test particles' orbits in the gravitational field of stringy black holes. We get the innermost stable circular orbit which occurs at r min = 5.47422 and when the angular momentum b ≤ 4.3887 the test particles will fall into the black hole.

Bound orbits around modified Hayward black holes

2021 ◽  
Author(s):  
Bo Gao ◽  
Xue-Mei Deng
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Angular Momentum ◽  
Gravitational Field ◽  
Periodic Orbits ◽  
Kerr Black Hole ◽  
Periodic Oscillations ◽  
Test Particles ◽  
Spin Parameter ◽  
Bound Orbits

The neutral time-like particle’s bound orbits around modified Hayward black holes have been investigated. We find that both in the marginally bound orbits (MBO) and the innermost stable circular orbits (ISCO), the test particle’s radius and its angular momentum are all more sensitive to one of the parameters [Formula: see text]. Especially, modified Hayward black holes with [Formula: see text] could mimic the same ISCO radius around the Kerr black hole with the spin parameter up to [Formula: see text]. Small [Formula: see text] could mimic the ISCO of small-spinning test particles around Schwarzschild black holes. Meanwhile, rational (periodic) orbits around modified Hayward black holes have also been studied. The epicyclic frequencies of the quasi-circular motion around modified Hayward black holes are calculated and discussed with respect to the observed Quasi-periodic oscillations (QPOs) frequencies. Our results show that rational orbits around modified Hayward black holes have different values of the energy from the ones of Schwarzschild black holes. The epicyclic frequencies in modified Hayward black holes have different frequencies from Schwarzschild and Kerr ones. These might provide hints for distinguishing modified Hayward black holes from Schwarzschild and Kerr ones by using the dynamics of time-like particles around the strong gravitational field.

scholarly journals Null and Timelike Geodesics near the Throats of Phantom Scalar Field Wormholes

Universe ◽  
2020 ◽  
Vol 6 (10) ◽  
pp. 183
Author(s):  
Ivan Potashov ◽  
Julia Tchemarina ◽  
Alexander Tsirulev
Keyword(s):  
Black Holes ◽  
Scalar Field ◽  
Circular Orbit ◽  
Realistic Model ◽  
Test Particles ◽  
Stable Circular Orbit ◽  
Phantom Scalar ◽  
Metric Function ◽  
Bound Orbits ◽  
Phantom Scalar Field

We study geodesic motion near the throats of asymptotically flat, static, spherically symmetric traversable wormholes supported by a self-gravitating minimally coupled phantom scalar field with an arbitrary self-interaction potential. We assume that any such wormhole possesses the reflection symmetry with respect to the throat, and consider only its observable “right half”. It turns out that the main features of bound orbits and photon trajectories close to the throats of such wormholes are very different from those near the horizons of black holes. We distinguish between wormholes of two types, the first and second ones, depending on whether the redshift metric function has a minimum or maximum at the throat. First, it turns out that orbits located near the centre of a wormhole of any type exhibit retrograde precession, that is, the angle of pericentre precession is negative. Second, in the case of high accretion activity, wormholes of the first type have the innermost stable circular orbit at the throat while those of the second type have the resting-state stable circular orbit in which test particles are at rest at all times. In our study, we have in mind the possibility that the strongly gravitating objects in the centres of galaxies are wormholes, which can be regarded as an alternative to black holes, and the scalar field can be regarded as a realistic model of dark matter surrounding galactic centres. In this connection, we discuss qualitatively some observational aspects of results obtained in this article.

scholarly journals DISCUSSION ON SOME CHARACTERISTICS OF CHARGED BRANE-WORLD BLACK HOLES

2009 ◽  
Vol 24 (04) ◽  
pp. 719-739 ◽  
Author(s):  
M. KALAM ◽  
F. RAHAMAN ◽  
A. GHOSH ◽  
B. RAYCHAUDHURI
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Gravitational Field ◽  
Scalar Field ◽  
Brane World ◽  
Massless Scalar ◽  
Massless Scalar Field ◽  
Effective Potentials ◽  
Test Particles ◽  
Jacobi Formalism

Several physical natures of charged brane-world black holes are investigated. Firstly, the timelike and null geodesics of the charged brane-world black holes are presented. We also analyze all the possible motions by plotting the effective potentials for various parameters for circular and radial geodesics. Secondly, we investigate the motion of test particles in the gravitational field of the charged brane-world black holes using the Hamilton–Jacobi formalism. We consider charged and uncharged test particles and examine their behavior in both static and nonstatic cases. Thirdly, the thermodynamics of the charged brane-world black holes are studied. Finally, it is shown that there is no phenomenon of superradiance for an incident massless scalar field for such a black hole.

