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1996PhLB..388...51D

Absorption versus decay of black holes in string theory and T-symmetry

1996-01-01

['-']

[]

Classically a black hole can absorb but not emit energy. We discuss how this T-asymmetric property of black holes arises in the recently proposed (T-symmetric) microscopic models of black holes based on bound states of D-branes. In these string theory based models, the nonvanishing classical absorption is made possible essentially by the exponentially increasing degeneracy of quantum states with mass of the black hole. The classical limit of the absorption cross section computed in the microscopic model agrees with the result obtained from a classical analysis of a wave propagating in the background metric of the corresponding black hole (upto a numerical factor).

[]

https://arxiv.org/pdf/hep-th/9605234.pdf

1994PhRvL..72..183C

Supersymmetry of the (2+1)-dimensional black holes

1994-01-01

['-', '-', '-', '-', '-', '-', '-', '-', '-', '-', '-']

[]

The supersymmetry properties of the asymptotically anti-de Sitter (adS) black holes of Einstein theory in 2+1 dimensions are investigated. It is shown that (i) the zero-mass black hole has two exact supersymmetries; (ii) extreme lM=||J|| black holes with M≠0 have only one; and (iii) generic black holes do not have any. It is also argued that the zero-mass hole is the ground state of (1,1) adS supergravity with periodic (``Ramond'') boundary conditions on the spinor fields.

[]

https://arxiv.org/pdf/hep-th/9310194.pdf

2003PhLB..559...65V

Generalization of the KKW analysis for black hole radiation

2003-01-01

['-', '-']

[]

An extension of the Keski-Vakkuri, Kraus and Wilczek (KKW) analysis to black hole spacetimes which are not Schwarzschild-type is presented. Preserving the regularity at the horizon and stationarity of the metric in order to deal with the across-horizon physics, a more general coordinate transformation is introduced. In this analysis the Hawking radiation is viewed as a tunnelling process which emanates from the non-Schwarzschild-type black hole. Expressions for the temperature and entropy of these non-Schwarzschild-type black holes are extracted. As a paradigm, in the context of this generalization, we consider the Garfinkle-Horowitz-Strominger (GHS) black hole as a dynamical background and we derive the modified temperature and entropy of GHS black hole. Deviations are eliminated and corresponding standard results are recovered to the lowest order in the emitted shell of energy. The extremal GHS black hole is found to be non-“frozen” since it is characterized by a constant non-zero temperature. Furthermore, the modified extremality condition forbids naked singularities to form from the collapse of the GHS black hole.

[]

https://arxiv.org/pdf/hep-th/0209185.pdf

2003ApJ...592..767P

Accretion of Low Angular Momentum Material onto Black Holes: Two-dimensional Magnetohydrodynamic Case

2003-01-01

['accretion', 'accretion disks', 'black hole physics', 'galaxies active', 'galaxies nuclei', 'methods numerical', 'mhd', 'astrophysics']

[]

We report on the second phase of our study of slightly rotating accretion flows onto black holes. We consider magnetohydrodynamical (MHD) accretion flows with a spherically symmetric density distribution at the outer boundary but with spherical symmetry broken by the introduction of a small, latitude-dependent angular momentum and a weak radial magnetic field. We study accretion flows by means of numerical two-dimensional, axisymmetric, MHD simulations with and without resistive heating. Our main result is that the properties of the accretion flow depend mostly on an equatorial accretion torus that is made of the material that has too much angular momentum to be accreted directly. The torus accretes, however, because of the transport of angular momentum due to the magnetorotational instability (MRI). Initially, accretion is dominated by the polar funnel, as in the hydrodynamic inviscid case, where material has zero or very low angular momentum. At the later phase of the evolution, the torus thickens toward the poles and develops a corona or an outflow or both. Consequently, the mass accretion through the funnel is stopped. The accretion of rotating gas through the torus is significantly reduced compared with the accretion of nonrotating gas (i.e., the Bondi rate). It is also much smaller than the accretion rate in the inviscid, weakly rotating case. Our results do not change if we switch on or off resistive heating. Overall our simulations are very similar to those presented by Stone, Pringle, Hawley, and Balbus despite different initial and outer boundary conditions. Thus, we confirm that MRI is very robust and controls the nature of radiatively inefficient accretion flows. Although the time-averaged properties of our models approach a steady state, we find that the instantaneous mass-accretion rate in the latter stages of our simulations is highly time-dependent, with the inner flow displaying three generic flow patterns.

[]

https://arxiv.org/pdf/astro-ph/0303093.pdf

1995PhRvD..52.2254M

Cosmological production of charged black hole pairs

1995-01-01

['-', '-', '-', '-', '-', '-', '-', '-']

[]

We investigate the pair creation of charged black holes in a backgrond with a positive cosmological constant. We consider C metrics with a cosmological constant, and show that the conical singularities in the metric only disappear when it reduces to the Reissner-Nordström-de Sitter metric. We construct an instanton describing the pair production of extreme black holes and an instanton describing the pair production of nonextreme black holes from the Reissner-Nordström-de Sitter metric, and calculate their actions. There are a number of striking similarities between these instantons and the Ernst instantons, which describe pair production in a background electromagnetic field. We also observe that the type I instanton in the ordinary C metric with zero cosmological constant is actually the Reissner-Nordström solution.

[]

https://arxiv.org/pdf/gr-qc/9504015.pdf

1997MNRAS.284..318S

Capture of stellar mass compact objects by massive black holes in galactic cusps

1997-01-01

['black hole physics', 'galaxies nuclei', 'astrophysics']

[]

A significant fraction of the stellar population in the cusps around central black holes of galaxies consists of compact remnants of evolved stars, such as white dwarfs, neutron stars and stellar mass black holes. We estimate the rate of capture of compact objects by massive central black holes, assuming that most spiral galaxies have a central black hole of modest mass (~10^6Msolar), and a cuspy spheroid. It is likely that the total capture rate is dominated by nucleated spirals. We estimate the flux of gravitational wave radiation from such coalescences, and the estimated detectable source count for proposed space-based gravitational wave observatories such as LISA. About one event per year should be detectable within 1Gpc, given very conservative estimates of the black hole masses and central galactic densities. We expect 10^2-10^3 detectable sources at lower frequencies (10^-4Hz) `en route' to capture. If stellar mass black holes are ubiquitous, the signal may be dominated by stellar mass black holes coalescing with massive black holes. The rate of white dwarf-white dwarf mergers in the cores of nucleated spirals is estimated at ~10^-6 per year per galaxy.

[]

https://arxiv.org/pdf/astro-ph/9608093.pdf

2011MNRAS.418.2292M

Low-frequency oscillations in black holes: a spectral-timing approach to the case of GX 339-4

2011-01-01

['accretion', 'accretion disks', 'stars binaries close', '-', 'astronomy x rays', '-']

[]

We analysed Rossi X-ray Timing Explorer (RXTE)/PCA and HEXTE data of the transient black hole binary GX 339-4, collected over a time-span of 8 years. We studied the properties and the behaviour of low-frequency quasi-periodic oscillations (QPOs) as a function of the integrated broad-band variability and the spectral parameters during four outbursts (2002, 2004, 2007 and 2010). Most of the QPOs could be classified following the ABC classification which has been proposed before. Our results show that the ABC classification can be extended to include spectral dependencies and that the three QPO types have indeed intrinsically different properties. In terms of the relation between QPO frequency and power-law flux, types A and C QPOs may follow the same relation, whereas the type B QPOs trace out a very different relation. Type B QPO frequencies clearly correlate with the power-law flux and are connected to local increases of the count rate. The frequencies of all QPOs observed in the rising phase of the 2002, 2007 and 2010 outbursts correlate with the disc flux. Our results can be interpreted within the framework of the recently proposed QPO models involving Lense-Thirring precession. We suggest that types C and A QPOs might be connected and could be interpreted as being the result of the same phenomenon observed at different stages of the outburst evolution, while a different physical process produces type B QPOs.

[]

https://arxiv.org/pdf/1108.0540.pdf

2010PhRvL.105c1302E

Black Hole Entropy and SU(2) Chern-Simons Theory

2010-01-01

['-', '-', '-', '-', '-', '-']

[]

Black holes (BH’s) in equilibrium can be defined locally in terms of the so-called isolated horizon boundary condition given on a null surface representing the event horizon. We show that this boundary condition can be treated in a manifestly SU(2) invariant manner. Upon quantization, state counting is expressed in terms of the dimension of Chern-Simons Hilbert spaces on a sphere with punctures. Remarkably, when considering an ensemble of fixed horizon area a<SUB>H</SUB>, the counting can be mapped to simply counting the number of SU(2) intertwiners compatible with the spins labeling the punctures. The resulting BH entropy is proportional to a<SUB>H</SUB> with logarithmic corrections ΔS=-(3)/(2)log⁡a<SUB>H</SUB>. Our treatment from first principles settles previous controversies concerning the counting of states.

[]

https://arxiv.org/pdf/0905.3168.pdf

2010CQGra..27k4006L

Remnant masses, spins and recoils from the merger of generic black hole binaries

2010-01-01

['-', '-', '-', '-', '-']

[]

We obtain empirical formulae for the final remnant black hole mass, spin, and recoil velocity from merging black hole binaries (BHBs) with arbitrary mass ratios and spins. Our formulae are based on the mass ratio and spin dependence of the post-Newtonian expressions for the instantaneous radiated energy, linear momentum, and angular momentum, as well as the ISCO binding energy and angular momentum. The relative weight between the different terms is fixed by amplitude parameters chosen through a least-squares fit of recently available fully nonlinear numerical simulations. These formulae can be used for statistical studies of N-body simulations of galaxy cores and clusters, and the cosmological growth of supermassive black holes. As an example, we use these formulae to obtain a universal spin magnitude distribution of merged black holes and recoil velocity distributions for dry and hot/cold wet mergers. We also revisit the long-term orbital precession and resonances and discuss how they affect spin distributions before the merging regime.

[]

https://arxiv.org/pdf/0904.3541.pdf

2008Sci...321.1060B

Star Formation Around Supermassive Black Holes

2008-01-01

['-', 'astrophysics']

[]

The presence of young massive stars orbiting on eccentric rings within a few tenths of a parsec of the supermassive black hole in the galactic center is challenging for theories of star formation. The high tidal shear from the black hole should tear apart the molecular clouds that form stars elsewhere in the Galaxy, and transport of stars to the galactic center also appears unlikely during their lifetimes. We conducted numerical simulations of the infall of a giant molecular cloud that interacts with the black hole. The transfer of energy during closest approach allows part of the cloud to become bound to the black hole, forming an eccentric disk that quickly fragments to form stars. Compressional heating due to the black hole raises the temperature of the gas up to several hundred to several thousand kelvin, ensuring that the fragmentation produces relatively high stellar masses. These stars retain the eccentricity of the disk and, for a sufficiently massive initial cloud, produce an extremely top-heavy distribution of stellar masses. This potentially repetitive process may explain the presence of multiple eccentric rings of young stars in the presence of a supermassive black hole.

[]

https://arxiv.org/pdf/0810.2723.pdf

2005PhRvD..72b4021Z

Accurate black hole evolutions by fourth-order numerical relativity

2005-01-01

['-', '-', '-', '-', 'methods numerical', '-', 'perturbation theory', '-', 'waves', '-', '-']

[]

We present techniques for successfully performing numerical relativity simulations of binary black holes with fourth-order accuracy. Our simulations are based on a new coding framework which currently supports higher-order finite differencing for the Baumgarte-Shapiro-Shibata-Nakamura formulation of Einstein’s equations, but which is designed to be readily applicable to a broad class of formulations. We apply our techniques to a standard set of numerical relativity test problems, demonstrating the fourth-order accuracy of the solutions. Finally we apply our approach to binary black hole head-on collisions, calculating the waveforms of gravitational radiation generated and demonstrating significant improvements in waveform accuracy over second-order methods with typically achievable numerical resolution.

[]

https://arxiv.org/pdf/gr-qc/0505055.pdf

2004ApJ...601..428K

The Three Spectral Regimes Found in the Stellar Black Hole XTE J1550-564 in Its High/Soft State

2004-01-01

['accretion', 'accretion disks', 'black hole physics', '-', 'astronomy x rays', 'astronomy x rays', 'astrophysics']

[]

The present paper describes the analysis of multiple RXTE PCA data of the black hole binary with superluminal jet, XTE J1550-564, acquired during its 1998-1999 outburst. The X-ray spectra show features typical of the high/soft spectral state and can approximately be described by an optically thick disk spectrum plus a power-law tail. Three distinct spectral regimes, which we call the ``standard regime,'' the ``anomalous regime,'' and the ``apparently standard regime,'' have been found from the entire set of the observed spectra. When the X-ray luminosity is well below ~6×10<SUP>38</SUP> ergs s<SUP>-1</SUP> (assuming a distance of 5 kpc), XTE J1550-564 resides in the standard regime, in which the soft spectral component dominates the power-law component and the observed disk inner radius is kept constant. When the luminosity exceeds the critical luminosity, the apparently standard regime is realized, in which the luminosity of the optically thick disk rises less steeply with the temperature, and the spectral shape is moderately distorted from that of the standard accretion disk. In this regime, the radial temperature gradient of the disk has been found to be flatter than that of the standard accretion disk. The results of the apparently standard regime suggest a slim disk, which is a solution predicted for a high mass accretion rate. In the intermediate anomalous regime (or very high state in the literature), the spectrum becomes much harder, and the disk inner radius derived using a simple disk model spectrum apparently varies significantly with time. These properties can be explained as a result of significant thermal inverse Comptonization of the disk photons, as was found from GRO J1655-40 in its anomalous regime by Kubota and coworkers.

[]

https://arxiv.org/pdf/astro-ph/0310085.pdf

2004PhRvD..70j7501A

Severe constraints on the loop-quantum-gravity energy-momentum dispersion relation from the black-hole area-entropy law

2004-01-01

['-', '-', '-', '-', '-']

[]

We explore a possible connection between two aspects of loop quantum gravity which have been extensively studied in the recent literature: the black-hole area-entropy law and the energy-momentum dispersion relation. We observe that the original Bekenstein argument for the area-entropy law implicitly requires information on the energy-momentum dispersion relation and on the position-momentum uncertainty relation. Recent results show that in first approximation black-hole entropy in loop quantum gravity depends linearly on the area, with small correction terms which have logarithmic or inverse-power dependence on the area. And it has been argued that in loop quantum gravity the dispersion relation should include terms that depend linearly on the Planck length, while no evidence of modification of the position-momentum uncertainty relation has been found. We observe that this scenario with Planck-length-linear modification of the dispersion relation and unmodified position-momentum uncertainty relation is incompatible with the black-hole-entropy results, since it would give rise to a term in the entropy formula going like the square root of the area.

[]

https://arxiv.org/pdf/gr-qc/0405084.pdf

2014NanoL..14.6424W

Black Phosphorus Radio-Frequency Transistors

2014-01-01

['-']

[]

Few-layer and thin film forms of layered black phosphorus (BP) have recently emerged as a promising material for applications in high performance nanoelectronics and infrared optoelectronics. Layered BP thin film offers a moderate bandgap of around 0.3 eV and high carrier mobility, leading to transistors with decent on-off ratio and high on-state current density. Here, we demonstrate the gigahertz frequency operation of black phosphorus field-effect transistors for the first time. The BP transistors demonstrated here show excellent current saturation with an on-off ratio exceeding 2000. We achieved a current density in excess of 270 mA/mm and DC transconductance above 180 mS/mm for hole conduction. Using standard high frequency characterization techniques, we measured a short-circuit current-gain cut-off frequency fT of 12 GHz and a maximum oscillation frequency fmax of 20 GHz in 300 nm channel length devices. BP devices may offer advantages over graphene transistors for high frequency electronics in terms of voltage and power gain due to the good current saturation properties arising from their finite bandgap, thus enabling the future ubiquitous transistor technology that can operate in the multi-GHz frequency range and beyond.

