Evolution Of Black Holes Research Articles

Black Holes and Other Clues to the Quantum Structure of Gravity

Bringing gravity into a quantum-mechanical framework is likely the most profound remaining problem in fundamental physics. The “unitarity crisis” for black hole evolution appears to be a key facet of this problem, whose resolution will provide important clues. Investigating this raises the important structural question of how to think about subsystems and localization of information in quantum gravity. Paralleling field theory, the answer to this is expected to be an important ingredient in the mathematical structure of the theory. Perturbative gravity results indicate a structure different from that of quantum field theory, but suggest an avenue to defining subsystems. If black holes do behave similarly to familiar subsystems, unitarity demands new interactions that transfer entanglement from them. Such interactions can be parameterized in an effective approach, without directly addressing the question of the fundamental dynamics, whether that is associated with quantum spacetime, wormholes, or something else. Since such interactions need to extend outside the horizon, that raises the question of whether they can be constrained, or might be observed, by new electromagnetic or gravitational wave observations of strong gravity regions. This note overviews and provides connections between these developments.

Black Hole Science With the Laser Interferometer Space Antenna

The author reviews the scientific potential of the Laser Interferometer Space Antenna (LISA), a space-borne gravitational wave (GW) observatory to be launched in the early 30s. Thanks to its sensitivity in the milli-Hz frequency range, LISA will reveal a variety of GW sources across the Universe, from our Solar neighborhood potentially all the way back to the Big Bang, promising to be a game changer in our understanding of astrophysics, cosmology, and fundamental physics. This review dives in the LISA Universe, with a specific focus on black hole science, including the formation and evolution of massive black holes in galaxy centers, the dynamics of dense nuclei and formation of extreme mass ratio inspirals, and the astrophysics of stellar-origin black hole binaries.

Search for Black Hole Merger Families

Abstract The origin, environment, and evolution of stellar-mass black hole (BH) binaries are still a mystery. One of the proposed binary formation mechanisms is manifest in dynamical interactions between multiple BHs. A resulting framework of these dynamical interactions is the so-called hierarchical triple-merger scenario, which happens when three BHs become gravitationally bound, causing two successive BH mergers to occur. In such successive mergers, the BHs involved are directly related to each other, and hence this channel can be directly tested from the properties of the detected binary BH mergers. Here we present a search for hierarchical triple mergers among events within the first and second gravitational-wave transient catalogs of the Laser Interferometer Gravitational-Wave Observatory/Virgo, the eccentric localization of GW190521, and those found by the IAS-Princeton group. The search includes improved statistical quantification that also accounts for BH spins. We perform our analysis for different upper bounds on the mass distribution of first-generation BHs. Our results demonstrate the importance of the mass distributions’ properties for constraining the hierarchical merger scenario. We present the individually significant merger pairs. The search yields interesting candidate families and hints of its future impact.

Scalar field propagation in braneworld black hole scenario obtained from Nash theorem

We determine the scalar field evolution of a braneworld localized black hole with both dark matter and dark energy components, obtained within a dynamical and continuous embedding formalism by use of Nash’s theorem. We further extract the associated quasinormal modes for both de Sitter–Schwarzschild-Dark matter and anti-de Sitter–Schwarzschild-Dark matter solutions, for the different causal structures (one, two or three horizon spacetimes) given by the space of parameters. By comparison with standard solutions within stand alone general relativity, we conclude with comments on possible observable astrophysical differences via quasinormal spectra, and remark on the interpretations of previous AdS/CFT correspondence scenarios.

Observation of stationary spontaneous Hawking radiation and the time evolution of an analogue black hole

We observe the time dependence of the Hawking radiation in an analogue black hole. Soon after the formation of the horizon, there is little or no Hawking radiation. The Hawking radiation then ramps up during approximately one period of oscillation, until it reaches the quantity expected for spontaneous emission. This is similar to a black hole created from gravitational collapse. The spectrum remains approximately constant at the spontaneous level for some time, similar to a stationary black hole. An inner horizon then forms, in analogy with a charged black hole. The inner horizon causes stimulated Hawking radiation. Both types of stimulation predicted by Ted Jacobson and coworkers likely contribute, but the monochromatic stimulation probably contributes more than does the black-hole lasing.

