Exploration of a singular fluid spacetime

Remmen, Grant N.

doi:10.1007/s10714-021-02873-5

Cited by 4 publications

(6 citation statements)

References 36 publications

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“…( 12) diverges, in order to obtain asymptotically flat solution in the large limit of r the whole process must be conducted with caution. Namely, we can see that the interior metric solves the Einstein equations while the exterior the vacuum solution, in addition to that the metric is continuous but not smooth at r = R. Such a similar issue was recently discussed by Remmen (see for more details [25]) in the context of singular isothermal fluid. To resolve this issue, at the surface at Σ, we need to discuss the junction conditions.…”

Section: A Black Hole Surrounded By Anisotropic Dark Matter Fluidmentioning

confidence: 57%

“…As we are going to see the energy-momentum tensor of the surface violates the null energy condition, but as pointed out in [25] this can be simply rectified by adding an arbitrary surface density larger than σ. We can compute the a µ = (u ν ∇ ν u µ ), that is, the acceleration in both regions resulting with…”

Section: A Black Hole Surrounded By Anisotropic Dark Matter Fluidmentioning

confidence: 91%

“…The energy-momentum for the induced metric on Σ reads T ab = −σ(u a u b + γ ab ), where σ bis the surface density energy. In the full spacetime coordinates, we can write the extra energy-momentum tensor of the shell in the following form [25] ∆T…”

Section: A Black Hole Surrounded By Anisotropic Dark Matter Fluidmentioning

confidence: 99%

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Black holes surrounded by Einstein clusters as models of dark matter fluid

Jusufi¹

2022

Preprint

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We construct a novel class of spherically symmetric and asymptotically flat black holes and naked singularities surrounded by anisotropic dark matter fluid with the equation of state (EoS) of the form Pt = ωρ. We assume that dark matter is made of weakly interacting particles orbiting around the supermassive black hole in the galactic center and the dark matter halo is formed by means of Einstein clusters having only tangential pressure. In the large distance from the black hole we obtain the constant flat curve with the upper bound for the dark matter state parameter ω ∼ < 10 −7 . To this end, we also check the energy conditions of the dark matter fluid outside the black hole/naked singularity, the deflection of light by the galaxy, and the shadow images of the Sgr A black hole using the rotating and radiating particles. For the black hole case, we find that the effect of dark matter fluid on the shadow radius is small, in particular the angular radius of the black hole is shown to increase by the order 10 −4 µarcsec compared to the vacuum solution. For the naked singularity we obtain significantly smaller shadow radius compared to the black hole case. Finally, we study the stability of the S2 star orbit around Sgr A black hole under dark matter effects. It is argued that the motion of S2 star orbit is stable for values ω ∼ < 10 −7 , however further increase of ω leads to unstable orbits.

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Section: A Black Hole Surrounded By Anisotropic Dark Matter Fluidmentioning

confidence: 57%

Section: A Black Hole Surrounded By Anisotropic Dark Matter Fluidmentioning

confidence: 91%

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Black holes surrounded by Einstein clusters as models of dark matter fluid

Jusufi¹

2022

Preprint

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“…Under a scale transformation r → λ r, t → λ 1−γ t, the metric scales as ds 2 → λ 2 ds 2 . Examples of self-similar geometries have been found in the literature [23,24], sourced by a perfect fluid equation of state.…”

Section: The Geometry Of the Vector Starmentioning

confidence: 99%

“…[18] for a general discussion). The singular isothermal sphere [19][20][21][22][23], a self-similar configurations supported by a perfect fluid in its interior which contains a naked singularity [24], and which has been investigated also in the context of exceptions to the cosmic censorship hypothesis (see e.g. [25] for a review).…”

Section: Introductionmentioning

confidence: 99%

Ultracompact vector stars

Tasinato

2022

Phys. Rev. D

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We analytically investigate a new family of horizonless compact objects in vector-tensor theories of gravity, called ultracompact vector stars. They are sourced by a vector condensate, induced by a non-minimal coupling with gravity. They can be as compact as black holes, thanks to their internal anisotropic stress. In the spherically symmetric case their interior resembles an isothermal sphere, with a singularity that can be resolved by tuning the available integration constants. The star interior smoothly matches to an exterior Schwarzschild geometry, with no need of extra energy momentum tensor at the star surface. We analyse the behaviour of geodesics within the star interior, where stable circular orbits are allowed, as well as trajectories crossing in both ways the star surface. We analytically study stationary deformations of the vector field and of the geometry, which break spherical symmetry, and whose features depend on the vector-tensor theory we consider. We introduce and determine the vector magnetic susceptibility as a probe of the star properties, and we analyze how the rate of rotation of the star is affected by the vector charges.

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Black holes surrounded by Einstein clusters as models of dark matter fluid

Jusufi

2023

Eur. Phys. J. C

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We construct a novel class of spherically symmetric and asymptotically flat black holes and naked singularities surrounded by anisotropic dark matter fluid with the equation of state (EoS) of the form $$P_t=\omega \rho $$ P t = ω ρ . We assume that dark matter is made of weakly interacting particles orbiting around the supermassive black hole in the galactic center and the dark matter halo is formed by means of Einstein clusters having only tangential pressure. In the large distance from the black hole we obtain the constant flat curve with the upper bound for the dark matter state parameter $$\omega \lesssim 10^{-7}$$ ω ≲ 10 - 7 . To this end, we also check the energy conditions of the dark matter fluid outside the black hole/naked singularity, the deflection of light by the galaxy, and the shadow images of the Sgr A$$^\star $$ ⋆ black hole using the rotating and radiating particles. For the black hole case, we find that the effect of dark matter fluid on the shadow radius is small, in particular the angular radius of the black hole is shown to increase by the order $$10^{-4}\, \upmu $$ 10 - 4 μ arcsec compared to the vacuum solution. For the naked singularity we obtain significantly smaller shadow radius compared to the black hole case. Finally, we study the stability of the S2 star orbit around Sgr A$$^\star $$ ⋆ black hole under dark matter effects. It is argued that the motion of S2 star orbit is stable for values $$\omega \lesssim 10^{-7}$$ ω ≲ 10 - 7 , however further increase of $$\omega $$ ω leads to unstable orbits. Using the observational result for the shadow images of the Sgr A$$^\star $$ ⋆ reported by the EHT along with the tightest constraint for $$\omega $$ ω found from the constant flat curve, we show that the black hole model is consistent with the data while the naked singularity in our model can be ruled out.

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Exploration of a singular fluid spacetime

Cited by 4 publications

References 36 publications

Black holes surrounded by Einstein clusters as models of dark matter fluid

Black holes surrounded by Einstein clusters as models of dark matter fluid

Ultracompact vector stars

Black holes surrounded by Einstein clusters as models of dark matter fluid

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