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Journal ArticleDOI

Orbital and epicyclic motion of charged test particles around non-rotating Einstein-Æther black holes

TL;DR: In this paper, the trajectories of charged test particles in the background of non-rotating Einstein-AEther black holes in the presence of external uniform magnetic field were numerically integrated.
About: This article is published in Chinese Journal of Physics.The article was published on 2021-10-01. It has received 2 citations till now. The article focuses on the topics: Black hole & Test particle.
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Journal ArticleDOI
TL;DR: In this paper, the dynamics of both neutral and charged particles orbiting near a rotating black hole in scalar-tensor-vector gravity were explored and the conditions for the particle to escape at the innermost stable circular orbit.
Abstract: This paper explores the dynamics of both neutral as well as charged particles orbiting near a rotating black hole in scalar-tensor-vector gravity. We study the conditions for the particle to escape at the innermost stable circular orbit. We investigate stability of orbits through effective potential and Lyapunov exponent in the presence of magnetic field. The effective force acting on particle is also discussed. We also study the center of mass energy of particle collision near the horizon of this black hole. Finally, we compare our results with the particle motion around Schwarzschild, Kerr and Schwarzschild-MOG black holes. It is concluded that the external magnetic field, spin parameter as well as dimensionless parameter of the theory have strong effects on particle dynamics in modified gravity.

12 citations

Journal ArticleDOI
01 Oct 2022
TL;DR: In this paper , a maximally symmetric nonrotating solution of the Einstein-aether theory in isotropic coordinates was obtained in 2+1-dimensional de Sitter or anti-de Sitter space.
Abstract: Abstract Working in isotropic coordinates, we get some maximally symmetric nonrotating solutions of the Einstein-aether theory in $$2+1$$ 2 + 1 dimensions, all in analytical forms. Curvature singularities are not found in the Ricci and Kretschmann scalars, while conical singularities are avoidable by fixing some integration constants. In Schwarzschild type coordinates, most line elements become the metric of a black hole or a massive particle in the $$2+1$$ 2 + 1 -dimensional de Sitter or anti-de Sitter spacetime, but in some solutions the aether field cannot be written in closed forms.
References
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Book
01 Jan 1984

8,137 citations

Journal ArticleDOI
TL;DR: This review summarizes both the theoretical frameworks for tests of Lorentz invariance and experimental advances that have made new high precision tests possible.
Abstract: Motivated by ideas about quantum gravity, a tremendous amount of effort over the past decade has gone into testing Lorentz invariance in various regimes. This review summarizes both the theoretical frameworks for tests of Lorentz invariance and experimental advances that have made new high precision tests possible. The current constraints on Lorentz violating effects from both terrestrial experiments and astrophysical observations are presented.

1,008 citations

Journal ArticleDOI
TL;DR: In this article, a general covariant model of the aether was studied, in which local Lorentz invariance is broken by a dynamical unit timelike vector field.
Abstract: We study a generally covariant model in which local Lorentz invariance is broken by a dynamical unit timelike vector field ${u}^{a}$---the ``aether.'' Such a model makes it possible to study the gravitational and cosmological consequences of preferred frame effects, such as ``variable speed of light'' or high frequency dispersion, while preserving a generally covariant metric theory of gravity. In this paper we restrict attention to an action for an effective theory of the aether which involves only the antisymmetrized derivative ${\ensuremath{ abla}}_{[a}{u}_{b]}.$ Without matter this theory is equivalent to a sector of the Einstein-Maxwell-charged dust system. The aether has two massless transverse excitations, and the solutions of the model include all vacuum solutions of general relativity (as well as other solutions). However, the aether generally develops gradient singularities which signal a breakdown of this effective theory. Including the symmetrized derivative in the action for the aether field may cure this problem.

875 citations

Journal ArticleDOI
19 Sep 2013-Nature
TL;DR: Multi-frequency radio measurements of a newly discovered pulsar close to the Galactic Centre are reported and it is shown that the pulsar’s unusually large Faraday rotation indicates that there is a dynamically important magnetic field near the black hole.
Abstract: Earth's nearest candidate supermassive black hole lies at the centre of the Milky Way Its electromagnetic emission is thought to be powered by radiatively inefficient accretion of gas from its environment, which is a standard mode of energy supply for most galactic nuclei X-ray measurements have already resolved a tenuous hot gas component from which the black hole can be fed The magnetization of the gas, however, which is a crucial parameter determining the structure of the accretion flow, remains unknown Strong magnetic fields can influence the dynamics of accretion, remove angular momentum from the infalling gas, expel matter through relativistic jets and lead to synchrotron emission such as that previously observed Here we report multi-frequency radio measurements of a newly discovered pulsar close to the Galactic Centre and show that the pulsar's unusually large Faraday rotation (the rotation of the plane of polarization of the emission in the presence of an external magnetic field) indicates that there is a dynamically important magnetic field near the black hole If this field is accreted down to the event horizon it provides enough magnetic flux to explain the observed emission-from radio to X-ray wavelengths-from the black hole

437 citations

Journal ArticleDOI
TL;DR: In this article, a pair of kHz quasiperiodic oscillations (QPOs) in the Fourier spectra of two low-mass x-ray binaries, Sco X-1 and 4U1608-52, hosting an old accreting neutron star were analyzed.
Abstract: We consider the interpretation of a pair of kHz quasiperiodic oscillations (QPOs) in the Fourier spectra of two low-mass x-ray binaries, Sco X-1 and 4U1608-52, hosting an old accreting neutron star. The observed frequency difference of these QPOs decreases as their frequency increases, contrary to simple beat frequency models. We show that the behavior of these QPOs is instead well matched in terms of the fundamental frequencies for test particle motion in the gravitational field of the neutron star, for reasonable star masses, and nearly independent of the star spin. These results are not reproduced through the post--Newtonian approximation of general relativity. kHz QPOs from x-ray binaries likely provide an accurate laboratory for strong-field general relativity.

389 citations