[]

https://arxiv.org/pdf/1410.3880.pdf

2017MNRAS.472.2422M

The cosmic merger rate of stellar black hole binaries from the Illustris simulation

2017-01-01

['black hole physics', 'gravitational waves', 'methods numerical', 'stars black holes', 'stars luminosity function;mass function', '-', '-', '-', '-']

[]

The cosmic merger rate density of black hole binaries (BHBs) can give us an essential clue to constraining the formation channels of BHBs, in light of current and forthcoming gravitational wave detections. Following a Monte Carlo approach, we couple new population-synthesis models of BHBs with the Illustris cosmological simulation, to study the cosmic history of BHB mergers. We explore six population-synthesis models, varying the prescriptions for supernovae, common envelope and natal kicks. In most considered models, the cosmic BHB merger rate follows the same trend as the cosmic star formation rate. The normalization of the cosmic BHB merger rate strongly depends on the treatment of common envelope and on the distribution of natal kicks. We find that most BHBs merging within LIGO's instrumental horizon come from relatively metal-poor progenitors (&lt;0.2 Z<SUB>⊙</SUB>). The total masses of merging BHBs span a large range of values, from ∼6 to ∼82 M<SUB>⊙</SUB>. In our fiducial model, merging BHBs consistent with GW150914, GW151226 and GW170104 represent ∼6, 3 and 12 per cent of all BHBs merging within the LIGO horizon, respectively. The heavy systems, like GW150914, come from metal-poor progenitors (&lt;0.15 Z<SUB>⊙</SUB>). Most GW150914-like systems merging in the local Universe appear to have formed at high redshift, with a long delay time. In contrast, GW151226-like systems form and merge all the way through the cosmic history, from progenitors with a broad range of metallicities. Future detections will be crucial to put constraints on common envelope, on natal kicks, and on the BHB mass function.

[]

https://arxiv.org/pdf/1708.05722.pdf

2009PhRvA..80d3601M

Black-hole radiation in Bose-Einstein condensates

2009-01-01

['-', '-', '-', 'dynamical systems', '-', '-', '-', '-', '-']

[]

We study the phonon fluxes emitted when the condensate velocity crosses the speed of sound, i.e., in backgrounds which are analogous to that of a black hole. We focus on elongated one-dimensional condensates and on stationary flows. Our theoretical analysis and numerical results are based on the Bogoliubov-de Gennes equation without further approximation. The spectral properties of the fluxes and of the long distance density-density correlations are obtained, both with and without an initial temperature. In realistic conditions, we show that the condensate temperature dominates the fluxes and thus hides the presence of the spontaneous emission (the Hawking effect). We also explain why the temperature amplifies the long distance correlations which are intrinsic to this effect. This confirms that the correlation pattern offers a neat signature of the Hawking effect. Optimal conditions for observing the pattern are discussed, as well as correlation patterns associated with scattering of classical waves. Flows associated with white holes are also considered.

[]

https://arxiv.org/pdf/0905.3634.pdf

2019JHEP...05..205Y

The quantum gravity dynamics of near extremal black holes

2019-01-01

['-', '-', 'black hole physics', '-', '-', '-']

[]

We study the quantum effects of Near-Extremal black holes near their horizons. The gravitational dynamics in such backgrounds are closely connected to a particle in AdS <SUB>2</SUB> with constant electric field. We use this picture to solve the theory exactly. We will give a formula to calculate all correlation functions with quantum gravity backreactions as well as the exact Wheeler-DeWitt wavefunction. Using the WdW wavefunction, we investigate the complexity growth in quantum gravity.

[]

https://arxiv.org/pdf/1809.08647.pdf

2016ASSL..418..263G

Galaxy Bulges and Their Massive Black Holes: A Review

2016-01-01

['-', '-', '-', '-', '-']

[]

With references to both key and often forgotten pioneering works, this article starts by presenting a review into how we came to believe in the existence of massive black holes at the centers of galaxies. It then presents the historical development of the near-linear (black hole)-(host spheroid) mass relation, before explaining why this has recently been dramatically revised. Past disagreement over the slope of the (black hole)-(velocity dispersion) relation is also explained, and the discovery of sub-structure within the (black hole)-(velocity dispersion) diagram is discussed. As the search for the fundamental connection between massive black holes and their host galaxies continues, the competing array of additional black hole mass scaling relations for samples of predominantly inactive galaxies are presented.

[]

https://arxiv.org/pdf/1501.02937.pdf

2015PhRvL.114o1102G

No-Hair Theorem for Black Holes in Astrophysical Environments

2015-01-01

['-', '-', '-', '-', '-', 'methods analytical', '-', '-', '-', '-']

[]

According to the no-hair theorem, static black holes are described by a Schwarzschild spacetime provided there are no other sources of the gravitational field. This requirement, however, is in astrophysical realistic scenarios often violated, e.g., if the black hole is part of a binary system or if it is surrounded by an accretion disk. In these cases, the black hole is distorted due to tidal forces. Nonetheless, the subsequent formulation of the no-hair theorem holds: The contribution of the distorted black hole to the multipole moments that describe the gravitational field close to infinity and, thus, all sources is that of a Schwarzschild black hole. It still has no hair. This implies that there is no multipole moment induced in the black hole and that its second Love numbers, which measure some aspects of the distortion, vanish as was already shown in approximations to general relativity. But here we prove this property for astrophysical relevant black holes in full general relativity.

[]

https://arxiv.org/pdf/1503.03240.pdf

2016MNRAS.456.3929S

Three-dimensional simulations of supercritical black hole accretion discs - luminosities, photon trapping and variability

2016-01-01

['accretion', 'accretion disks', 'black hole physics', 'relativity', 'methods numerical', '-']

[]

We present a set of four three-dimensional, general relativistic, radiation magnetohydrodynamical simulations of black hole accretion at supercritical mass accretion rates, dot{M} &gt; dot{M}_Edd. We use these simulations to study how disc properties are modified when we vary the black hole mass, the black hole spin, or the mass accretion rate. In the case of a non-rotating black hole, we find that the total efficiency is of the order of 3 per cent dot{M} c^2, approximately a factor of 2 less than the efficiency of a standard thin accretion disc. The radiation flux in the funnel along the axis is highly super-Eddington, but only a small fraction of the energy released by accretion escapes in this region. The bulk of the 3 per cent dot{M} c^2 of energy emerges farther out in the disc, either in the form of photospheric emission or as a wind. In the case of a black hole with a spin parameter of 0.7, we find a larger efficiency of about 8 per cent dot{M} c^2. By comparing the relative importance of advective and diffusive radiation transport, we show that photon trapping is effective near the equatorial plane. However, near the disc surface, vertical transport of radiation by diffusion dominates. We compare the properties of our fiducial three-dimensional run with those of an equivalent two-dimensional axisymmetric model with a mean-field dynamo. The latter simulation runs nearly 100 times faster than the three-dimensional simulation, and gives very similar results for time-averaged properties of the accretion flow, but does not reproduce the time-variability.

[]

https://arxiv.org/pdf/1509.03168.pdf

2002PhRvD..66d4009K

Quasinormal modes of a small Schwarzschild-anti-de Sitter black hole

2002-01-01

['-', '-', '-', '-', '-', '-', '-', '-']

[]

We compute the quasinormal modes associated with the decay of the massless scalar field around a small Schwarzschild-anti-de Sitter black hole. The computations show that when the horizon radius is much less than the anti-de Sitter radius, the imaginary part of the frequency goes to zero as r<SUP>d-2</SUP><SUB>+</SUB> while the real part of ω decreases to its minimum and then goes to d-1. Thus the quasinormal modes approach the usual AdS modes in the limit r<SUB>+</SUB>--&gt;0. This agrees with suggestions of Horowitz and Hubeny [Phys. Rev. D 62, 024027 (2000)].

[]

https://arxiv.org/pdf/hep-ph/0205142.pdf

2001CQGra..18.2877G

Logarithmic correction to the Bekenstein-Hawking entropy of the BTZ black hole

2001-01-01

['-', '-']

[]

We derive an exact expression for the partition function of the Euclidean BTZ black hole. Using this, we show that for a black hole with large horizon area, the correction to the Bekenstein-Hawking entropy is -<SUP>3</SUP>/<SUB>2</SUB>log area), in agreement with that for the Schwarzschild black hole obtained in the four-dimensional canonical gravity formalism and also in a Lorentzian computation of BTZ black hole entropy. We find that the correct expression for the logarithmic correction in the context of the BTZ black hole comes from the modular invariance associated with the toroidal boundary of the black hole.

[]

https://arxiv.org/pdf/gr-qc/0104010.pdf

2005ApJ...623...23S

The Gravitational Wave Signal from Massive Black Hole Binaries and Its Contribution to the LISA Data Stream

2005-01-01

['black hole physics', 'cosmology theory', 'cosmology early universe', 'gravitational waves', 'relativity', 'astrophysics']

[]

Massive black hole binaries, with masses in the range 10<SUP>3</SUP>-10<SUP>8</SUP> M<SUB>solar</SUB>, are expected to be the most powerful sources of gravitational radiation at mHz frequencies, and hence are among the primary targets for the planned Laser Interferometer Space Antenna (LISA). We extend and refine our previous analysis, detailing the gravitational wave signal expected from a cosmological population of massive black hole binaries. As done in our previous paper, we follow the merger history of dark matter halos, the dynamics of the massive black holes they host, and their growth via gas accretion and binary coalescences in a ΛCDM cosmology. Stellar dynamical processes dominates the orbital evolution of black hole binaries at large separations, while gravitational wave emission takes over at small radii, causing the final coalescence of the pairs. We show that the GW signal from this population, in a 3 yr LISA observation, will be resolved into ~=90 discrete events with S/N&gt;=5, among which ~=35 will be observed above threshold until coalescence. These ``merging events'' involve relatively massive binaries, M~10<SUP>5</SUP> M<SUB>solar</SUB>, in the redshift range 2&lt;~z&lt;~6. The remaining ~=55 events come from higher redshift, less massive binaries (M~5×10<SUP>3</SUP> M<SUB>solar</SUB> at z&gt;~6) and, although their S/N integrated over the duration of the observation can be substantial, the final coalescence phase is at too high a frequency to be directly observable by space-based interferometeres such as LISA. LISA will be able to detect a fraction &gt;~90% of all the coalescences of massive black hole binaries occurring at z&lt;~5. The residual confusion noise from unresolved massive black hole binaries is expected to be at least an order of magnitude below the estimated stochastic noise.

[]

https://arxiv.org/pdf/astro-ph/0409255.pdf

2000ApJ...531L..41C

Correlation among Quasi-Periodic Oscillation Frequencies and Quiescent-State Duration in Black Hole Candidate GRS 1915+105

2000-01-01

['accretion', 'accretion disks', 'black hole physics', 'hydrodynamics', 'shock waves', '-', 'astronomy x rays', 'astrophysics']

[]

We discover a definite correlation between the frequency of the quasi-periodic oscillations (QPOs) in quiescent states and the duration of the quiescent state of the transient X-ray source GRS 1915+105. We find that while the QPO frequency can be explained by the oscillation of shocks in accretion flows, the switching of burst to quiescent states (and vice versa) and their duration can be explained by assuming an outflow from the postshock region. The duration of the quiescent state is inversely related to the QPO frequency. We derive this relation. We also find the correlation between the observed low (~0.001-0.01 Hz) and the intermediate (1-10 Hz) QPO frequencies. Our analytical solutions are verified by analyzing several days of public domain data from the Rossi X-Ray Timing Explorer.

[]

https://arxiv.org/pdf/astro-ph/9910012.pdf

2005GReGr..37.1255B

(Anti-)de Sitter black hole thermodynamics and the generalized uncertainty principle

2005-01-01

['-', '-', '-', '-', '-']

[]

We extend the derivation of the Hawking temperature of a Schwarzschild black hole via the Heisenberg uncertainty principle to the de Sitter and anti-de Sitter spacetimes. The thermodynamics of the Schwarzschild-(anti-)de Sitter black holes is obtained from the generalized uncertainty principle of string theory and non-commutative geometry. This may explain why the thermodynamics of (anti-)de Sitter-like black holes admits a holographic description in terms of a dual quantum conformal field theory, whereas the thermodynamics of Schwarzschild-like black holes does not.

[]

https://arxiv.org/pdf/gr-qc/0411086.pdf

2007ApJ...671...85N

Production of TeV Gamma Radiation in the Vicinity of the Supermassive Black Hole in the Giant Radio Galaxy M87

2007-01-01

['black hole physics', 'galaxies active', 'galaxies', 'gamma rays', 'astrophysics']

[]

Although the giant radio galaxy M87 harbors many distinct regions of broadband nonthermal emission, the recently reported fast variability of TeV γ-rays from M87, on a timescale of days, strongly constrains the range of speculations concerning the possible sites and scenarios of particle acceleration responsible for the observed TeV emission. A natural production site of this radiation is the immediate vicinity of the central supermassive black hole (BH). Because of its low bolometric luminosity, the nucleus of M87 can be effectively transparent for γ-rays up to an energy of 10 TeV, which makes this source an ideal laboratory for the study of particle acceleration processes close to the BH event horizon. We critically analyze different possible radiation mechanisms in this region and argue that the observed very high energy γ-ray emission can be explained as the inverse Compton emission of ultrarelativistic electron-positron pairs produced through the development of an electromagnetic cascade in the BH magnetosphere. We demonstrate, through detailed numerical calculations of acceleration and radiation of electrons in the magnetospheric vacuum gap, that this ``pulsar magnetosphere-like'' scenario can satisfactorily explain the main properties of the TeV γ-ray emission from M87.

[]

https://arxiv.org/pdf/0704.3282.pdf

2004ApJ...606..799J

Constraining the Properties of Supermassive Black Hole Systems Using Pulsar Timing: Application to 3C 66B

2004-01-01

['black hole physics', 'gravitational waves', '-', '-', 'astrophysics']

[]

General expressions for the expected timing residuals induced by gravitational wave (G-wave) emission from a slowly evolving, eccentric, binary black hole system are derived here for the first time. These expressions are used to search for the signature of G-waves emitted by the proposed supermassive binary black hole system in 3C 66B. We use data from long-term timing observations of the radio pulsar PSR B1855+09. For the case of a circular orbit, the emitted G-waves should generate clearly detectable fluctuations in the pulse-arrival times of PSR B1855+09. Since no G-waves are detected, the waveforms are used in a Monte Carlo analysis in order to place limits on the mass and eccentricity of the proposed black hole system. The analysis presented here rules out the adopted system with 95% confidence. The reported analysis also demonstrates several interesting features of a G-wave detector based on pulsar timing.

[]

https://arxiv.org/pdf/astro-ph/0310276.pdf

2004PhRvD..70l4009M

Disappearance of the black hole singularity in loop quantum gravity

2004-01-01

['-', '-', '-', '-', '-']

[]

We apply techniques recently introduced in quantum cosmology to the Schwarzschild metric inside the horizon and near the black hole singularity at r=0. In particular, we use the quantization introduced by Husain and Winkler, which is suggested by Loop Quantum Gravity and is based on an alternative to the Schrödinger representation introduced by Halvorson. Using this quantization procedure, we show that the black hole singularity disappears and spacetime can be dynamically extended beyond the classical singularity.

[]

https://arxiv.org/pdf/gr-qc/0407097.pdf

2019JCAP...11..012Y

Primordial black hole formation and abundance: contribution from the non-linear relation between the density and curvature perturbation

2019-01-01

['-']

[]

The formation and abundance of primordial black holes (PBHs) arising from the curvature perturbation ζ is studied. The non-linear relation between ζ and the density contrast δ means that, even when ζ has an exactly Gaussian distribution, significant non-Gaussianities affecting PBH formation must be considered. Numerical simulations are used to investigate the critical value and the mass of PBHs which form, and peaks theory is used to calculate the mass fraction of the universe collapsing to form PBHs at the time of formation. A formalism to calculate the total present day PBH abundance and mass function is also derived. It is found that the abundance of PBHs is very sensitive to the non-linear effects, and that the power spectrum Script P<SUB>ζ</SUB> must be a factor of Script O (2) larger to produce the same number of PBHs as if using the linear relation between ζ and δ (where the exact value depends on the critical value for a region to collapse and form a PBH). This also means that the derived constraints on the small-scale power spectrum from constraints on the abundance of PBHs are weaker by the same factor.

