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 Further evidence for the non-existence of a unified hoop conjecture

2020 ◽  
Vol 80 (10) ◽  
Author(s):  
Shahar Hod
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Critical Mass ◽  
Compact Object ◽  
Compact Objects ◽  
Necessary Condition ◽  
Adm Mass ◽  
Black Hole Spacetimes ◽  
Opposite Inequality ◽  
Hoop Conjecture

AbstractThe hoop conjecture, introduced by Thorne almost five decades ago, asserts that black holes are characterized by the mass-to-circumference relation $$4\pi {\mathcal {M}}/{\mathcal {C}}\ge 1$$ 4 π M / C ≥ 1 , whereas horizonless compact objects are characterized by the opposite inequality $$4\pi {\mathcal {M}}/{\mathcal {C}}<1$$ 4 π M / C < 1 (here $${\mathcal {C}}$$ C is the circumference of the smallest ring that can engulf the self-gravitating compact object in all azimuthal directions). It has recently been proved that a necessary condition for the validity of this conjecture in horizonless spacetimes of spatially regular charged compact objects is that the mass $${\mathcal {M}}$$ M be interpreted as the mass contained within the engulfing sphere (and not as the asymptotically measured total ADM mass). In the present paper we raise the following physically intriguing question: is it possible to formulate a unified version of the hoop conjecture which is valid for both black holes and horizonless compact objects? In order to address this important question, we analyze the behavior of the mass-to-circumference ratio of Kerr–Newman black holes. We explicitly prove that if the mass $${\mathcal {M}}$$ M in the hoop relation is interpreted as the quasilocal Einstein–Landau–Lifshitz–Papapetrou and Weinberg mass contained within the black-hole horizon, then these charged and spinning black holes are characterized by the sub-critical mass-to-circumference ratio $$4\pi {\mathcal {M}}/{\mathcal {C}}<1$$ 4 π M / C < 1 . Our results provide evidence for the non-existence of a unified version of the hoop conjecture which is valid for both black-hole spacetimes and spatially regular horizonless compact objects.

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 Black Component of Dark Matter

2014 ◽  
Vol 2014 ◽  
pp. 1-6 ◽  
Author(s):  
A. V. Grobov ◽  
S. G. Rubin ◽  
V. Yu. Shalamova
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Dark Matter ◽  
Mass Spectrum ◽  
Energy Density ◽  
Extra Dimensions ◽  
Primordial Black Hole ◽  
Hole Formation ◽  
Specific Mass ◽  
Black Hole Formation

A mechanism of primordial black hole formation with specific mass spectrum is discussed. It is shown that these black holes could contribute to the energy density of dark matter. Our approach is elaborated in the framework of universal extra dimensions.

scholarly journals Inventory of black hole binaries

2003 ◽  
Vol 212 ◽  
pp. 365-371 ◽  
Author(s):  
Jerome A. Orosz
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Binary Systems ◽  
Compact Object ◽  
X Rays ◽  
Optical Studies ◽  
Dynamical Mass ◽  
X Ray ◽  
Black Hole Binaries ◽  
X Ray Binaries

A small group of X-ray binaries currently provides the best evidence for the existence of stellar-mass black holes. These objects are interacting binary systems where the X-rays arise from accretion of material onto a compact object (i.e., an object with a radius of less than a few hundred km). In some favourable cases, optical studies of the companion star lead to dynamical mass estimates for both components. In 17 cases, the mass of the compact object in an X-ray binary has been shown to exceed the maximum mass of a stable neutron star (about 3 M⊙), which leads to the conclusion that these objects are black holes. In this contribution I will review the basic properties of these black hole binaries.

scholarly journals The primordial black hole mass range

2016 ◽  
Vol 31 (12) ◽  
pp. 1650064 ◽  
Author(s):  
Paul H. Frampton
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Dark Matter ◽  
Early Universe ◽  
Parametric Resonance ◽  
Mass Range ◽  
Primordial Black Hole ◽  
Black Hole Mass ◽  
Arbitrary Mass ◽  
Hybrid Inflation

We investigate Primordial Black Hole (PBH) formation by which we mean black holes produced in the early Universe during radiation domination. After discussing the range of PBH mass permitted in the original mechanism of Carr and Hawking, hybrid inflation with parametric resonance is presented as an existence theorem for PBHs of arbitrary mass. As proposed in arXiv:1510.00400, PBHs with many solar masses can provide a solution to the dark matter problem in galaxies. PBHs can also explain dark matter observed in clusters and suggest a primordial origin for Supermassive Black Holes (SMBHs) in galactic cores.

scholarly journals The minimum testable abundance of primordial black holes at future gravitational-wave detectors

2021 ◽  
Vol 2021 (11) ◽  
pp. 039
Author(s):  
Valerio De Luca ◽  
Gabriele Franciolini ◽  
Paolo Pani ◽  
Antonio Riotto
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Dark Matter ◽  
Gravitational Wave ◽  
Primordial Black Hole ◽  
Spatial Distributions ◽  
Primordial Black Holes ◽  
Next Generation ◽  
Einstein Telescope ◽  
Gravitational Wave Detectors

Abstract The next generation of gravitational-wave experiments, such as Einstein Telescope, Cosmic Explorer and LISA, will test the primordial black hole scenario. We provide a forecast for the minimum testable value of the abundance of primordial black holes as a function of their masses for both the unclustered and clustered spatial distributions at formation. In particular, we show that these instruments may test abundances, relative to the dark matter, as low as 10-10.

scholarly journals Mechanical feedback effects on primordial black hole accretion

2020 ◽  
Vol 638 ◽  
pp. A132 ◽  
Author(s):  
V. Bosch-Ramon ◽  
N. Bellomo
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Accretion Rate ◽  
Compact Object ◽  
Primordial Black Hole ◽  
Primordial Black Holes ◽  
Black Hole Accretion ◽  
The Impact ◽  
Hole Accretion ◽  
Mechanical Feedback

Context. Dark matter may consist, at least partially, of primordial black holes formed during the radiation-dominated era. The radiation produced by accretion onto primordial black holes leaves characteristic signatures on the properties of the medium at high redshift, before and after hydrogen recombination. Therefore, reliable modeling of accretion onto these objects is required to obtain robust constraints on their abundance. Aims. We investigate the effect of mechanical feedback, that is, the impact of outflows (winds and– or –jets) on the medium, on primordial black hole accretion, and thereby on the associated radiation. Methods. Using analytical and numerical calculations, we studied for the first time the possibility that outflows can reduce the accretion rate of primordial black holes with masses similar to those detected by the LIGO-Virgo collaboration. Results. Despite the complexity of the accretion rate evolution, mechanical feedback is useful in to significantly reducing the primordial black hole accretion rate, at least by one order of magnitude, when outflows are aligned with the motion of the compact object. If the outflow is perpendicular to the direction of motion, the effect is less important, but it is still non-negligible. Conclusions. Outflows from primordial black holes, even rather weak ones, can significantly decrease the accretion rate, effectively weakening abundance constraints on these objects. Our results motivate further numerical simulations with a more realistic setup, which would yield more precise quantitative predictions.

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