The Pairing Probability of Massive Black Holes in Merger Galaxies in the Presence of Radiative Feedback

Abstract Dynamical friction (DF) against stars and gas is thought to be an important mechanism for orbital evolution of massive black holes (MBHs) in merger remnant galaxies. Recent theoretical investigations, however, show that DF does not always lead to MBH inspiral. For MBHs evolving in gas-rich backgrounds, the ionizing radiation that emerges from the innermost parts of their accretion flow can affect the surrounding gas in such a way to cause the MBHs to accelerate and gain orbital energy. This effect was dubbed “negative DF.” We use a semianalytic model to study the impact of negative DF on pairs of MBHs in merger remnant galaxies evolving under the combined influence of stellar and gaseous DF. Our results show that for a wide range of merger galaxy and MBH properties negative DF reduces the MBH pairing probability by ∼46%. The suppression of MBH pairing is most severe in galaxies with one or more of these properties: (1) a gas fraction of f g ≥ 0.1; (2) a galactic gas disk rotating close to the circular velocity; (3) MBH pairs in prograde, low eccentricity orbits; and (4) MBH pairs with mass <108 M ⊙. The last point is of importance because MBH pairs in this mass range are direct progenitors of merging binaries targeted by the future space-based gravitational wave observatory the Laser Interferometer Space Antenna (LISA).

On the evolution of compact binary black holes

Based on the consideration of potential energy of the di-black-hole as a function of mass asymmetry (transfer) collective coordinate, the possibility of matter transfer between the black holes in a binary system is investigated. The sensitivity of the calculated results is studied to the value of the total mass of binary system. The conditions for the merger of two black holes are analyzed in the context of gravitational wave emission.

A modified hybrid algorithm based on black hole and differential evolution algorithms to search for the critical probabilistic slip surface of slopes

Optimization algorithms play an important role in the reliability analysis of slopes to determine the critical slip surface. In this study, the original hybrid algorithm based on black hole and differential evolution algorithms (BHDE) is modified to speed up the convergence rate. Subsequently, the modified BHDE (MBHDE) combined with the subset simulation (SS) is firstly applied to search for the critical probabilistic slip surface of a slope where Bishop simplified method is employed to calculate the safety factor. Finally, four typical examples of soil slope are analyzed to illustrate the merits in convergence rate for MBHDE. The results achieved by MBHDE combined with SS also indicate its applicability and efficiency in the reliability analysis of slopes.

Black hole spin evolution in warped accretion discs

ABSTRACT Massive black holes (BHs) inhabiting galactic nuclei can be described by two parameters only, i.e. mass and spin, that change through cosmic time in response to accretion and merger events. While most numerical simulations accurately track the BH mass, spin evolution is rarely taken into account. In this work, we implement and validate a self-consistent sub-grid model for the evolution of the BH mass and spin via gas accretion in the hydrodynamics code gizmo. The model assumes that accretion from resolved scales does not occur instantaneously but is mediated by a sub-grid geometrically thin α-disc. After validating our model semi-analytically, we test it in an idealized environment consisting of a circumnuclear disc, where gas accretion on to the accretion disc is consistently determined by gizmo. In the absence of any accretion-related feedback, the spin evolution closely traces that observed in the semi-analytical models, and depends on the free parameters of our implementation, such as the initial BH spin, angular momentum of the accretion disc, and radius at which the gas inflow circularizes. In gizmo, we also couple our model with the biconical-outflow model presented in a companion paper, wherein the feedback axis is always aligned with the BH spin. In this last case, the evolution of the central BH differs significantly from the previous cases, since the feedback process modifies the gas dynamics and its inflow rates from resolved scales. Such an interaction cannot be modelled by simple semi-analytical models and should be treated using full N-body hydrodynamical simulations.

