Stable bound orbits in black lens backgrounds

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.

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Asymptotically flat vacuum solution in modified theory of Einstein’s gravity

The European Physical Journal C ◽

10.1140/epjc/s10052-019-7396-x ◽

2019 ◽

Vol 79 (10) ◽

Author(s):

Surajit Kalita ◽

Banibrata Mukhopadhyay

Keyword(s):

General Relativity ◽

Vacuum Solution ◽

Compact Objects ◽

Schwarzschild Solution ◽

Asymptotically Flat ◽

Symmetric Vacuum ◽

Theory Of Gravity ◽

Bound Orbits ◽

Vacuum Spacetime ◽

The Universe

Abstract A number of recent observations have suggested that the Einstein’s theory of general relativity may not be the ultimate theory of gravity. The f(R) gravity model with R being the scalar curvature turns out to be one of the best bet to surpass the general relativity which explains a number of phenomena where Einstein’s theory of gravity fails. In the f(R) gravity, behaviour of the spacetime is modified as compared to that of given by the Einstein’s theory of general relativity. This theory has already been explored for understanding various compact objects such as neutron stars, white dwarfs etc. and also describing evolution of the universe. Although researchers have already found the vacuum spacetime solutions for the f(R) gravity, yet there is a caveat that the metric does have some diverging terms and hence these solutions are not asymptotically flat. We show that it is possible to have asymptotically flat spherically symmetric vacuum solution for the f(R) gravity, which is different from the Schwarzschild solution. We use this solution for explaining various bound orbits around the black hole and eventually, as an immediate application, in the spherical accretion flow around it.

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MOTION OF A TEST PARTICLE IN THE TRANSVERSE SPACE OF Dp-BRANES

International Journal of Modern Physics D ◽

10.1142/s0218271812500563 ◽

2012 ◽

Vol 21 (11) ◽

pp. 1250056 ◽

Cited By ~ 1

Author(s):

ANINDITA BHATTACHARJEE ◽

ASHOK DAS ◽

LEVI GREENWOOD ◽

SUDHAKAR PANDA

Keyword(s):

Test Particle ◽

Massive Particle ◽

Higher Dimensions ◽

Geodesic Equation ◽

Point Particle ◽

Elliptic Motion ◽

Dimensional Spacetime ◽

Extended Sources ◽

Bound Orbits ◽

Schwarzschild Background

We investigate the motion of a test particle in higher dimensions due to the presence of extended sources like Dp-branes by studying the motion in the transverse space of the brane. This is contrasted with the motion of a point particle in the Schwarzschild background in higher dimensions. Since Dp-branes are specific to 10-dimensional spacetime and exact solutions of geodesic equations for this particular spacetime has not been possible so far for the Schwarzschild background, we focus here to find the leading order solution of the geodesic equation (for motion of light rays). This enables us to compute the bending of light in both the backgrounds. We show that contrary to the well known result of no noncircular bound orbits for a massive particle, in Schwarzschild background, for d ≥ 5, the Dp-brane background does allow bound elliptic motion only for p = 6 and the perihelion of the ellipse regresses instead of advancement. We also find that circular orbits for photon are allowed only for p ≤ 3.

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

Universe ◽

10.3390/universe6100183 ◽

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.

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Computation of bound orbits in the plane of a galaxy with a flat rotation curve

European Journal of Physics ◽

10.1088/0143-0807/32/3/c02 ◽

2011 ◽

Vol 32 (3) ◽

pp. 847-847

Author(s):

M E Bacon ◽

Amber Sharrar

Keyword(s):

Rotation Curve ◽

Flat Rotation Curve ◽

Bound Orbits

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Global embeddings and hydrodynamic properties of Kerr black hole

Modern Physics Letters A ◽

10.1142/s0217732316502047 ◽

2016 ◽

Vol 31 (35) ◽

pp. 1650204

Author(s):

Soon-Tae Hong

Keyword(s):

Black Holes ◽

Black Hole ◽

Equatorial Plane ◽

Kerr Black Hole ◽

Kerr Spacetime ◽

Stable Circular Orbit ◽

Massive Particles ◽

Flat Embedding ◽

Bound Orbits ◽

The Impact

In the presence of a rotating Kerr black hole, we investigate hydrodynamics of the massive particles and massless photons to construct relations among number density, pressure and internal energy density of the massive particles and photons around the rotating Kerr black hole and to study an accretion onto the black hole. On equatorial plane of the Kerr black hole, we investigate the bound orbits of the massive particles and photons around the black hole to produce their radial, azimuthal and precession frequencies. With these frequencies, we study the black holes GRO J1655-40 and 4U 1543-47 to explicitly obtain the radial, azimuthal and precession frequencies of the massive particles in the flow of perfect fluid. We next consider the massive particles in the stable circular orbit of radius of 1.0 ly around the supernovas SN 1979C, SN 1987A and SN 2213-1745 in the Kerr curved spacetime, and around the potential supermassive Schwarzschild black holes M87, NGC 3115, NGC 4594, NGC 3377, NGC 4258, M31, M32 and Galatic center, to estimate their radial and azimuthal frequencies, which are shown to be the same results as those in no precession motion. The photon unstable orbit is also discussed in terms of the impact parameter of the photon trajectory. Finally, on the equatorial plane of the Kerr black hole, we construct the global flat embedding structures possessing (9 + 3) dimensionalities outside and inside the event horizon of the rotating Kerr black hole. Moreover, on the plane, we investigate the warp products of the Kerr spacetime.

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On the black holes in alternative theories of gravity: The case of nonlinear massive gravity

International Journal of Modern Physics D ◽

10.1142/s0218271815500224 ◽

2015 ◽

Vol 24 (03) ◽

pp. 1550022 ◽

Cited By ~ 16

Author(s):

Ivan Arraut

Keyword(s):

Black Holes ◽

Black Hole ◽

Degrees Of Freedom ◽

Massive Gravity ◽

Alternative Theories Of Gravity ◽

De Sitter ◽

Theories Of Gravity ◽

Bound Orbits ◽

Black Hole Temperature ◽

Alternative Theories

I derive general conditions in order to explain the origin of the Vainshtein radius inside dRGT. The set of equations, which I have called "Vainshtein" conditions are extremal conditions of the dynamical metric (gμν) containing all the degrees of freedom of the theory. The Vainshtein conditions are able to explain the coincidence between the Vainshtein radius in dRGT and the scale [Formula: see text], obtained naturally from the Schwarzschild de-Sitter (S-dS) space inside general relativity (GR). In GR, this scale was interpreted as the maximum distance in order to get bound orbits. The same scale corresponds to the static observer position if we want to define the black hole temperature in an asymptotically de-Sitter space. In dRGT, the scale marks a limit after which the extra degrees of freedom of the theory become relevant.

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