[]

https://arxiv.org/pdf/1904.00984.pdf

2020PhRvL.125w1101D

Spin-Induced Black Hole Spontaneous Scalarization

2020-01-01

['-', '-', '-']

[]

We study scalar fields in a black hole background and show that, when the scalar is suitably coupled to curvature, rapid rotation can induce a tachyonic instability. This instability, which is the hallmark of spontaneous scalarization in the linearized regime, is expected to be quenched by nonlinearities and endow the black hole with scalar hair. Hence, our results demonstrate the existence of a broad class of theories that share the same stationary black hole solutions with general relativity at low spins, but which exhibit black hole hair at sufficiently high spins (a /M ≳0.5 ). This result has clear implications for tests of general relativity and the nature of black holes with gravitational and electromagnetic observations.

[]

https://arxiv.org/pdf/2006.03095.pdf

2020JHEP...05..004R

Information radiation in BCFT models of black holes

2020-01-01

['-', 'black hole physics', '-', '-', '-', '-']

[]

In this note, following [1-3], we introduce and study various holographic systems which can describe evaporating black holes. The systems we consider are boundary conformal field theories for which the number of local degrees of freedom on the boundary (c<SUB>bdy</SUB>) is large compared to the number of local degrees of freedom in the bulk CFT (c<SUB>bulk</SUB>). We consider states where the boundary degrees of freedom on their own would describe an equilibrium black hole, but the coupling to the bulk CFT degrees of freedom allows this black hole to evaporate. The Page time for the black hole is controlled by the ratio c<SUB>bdy</SUB>/c<SUB>bulk</SUB>. Using both holographic calculations and direct CFT calculations, we study the evolution of the entanglement entropy for the subset of the radiation system (i.e. the bulk CFT) at a distance d &gt; a from the boundary. We find that the entanglement entropy for this subsystem increases until time a + t<SUB>Page</SUB> and then undergoes a phase transition after which the entanglement wedge of the radiation system includes the black hole interior. Remarkably, this occurs even if the radiation system is initially at the same temperature as the black hole so that the two are in thermal equilibrium. In this case, even though the black hole does not lose energy, it "radiates" information through interaction with the radiation system until the radiation system contains enough information to reconstruct the black hole interior.

[]

https://arxiv.org/pdf/1910.12836.pdf

2012PhRvD..86d3512B

Primordial black holes as a tool for constraining non-Gaussianity

2012-01-01

['-', 'cosmology dark matter', '-', '-']

[]

Primordial black holes (PBHs) can form in the early Universe from the collapse of large density fluctuations. Tight observational limits on their abundance constrain the amplitude of the primordial fluctuations on very small scales which cannot otherwise be constrained, with PBHs only forming from the extremely rare large fluctuations. The number of PBHs formed is therefore sensitive to small changes in the shape of the tail of the fluctuation distribution, which itself depends on the amount of non-Gaussianity present. We study, for the first time, how quadratic and cubic local non-Gaussianity of arbitrary size (parametrized by f<SUB>NL</SUB> and g<SUB>NL</SUB> respectively) affects the PBH abundance and the resulting constraints on the amplitude of the fluctuations on very small scales. Intriguingly we find that even nonlinearity parameters of order unity have a significant impact on the PBH abundance. The sign of the non-Gaussianity is particularly important, with the constraint on the allowed fluctuation amplitude tightening by an order of magnitude as f<SUB>NL</SUB> changes from just -0.5 to 0.5. We find that if PBHs are observed in the future, then regardless of the amplitude of the fluctuations, non-negligible negative f<SUB>NL</SUB> would be ruled out. Finally we show that g<SUB>NL</SUB> can have an even larger effect on the number of PBHs formed than f<SUB>NL</SUB>.

[]

https://arxiv.org/pdf/1206.4188.pdf

2017PhRvL.118b1301H

Superfluid Black Holes

2017-01-01

['-', '-']

[]

We present what we believe is the first example of a "λ -line" phase transition in black hole thermodynamics. This is a line of (continuous) second order phase transitions which in the case of liquid <SUP>4</SUP>He marks the onset of superfluidity. The phase transition occurs for a class of asymptotically anti-de Sitter hairy black holes in Lovelock gravity where a real scalar field is conformally coupled to gravity. We discuss the origin of this phase transition and outline the circumstances under which it (or generalizations of it) could occur.

[]

https://arxiv.org/pdf/1609.02564.pdf

2016ApJ...823L..25K

LIGO Gravitational Wave Detection, Primordial Black Holes, and the Near-IR Cosmic Infrared Background Anisotropies

2016-01-01

['cosmology dark matter', 'cosmology diffuse radiation', 'cosmology early universe', 'gravitational waves', '-']

[]

LIGO's discovery of a gravitational wave from two merging black holes (BHs) of similar masses rekindled suggestions that primordial BHs (PBHs) make up the dark matter (DM). If so, PBHs would add a Poissonian isocurvature density fluctuation component to the inflation-produced adiabatic density fluctuations. For LIGO's BH parameters, this extra component would dominate the small-scale power responsible for collapse of early DM halos at z ≳ 10, where first luminous sources formed. We quantify the resultant increase in high-z abundances of collapsed halos that are suitable for producing the first generation of stars and luminous sources. The significantly increased abundance of the early halos would naturally explain the observed source-subtracted near-IR cosmic infrared background (CIB) fluctuations, which cannot be accounted for by known galaxy populations. For LIGO's BH parameters, this increase is such that the observed CIB fluctuation levels at 2-5 μm can be produced if only a tiny fraction of baryons in the collapsed DM halos forms luminous sources. Gas accretion onto these PBHs in collapsed halos, where first stars should also form, would straightforwardly account for the observed high coherence between the CIB and unresolved cosmic X-ray background in soft X-rays. We discuss modifications possibly required in the processes of first star formation if LIGO-type BHs indeed make up the bulk or all of DM. The arguments are valid only if the PBHs make up all, or at least most, of DM, but at the same time the mechanism appears inevitable if DM is made of PBHs.

[]

https://arxiv.org/pdf/1605.04023.pdf

2021PhRvD.103i5019B

Black hole superradiance of self-interacting scalar fields

2021-01-01

['-', '-', '-', '-']

[]

Black hole superradiance is a powerful probe of light, weakly coupled hidden sector particles. Many candidate particles, such as axions, generically have self-interactions that can influence the evolution of the superradiant instability. As pointed out in [A. Gruzinov, arXiv:1604.06422.] in the context of a toy model, much of the existing literature on spin-0 superradiance does not take into account the most important self-interaction-induced processes. These processes lead to energy exchange between quasi-bound levels and particle emission to infinity; for large self-couplings, superradiant growth is saturated at a quasi-equilibrium configuration of reduced level occupation numbers. In this paper, we perform a detailed analysis of the rich dynamics of spin-0 superradiance with self-interactions, and the resulting observational signatures. We focus on quartic self-interactions, which dominate the evolution for most models of interest. We explore multiple distinct regimes of parameter space introduced by a nonzero self-interaction, including the simultaneous population of two or more bound levels; at large coupling, we confirm the basic picture of quasiequilibrium saturation and provide evidence that the "bosenova" collapse does not occur in most of the astrophysical parameter space. Compared to gravitational superradiance, we find that gravitational wave "annihilation" signals and black hole spin-down are parametrically suppressed with increasing interactions, while new gravitational wave "transition" signals can take place for moderate interactions. The novel phenomenon of scalar wave emission is less suppressed at large couplings, and if the particle has Standard Model interactions, then coherent, monochromatic axion wave signals from black hole superradiance may be detectable in proposed axion dark matter experiments.

[]

https://arxiv.org/pdf/2011.11646.pdf

1998PhRvD..57.2436B

(Anti-)evaporation of Schwarzschild-de Sitter black holes

1998-01-01

['-', '-', '-', '-', '-', '-', '-', '-', 'astrophysics', '-']

[]

We study the quantum evolution of black holes immersed in a de Sitter background space. For black holes whose size is comparable to that of the cosmological horizon, this process differs significantly from the evaporation of asymptotically flat black holes. Our model includes the one-loop effective action in the s-wave and large N approximation. Black holes of the maximal mass are in equilibrium. Unexpectedly, we find that nearly maximal quantum Schwarzschild-de Sitter black holes anti-evaporate. However, there is a different perturbative mode that leads to evaporation. We show that this mode will always be excited when a pair of cosmological holes nucleates.

[]

https://arxiv.org/pdf/hep-th/9709224.pdf

2000ApJ...532L..29G

Binary Black Hole Mergers from Planet-like Migrations

2000-01-01

['accretion', 'accretion disks', 'stars binaries close', 'black hole physics', 'galaxies quasars', 'astrophysics']

[]

If supermassive black holes (BHs) are generically present in galaxy centers, and if galaxies are built up through hierarchical merging, BH binaries are at least temporary features of most galactic bulges. Observations suggest, however, that binary BHs are rare, pointing toward a binary lifetime far shorter than the Hubble time. We show that, almost regardless of the detailed mechanism, all stellar dynamical processes are too slow in reducing the orbital separation once orbital velocities in the binary exceed the virial velocity of the system. We propose that a massive gas disk surrounding a BH binary can effect its merger rapidly, in a scenario analogous to the orbital decay of super-Jovian planets due to a proto-planetary disk. As in the case of planets, gas accretion onto the secondary (here a supermassive BH) is integrally connected with its inward migration. Such accretion would give rise to quasar activity. BH binary mergers could therefore be responsible for many or most quasars.

[]

https://arxiv.org/pdf/astro-ph/9912111.pdf

2007PASJ...59S.315M

Suzaku Observations of the Hard X-Ray Variability of MCG -6-30-15: the Effects of Strong Gravity around a Kerr Black Hole

2007-01-01

['galaxies active', 'galaxies', 'galaxies seyfert', 'astronomy x rays', 'astrophysics']

[]

Suzaku has, for the first time, enabled the hard X-ray variability of the Seyfert 1 galaxy MCG -6-30-15 to be measured. The variability in the 14-45keV band, which is dominated by a strong reflection hump, is quenched relative to that at a few keV. This directly demonstrates that the whole reflection spectrum is much less variable than the power-law continuum. The broadband spectral variability can be decomposed into two components -- a highly variable power-law and constant reflection -- as previously inferred from other observations in the 2-10keV band. The strong reflection and high iron abundance give rise to a strong broad iron line, which requires the inner disc radius to be at about 2 gravitational radii. Our results are consistent with the predictions of the light bending model which invokes the very strong gravitational effects expected very close to a rapidly spinning black hole.

[]

https://arxiv.org/pdf/astro-ph/0609521.pdf

2009PhRvD..79l4028B

Effective-one-body waveforms calibrated to numerical relativity simulations: Coalescence of nonspinning, equal-mass black holes

2009-01-01

['-', '-', '-', '-', 'methods numerical', 'methods numerical', '-', 'perturbation theory', '-', '-', '-']

[]

We calibrate the effective-one-body (EOB) model to an accurate numerical simulation of an equal-mass, nonspinning binary black-hole coalescence produced by the Caltech-Cornell Collaboration. Aligning the EOB and numerical waveforms at low frequency over a time interval of ∼1000M, and taking into account the uncertainties in the numerical simulation, we investigate the significance and degeneracy of the EOB-adjustable parameters during inspiral, plunge, and merger, and determine the minimum number of EOB-adjustable parameters that achieves phase and amplitude agreements on the order of the numerical error. We find that phase and fractional amplitude differences between the numerical and EOB values of the dominant gravitational-wave mode h<SUB>22</SUB> can be reduced to 0.02 radians and 2%, respectively, until a time 20M before merger, and to 0.04 radians and 7%, respectively, at a time 20M after merger (during ringdown). Using LIGO, Enhanced LIGO, and Advanced LIGO noise curves, we find that the overlap between the EOB and the numerical h<SUB>22</SUB>, maximized only over the initial phase and time of arrival, is larger than 0.999 for equal-mass binary black holes with total mass 30-150M<SUB>⊙</SUB>. In addition to the leading gravitational mode (2, 2), we compare the dominant subleading modes (4, 4) and (3, 2) for the inspiral and find phase and amplitude differences on the order of the numerical error. We also determine the mass-ratio dependence of one of the EOB-adjustable parameters by calibrating to numerical inspiral waveforms for black-hole binaries with mass ratios 2∶1 and 3∶1. The results presented in this paper improve and extend recent successful attempts aimed at providing gravitational-wave data analysts the best analytical EOB model capable of interpolating accurate numerical simulations.

[]

https://arxiv.org/pdf/0902.0790.pdf

2014SSRv..183..189C

Massive Binary Black Holes in Galactic Nuclei and Their Path to Coalescence

2014-01-01

['black hole physics', 'dynamical systems', '-', 'black hole physics', '-']

[]

Massive binary black holes form at the centre of galaxies that experience a merger episode. They are expected to coalesce into a larger black hole, following the emission of gravitational waves. Coalescing massive binary black holes are among the loudest sources of gravitational waves in the Universe, and the detection of these events is at the frontier of contemporary astrophysics. Understanding the black hole binary formation path and dynamics in galaxy mergers is therefore mandatory. A key question poses: during a merger, will the black holes descend over time on closer orbits, form a Keplerian binary and coalesce shortly after? Here we review progress on the fate of black holes in both major and minor mergers of galaxies, either gas-free or gas-rich, in smooth and clumpy circum-nuclear discs after a galactic merger, and in circum-binary discs present on the smallest scales inside the relic nucleus.

[]

https://arxiv.org/pdf/1407.3102.pdf

2006CQGra..23.5643E

Black holes in Einstein-aether theory

2006-01-01

['-', 'astrophysics', '-']

[]

We study black hole solutions in general relativity coupled to a unit timelike vector field dubbed the 'aether'. To be causally isolated, a black hole interior must trap matter fields as well as all aether and metric modes. The theory possesses spin-0, spin-1 and spin-2 modes whose speeds depend on four coupling coefficients. We find that the full three-parameter family of local spherically symmetric static solutions is always regular at a metric horizon, but only a two-parameter subset is regular at a spin-0 horizon. Asymptotic flatness imposes another condition, leaving a one-parameter family of regular black holes. These solutions are compared to the Schwarzschild solution using numerical integration for a special class of coupling coefficients. They are very close to Schwarzschild outside the horizon for a wide range of couplings, and have a spacelike singularity inside, but differ inside quantitatively. Some quantities constructed from the metric and aether oscillate in the interior as the singularity is approached. The aether is at rest at spatial infinity and flows into the black hole, but differs significantly from the 4-velocity of freely falling geodesics.

[]

https://arxiv.org/pdf/gr-qc/0604088.pdf

2015MNRAS.448.1504S

A refined sub-grid model for black hole accretion and AGN feedback in large cosmological simulations

2015-01-01

['black hole physics', 'methods numerical', 'galaxies active', 'galaxies evolution', 'galaxies nuclei', 'galaxies quasars', '-']

[]

In large-scale cosmological hydrodynamic simulations simplified sub-grid models for gas accretion on to black holes and AGN feedback are commonly used. Such models typically depend on various free parameters, which are not well constrained. We present a new advanced model containing a more detailed description of AGN feedback, where those parameters reflect the results of recent observations. The model takes the dependence of these parameters on the black hole properties into account and describes a continuous transition between the feedback processes acting in the so-called radio-mode and quasar-mode. In addition, we implement a more detailed description of the accretion of gas on to black holes by distinguishing between hot and cold gas accretion. Our new implementations prevent black holes from gaining too much mass, particularly at low redshifts, so that our simulations are successful in reproducing the observed present-day black hole mass function. Our new model also suppresses star formation in massive galaxies slightly more efficiently than many state-of-the-art models. Therefore, the simulations that include our new implementations produce a more realistic population of quiescent and star-forming galaxies compared to recent observations, even if some discrepancies remain. In addition, the baryon conversion efficiencies in our simulation are - except for the high-mass end - consistent with observations presented in the literature over the mass range resolved by our simulations. Finally, we discuss the significant impact of the feedback model on the low-luminous end of the AGN luminosity function.

