scholarly journals Scalar field effects on the orbit of S2 star

2019 ◽  
Vol 489 (4) ◽  
pp. 4606-4621 ◽  
Author(s):  
◽  
A Amorim ◽  
M Bauböck ◽  
M Benisty ◽  
J-P Berger ◽  
...  
Keyword(s):  
Black Hole ◽  
Dark Matter ◽  
Scalar Field ◽  
Coupling Parameter ◽  
Kerr Black Hole ◽  
Compact Object ◽  
Relative Mass ◽  
Exact Nature ◽  
Main Effect ◽  
Open Debate

ABSTRACT Precise measurements of the S-stars orbiting SgrA* have set strong constraints on the nature of the compact object at the centre of the Milky Way. The presence of a black hole in that region is well established, but its neighbouring environment is still an open debate. In that respect, the existence of dark matter in that central region may be detectable due to its strong signatures on the orbits of stars: the main effect is a Newtonian precession which will affect the overall pericentre shift of S2, the latter being a target measurement of the GRAVITY instrument. The exact nature of this dark matter (e.g. stellar dark remnants or diffuse dark matter) is unknown. This article assumes it to be a scalar field of toroidal distribution, associated with ultralight dark matter particles, surrounding the Kerr black hole. Such a field is a form of ‘hair’ expected in the context of superradiance, a mechanism that extracts rotational energy from the black hole. Orbital signatures for the S2 star are computed and shown to be detectable by GRAVITY. The scalar field can be constrained because the variation of orbital elements depends both on the relative mass of the scalar field to the black hole and on the field mass coupling parameter.

scholarly journals Spin-induced scalarization of Kerr black holes with a massive scalar field

2020 ◽  
Vol 80 (12) ◽  
Author(s):  
Daniela D. Doneva ◽  
Lucas G. Collodel ◽  
Christian J. Krüger ◽  
Stoytcho S. Yazadjiev
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Scalar Field ◽  
Coupling Parameter ◽  
Kerr Black Hole ◽  
Instability Region ◽  
Perturbation Equation ◽  
Massive Scalar ◽  
Field Mass ◽  
Massive Scalar Field

AbstractIn the present paper we study the onset of the spin-induced scalarization of a Kerr black hole in scalar-Gauss–Bonnet gravity with a massive scalar field. Our approach is based on a $$(2+1)$$ ( 2 + 1 ) time evolution of the relevant linearized scalar field perturbation equation. We examine the region where the Kerr black hole becomes unstable giving rise to new scalarized rotating black holes with a massive scalar field. With increasing of the scalar field mass, the minimum value of the Gauss–Bonnet coupling parameter at which scalarization is possible, increases and thus the instability region shrinks. Interestingly, the introduction of scalar field mass does not change the critical minimal value of the black hole angular momentum $$a_{\mathrm{crit}}/M$$ a crit / M where the instability of the Kerr black hole develops.

scholarly journals Spinning boson stars and hairy black holes with nonminimal coupling

2018 ◽  
Vol 27 (11) ◽  
pp. 1843009 ◽  
Author(s):  
Carlos A. R. Herdeiro ◽  
Eugen Radu
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Scalar Field ◽  
Coupling Parameter ◽  
Nonminimal Coupling ◽  
Boson Stars ◽  
Hairy Black Holes ◽  
Black Hole Solutions ◽  
Hairy Black Hole ◽  
Coupled Theory

We obtain spinning boson star solutions and hairy black holes with synchronized hair in the Einstein–Klein–Gordon model, wherein the scalar field is massive, complex and with a nonminimal coupling to the Ricci scalar. The existence of these hairy black holes in this model provides yet another manifestation of the universality of the synchronization mechanism to endow spinning black holes with hair. We study the variation of the physical properties of the boson stars and hairy black holes with the coupling parameter between the scalar field and the curvature, showing that they are, qualitatively, identical to those in the minimally coupled case. By discussing the conformal transformation to the Einstein frame, we argue that the solutions herein provide new rotating boson star and hairy black hole solutions in the minimally coupled theory, with a particular potential, and that no spherically symmetric hairy black hole solutions exist in the nonminimally coupled theory, under a condition of conformal regularity.