Gravitational wave sensitivity curve of pulsar timing arrays affected by correlated noises

The detection of gravitational waves (GWs) by pulsar timing arrays (PTAs) is not only a very important supplementation of the verification of general relativity but also a new window to study the evolution of supermassive binary black holes and the early universe. However, so far the detection sensitivity of PTAs is not good enough to catch signals of GWs due to the disturbance of various noises. In this paper we explore the influences of the correlated noises caused by the reference clock errors and solar system ephemeris errors in pulsar timing on the detection of stochastic gravitational waves background (GWB). We demonstrate the power-law integrated sensitivity curves of GWB detection under the impacts from these correlated noises. From the simulated data, we find that the influence of different reference time-scale is non-negligible, and the influence is even quite huge if one uses a very old version of solar system ephemeris. However, the impact from these correlated noises on the sensitivity curve is very limited for the real observational data released by international pulsar timing arrays (IPTA). We also calculate the signal-to-noise ratios based on the theoretical GW amplitude permitted by observations. Moreover, we study how the detection sensitivity increases with more pulsar number and longer observation.

The impact on distant fly-bys on the rate of binary primordial black hole mergers

By performing Monte Carlo simulations of the evolution of binary primordial black hole (PBH) systems, we estimate the effect of distant encounters with single PBHs upon the coalescence time and merger rate of binary PBHs. We find that, for models where PBHs compose a large fraction of dark matter, fPBH∼ 1, the expected fractional change in coalescence time is negligible, of order 10−6 for most binaries. For models with significantly lower PBH abundances, fPBH≪ 1, we find that the average change in binary lifetime due to encounters can be as large as \U0001d4aa(10−2), with a small number of binaries experiencing an order unity change in lifetime. In the absence of encounters, we also compare the use of an analytic approximation for the coalescence time to numerically evolving the binary system, finding that the analytic approximation results in an order 10% error in the coalescence time. However, when these effects are taken into consideration, there is a negligible change to the calculated merger rate, placing previous constraints on the PBH abundance arising from observed gravitational wave signals from merging binary black holes on a more secure footing.

Optimal Design of Electromagnetic Devices Assisted by Black Hole and Differential Evolution Algorithms

Recently, many design problems in the field of electrical engineering tend to be more complex, which are characterized by large scale in size, strong nonlinearity for performance analysis, and multi-dimensional design parameters. Therefore, it is not easy to seek for optimum effectively by traditional optimization algorithms. In order to solve optimal design of complex practical problems, in this paper, a novel hybrid optimization algorithm based on the differential evolution algorithm and the black hole theory is proposed and investigated. The differential evolution (DE) algorithm owns good diversity and flexibility, while the black-hole based optimization algorithm (BHBO) possesses faster convergence. In addition, these two algorithms have simple structures. The proposed algorithm with better merits combination may guarantee better convergence and stronger robustness than its independent counterparts of DE and BHBO. The searching performance is deeply investigated through numerical experiments on benchmark functions and practical electromagnetic applications.

Thermodynamic Phase Transition of Black Hole

In the thermodynamic evolution of black holes, the generalized uncertainty principle and quantum tunneling effect prevent the complete evaporation of black holes and produce remnants, and thermodynamic phase transition occurs during evaporation. Based on the generalized uncertainty principle and the method of quantum tunneling, we study the phase transition of the quantum–corrected black hole. Using the modified Hamiltonian–Jacobi equation to analyze the corrected thermodynamic quantity, we find that the thermodynamic phase transition of the black hole is not only depending on the nature of the black hole itself, it also depends on quantum parameter ξ, generalized uncertainty parameter β and parameter λ.

Black hole dynamics in power-law based metric f(R) gravity

In this work, we use power-law cosmology to investigate the evolution of black holes within the context of metric $f(R)$ gravity satisfying the conditions provided by Starobinsky model. In our study, it is observed that presently accelerated expansion of the universe can be suitably explained by this integrated model without the need for dark energy. We also found that mass of a black hole decreases by absorbing surroundings energy-matter due to modification of gravity and more the accretion rate more is mass loss. Particularly the black holes, whose formation masses are nearly $10^{20}$ gm and above, are evaporated at a particular time irrespective of their formation mass. Again our analysis reveals that the maximum mass of a black hole supported by metric $f(R)$ gravity is $10^{12} M_{\odot}$, where $M_{\odot}$ represents the solar mass.