[]

https://arxiv.org/pdf/1409.3221.pdf

2020JHEP...06..085H

Islands in Schwarzschild black holes

2020-01-01

['black hole physics', 'black hole physics', '-', '-']

[]

We study the Page curve for asymptotically flat eternal Schwarzschild black holes in four and higher spacetime dimensions. Before the Page time, the entanglement entropy grows linearly in time. After the Page time, the entanglement entropy of a given region outside the black hole is largely modified by the emergence of an island, which extends to the outer vicinity of the event horizon. As a result, it remains a constant value which reproduces the Bekenstein-Hawking entropy, consistent with the finiteness of the von Neumann entropy for an eternal black hole.

[]

https://arxiv.org/pdf/2004.05863.pdf

2017ApJ...846...82Z

Constraining Formation Models of Binary Black Holes with Gravitational-wave Observations

2017-01-01

['-', 'gravitational waves', 'methods statistical', 'stars black holes', 'stars novae;cataclysmic variables', '-', '-', '-', '-']

[]

Gravitational waves (GWs) from binary black hole (BBH) mergers provide a new probe of massive-star evolution and the formation channels of binary compact objects. By coupling the growing sample of BBH systems with population synthesis models, we can begin to constrain the parameters of such models and glean unprecedented knowledge about the inherent physical processes that underpin binary stellar evolution. In this study, we apply a hierarchical Bayesian model to mass measurements from a synthetic GW sample to constrain the physical prescriptions in population models and the relative fraction of systems generated from various channels. We employ population models of two canonical formation scenarios in our analysis—isolated binary evolution involving a common-envelope phase and dynamical formation within globular clusters—with model variations for different black hole natal kick prescriptions. We show that solely with chirp mass measurements, it is possible to constrain natal kick prescriptions and the relative fraction of systems originating from each formation channel with { O }(100) of confident detections. This framework can be extended to include additional formation scenarios, model parameters, and measured properties of the compact binary.

[]

https://arxiv.org/pdf/1704.07379.pdf

2014MNRAS.437.2744T

Swift J1644+57 gone MAD: the case for dynamically important magnetic flux threading the black hole in a jetted tidal disruption event

2014-01-01

['accretion', 'accretion disks', 'black hole physics', 'mhd', 'gamma rays', 'astronomy x rays', '-', '-', '-']

[]

The unusual transient Swift J1644+57 likely resulted from a collimated relativistic jet, powered by the sudden onset of accretion on to a massive black hole (BH) following the tidal disruption (TD) of a star. However, several mysteries cloud the interpretation of this event, including (1) the extreme flaring and `plateau' shape of the X-ray/γ-ray light curve during the first t - t<SUB>trig</SUB> ∼ 10 d after the γ-ray trigger; (2) unexpected rebrightening of the forward shock radio emission at t - t<SUB>trig</SUB> ∼ months; (3) lack of obvious evidence for jet precession, despite the misalignment typically expected between the angular momentum of the accretion disc and BH; (4) recent abrupt shut-off in the jet X-ray emission at t - t<SUB>trig</SUB> ∼ 1.5 yr. Here, we show that all of these seemingly disparate mysteries are naturally resolved by one assumption: the presence of strong magnetic flux Φ<SUB>•</SUB> threading the BH. Just after the TD event, Φ<SUB>•</SUB> is dynamically weak relative to the high rate of fall-back accretion dot{M}, such that the accretion disc (jet) freely precesses about the BH axis = our line of sight. As dot{M} decreases, however, Φ<SUB>•</SUB> becomes dynamically important, leading to a state of `magnetically arrested disk' (MAD). MAD naturally aligns the jet with the BH spin, but only after an extended phase of violent rearrangement (jet wobbling), which in Swift J1644+57 starts a few days before the γ-ray trigger and explains the erratic early light curve. Indeed, the entire X-ray light curve can be fitted to the predicted power-law decay dot{M} ∝ t^{-α } (α ≃ 5/3 - 2.2) if the TD occurred a few weeks prior to the γ-ray trigger. Jet energy directed away from the line of sight, either prior to the trigger or during the jet alignment process, eventually manifests as the observed radio rebrightening, similar to an off-axis (orphan) γ-ray burst afterglow. As suggested recently, the late X-ray shut-off occurs when the disc transitions to a geometrically thin (jetless) state once dot{M} drops below ∼the Eddington rate. We predict that, in several years, a transition to a low/hard state will mark a revival of the jet and its associated X-ray emission. We use our model for Swift J1644+57 to constrain the properties of the BH and disrupted star, finding that a solar mass main-sequence star disrupted by a relatively low-mass M<SUB>•</SUB> ∼ 10<SUP>5</SUP>-10<SUP>6</SUP> M<SUB>⊙</SUB> BH is consistent with the data, while a white dwarf disruption (though still possible) is disfavoured. The magnetic flux required to power Swift J1644+57 is much too large to be supplied by the star itself, but it could be collected from a quiescent `fossil' accretion disc that was present in the galactic nucleus prior to the TD. The presence (lack of) of such a fossil disc could be a deciding factor in what TD events are accompanied by powerful jets.

[]

https://arxiv.org/pdf/1301.1982.pdf

2018PhRvL.121p1103F

Black Hole Mergers from an Evolving Population of Globular Clusters

2018-01-01

['-', '-']

[]

The high rate of black hole (BH) mergers detected by LIGO/Virgo opened questions on their astrophysical origin. One possibility is the dynamical channel, in which binary formation and hardening is catalyzed by dynamical encounters in globular clusters (GCs). Previous studies have shown that the BH merger rate from the present day GC density in the Universe is lower than the observed rate. In this Letter, we study the BH merger rate by accounting for the first time for the evolution of GCs within their host galaxies. The mass in GCs was initially ∼8 ×higher , which decreased to its present value due to evaporation and tidal disruption. Many BH binaries that were ejected long before their merger originated in GCs that no longer exist. We find that the comoving merger rate in the dynamical channel from GCs varies between 18 to 35 Gpc<SUP>-3</SUP> yr<SUP>-1</SUP> between redshift z =0.5 to 2, and the total rate is 1, 5, 24 events per day within z =0.5 , 1, and 2, respectively. The cosmic evolution and disruption of GCs systematically increases the present-day merger rate by a factor ∼2 relative to isolated clusters. Gravitational wave detector networks offer an unique observational probe of the initial number of GC populations and their subsequent evolution across cosmic time.

[]

https://arxiv.org/pdf/1806.02351.pdf

1995CQGra..12.1699C

The off-shell black hole

1995-01-01

['-', '-']

[]

The standard (Euclidean) action principle for the gravitational field implies that for spacetimes with black hole topology, the opening angle at the horizon and the horizon area are canonical conjugates. It is shown that the opening angle bears the same relation to the horizon area that the time separation bears to the mass at infinity. The dependence of the wave function on this new degree of freedom is governed by an extended Wheeler-DeWitt equation. Summing over all horizon areas yields the black hole entropy.

[]

https://arxiv.org/pdf/gr-qc/9312002.pdf

2009JHEP...07..011O

Three-dimensional black holes, gravitational solitons, kinks and wormholes for BHT massive gravity

2009-01-01

['-', '-']

[]

The theory of massive gravity in three dimensions recently proposed by Bergshoeff, Hohm and Townsend (BHT) is considered. At the special case when the theory admits a unique maximally symmetric solution, a conformally flat solution that contains black holes and gravitational solitons for any value of the cosmological constant is found. For negative cosmological constant, the black hole is characterized in terms of the mass and the ``gravitational hair'' parameter, providing a lower bound for the mass. For negative mass parameter, the black hole acquires an inner horizon, and the entropy vanishes at the extremal case. Gravitational solitons and kinks, being regular everywhere, can be obtained from a double Wick rotation of the black hole. A wormhole solution in vacuum that interpolates between two static universes of negative spatial curvature is obtained as a limiting case of the gravitational soliton with a suitable identification. The black hole and the gravitational soliton fit within a set of relaxed asymptotically AdS conditions as compared with the one of Brown and Henneaux. In the case of positive cosmological constant the black hole possesses an event and a cosmological horizon, whose mass is bounded from above. Remarkably, the temperatures of the event and the cosmological horizons coincide, and at the extremal case one obtains the analogue of the Nariai solution, dS<SUB>2</SUB> × S<SUP>1</SUP>. A gravitational soliton is also obtained through a double Wick rotation of the black hole. The Euclidean continuation of these solutions describes instantons with vanishing Euclidean action. For vanishing cosmological constant the black hole and the gravitational soliton are asymptotically locally flat spacetimes. The rotating solutions can be obtained by boosting the previous ones in the t-phi plane.

[]

https://arxiv.org/pdf/0905.1545.pdf

2012PhRvD..85d4024B

On black holes in massive gravity

2012-01-01

['-', '-', '-', '-', '-']

[]

In massive gravity, the black hole solutions found so far on Minkowski space happen to convert horizons into a certain type of singularities. Here, we explore whether these singularities can be avoided if space-time is not asymptotically Minkowskian. We find an exact analytic black hole (BH) solution, which evades the above problem by a transition at large scales to self-induced de Sitter space-time, with the curvature scale set by the graviton mass. This solution is similar to the ones discovered by Koyama, Niz, and Tasinato, and by Nieuwenhuizen, but differs in detail. The solution demonstrates that in massive general relativity, in the Schwarzschild coordinate system, a BH metric has to be accompanied by the Stückelberg fields with nontrivial backgrounds to prevent the horizons to convert into the singularities. We also find an analogous solution for a Reissner-Nordström BH on de Sitter space. A limitation of our approach is that we find the solutions only for specific values of the two free parameters of the theory, for which both the vector and scalar fluctuations lose their kinetic terms; however, we hope our solutions represent a broader class with better-behaved perturbations.

[]

https://arxiv.org/pdf/1111.3613.pdf

2017PhRvD..95f4024J

Hierarchical data-driven approach to fitting numerical relativity data for nonprecessing binary black holes with an application to final spin and radiated energy

2017-01-01

['-', '-']

[]

Numerical relativity is an essential tool in studying the coalescence of binary black holes (BBHs). It is still computationally prohibitive to cover the BBH parameter space exhaustively, making phenomenological fitting formulas for BBH waveforms and final-state properties important for practical applications. We describe a general hierarchical bottom-up fitting methodology to design and calibrate fits to numerical relativity simulations for the three-dimensional parameter space of quasicircular nonprecessing merging BBHs, spanned by mass ratio and by the individual spin components orthogonal to the orbital plane. Particular attention is paid to incorporating the extreme-mass-ratio limit and to the subdominant unequal-spin effects. As an illustration of the method, we provide two applications, to the final spin and final mass (or equivalently: radiated energy) of the remnant black hole. Fitting to 427 numerical relativity simulations, we obtain results broadly consistent with previously published fits, but improving in overall accuracy and particularly in the approach to extremal limits and for unequal-spin configurations. We also discuss the importance of data quality studies when combining simulations from diverse sources, how detailed error budgets will be necessary for further improvements of these already highly accurate fits, and how this first detailed study of unequal-spin effects helps in choosing the most informative parameters for future numerical relativity runs.

[]

https://arxiv.org/pdf/1611.00332.pdf

2005PhRvD..72j3517B

New signature of dark matter annihilations: Gamma rays from intermediate-mass black holes

2005-01-01

['-', '-', '-', '-', 'cosmology dark matter', 'black hole physics', '-', 'cosmic rays', 'astrophysics', '-']

[]

We study the prospects for detecting gamma rays from dark matter (DM) annihilations in enhancements of the DM density (mini-spikes) around intermediate-mass black holes (IMBH) with masses in the range 10<SUP>2</SUP>≲M/M<SUB>⊙</SUB>≲10<SUP>6</SUP>. Focusing on two different IMBH formation scenarios, we show that, for typical values of mass and cross section of common DM candidates, mini-spikes, produced by the adiabatic growth of DM around pregalactic IMBHs, would be bright sources of gamma rays, which could be easily detected with large field-of-view gamma-ray experiments such as GLAST, and further studied with smaller field-of-view, larger-area experiments like Air Cherenkov Telescopes CANGAROO, HESS, MAGIC, and VERITAS. The detection of many gamma-ray sources not associated with a luminous component of the Local Group, and with identical cutoffs in their energy spectra at the mass of the DM particle, would provide a potential smoking-gun signature of DM annihilations and shed new light on the nature of intermediate and supermassive black holes.

[]

https://arxiv.org/pdf/astro-ph/0509565.pdf

2012PThPh.128..153Y

Bosenova Collapse of Axion Cloud around a Rotating Black Hole

2012-01-01

['-', '-', '-', '-', '-']

[]

Motivated by possible existence of stringy axions with ultralight mass, we study the behavior of an axion field around a rapidly rotating black hole (BH) obeying the sine-Gordon equation by numerical simulations. Due to superradiant instability, the axion field extracts the rotational energy of the BH and the nonlinear self-interaction becomes important as the field grows larger. We present clear numerical evidences that the nonlinear effect leads to a collapse of the axion cloud and a subsequent explosive phenomena, which is analogous to the ``bosenova'' observed in experiments of Bose-Einstein condensate. The criterion for the onset of the bosenova collapse is given. We also discuss the reason why the bosenova happens by constructing an effective theory of a wavepacket model under the nonrelativistic approximation.

[]

https://arxiv.org/pdf/1203.5070.pdf

2017MNRAS.471.4256V

Forming short-period Wolf-Rayet X-ray binaries and double black holes through stable mass transfer

2017-01-01

['stars black holes', 'stars wolf rayet', 'astronomy x rays', '-', '-']

[]

We show that black hole high-mass X-ray binaries (HMXBs) with O- or B-type donor stars and relatively short orbital periods, of order one week to several months may survive spiral-in, to then form Wolf-Rayet (WR) X-ray binaries with orbital periods of order a day to a few days; while in systems where the compact star is a neutron star, HMXBs with these orbital periods never survive spiral-in. We therefore predict that WR X-ray binaries can only harbour black holes. The reason why black hole HMXBs with these orbital periods may survive spiral-in is: the combination of a radiative envelope of the donor star and a high mass of the compact star. In this case, when the donor begins to overflow its Roche lobe, the systems are able to spiral in slowly with stable Roche lobe overflow, as is shown by the system SS433. In this case, the transferred mass is ejected from the vicinity of the compact star (so-called isotropic re-emission mass-loss mode, or SS433-like mass-loss), leading to gradual spiral-in. If the mass ratio of donor and black hole is ≳3.5, these systems will go into common-envelope evolution and are less likely to survive. If they survive, they produce WR X-ray binaries with orbital periods of a few hours to one day. Several of the well-known WR+O binaries in our Galaxy and the Magellanic Clouds, with orbital periods in the range between a week and several months, are expected to evolve into close WR-black hole binaries, which may later produce close double black holes. The galactic formation rate of double black holes resulting from such systems is still uncertain, as it depends on several poorly known factors in this evolutionary picture. It might possibly be as high as ∼10<SUP>-5</SUP> yr<SUP>-1</SUP>.