Black hole in balance with dark matter

2020 ◽  
Vol 35 (02n03) ◽  
pp. 2040050
Author(s):  
Boris E. Meierovich
Keyword(s):  
Black Hole ◽  
Dark Matter ◽  
Phase Equilibrium ◽  
Vector Field ◽  
Scalar Field ◽  
Total Mass ◽  
Metric Tensor ◽  
Static Solutions ◽  
Tensor Formula ◽  
Galaxy Rotation Curves

Equilibrium of a gravitating scalar field inside a black hole compressed to the state of a boson matter, in balance with a longitudinal vector field (dark matter) from outside is considered. Analytical consideration, confirmed numerically, shows that there exist static solutions of Einstein’s equations with arbitrary high total mass of a black hole, where the component of the metric tensor [Formula: see text] changes its sign twice. The balance of the energy-momentum tensors of the scalar field and the longitudinal vector field at the interface ensures the equilibrium of these phases. Considering a gravitating scalar field as an example, the internal structure of a black hole is revealed. Its phase equilibrium with the longitudinal vector field, describing dark matter on the periphery of a galaxy, determines the dependence of the velocity on the plateau of galaxy rotation curves on the mass of a black hole, located in the center of a galaxy.

scholarly journals Cosmological black holes are not described by the Thakurta metric: LIGO-Virgo bounds on PBHs remain unchanged

2021 ◽  
Vol 81 (11) ◽  
Author(s):  
Gert Hütsi ◽  
Tomi Koivisto ◽  
Martti Raidal ◽  
Ville Vaskonen ◽  
Hardi Veermäe
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Dark Matter ◽  
Compact Object ◽  
Compact Objects ◽  
Primordial Black Hole ◽  
Mass Growth ◽  
Black Hole Binaries ◽  
Physical Conditions ◽  
Accretion Physics

AbstractWe show that the physical conditions which induce the Thakurta metric, recently studied by Bœhm et al. in the context of time-dependent black hole masses, correspond to a single accreting compact object in the entire Universe filled with isotropic non-interacting dust. In such a case, accretion physics is not local but tied to the properties of the whole Universe. We show that radiation, primordial black holes or particle dark matter cannot produce the specific energy flux required for supporting the mass growth of the compact objects described by the Thakurta metric. In particular, this solution does not apply to black hole binaries. We conclude that compact dark matter candidates and their mass growth cannot be described by the Thakurta metric, and thus existing constraints on the primordial black hole abundance from the LIGO-Virgo and the CMB measurements remain valid.

scholarly journals Magnetized Particle Motion in γ-Spacetime in a Magnetic Field

Galaxies ◽  
2020 ◽  
Vol 8 (4) ◽  
pp. 76
Author(s):  
Ahmadjon Abdujabbarov ◽  
Javlon Rayimbaev ◽  
Farruh Atamurotov ◽  
Bobomurat Ahmedov
Keyword(s):  
Magnetic Field ◽  
Black Hole ◽  
Center Of Mass ◽  
Kerr Black Hole ◽  
Compact Object ◽  
Magnetic Interaction ◽  
Mass Energy ◽  
Circular Orbits ◽  
Center Of Mass Energy ◽  
Astrophysical Scenario

In the present work we explored the dynamics of magnetized particles around the compact object in γ-spacetime in the presence of an external asymptotically-uniform magnetic field. The analysis of the circular orbits of magnetized particles around the compact object in the spacetime of a γ-object immersed in the external magnetic field has shown that the area of stable circular orbits of magnetized particles increases with the increase of γ-parameter. We have also investigated the acceleration of the magnetized particles near the γ-object and shown that the center-of-mass energy of colliding magnetized particles increases with the increase of γ-parameter. Finally, we have applied the obtained results to the astrophysical scenario and shown that the values of γ-parameter in the range of γ∈(0.5,1) can mimic the spin of Kerr black hole up to a≃0.85, while the magnetic interaction can mimic the γ-parameter at γ∈(0.8,1) and spin of a Kerr black hole up to a≃0.3.

scholarly journals Constraint on Hybrid Stars with Gravitational Wave Events

Universe ◽  
2020 ◽  
Vol 6 (12) ◽  
pp. 231
Author(s):  
Kilar Zhang ◽  
Feng-Li Lin
Keyword(s):  
Black Hole ◽  
Dark Matter ◽  
Neutron Star ◽  
Gravitational Wave ◽  
Compact Object ◽  
Compact Objects ◽  
Compact Stars ◽  
Hybrid Star ◽  
Hybrid Stars

Motivated by the recent discoveries of compact objects from LIGO/Virgo observations, we study the possibility of identifying some of these objects as compact stars made of dark matter called dark stars, or the mix of dark and nuclear matters called hybrid stars. In particular, in GW190814, a new compact object with 2.6 M⊙ is reported. This could be the lightest black hole, the heaviest neutron star, and a dark or hybrid star. In this work, we extend the discussion on the interpretations of the recent LIGO/Virgo events as hybrid stars made of various self-interacting dark matter (SIDM) in the isotropic limit. We pay particular attention to the saddle instability of the hybrid stars which will constrain the possible SIDM models.

scholarly journals The limit y of the incident particle under the superradiance of Kerr black hole