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.

scholarly journals Einstein’s Equation of motion for exterior test particles with spherical mass distribution having varied field, time and radial distance; Golden metric tensors approach.

2021 ◽  
Keyword(s):  
Gravitational Field ◽  
Polar Motion ◽  
Equations Of Motion ◽  
Radial Distance ◽  
Equation Of Motion ◽  
Metric Tensor ◽  
Test Particles ◽  
Einstein's Equation ◽  
Spherical Mass ◽  
Metric Tensors

Golden metric tensors exterior to hypothetical distribution of mass whose field varies with time and radial distance have been used to construct the coefficient of affine connections that invariably was used to obtained the Einstein’s equations of motion for test particles of non-zero rest masses. The expression for the variation of time on a clock moving in this gravitational field was derived using the time equation of motion. The test particles in this field under the condition of pure polar motion have an inverse square dependence velocity which depends on radial distance. Our result indicates that despite using the golden metric tensor, the inverse square dependence of the velocity on radial distance has not been changed.

Spinning test-particles in general relativity. I

1951 ◽  
Vol 209 (1097) ◽  
pp. 248-258 ◽  
Keyword(s):  
General Relativity ◽  
Gravitational Field ◽  
Equations Of Motion ◽  
Covariant Form ◽  
Test Particles

A method for the derivation of the equations of motion of test particles in a given gravitational field is developed. The equations of motion of spinning test particles are derived. The transformation properties are discussed and the equations of motion are written in a covariant form.

EQUILIBRIUM ORBITS OF PARTICLES UNDERGOING POYNTING-ROBERTSON EFFECT IN SCHWARZSCHILD SPACETIME

2012 ◽  
Vol 12 ◽  
pp. 247-255
Author(s):  
DONATO BINI ◽  
ANDREA GERALICO
Keyword(s):  
Angular Momentum ◽  
Gravitational Field ◽  
Radiation Field ◽  
Equatorial Plane ◽  
Circular Orbit ◽  
Radiation Flux ◽  
Multiple Equilibrium ◽  
Schwarzschild Spacetime ◽  
The Stability ◽  
Test Radiation

Equilibrium orbits of particles moving on the equatorial plane of a Schwarzschild spacetime are investigated when a test radiation field is superposed to the background gravitational field. The radiation flux is endowed with a fixed but arbitrary (non-zero) angular momentum. It is found that multiple equilibrium circular orbit exist provided that the photon angular momentum is sufficiently high. The stability of such orbits is also analyzed.

scholarly journals Orbital motion of test particles in regular Hayward black hole space–time

2019 ◽  
Vol 97 (1) ◽  
pp. 58-62 ◽  
Author(s):  
Jian-Ping Hu ◽  
Yu Zhang
Keyword(s):  
Black Hole ◽  
Phase Plane ◽  
Orbital Motion ◽  
Space Time ◽  
Plane Method ◽  
Test Particles ◽  
Stable Circular Orbit ◽  
Innermost Stable Circular Orbit ◽  
Central Energy ◽  
Phase Plane Method

In this paper, all possible orbits of test particles are investigated by using the phase plane method in regular Hayward black hole space–time. Our results show that the time-like orbits are divided into four types: unstable circular orbits, separates stable orbits, stable hyperbolic orbits, and elliptical orbits in regular Hayward black hole space–time. We find that the orbital properties vary with the change of ℓ (a convenient encoding of the central energy density 3/8πℓ2). If ℓ = 1/3 and b < 3.453 21, the test particles moving toward the black hole will definitely plunge into the black hole. In addition, it is obtained that the innermost stable circular orbit happens at rmin = 5.930 55 for b = 3.453 21.

DELTA GRAVITY AND THE ACCELERATED EXPANSION OF THE UNIVERSE

2011 ◽  
Vol 20 (supp01) ◽  
pp. 65-72
Author(s):  
JORGE ALFARO
Keyword(s):  
General Relativity ◽  
Gravitational Field ◽  
Cosmological Constant ◽  
Equivalence Principle ◽  
Equations Of Motion ◽  
Accelerated Expansion ◽  
Symmetric Tensors ◽  
Test Particles ◽  
Expansion Of The Universe ◽  
The Universe

We study a model of the gravitational field based on two symmetric tensors. The equations of motion of test particles are derived. We explain how the Equivalence principle is recovered. Outside matter, the predictions of the model coincide exactly with General Relativity, so all classical tests are satisfied. In Cosmology, we get accelerated expansion without a cosmological constant.

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