[]

https://arxiv.org/pdf/1701.02355.pdf

2017MNRAS.467..524B

Stellar-mass black holes in young massive and open stellar clusters and their role in gravitational-wave generation

2017-01-01

['clusters open', 'clusters globular', 'stars kinematics and dynamics', 'stars black holes', 'methods numerical', 'gravitational waves', '-', '-']

[]

Stellar-remnant black holes (BH) in dense stellar clusters have always drawn attention due to their potential in a number of phenomena, especially the dynamical formation of binary black holes (BBH), which potentially coalesce via gravitational-wave radiation. This study presents a preliminary set of evolutionary models of compact stellar clusters with initial masses ranging over 1.0 × 10<SUP>4</SUP>-5.0 × 10<SUP>4</SUP> M<SUB>⊙</SUB>, and half-mass radius of 2 or 1 pc, which is typical for young massive and starburst clusters. They have metallicities between 0.05 Z<SUB>⊙</SUB> and Z<SUB>⊙</SUB>. Including contemporary schemes for stellar wind and remnant formation, such model clusters are evolved, for the first time, using the state-of-the-art direct N-body evolution program nbody7, until their dissolution or at least for 10 Gyr. That way, a self-regulatory behaviour in the effects of dynamical interactions among the BHs is demonstrated. In contrast to earlier studies, the BBH coalescences obtained in these models show a prominence in triple-mediated coalescences while being bound to the clusters, compared to those occurring among the BBHs that are dynamically ejected from the clusters. A broader mass spectrum of the BHs and lower escape velocities of the clusters explored here might cause this difference, which is yet to be fully understood. Among the BBH coalescences obtained here, there are ones that resemble the detected GW151226, LVT151012 and GW150914 events and also ones that are even more massive. A preliminary estimate suggests few 10-100 s of BBH coalescences per year, originating due to dynamics in stellar clusters that can be detected by the Laser Interferometer Gravitational-Wave Observatory (LIGO) at its design sensitivity.

[]

https://arxiv.org/pdf/1611.09357.pdf

2018EPJC...78..960O

Black holes by gravitational decoupling

2018-01-01

['-']

[]

We investigate how a spherically symmetric fluid modifies the Schwarzschild vacuum solution when there is no exchange of energy-momentum between the fluid and the central source of the Schwarzschild metric. This system is described by means of the gravitational decoupling realised via the minimal geometric deformation approach, which allows us to prove that the fluid must be anisotropic. Several cases are then explicitly shown.

[]

https://arxiv.org/pdf/1804.03468.pdf

2018PASJ...70S..37G

Galaxy interactions trigger rapid black hole growth: An unprecedented view from the Hyper Suprime-Cam survey

2018-01-01

['galaxies active', 'galaxies evolution', 'galaxies interactions', '-', '-']

[]

Collisions and interactions between gas-rich galaxies are thought to be pivotal stages in their formation and evolution, causing the rapid production of new stars, and possibly serving as a mechanism for fueling supermassive black holes (BHs). Harnessing the exquisite spatial resolution (∼0{^''<SUB>.</SUB>}5) afforded by the first ∼170 deg<SUP>2</SUP> of the Hyper Suprime-Cam (HSC) survey, we present our new constraints on the importance of galaxy-galaxy major mergers (1 : 4) in growing BHs throughout the last ∼8 Gyr. Utilizing mid-infrared observations in the WISE all-sky survey, we robustly select active galactic nuclei (AGN) and mass-matched control galaxy samples, totaling ∼140000 spectroscopically confirmed systems at i &lt; 22 mag. We identify galaxy interaction signatures using a novel machine-learning random forest decision tree technique allowing us to select statistically significant samples of major mergers, minor mergers / irregular systems, and non-interacting galaxies. We use these samples to show that galaxies undergoing mergers are a factor of ∼2-7 more likely to contain luminous obscured AGN than non-interacting galaxies, and this is independent of both stellar mass and redshift to z &lt; 0.9. Furthermore, based on our comparison of AGN fractions in mass-matched samples, we determine that the most luminous AGN population (L<SUB>AGN</SUB> ≳ 10<SUP>45</SUP> erg s<SUP>-1</SUP>) systematically reside in merging systems over non-interacting galaxies. Our findings show that galaxy-galaxy interactions do, on average, trigger luminous AGN activity substantially more often than in secularly evolving non-interacting galaxies, and we further suggest that the BH growth rate may be closely tied to the dynamical time of the merger system.

[]

https://arxiv.org/pdf/1706.07436.pdf

2024NatAs...8..126B

Evidence for heavy-seed origin of early supermassive black holes from a z ≈ 10 X-ray quasar

2024-01-01

['-', '-']

[]

Observations of quasars reveal that many supermassive black holes (BHs) were in place less than 700 Myr after the Big Bang. However, the origin of the first BHs remains a mystery. Seeds of the first BHs are postulated to be either light (that is, 10−100 M<SUB>⊙</SUB>), remnants of the first stars, or heavy (that is, 10−10<SUP>5</SUP> M<SUB>⊙</SUB>), originating from the direct collapse of gas clouds. Here, harnessing recent data from the Chandra X-ray Observatory, we report the detection of an X-ray-luminous massive BH in a gravitationally lensed galaxy identified by the James Webb Space Telescope at redshift z ≈ 10.3 behind the cluster lens Abell 2744. This heavily obscured quasar with a bolometric luminosity of ~5 × 10<SUP>45</SUP> erg s<SUP>−1</SUP> harbours an ~10<SUP>7</SUP>−10<SUP>8</SUP> M<SUB>⊙</SUB> BH assuming accretion at the Eddington limit. This mass is comparable to the inferred stellar mass of its host galaxy, in contrast to what is found in the local Universe wherein the BH mass is ~0.1% of the host galaxy's stellar mass. The combination of such a high BH mass and large BH-to-galaxy stellar mass ratio just ~500 Myr after the Big Bang was theoretically predicted and is consistent with a picture wherein BHs originated from heavy seeds.

[]

https://arxiv.org/pdf/2305.15458.pdf

2015PhRvL.115l1102B

Fast and Accurate Prediction of Numerical Relativity Waveforms from Binary Black Hole Coalescences Using Surrogate Models

2015-01-01

['-', '-', '-', '-', 'methods numerical', 'methods numerical', '-', 'waves', '-', '-', 'methods numerical', '-', '-', '-', '-']

[]

Simulating a binary black hole coalescence by solving Einstein's equations is computationally expensive, requiring days to months of supercomputing time. Using reduced order modeling techniques, we construct an accurate surrogate model, which is evaluated in a millisecond to a second, for numerical relativity (NR) waveforms from nonspinning binary black hole coalescences with mass ratios in [1, 10] and durations corresponding to about 15 orbits before merger. We assess the model's uncertainty and show that our modeling strategy predicts NR waveforms not used for the surrogate's training with errors nearly as small as the numerical error of the NR code. Our model includes all spherical-harmonic <SUP>-2</SUP>Y<SUB>ℓm</SUB> waveform modes resolved by the NR code up to ℓ=8 . We compare our surrogate model to effective one body waveforms from 50 M<SUB>⊙</SUB> to 300 M<SUB>⊙</SUB> for advanced LIGO detectors and find that the surrogate is always more faithful (by at least an order of magnitude in most cases).

[]

https://arxiv.org/pdf/1502.07758.pdf

2010ApJ...719.1315K

Constraints on Black Hole Growth, Quasar Lifetimes, and Eddington Ratio Distributions from the SDSS Broad-line Quasar Black Hole Mass Function

2010-01-01

['black hole physics', 'galaxies active', 'galaxies luminosity function;mass function', 'stars luminosity function;mass function', 'galaxies nuclei', 'galaxies statistics', 'galaxies quasars', '-']

[]

We present an estimate of the black hole mass function of broad-line quasars (BLQSOs) that self-consistently corrects for incompleteness and the statistical uncertainty in the mass estimates, based on a sample of 9886 quasars at 1 &lt; z &lt; 4.5 drawn from the Sloan Digital Sky Survey (SDSS). We find evidence for "cosmic downsizing" of black holes in BLQSOs, where the peak in their number density shifts to higher redshift with increasing black hole mass. The cosmic mass density for black holes seen as BLQSOs peaks at z ~ 2. We estimate the completeness of the SDSS as a function of the black hole mass and Eddington ratio, and find that at z &gt; 1 it is highly incomplete at M <SUB>BH</SUB> &lt;~ 10<SUP>9</SUP> M <SUB>sun</SUB> and L/L <SUB>Edd</SUB> &lt;~ 0.5. We estimate a lower limit on the lifetime of a single BLQSO phase to be t <SUB>BL</SUB> &gt; 150 ± 15 Myr for black holes at z = 1 with a mass of M <SUB>BH</SUB> = 10<SUP>9</SUP> M <SUB>sun</SUB>, and we constrain the maximum mass of a black hole in a BLQSO to be ~3 × 10<SUP>10</SUP> M <SUB>sun</SUB>. Our estimated distribution of BLQSO Eddington ratios peaks at L/L <SUB>Edd</SUB> ~ 0.05 and has a dispersion of ~0.4 dex, implying that most BLQSOs are not radiating at or near the Eddington limit; however, the location of the peak is subject to considerable uncertainty. The steep increase in number density of BLQSOs toward lower Eddington ratios is expected if the BLQSO accretion rate monotonically decays with time. Furthermore, our estimated lifetime and Eddington ratio distributions imply that the majority of the most massive black holes spend a significant amount of time growing in an earlier obscured phase, a conclusion which is independent of the unknown obscured fraction. These results are consistent with models for self-regulated black hole growth, at least for massive systems at z &gt; 1, where the BLQSO phase occurs at the end of a fueling event when black hole feedback unbinds the accreting gas, halting the accretion flow.

[]

https://arxiv.org/pdf/1006.3561.pdf

2010CQGra..27a5010N

Noncommutative geometry-inspired dirty black holes

2010-01-01

['-']

[]

We provide a new exact solution of the Einstein equations which generalize the noncommutative geometry-inspired Schwarzschild metric, we previously obtained. We consider here a more general relation between the energy density and the radial pressure and find new geometries describing a regular 'dirty black hole'. We discuss strong and weak energy condition violation and various aspects of the regular dirty black hole thermodynamics.

[]

https://arxiv.org/pdf/0902.4654.pdf

2009ApJ...698..766M

Accretion onto "Seed" Black Holes in the First Galaxies

2009-01-01

['black hole physics', 'cosmology theory', 'galaxies active', 'hydrodynamics', 'galaxies quasars', 'radiation', 'astrophysics']

[]

The validity of the hypothesis that the massive black holes in high redshift quasars grew from stellar-sized "seeds" is contingent on a seed's ability to double its mass every few 10 million years. This requires that the seed accrete at approximately the Eddington-limited rate. In the specific case of radiatively efficient quasi-radial accretion in a metal-poor protogalactic medium, for which the Bondi accretion rate is often prescribed in cosmological simulations of massive black hole formation, we examine the effects of the radiation emitted near the black hole's event horizon on the structure of the surrounding gas flow. We find that photoheating and radiation pressure from photoionization significantly reduce the steady-state accretion rate and potentially render the quasi-radial accretion flow unsteady and inefficient. The time-averaged accretion rate is always a small fraction of the "Bondi" accretion rate calculated ignoring radiative feedback. The pressure of Lyα photons trapped near the H II region surrounding the black hole may further attenuate the inflow. These results suggest that an alternative to quasi-radial, radiatively efficient Bondi-like accretion should be sought to explain the rapid growth of quasar-progenitor seed black holes.

[]

https://arxiv.org/pdf/0809.2404.pdf

2004MNRAS.353.1035M

The anti-hierarchical growth of supermassive black holes

2004-01-01

['accretion', 'accretion disks', 'black hole physics', 'galaxies active', 'galaxies evolution', 'galaxies quasars', 'astrophysics']

[]

I present a new method to unveil the history of cosmic accretion and the build-up of supermassive black holes (SMBHs) in the nuclei of galaxies, based on observations of the evolving radio and (hard) X-ray luminosity functions of active galactic nuclei (AGN). The fundamental plane of black hole activity discovered by Merloni, Heinz &amp; Di Matteo, which defines a universal correlation among black hole mass (M), 2-10keV X-ray luminosity and 5-GHz radio luminosity is used as a mass and accretion rate estimator, provided a specific functional form for the dependency of the X-ray luminosity on the dimensionless accretion rate mdot is assumed. I adopt the local black hole mass function (BHMF) as derived from the velocity dispersion (σ) distributions of nearby galaxies coupled with the M-σ relation as a boundary condition to integrate backwards in time the continuity equation for the evolution of SMBH, neglecting the role of mergers in shaping up the BHMF. Under the most general assumption that, independently on M, black hole accretion proceeds in a radiatively efficient way above a certain rate, and in a radiatively inefficient way below it, the redshift evolution of the BHMF and the black hole accretion rate (BHAR) function (i.e. the distribution of the Eddington scaled accretion rates for objects of any given mass) are calculated self-consistently. The only tunable parameters are the overall efficiency of extracting gravitational energy from the accreting gas, ɛ, and the critical ratio of the X-ray to Eddington luminosity, L<SUB>2-10keV,cr</SUB>/L<SUB>Edd</SUB>≡x<SUB>cr</SUB>, at which the transition between accretion modes takes place. For fiducial values of these parameters (ɛ= 0.1 and x<SUB>cr</SUB>= 10<SUP>-3</SUP>), I found that half (~85 per cent) of the local black hole mass density was accumulated at redshift z &lt; 1 (z &lt; 3), mostly in radiatively efficient episodes of accretion. The evolution of the BHMF between z= 0 and z~ 3 shows clear signs of an anti-hierarchical behaviour: while the majority of the most massive objects (M&gt;~ 10<SUP>9</SUP>) were already in place at z~ 3, lower mass ones mainly grew at progressively lower redshift, so that the average black hole mass increases with increasing redshift. In addition, the average accretion rate decreases towards lower redshift. Consequently, sources in the radiatively inefficient regime of accretion only begin to dominate the comoving accretion energy density in the Universe at z &lt; 1 (with the exact value of z depending on x<SUB>cr</SUB>), while at the peak of the BHAR history, radiatively efficient accretion dominates by almost an order of magnitude. I will discuss the implications of these results for the efficiency of accretion on to SMBH, the lifetimes of quasars and duty cycles, the history of AGN feedback in the form of mechanical energy output and, more generally, for the cosmological models of structure formation in the Universe.

[]

https://arxiv.org/pdf/astro-ph/0402495.pdf

2011ApJ...735..110B

Evidence for Low Black Hole Spin and Physically Motivated Accretion Models from Millimeter-VLBI Observations of Sagittarius A*

2011-01-01

['accretion', 'accretion disks', 'black hole physics', 'galaxy center', 'astronomy submillimeter', 'techniques interferometric', '-']

[]

Millimeter very long baseline interferometry (mm-VLBI) provides the novel capacity to probe the emission region of a handful of supermassive black holes on sub-horizon scales. For Sagittarius A* (Sgr A*), the supermassive black hole at the center of the Milky Way, this provides access to the region in the immediate vicinity of the horizon. Broderick et al. have already shown that by leveraging spectral and polarization information as well as accretion theory, it is possible to extract accretion-model parameters (including black hole spin) from mm-VLBI experiments containing only a handful of telescopes. Here we repeat this analysis with the most recent mm-VLBI data, considering a class of aligned, radiatively inefficient accretion flow (RIAF) models. We find that the combined data set rules out symmetric models for Sgr A*'s flux distribution at the 3.9σ level, strongly favoring length-to-width ratios of roughly 2.4:1. More importantly, we find that physically motivated accretion flow models provide a significantly better fit to the mm-VLBI observations than phenomenological models, at the 2.9σ level. This implies that not only is mm-VLBI presently capable of distinguishing between potential physical models for Sgr A*'s emission, but further that it is sensitive to the strong gravitational lensing associated with the propagation of photons near the black hole. Based upon this analysis we find that the most probable magnitude, viewing angle, and position angle for the black hole spin are a = 0.0<SUP>+0.64 + 0.86</SUP>, \theta ={68^\circ }^{+5^\circ +9^\circ }_{-20^\circ -28^\circ }, and \xi ={-52^\circ }^{+17^\circ +33^\circ }_{-15^\circ -24^\circ } east of north, where the errors quoted are the 1σ and 2σ uncertainties.