2021 ◽  
Author(s):  
Wen-Xiang Chen
Keyword(s):  
Black Hole ◽  
Scalar Field ◽  
Kerr Black Hole ◽  
Weak Field ◽  
Incident Particle ◽  
Field Coupling ◽  
Field System ◽  
Field Behavior

It is important to emphasize that as the reference has proved well, the critical storage line of black hole field system is universal, that is, different scalar field coupling functions with the same weak field behavior are $\{C(\phi) \} , C (\phi) =1+\alpha\phi ^{2} + o(\phi ^{4})$, and have the same function behavior $\alpha=\alpha (\mu); a / M) $. The purpose of this paper is to find out the limit $y$ of the incident particle under the superradiance of the preset boundary (${\mu} = {y}{\omega}$).

scholarly journals Oscillating Universe with a Quantized Black Hole

2021 ◽  
Author(s):  
Sascha Kulas
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Dark Matter ◽  
Scalar Field ◽  
Vacuum Energy ◽  
Casimir Effect ◽  
Phenomenological Approach ◽  
The Other ◽  
Universe Model ◽  
Energy Field

In cosmology dark energy and dark matter are included in the CDM model, but they are still completely unknown. On the other hand the trans-Planckian problem leads to unlikely high photon energies for black holes. We introduce a model with quantized black hole matter. This minimizes the trans- Planckian problem extremely and leads to a scalar field in the oscillating universe model. We show that the scalar field has the same characteristics as a vacuum energy field and leads to the same Casimir effect. Shortly after the beginning of the big bounce this field decays locally and leads to the production of dark matter. In this model no inflation theory is needed. We emphasize that this model is mainly a phenomenological approach with the aim of new impetus to the discussion.

Dynamics of Magnetized and Magnetically Charged Particles around Regular Nonminimal Magnetic Black Holes

Galaxies ◽  
2021 ◽  
Vol 9 (4) ◽  
pp. 71
Author(s):  
Javlon Rayimbaev ◽  
Bakhtiyor Narzilloev ◽  
Ahmadjon Abdujabbarov ◽  
Bobomurat Ahmedov
Keyword(s):  
Black Hole ◽  
Magnetic Charge ◽  
Coupling Parameter ◽  
Charged Particles ◽  
Kerr Black Hole ◽  
Harmonic Oscillations ◽  
Yang Mills ◽  
Keplerian Orbits ◽  
Maximum Value ◽  
Mills Field

The present paper is devoted to the study of the event horizon properties of spacetime around a regular nonminimal magnetic black hole (BH), together with dynamics of magnetized and magnetically charged particles in the vicinity of the BH. It is shown that the minimum value of the outer horizon of the extreme charged BH increases with the increase in coupling parameter. It reaches its maximum value of 1.5M when q→∞, while the maximal value of the BH charge decreases and tends toward zero. We also present a detailed analysis of magnetized particles’ motion around a regular nonminimal magnetic black hole. The particle’s innermost circular stable orbits (ISCOs) radius decreases as the magnetic charge and the parameter β increase and the coupling parameter of Yang–Mills field causes a decrease at the values of the magnetic charge near to its maximum. We show that the magnetic charge can mimic the spin of a rotating Kerr black hole up to the value of a=0.7893M, providing the same value for an ISCO of a magnetized particle with the parameter β=10.2 when the coupling parameter is q=0. Moreover, Lyapunov exponents, Keplerian orbits and harmonic oscillations of magnetized particles motion are also discussed.

scholarly journals Testing Gravity Theory With Extreme Mass-Ratio Inspirals: Recent Progress

Proceedings ◽  
2019 ◽  
Vol 17 (1) ◽  
pp. 11
Author(s):  
Shucheng Yang ◽  
Shuo Xin ◽  
Chen Zhang ◽  
Wenbiao Han
Keyword(s):  
Black Hole ◽  
Gravitational Wave ◽  
Recent Progress ◽  
Central Body ◽  
Low Frequency ◽  
Kerr Black Hole ◽  
Compact Object ◽  
Wave Dispersion ◽  
Gravity Theory ◽  
Mass Ratio

A compact object captured by a supermassive black hole, named as extreme-mass-ratio inspiral (EMRI), is one of the most important gravitational wave sources for low-frequency interferometers such as LISA, Taiji, and TianQin. EMRIs can be used to accurately map the space-time of the central massive body. In the present paper, we introduce our recent progress on testing gravity theory with EMRIs. We demonstrate how to constrain gravitational wave dispersion and measure the deviation of the central body from the Kerr black hole. By using binary-EMRIs, the gravitational recoil and mass loss due to merger will be measured in a higher accuracy compared with the current LIGO observations. All these potential constrains and measurements will be useful for test of the gravity theory.

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