[]

https://arxiv.org/pdf/1011.2770.pdf

2010MNRAS.405L...1B

Dark matter haloes determine the masses of supermassive black holes

2010-01-01

['hydrodynamics', 'galaxies active', 'galaxies evolution', 'galaxies formation', 'galaxies quasars', 'cosmology theory', '-']

[]

The energy and momentum deposited by the radiation from accretion flows on to the supermassive black holes (BHs) that reside at the centres of virtually all galaxies can halt or even reverse gas inflow, providing a natural mechanism for supermassive BHs to regulate their growth and to couple their properties to those of their host galaxies. However, it remains unclear whether this self-regulation occurs on the scale at which the BH is gravitationally dominant, on that of the stellar bulge, the galaxy or that of the entire dark matter halo. To answer this question, we use self-consistent simulations of the co-evolution of the BH and galaxy populations that reproduce the observed correlations between the masses of the BHs and the properties of their host galaxies. We first confirm unambiguously that the BHs regulate their growth: the amount of energy that the BHs inject into their surroundings remains unchanged when the fraction of the accreted rest mass energy that is injected is varied by four orders of magnitude. The BHs simply adjust their masses so as to inject the same amount of energy. We then use simulations with artificially reduced star formation rates to demonstrate explicitly that BH mass is not set by the stellar mass. Instead, we find that it is determined by the mass of the dark matter halo with a secondary dependence on the halo concentration, of the form that would be expected if the halo binding energy were the fundamental property that controls the mass of the BH. We predict that the BH mass, m<SUB>BH</SUB>, scales with halo mass as m<SUB>BH</SUB> ~ m<SUP>α</SUP><SUB>halo</SUB>, with α ~ 1.55 +/- 0.05, and that the scatter around the mean relation in part reflects the scatter in the halo concentration-mass relation.

[]

https://arxiv.org/pdf/0911.0935.pdf

1999PhRvD..59l4014J

Primordial black hole formation during first-order phase transitions

1999-01-01

['-', '-', '-', '-', '-', 'methods numerical', 'black hole physics', 'particles', 'astrophysics', '-', '-']

[]

Primordial black holes (PBHs) may form in the early universe when pre-existing adiabatic density fluctuations enter into the cosmological horizon and recollapse. It has been suggested that PBH formation may be facilitated when fluctuations enter into the horizon during a strongly first-order phase transition which proceeds in approximate equilibrium. We employ general-relativistic hydrodynamics numerical simulations in order to follow the collapse of density fluctuations during first-order phase transitions. We find that during late stages of the collapse fluctuations separate into two regimes, an inner part existing exclusively in the high-energy density phase with energy density ɛ<SUB>h</SUB>, surrounded by an outer part which exists exclusively in the low-energy density phase with energy density ɛ<SUB>h</SUB>-L, where L is the latent heat of the transition. We confirm that the fluctuation density threshold δɛ/ɛ required for the formation of PBHs during first-order transitions decreases with increasing L and falls below that for PBH formation during ordinary radiation dominated epochs. Our results imply that, in case PBHs form at all in the early universe, their mass spectrum is most likely dominated by the approximate horizon masses during epochs when the universe undergoes phase transitions.

[]

https://arxiv.org/pdf/astro-ph/9901293.pdf

2002ApJ...579..639B

Gravitational Microlensing Events Due to Stellar-Mass Black Holes

2002-01-01

['galaxy bulge', 'gravitational lensing', 'astrophysics']

[]

We present an analysis of the longest timescale microlensing events discovered by the MACHO Collaboration during a 7 year survey of the Galactic bulge. We find six events that exhibit very strong microlensing parallax signals due, in part, to accurate photometric data from the GMAN and MPS collaborations. The microlensing parallax fit parameters are used in a likelihood analysis, which is able to estimate the distances and masses of the lens objects based on a standard model of the Galactic velocity distribution. This analysis indicates that the most likely masses of five of the six lenses are greater than 1 M<SUB>solar</SUB>, which suggests that a substantial fraction of the Galactic lenses may be massive stellar remnants. This could explain the observed excess of long-timescale microlensing events. The lenses for events MACHO-96-BLG-5 and MACHO-98-BLG-6 are the most massive, with mass estimates of M/M<SUB>solar</SUB>=6<SUP>+10</SUP><SUB>-3</SUB> and M/M<SUB>solar</SUB>=6<SUP>+7</SUP><SUB>-3</SUB>, respectively. The observed upper limits on the absolute brightness of main-sequence stars for these lenses are less than 1 L<SUB>solar</SUB>, so both lenses are black hole candidates. The black hole interpretation is also favored by a likelihood analysis with a Bayesian prior using a conventional model for the lens mass function. We consider the possibility that the source stars for some of these six events may lie in the foreground Galactic disk or in the Sagittarius (Sgr) dwarf galaxy behind the bulge, but we find that bulge sources are likely to dominate our microlensing parallax event sample. Future Hubble Space Telescope observations of these events can either confirm the black hole lens hypothesis or detect the lens stars and provide a direct measurement of their masses. Future observations of similar events by the Space Interferometry Mission or the Keck or VLT interferometers, as explained by Delplancke, Górski, &amp; Richichi, will allow direct measurements of the lens masses for stellar remnant lenses as well. Based in part on observations from NASA's Hubble Space Telescope.

[]

https://arxiv.org/pdf/astro-ph/0109467.pdf

2005PhRvD..71b7502G

Log correction to the black hole area law

2005-01-01

['-', '-', '-', '-', '-', '-']

[]

Various approaches to black hole entropy yield the area law with logarithmic corrections, many involving a coefficient 1/2, and some involving 3/2. It is pointed out here that the standard quantum geometry formalism with spin one-half at each puncture is not consistent with 3/2.

[]

https://arxiv.org/pdf/gr-qc/0401070.pdf

2020JCAP...09..030I

Gravitational lensing by black holes in the 4D Einstein-Gauss-Bonnet gravity

2020-01-01

['-']

[]

Recently, a non-trivial 4D Einstein-Gauss-Bonnet (EGB) theory of gravity, by rescaling the GB coupling parameter as α/(D-4), was formulated in [1], which bypasses Lovelock's theorem and avoids Ostrogradsky instability. The theory admits a static spherically symmetric black hole, unlike 5D EGB or general relativity counterpart, which can have both Cauchy and event horizons. We generalize previous work, on gravitational lensing by a Schwarzschild black hole, in the strong and weak deflection limits to the 4D EGB black holes to calculate the deflection coefficients ā and bar b, while former increases and later decrease with increasing α. We also find that the deflection angle α<SUB>D</SUB>, angular position θ<SUB>∞</SUB> and u<SUB>m</SUB> decreases, but angular separation s increases with α. The effect of the GB coupling parameter α on positions and magnification of the source relativistic images is discussed in the context of SgrA* and M87* black holes. A brief description of the weak gravitational lensing using the Gauss-Bonnet theorem is presented.

[]

https://arxiv.org/pdf/2004.01038.pdf

2013Natur.503..500L

Puzzling accretion onto a black hole in the ultraluminous X-ray source M 101 ULX-1

2013-01-01

['-']

[]

There are two proposed explanations for ultraluminous X-ray sources (ULXs) with luminosities in excess of 10<SUP>39</SUP> erg s<SUP>-1</SUP>. They could be intermediate-mass black holes (more than 100-1,000 solar masses, ) radiating at sub-maximal (sub-Eddington) rates, as in Galactic black-hole X-ray binaries but with larger, cooler accretion disks. Alternatively, they could be stellar-mass black holes radiating at Eddington or super-Eddington rates. On its discovery, M 101 ULX-1 had a luminosity of 3 × 10<SUP>39</SUP> erg s<SUP>-1</SUP> and a supersoft thermal disk spectrum with an exceptionally low temperature--uncomplicated by photons energized by a corona of hot electrons--more consistent with the expected appearance of an accreting intermediate-mass black hole. Here we report optical spectroscopic monitoring of M 101 ULX-1. We confirm the previous suggestion that the system contains a Wolf-Rayet star, and reveal that the orbital period is 8.2 days. The black hole has a minimum mass of 5, and more probably a mass of 20-30, but we argue that it is very unlikely to be an intermediate-mass black hole. Therefore, its exceptionally soft spectra at high Eddington ratios violate the expectations for accretion onto stellar-mass black holes. Accretion must occur from captured stellar wind, which has hitherto been thought to be so inefficient that it could not power an ultraluminous source.

[]

https://arxiv.org/pdf/1312.0337.pdf

2018ApJ...863....1C

A Population of Bona Fide Intermediate-mass Black Holes Identified as Low-luminosity Active Galactic Nuclei

2018-01-01

['cosmology observations', 'cosmology early universe', 'galaxies active', 'galaxies nuclei', 'galaxies seyfert', 'galaxies quasars', '-', '-', '-']

[]

Nearly every massive galaxy harbors a supermassive black hole (SMBH) in its nucleus. SMBH masses are millions to billions of solar mass, and they correlate with properties of spheroids of their host galaxies. While the SMBH growth channels, mergers, and gas accretion are well established, their origin remains uncertain: they could have emerged either from massive “seeds” (10<SUP>5</SUP>-10<SUP>6</SUP> M<SUB>⊙</SUB>) formed by direct collapse of gas clouds in the early universe or from smaller (100 M<SUB>⊙</SUB>) BHs, end products of first stars. The latter channel would leave behind numerous intermediate-mass BHs (IMBHs, 10<SUP>2</SUP>-10<SUP>5</SUP> M<SUB>⊙</SUB>). Although many IMBH candidates have been identified, none are accepted as definitive; thus, their very existence is still debated. Using data mining in wide-field sky surveys and applying dedicated analysis to archival and follow-up optical spectra, we identified a sample of 305 IMBH candidates having masses 3× {10}<SUP>4</SUP> {M}<SUB>⊙ </SUB>&lt; {M}<SUB>BH</SUB>}&lt; 2× {10}<SUP>5</SUP> {M}<SUB>⊙ </SUB>, which reside in galaxy centers and are accreting gas that creates characteristic signatures of a type I active galactic nucleus (AGN). We confirmed the AGN nature of 10 sources (including five previously known objects that validate our method) by detecting the X-ray emission from their accretion disks, thus defining the first bona fide sample of IMBHs in galactic nuclei. All IMBH host galaxies possess small bulges and sit on the low-mass extension of the {M}<SUB>BH</SUB>}{--}{M}<SUB>bulge</SUB>} scaling relation, suggesting that they must have experienced very few if any major mergers over their lifetime. The very existence of nuclear IMBHs supports the stellar-mass seed scenario of the massive BH formation.

[]

https://arxiv.org/pdf/1805.01467.pdf

2018PhRvD..98h4011B

Radial perturbations of the scalarized Einstein-Gauss-Bonnet black holes

2018-01-01

['-']

[]

Recently a new class of scalarized black holes in Einstein-Gauss-Bonnet (EGB) theories was discovered. What is special for these black hole solutions is that the scalarization is not due to the presence of matter, but it is induced by the curvature of spacetime itself. Moreover, more than one branch of scalarized solutions can bifurcate from the Schwarzschild branch, and these scalarized branches are characterized by the number of nodes of the scalar field. The next step is to consider the linear stability of these solutions, which is particularly important due to the fact that the Schwarzschild black holes lose stability at the first point of bifurcation. Therefore we here study in detail the radial perturbations of the scalarized EGB black holes. The results show that all branches with a nontrivial scalar field with one or more nodes are unstable. The stability of the solutions on the fundamental branch, whose scalar field has no radial nodes, depends on the particular choice of the coupling function between the scalar field and the Gauss-Bonnet invariant. We consider two particular cases based on the previous studies of the background solutions. If this coupling has the form used in [D. D. Doneva and S. S. Yazadjiev, Phys. Rev. Lett. 120, 131103 (2018)] the fundamental branch of solutions is stable, except for very small masses. In the case of a coupling function quadratic in the scalar field [H. O. Silva, J. Sakstein, L. Gualtieri, T. P. Sotiriou, and E. Berti, Phys. Rev. Lett. 120, 131104 (2018)], though, the whole fundamental branch is unstable.

[]

https://arxiv.org/pdf/1805.05755.pdf

2015ApJ...813...84G

X-Ray Reflection Spectroscopy of the Black Hole GX 339--4: Exploring the Hard State with Unprecedented Sensitivity

2015-01-01

['accretion', 'accretion disks', 'atoms', 'black hole physics', 'line formation', 'astronomy x rays', '-']

[]

We analyze simultaneously six composite RXTE spectra of GX 339-4 in the hard state comprising 77 million counts collected over 196 ks. The source spectra are ordered by luminosity and span the range 1.6%-17% of the Eddington luminosity. Crucially, using our new tool pcacorr, we re-calibrate the data to a precision of 0.1%, an order of magnitude improvement over all earlier work. Using our advanced reflection model relxill, we target the strong features in the component of emission reflected from the disk, namely, the relativistically broadened Fe K emission line, the Fe K edge, and the Compton hump. We report results for two joint fits to the six spectra: For the first fit, we fix the spin parameter to its maximal value (a<SUB>*</SUB> = 0.998) and allow the inner disk radius R<SUB>in</SUB> to vary. Results include (i) precise measurements of R<SUB>in</SUB>, with evidence that the disk becomes slightly truncated at a few percent of Eddington and (ii) an order-of-magnitude swing with luminosity in the high energy cutoff, which reaches &gt;890 keV at our lowest luminosity. For the second fit, we make the standard assumption in estimating spin that the inner edge of the accretion disk is located at the innermost stable circular orbit (R<SUB>in</SUB> = R<SUB>ISCO</SUB>) and find {a}<SUB>*</SUB>={0.95}<SUB>-0.05</SUB><SUP>+0.03</SUP> (90% confidence, statistical). For both fits, and at the same level of statistical confidence, we estimate that the disk inclination is i = 48° ± 1° and that the Fe abundance is super-solar, A<SUB>Fe</SUB> = 5 ± 1.

[]

https://arxiv.org/pdf/1505.03607.pdf

2013MNRAS.436.3856S

Energy, momentum and mass outflows and feedback from thick accretion discs around rotating black holes

2013-01-01

['accretion', 'accretion disks', 'black hole physics', 'relativity', 'methods numerical', 'galaxies jets', '-']

[]

Using long-duration general relativistic magnetohydrodynamic simulations of radiatively inefficient accretion discs, the energy, momentum and mass outflow rates from such systems are estimated. Outflows occur via two fairly distinct modes: a relativistic jet and a subrelativistic wind. The jet power depends strongly on the black hole spin and on the magnetic flux at the horizon. Unless these are very small, the energy output in the jet dominates over that in the wind. For a rapidly spinning black hole accreting in the magnetically arrested limit, it is confirmed that jet power exceeds the total rate of accretion of rest mass energy. However, because of strong collimation, the jet probably does not have a significant feedback effect on its immediate surroundings. The power in the wind is more modest and shows a weaker dependence on black hole spin and magnetic flux. Nevertheless, because the wind subtends a large solid angle, it is expected to provide efficient feedback on a wide range of scales inside the host galaxy. Empirical formulae are obtained for the energy and momentum outflow rates in the jet and the wind.

[]

https://arxiv.org/pdf/1307.1143.pdf

2019PhRvD.100b3011V

New search pipeline for compact binary mergers: Results for binary black holes in the first observing run of Advanced LIGO

2019-01-01

['-', '-', '-']

[]

In this paper, we report on the construction of a new and independent pipeline for analyzing the public data from the first observing run of Advanced LIGO for mergers of compact binary systems. The pipeline incorporates different techniques and makes independent implementation choices in all its stages including the search design, the method to construct template banks, the automatic routines to detect bad data segments ("glitches") and to insulate good data from them, the procedure to account for the nonstationary nature of the detector noise, the signal-quality vetoes at the single-detector level and the methods to combine results from multiple detectors. Our pipeline enabled us to identify a new binary black hole merger GW151216 in the public LIGO data. This paper serves as a bird's eye view of the pipeline's important stages. Full details and derivations underlying the various stages will appear in accompanying papers.

[]

https://arxiv.org/pdf/1902.10341.pdf

2012ApJ...746..168D

The Relationship between Black Hole Growth and Star Formation in Seyfert Galaxies

2012-01-01

['galaxies active', 'galaxies nuclei', 'galaxies seyfert', '-', '-']

[]

We present estimates of black hole accretion rates (BHARs) and nuclear, extended, and total star formation rates for a complete sample of Seyfert galaxies. Using data from the Spitzer Space Telescope, we measure the active galactic nucleus (AGN) luminosity using the [O IV] λ25.89 μm emission line and the star-forming luminosity using the 11.3 μm aromatic feature and extended 24 μm continuum emission. We find that black hole growth is strongly correlated with nuclear (r &lt; 1 kpc) star formation, but only weakly correlated with extended (r &gt; 1 kpc) star formation in the host galaxy. In particular, the nuclear star formation rate (SFR) traced by the 11.3 μm aromatic feature follows a relationship with the BHAR of the form SFR\propto \dot{M}_{BH}^{0.8}, with an observed scatter of 0.5 dex. This SFR-BHAR relationship persists when additional star formation in physically matched r = 1 kpc apertures is included, taking the form SFR\propto \dot{M}_{BH}^{0.6}. However, the relationship becomes almost indiscernible when total SFRs are considered. This suggests a physical connection between the gas on sub-kiloparsec and sub-parsec scales in local Seyfert galaxies that is not related to external processes in the host galaxy. It also suggests that the observed scaling between star formation and black hole growth for samples of AGNs will depend on whether the star formation is dominated by a nuclear or an extended component. We estimate the integrated black hole and bulge growth that occurs in these galaxies and find that an AGN duty cycle of 5%-10% would maintain the ratio between black hole and bulge masses seen in the local universe.

[]

https://arxiv.org/pdf/1106.3565.pdf

1992PhRvD..46.2445V

Dirty black holes: Thermodynamics and horizon structure

1992-01-01

['-', '-', '-', '-', 'black hole physics', '-']

[]

Considerable interest has recently been expressed in (static spherically symmetric) black holes in interaction with various classical matter fields (such as electromagnetic fields, dilaton fields, axion fields, Abelian Higgs fields, non-Abelian gauge fields, etc.). A common feature of these investigations that has not previously been remarked upon is that the Hawking temperature of such systems appears to be suppressed relative to that of a vacuum black hole of equal horizon area. That is, kT<SUB>H</SUB>&lt;=ħ/(4πr<SUB>H</SUB>)==ħ/ √4πA<SUB>H</SUB> . This paper will argue that this suppression is generic. Specifically, it will be shown that kT<SUB>H</SUB>=(ħ/4πr<SUB>H</SUB>)e<SUP>-φ(r</SUP><SUB>H</SUB>) (1-8πGρ<SUB>H</SUB>r<SUP>2</SUP><SUB>H</SUB>). Here φ(r<SUB>H</SUB>) is an integral quantity, depending on the distribution of matter, that is guaranteed to be positive if the weak energy condition is satisfied. Several examples of this behavior will be discussed. Generalizations of this behavior to nonsymmetric nonstatic black holes are conjectured.

[]

https://arxiv.org/pdf/hep-th/9203057.pdf

2008ApJ...681..925W

Cosmic Evolution of Black Holes and Spheroids. III. The M<SUB>BH</SUB>-σ<SUB>*</SUB> Relation in the Last Six Billion Years

2008-01-01

['accretion', 'accretion disks', 'galaxies active', 'galaxies evolution', 'galaxies quasars', 'astrophysics']

[]

We measure the evolution of the correlation between black hole mass and host spheroid velocity dispersion (M<SUB>BH</SUB>-σ<SUB>*</SUB>) over the last 6 billion years, by studying three carefully selected samples of active galaxies at z = 0.57, z = 0.36 and z &lt; 0.1. For all three samples, virial black hole masses are consistently estimated using the line dispersion of Hβ and the continuum luminosity at 5100 Å or Hα line luminosity, based on our cross calibration of the broad-line region size-luminosity relation. For the z = 0.57 sample, new stellar velocity dispersions are measured from high signal-to-noise ratio spectra obtained at the Keck Telescope, while for the two lower redshift samples they are compiled from previous works. Extending our previous result at z = 0.36, we find an offset from the local relation, suggesting that for fixed M<SUB>BH</SUB>, distant spheroids have on average smaller velocity dispersions than local ones. The measured offset at z = 0.57 is Δ log σ<SUB>*</SUB> = 0.12 +/- 0.05 +/- 0.06 (or Δ log M<SUB>BH</SUB> = 0.50 +/- 0.22 +/- 0.25), i.e., Δ log M<SUB>BH</SUB> = (3.1 +/- 1.5) log (1 + z) + 0.05 +/- 0.21. This is inconsistent with a tight and nonevolving universal M<SUB>BH</SUB>-σ<SUB>*</SUB> relation at the 95% CL.

[]

https://arxiv.org/pdf/0804.0235.pdf

1998PhRvD..57.7145I

Nonlinear metric perturbations and production of primordial black holes

1998-01-01

['-', '-', '-', '-', 'particles', 'black hole physics', 'background', 'astrophysics']

[]

We consider a simple inflationary model with a peculiarity in the form of a ``plateau'' in the inflaton potential. We use the formalism of a coarse-grained field in order to describe the production of metric perturbations h of an arbitrary amplitude, and obtain a non-Gaussian probability function for such metric perturbations. We associate the spatial regions having large perturbations h~1 with the regions going to primordial black holes after inflation. We show that in our model the nonlinear effects can lead to overproduction of primordial black holes.

[]

https://arxiv.org/pdf/astro-ph/9708224.pdf

2001ApJ...551...72K

Systematic Errors in the Estimation of Black Hole Masses by Reverberation Mapping

2001-01-01

['black hole physics', 'galaxies active', 'galaxies nuclei', 'galaxies seyfert', 'methods data analysis', 'astrophysics']

[]

The mass of the central black hole in many active galactic nuclei has been estimated on the basis of the assumption that the dynamics of the broad emission line gas are dominated by the gravity of the black hole. The most commonly employed method is to estimate a characteristic size-scale r<SUB>*</SUB> from reverberation mapping experiments and combine it with a characteristic velocity v<SUB>*</SUB> taken from the line profiles; the inferred mass is then estimated by r<SUB>*</SUB>v<SUP>2</SUP><SUB>*</SUB>/G. We critically discuss the evidence supporting the assumption of gravitational dynamics and find that the arguments are still inconclusive. We then explore the range of possible systematic error if the assumption of gravitational dynamics is granted. Inclination relative to a flattened system may cause a systematic underestimate of the central mass by a factor of ~(h/r)<SUP>2</SUP>, where h/r is the aspect ratio of the flattening. The coupled effects of a broad radial emissivity distribution, an unknown angular radiation pattern of line emission, and suboptimal sampling in the reverberation experiment can cause additional systematic errors as large as a factor of 3 or more in either direction.

[]

https://arxiv.org/pdf/astro-ph/0012134.pdf

2006JHEP...04..044F

Excursions beyond the horizon: black hole singularities in Yang-Mills theories (I)

2006-01-01

['-']

[]

We study black hole singularities in the AdS/CFT correspondence. These singularities show up in CFT in the behavior of finite-temperature correlation functions. We first establish a direct relation between space-like geodesics in the bulk and momentum space Wightman functions of CFT operators of large dimensions. This allows us to probe the regions inside the horizon and near the singularity using the CFT. Information about the black hole singularity is encoded in the exponential falloff of finite-temperature correlators at large imaginary frequency. We construct new gauge invariant observables whose divergences reflect the presence of the singularity. We also find a UV/UV connection that governs physics inside the horizon. Additionally, we comment on the possible resolution of the singularity.

[]

https://arxiv.org/pdf/hep-th/0506202.pdf

2008PhRvL.101p1101S

High-Energy Collision of Two Black Holes

2008-01-01

['-', '-', '-', 'methods numerical', 'methods numerical', '-', '-', '-', '-']

[]

We study the head-on collision of two highly boosted equal mass, nonrotating black holes. We determine the waveforms, radiated energies, and mode excitation in the center of mass frame for a variety of boosts. For the first time we are able to compare analytic calculations, black-hole perturbation theory, and strong field, nonlinear numerical calculations for this problem. Extrapolation of our results, which include velocities of up to 0.94c, indicate that in the ultrarelativistic regime about 14±3% of the energy is converted into gravitational waves. This gives rise to a luminosity of order 10<SUP>-2</SUP>c<SUP>5</SUP>/G, the largest known so far in a black-hole merger.

[]

https://arxiv.org/pdf/0806.1738.pdf

2008PhRvD..78b4009D

Effective one body approach to the dynamics of two spinning black holes with next-to-leading order spin-orbit coupling

2008-01-01

['-', '-', '-', 'theory', '-', 'perturbation theory', '-', '-']

[]

Using a recent, novel Hamiltonian formulation of the gravitational interaction of spinning binaries, we extend the effective one body (EOB) description of the dynamics of two spinning black holes to next-to-leading order (NLO) in the spin-orbit interaction. The spin-dependent EOB Hamiltonian is constructed from four main ingredients: (i) a transformation between the “effective” Hamiltonian and the “real” one; (ii) a generalized effective Hamilton-Jacobi equation involving higher powers of the momenta; (iii) a Kerr-type effective metric (with Padé-resummed coefficients) which depends on the choice of some basic “effective spin vector” S<SUB>eff</SUB>, and which is deformed by comparable-mass effects; and (iv) an additional effective spin-orbit interaction term involving another spin vector σ. As a first application of the new, NLO spin-dependent EOB Hamiltonian, we compute the binding energy of circular orbits (for parallel spins) as a function of the orbital frequency, and of the spin parameters. We also study the characteristics of the last stable circular orbit: binding energy, orbital frequency, and the corresponding dimensionless spin parameter a^<SUB>LSO</SUB>≡cJ<SUB>LSO</SUB>/(G(H<SUB>LSO</SUB>/c<SUP>2</SUP>)<SUP>2</SUP>). We find that the inclusion of NLO spin-orbit terms has a significant “moderating” effect on the dynamical characteristics of the circular orbits for large and parallel spins.

[]

https://arxiv.org/pdf/0803.0915.pdf

2008PhRvD..78h4017L

Binary-black-hole initial data with nearly extremal spins

2008-01-01

['-', '-', '-', '-', 'methods numerical', 'techniques spectroscopic', '-', 'methods numerical', '-']

[]

There is a significant possibility that astrophysical black holes with nearly extremal spins exist. Numerical simulations of such systems require suitable initial data. In this paper, we examine three methods of constructing binary-black-hole initial data, focusing on their ability to generate black holes with nearly extremal spins: (i) Bowen-York initial data, including standard puncture data (based on conformal flatness and Bowen-York extrinsic curvature), (ii) standard quasiequilibrium initial data (based on the extended-conformal-thin-sandwich equations, conformal flatness, and maximal slicing), and (iii) quasiequilibrium data based on the superposition of Kerr-Schild metrics. We find that the two conformally flat methods (i) and (ii) perform similarly, with spins up to about 0.99 obtainable at the initial time. However, in an evolution, we expect the spin to quickly relax to a significantly smaller value around 0.93 as the initial geometry relaxes. For quasiequilibrium superposed Kerr-Schild data [method (iii)], we construct initial data with initial spins as large as 0.9997. We evolve superposed Kerr-Schild data sets with spins of 0.93 and 0.97 and find that the spin drops by only a few parts in 10<SUP>4</SUP> during the initial relaxation; therefore, we expect that superposed Kerr-Schild initial data will allow evolutions of binary black holes with relaxed spins above 0.99. Along the way to these conclusions, we also present several secondary results: the power-law coefficients with which the spin of puncture initial data approaches its maximal possible value; approximate analytic solutions for large spin puncture data; embedding diagrams for single spinning black holes in methods (i) and (ii); nonunique solutions for method (ii). All of the initial-data sets that we construct contain subextremal black holes, and when we are able to push the spin of the excision boundary surface into the superextremal regime, the excision surface is always enclosed by a second, subextremal apparent horizon. The quasilocal spin is measured by using approximate rotational Killing vectors, and the spin is also inferred from the extrema of the intrinsic scalar curvature of the apparent horizon. Both approaches are found to give consistent results, with the approximate-Killing-vector spin showing the least variation during the initial relaxation.

[]

https://arxiv.org/pdf/0805.4192.pdf

2008CQGra..25q5015N

Hawking radiation as quantum tunneling from a noncommutative Schwarzschild black hole

2008-01-01

['-']

[]

We study the tunneling process through the quantum horizon of a Schwarzschild black hole in noncommutative spacetime. This is done by considering the effect of smearing of the particle mass as a Gaussian profile in flat spacetime. We show that even in this noncommutative setup there will be no correlation between the different modes of radiation, which reflects the fact that information does not come out continuously during the evaporation process at least at late time. However, due to spacetime noncommutativity, information might be preserved by a stable black hole remnant.

[]

https://arxiv.org/pdf/0801.4074.pdf

2008PhRvD..77f4010M

High-spin binary black hole mergers

2008-01-01

['-', '-', '-', '-', 'methods numerical', '-', '-', 'black hole physics', '-']

[]

We study identical mass black hole binaries with spins perpendicular to the binary’s orbital plane. These binaries have individual spins ranging from s/m<SUP>2</SUP>=-0.90 to 0.90, (s<SUB>1</SUB>=s<SUB>2</SUB> in all cases) which is near the limit possible with standard Bowen-York puncture initial data. The extreme cases correspond to the largest initial spin simulations to date. Our results expand the parameter space covered by Rezzolla et al., and when combining both data sets, we obtain estimations for the minimum and maximum values for the intrinsic angular momenta of the remnant of binary black hole mergers of J/M<SUP>2</SUP>=0.341±0.004 and 0.951±0.004, respectively. Note, however, that these values are reached through extrapolation to the singular cases |s<SUB>1</SUB>|=|s<SUB>2</SUB>|=1 and thus remain as estimates until full-fledged numerical simulations provide confirmation.

[]

https://arxiv.org/pdf/0709.2160.pdf

2000PhRvD..62l4022O

Transition from inspiral to plunge for a compact body in a circular equatorial orbit around a massive, spinning black hole

2000-01-01

['-', '-', '-', 'waves', '-', 'black hole physics', '-']

[]

There are three regimes of gravitational-radiation-reaction-induced inspiral for a compact body with mass μ, in a circular, equatorial orbit around a Kerr black hole with mass M&gt;&gt;μ: (i) the adiabatic inspiral regime, in which the body gradually descends through a sequence of circular, geodesic orbits; (ii) a transition regime, near the innermost stable circular orbit (isco); (iii) the plunge regime, in which the body travels on a geodesic from slightly below the isco into the hole's horizon. This paper gives an analytic treatment of the transition regime and shows that, with some luck, gravitational waves from the transition might be measurable by the space-based LISA mission.

[]

https://arxiv.org/pdf/gr-qc/0003032.pdf

2013JHEP...10..107V

Black hole entanglement and quantum error correction

2013-01-01

['methods statistical', 'black hole physics', '-', '-']

[]

It was recently argued in [1] that black hole complementarity strains the basic rules of quantum information theory, such as monogamy of entanglement. Motivated by this argument, we develop a practical framework for describing black hole evaporation via unitary time evolution, based on a holographic perspective in which all black hole degrees of freedom live on the stretched horizon. We model the horizon as a unitary quantum system with finite entropy, and do not postulate that the horizon geometry is smooth. We then show that, with mild assumptions, one can reconstruct local effective field theory observables that probe the black hole interior, and relative to which the state near the horizon looks like a local Minkowski vacuum. The reconstruction makes use of the formalism of quantum error correcting codes, and works for black hole states whose entanglement entropy does not yet saturate the Bekenstein-Hawking bound. Our general framework clarifies the black hole final state proposal, and allows a quantitative study of the transition into the "firewall" regime of maximally mixed black hole states.

[]

https://arxiv.org/pdf/1211.6913.pdf

2020PhRvD.101d4031G

Lensing by Kerr black holes

2020-01-01

['-', '-', '-']

[]

Interpreting horizon-scale observations of astrophysical black holes demands a general understanding of null geodesics in the Kerr spacetime. These may be divided into two classes: "direct" rays that primarily determine the observational appearance of a given source, and highly bent rays that produce a nested sequence of exponentially demagnified images of the main emission: the so-called "photon ring." We develop heuristics that characterize the direct rays and study the highly bent geodesics analytically. We define three critical parameters γ , δ , and τ that respectively control the demagnification, rotation, and time delay of successive images of the source, thereby providing an analytic theory of the photon ring. These observable parameters encode universal effects of general relativity, independent of the details of the emitting matter.

[]

https://arxiv.org/pdf/1910.12873.pdf

2016PhRvL.117t1601B

Smooth Horizonless Geometries Deep Inside the Black-Hole Regime

2016-01-01

['-', '-']

[]

We construct the first family of horizonless supergravity solutions that have the same mass, charges, and angular momenta as general supersymmetric rotating D 1 -D 5 -P black holes in five dimensions. This family includes solutions with arbitrarily small angular momenta, deep within the regime of quantum numbers and couplings for which a large classical black hole exists. These geometries are well approximated by the black-hole solution, and in particular exhibit the same near-horizon throat. Deep in this throat, the black-hole singularity is resolved into a smooth cap. We also identify the holographically dual states in the N =(4 ,4 ) D 1 -D 5 orbifold conformal field theory (CFT). Our solutions are among the states counted by the CFT elliptic genus, and provide examples of smooth microstate geometries within the ensemble of supersymmetric black-hole microstates.

[]

https://arxiv.org/pdf/1607.03908.pdf

2016ApJ...825..126D

Supermassive Black Holes with High Accretion Rates in Active Galactic Nuclei. V. A New Size-Luminosity Scaling Relation for the Broad-line Region

2016-01-01

['accretion', 'accretion disks', 'galaxies active', 'galaxies nuclei', '-', '-']

[]

This paper reports results of the third-year campaign of monitoring super-Eddington accreting massive black holes (SEAMBHs) in active galactic nuclei (AGNs) between 2014 and 2015. Ten new targets were selected from the quasar sample of the Sloan Digital Sky Survey (SDSS), which have generally been more luminous than the SEAMBH candidates in the last two years. Hβ lags ({τ }<SUB>{{H</SUB>}β }) in five of the 10 quasars have been successfully measured in this monitoring season. We find that the lags are generally shorter, by large factors, than those of objects with same optical luminosity, in light of the well-known R <SUB>H</SUB> <SUB>β</SUB>-L <SUB>5100</SUB> relation. The five quasars have dimensionless accretion rates of \dot{{M}\quad }=10-10<SUP>3</SUP>. Combining these with measurements of the previous SEAMBHs, we find that the reduction of Hβ lags depends tightly on accretion rates, {τ }<SUB>{{H</SUB>}β }/{τ }<SUB>R-L</SUB>\propto {\dot{{M}}}<SUP>-0.42</SUP>, where {τ }<SUB>R-L</SUB> is the Hβ lag from the normal R <SUB>H</SUB> <SUB>β</SUB>-L <SUB>5100</SUB> relation. Fitting 63 mapped AGNs, we present a new scaling relation for the broad-line region: {R}<SUB>{{H</SUB>}β }={α }<SUB>1</SUB>{{\ell }}<SUB>44</SUB><SUP>{β </SUP><SUB>1</SUB>} {min} [1,{(\dot{{M}}/{\dot{{M}}}<SUB>c</SUB>)}<SUP>-{γ </SUP><SUB>1</SUB>}], where {{\ell }}<SUB>44</SUB>={L}<SUB>5100</SUB>/{10}<SUP>44</SUP> {erg} {{{s}}}<SUP>-1</SUP> is the 5100 Å continuum luminosity, and the coefficients are {α }<SUB>1</SUB>={29.6}<SUB>-2.8</SUB><SUP>+2.7</SUP> lt-day, {β }<SUB>1</SUB>={0.56}<SUB>-0.03</SUB><SUP>+0.03</SUP>, {γ }<SUB>1</SUB>={0.52}<SUB>-0.16</SUB><SUP>+0.33</SUP>, and {\dot{{M}}}<SUB>c</SUB>={11.19}<SUB>-6.22</SUB><SUP>+2.29</SUP>. This relation is applicable to AGNs over a wide range of accretion rates, from 10<SUP>-3</SUP> to 10<SUP>3</SUP>. Implications of this new relation are briefly discussed.

[]

https://arxiv.org/pdf/1604.06218.pdf

2015JHEP...11..157H

Einstein-Born-Infeld-massive gravity: adS-black hole solutions and their thermodynamical properties

2015-01-01

['black hole physics', '-', '-', '-', '-']

[]

In this paper, we study massive gravity in the presence of Born-Infeld nonlinear electrodynamics. First, we obtain metric function related to this gravity and investigate the geometry of the solutions and find that there is an essential singularity at the origin ( r = 0). It will be shown that due to contribution of the massive part, the number, type and place of horizons may be changed. Next, we calculate the conserved and thermodynamic quantities and check the validation of the first law of thermodynamics. We also investigate thermal stability of these black holes in context of canonical ensemble. It will be shown that number, type and place of phase transition points are functions of different parameters which lead to dependency of stability conditions to these parameters. Also, it will be shown how the behavior of temperature is modified due to extension of massive gravity and strong nonlinearity parameter. Next, critical behavior of the system in extended phase space by considering cosmological constant as pressure is investigated. A study regarding neutral Einstein-massive gravity in context of extended phase space is done. Geometrical approach is employed to study the thermodynamical behavior of the system in context of heat capacity and extended phase space. It will be shown that GTs, heat capacity and extended phase space have consistent results. Finally, critical behavior of the system is investigated through use of another method. It will be pointed out that the results of this method is in agreement with other methods and follow the concepts of ordinary thermodynamics.

[]

https://arxiv.org/pdf/1508.01311.pdf

2001PhLB..521...87N

Anti-de-Sitter black hole thermodynamics in higher derivative gravity and new confining-deconfining phases in dual CFT

2001-01-01

['thermodynamics', '-', '-', 'phase', '-', '-']

[]

The thermodynamics of d5 AdS BHs with positive, negative or zero curvature spatial section in higher derivative (HD) gravity is described. HD contribution to free energy may change its sign which leads to more complicated regime for Hawking-Page phase transitions. Some variant of d5 HD gravity is dual to N=2Sp(N) SCFT up to the next-to-leading order in large N. Then, according to Witten interpretation the stable AdS BH phase corresponds to deconfinement while global AdS phase corresponds to confinement. Unlike to Einstein gravity in HD theory the critical N appears. It may influence the phase transition structure. In particular, what was confining phase above the critical value becomes the deconfining phase below it and vice-versa.

[]

https://arxiv.org/pdf/hep-th/0109122.pdf

2004CQGra..21.4511C

How classical are TeV-scale black holes?

2004-01-01

['-', '-', '-']

[]

We show that the Hawking temperature and the entropy of black holes are subject to corrections from two sources: the generalized uncertainty principle and thermal fluctuations. Both effects increase the temperature and decrease the entropy, resulting in faster decay and 'less classical' black holes. We discuss the implications of these results for TeV-scale black holes that are expected to be produced at future colliders.

[]

https://arxiv.org/pdf/hep-th/0404050.pdf

2005ApJ...625..699M

The Murmur of the Sleeping Black Hole: Detection of Nuclear Ultraviolet Variability in LINER Galaxies

2005-01-01

['galaxies active', 'galaxies nuclei', 'galaxies seyfert', 'galaxies starburst', 'galaxies quasars', 'astronomy uv', 'astrophysics']

[]

LINER nuclei, which are present in many nearby galactic bulges, may be the manifestation of low-rate or low-radiative-efficiency accretion onto supermassive central black holes. However, it has been unclear whether the compact UV nuclear sources present in many LINERs are clusters of massive stars, rather than being directly related to the accretion process. We have used the Hubble Space Telescope to monitor the UV variability of a sample of 17 galaxies with LINER nuclei and compact nuclear UV sources. Fifteen of the 17 galaxies were observed more than once, with two to five epochs per galaxy, spanning up to a year. We detect significant variability in most of the sample, with peak-to-peak amplitudes from a few percent to 50%. In most cases, correlated variations are seen in two independent bands (F250W and F330W). Comparison to previous UV measurements indicates, for many objects, long-term variations by factors of a few over decade timescales. Variability is detected in LINERs with and without detected compact radio cores, in LINERs that have broad Hα wings detected in their optical spectra (``LINER 1s''), and in those that do not (``LINER 2s''). This variability demonstrates the existence of a nonstellar component in the UV continuum of all types and sets a lower limit to the luminosity of this component. Interestingly, all the LINERs that have detected radio cores have variable UV nuclei, as one would expect from bona fide active galactic nuclei. We note a trend in the UV color (F250W/F330W) with spectral type-LINER 1s tend to be bluer than LINER 2s. This trend may indicate a link between the shape of the nonstellar continuum and the presence or the visibility of a broad-line region. In one target, the poststarburst galaxy NGC 4736, we detect variability in a previously noted UV source that is offset by 2.5" (~60 pc in projection) from the nucleus. This may be the nearest example of a binary active nucleus and of the process leading to black hole merging. <P />Based on observations with the Hubble Space Telescope, which is operated by AURA, Inc., under NASA contract NAS 5-26555.

[]

https://arxiv.org/pdf/astro-ph/0502347.pdf

2009MNRAS.400..677Z

Low-metallicity natal environments and black hole masses in ultraluminous X-ray sources

2009-01-01

['accretion', 'accretion disks', 'black hole physics', 'astronomy x rays', '-', '-']

[]

We review the available estimates of the masses of the compact object in ultraluminous X-ray sources (ULXs) and critically reconsider the stellar mass versus intermediate-mass black hole (BH) interpretations. BHs of several hundreds to thousands of M<SUB>solar</SUB> are not required for the majority of ULXs, although they might be present in the handful of known hyperluminous (~10<SUP>41</SUP> erg s<SUP>-1</SUP>) objects and/or some sources showing timing features in their power density spectra. At the same time, however, stellar mass BHs may be quite a reasonable explanation for ULXs below ~10<SUP>40</SUP> erg s<SUP>-1</SUP>, but they need super-Eddington accretion and some suitable dependence of the beaming factor on the accretion rate in order to account for ULXs above this (isotropic) luminosity. We investigate in detail a `third way' in which a proportion of ULXs contain ~30-90M<SUB>solar</SUB> BHs formed in a low metallicity environment and accreting in a slightly critical regime and find that it can consistently account for the properties of bright ULXs. Surveys of ULX locations looking for a statistically meaningful relationship between ULX position, average luminosity and local metallicity will provide a definitive test of our proposal.

[]

https://arxiv.org/pdf/0909.1017.pdf

2003Sci...300.1119M

Formation of a Black Hole in the Dark

2003-01-01

['-', 'astrophysics']

[]

We show that the black hole in the x-ray binary Cygnus X-1 was formed in situ and did not receive an energetic trigger from a nearby supernova. The progenitor of the black hole had an initial mass greater than 40 solar masses, and during the collapse to form the ~10-solar mass black hole of Cygnus X-1, the upper limit for the mass that could have been suddenly ejected is ~1 solar mass, much less than the mass ejected in a supernova. The observations suggest that high-mass stellar black holes may form promptly, when massive stars disappear silently.

[]

https://arxiv.org/pdf/astro-ph/0305205.pdf

2013EPJC...73.2645Z

On the critical phenomena and thermodynamics of charged topological dilaton AdS black holes

2013-01-01

['-', 'critical phenomena', '-', 'critical phenomena', 'critical phenomena', '-', '-']

[]

In this paper, we study the phase structure and equilibrium state space geometry of charged topological dilaton black holes in (n+1)-dimensional anti-de Sitter spacetime. By considering the pairs of parameters (P∼V) and (Q∼U) as variables, we analyze the phase structure and critical phenomena of black holes and discuss the relation between the two kinds of critical phenomena. We find that the phase structures and critical phenomena drastically depend on the cosmological constant l (or the static electric charge Q of the black holes), dimensionality n and dilaton field Φ.

[]

https://arxiv.org/pdf/1305.3725.pdf

2012PhRvD..85h4015L

Gravitational recoil from accretion-aligned black-hole binaries

2012-01-01

['-', '-', '-', '-', 'methods numerical', '-', 'perturbation theory', '-', 'waves', '-', '-', '-', '-', '-']

[]

We explore the newly discovered “hangup-kick” effect, which greatly amplifies the recoil for configurations with partial spin-/orbital angular momentum alignment, by studying a set of 48 new simulations of equal-mass, spinning black-hole binaries. We propose a phenomenological model for the recoil that takes this new effect into account and then use this model, in conjunction with statistical distributions for the spin magnitude and orientations, based on accretion simulations, to find the probabilities for observing recoils of several thousand kms<SUP>-1</SUP>. In addition, we provide initial parameters, eccentricities, radiated linear and angular momentum, precession rates and remnant mass, spin, and recoils for all 48 configurations. Our results indicate that surveys exploring peculiar (redshifted or blueshifted) differential line-of-sight velocities should observe at least one case above 2000kms<SUP>-1</SUP> out of 4000 merged galaxies. On the other hand, the probability that a remnant black hole recoils in any direction at a velocity exceeding the ∼2000kms<SUP>-1</SUP> escape velocity of large elliptical galaxies is 0.03%. Probabilities of recoils exceeding the escape velocity quickly rise to 5% for galaxies with escape velocities of 1000kms<SUP>-1</SUP> and nearly 20% for galaxies with escape velocities of 500kms<SUP>-1</SUP>. In addition the direction of these large recoils is strongly peaked toward the angular momentum axis, with very low probabilities of recoils exceeding 350kms<SUP>-1</SUP> for angles larger than 45° with respect to the orbital angular momentum axis.

[]

https://arxiv.org/pdf/1201.1923.pdf

2014PhRvD..89h4038C

Asymptotically locally AdS and flat black holes in the presence of an electric field in the Horndeski scenario

2014-01-01

['-', '-', '-', '-', '-', '-', '-']

[]

Asymptotically locally anti-de Sitter and asymptotically flat black hole solutions are found for a particular case of the Horndeski action. The action contains the Einstein-Hilbert term with a cosmological constant, a real scalar field with a nonminimal kinetic coupling given by the Einstein tensor, the minimal kinetic coupling, and the Maxwell term. There is no scalar potential. The solution has two integration constants related with the mass and the electric charge. The solution is given for all dimensions. A new class of asymptotically locally flat spherically symmetric black holes is found when the minimal kinetic coupling vanishes and the cosmological constant is present. In this case, we get a solution which represents an electric universe. The electric field at infinity is only supported by Λ. When the cosmological constant vanishes, the black hole is asymptotically flat.

[]

https://arxiv.org/pdf/1401.4479.pdf

2019CQGra..36p5002D

Carrollian physics at the black hole horizon

2019-01-01

['-', '-']

[]

We show that the geometry of a black hole horizon can be described as a Carrollian geometry emerging from an ultra-relativistic limit where the near-horizon radial coordinate plays the role of a virtual velocity of light tending to zero. We prove that the laws governing the dynamics of a black hole horizon, the null Raychaudhuri and Damour equations, are Carrollian conservation laws obtained by taking the ultra-relativistic limit of the conservation of an energy-momentum tensor; we also discuss their physical interpretation. We show that the vector fields preserving the Carrollian geometry of the horizon, dubbed Carrollian Killing vectors, include BMS-like supertranslations and superrotations and that they have non-trivial associated conserved charges on the horizon. In particular, we build a generalization of the angular momentum to the case of non-stationary black holes. Finally, we discuss the relation of these conserved quantities to the infinite tower of charges of the covariant phase space formalism.

[]

https://arxiv.org/pdf/1903.09654.pdf