Dynamics of a symmetric EdGB gravity in spherical symmetry

We report on a numerical investigation of black hole evolution in an Einstein dilaton Gauss–Bonnet (EdGB) gravity theory where the Gauss–Bonnet coupling and scalar (dilaton) field potential are symmetric under a global change in sign of the scalar field (a ‘’ symmetry). We find that for sufficiently small Gauss–Bonnet couplings Schwarzschild black holes are stable to radial scalar field perturbations, and are unstable to such perturbations for sufficiently large couplings. For the latter case, we provide numerical evidence that there is a band of coupling parameters and black hole masses where the end states are stable scalarized black hole solutions, in general agreement with the results of Macedo et al (2019 Phys. Rev. D 99 104041). For Gauss–Bonnet couplings larger than those in the stable band, we find that an ‘elliptic region’ forms outside of the black hole horizon, indicating the theory does not possess a well-posed initial value formulation in that regime.

Supermassive binary black hole evolution can be traced by a small SKA pulsar timing array

Supermassive black holes are commonly found in the center of galaxies and evolve with their hosts. The supermassive binary black holes (SMBBH) are thus expected to exist in close galaxy pairs, however, none has been unequivocally detected. The square kilometre array (SKA) is a multi-purpose radio telescope with a collecting area approaching 1 million square metres, with great potential for detecting nanohertz gravitational waves (GWs). In this paper, we quantify the GW detectability by SKA for a realistic SMBBH population using pulsar timing array (PTA) technique and quantify its impact on revealing SMBBH evolution with redshift for the first time. With only $\sim20$ pulsars, much smaller a requirement than in previous work, the SKA PTA is expected to obtain detection within about 5 years of operation and to achieve a detection rate of more than 100 SMBBHs/yr after about 10 years. Although beyond the scope of this paper, we must acknowledge that the presence of persistent red noise will reduce the number of expected detections here. It is thus imperative to understand and mitigate red noise in the PTA data. The GW signatures from a few well-known SMBBH candidates, such as OJ 287, 3C 66B, NGC 5548 and Ark 120, will be detected given the currently best-known parameters of each system. Within 30 years of operation, about 60 individual SMBBHs detection with $z<0.05$ and more than $10^4$ with $z<1$ are expected. The detection rate drops precipitately beyond $z=1$. The substantial number of expected detections and their discernible evolution with redshift by SKA PTA will make SKA a significant tool for studying SMBBHs.

Dynamical Evolution of Cosmic Supermassive Binary Black Holes and Their Gravitational-wave Radiation

Abstract We investigate the evolution of supermassive binary black holes (BBHs) in galaxies with realistic property distributions and the gravitational-wave (GW) radiation from the cosmic population of these BBHs. We incorporate a comprehensive treatment of the dynamical interactions of the BBHs with their environments by including the effects of galaxy triaxial shapes and inner stellar distributions, and generate a large number of BBH evolution tracks. By combining these BBH evolution tracks, galaxy mass functions, galaxy merger rates, and supermassive black hole–host galaxy relations into our model, we obtain statistical distributions of surviving BBHs, BBH coalescence rates, the strength of their GW radiation, and the stochastic GW background (GWB) contributed by the cosmic BBH population. About ∼1%–3% (or ) of supermassive BHs at nearby galactic centers are expected to be binaries with mass ratio (or ). The characteristic strain amplitude of the GWB at frequency is estimated to be , and the upper bound of its results obtained with the different BH–host galaxy relations can be up to , which await testing by future experiments (e.g., the Square Kilometer Array, FAST, Next-Generation Very Large Array). The turnover frequency of the GWB spectrum is at . The uncertainties on the above estimates and prospects for detecting individual sources are also discussed. The application of the cosmic BBH population to the Laser Interferometer Space Antenna (LISA) band provides a lower limit to the detection rate of BBHs by LISA, .

Revisiting the Sołtan Argument Based on a Semianalytical Model for Galaxy and Black Hole Evolution

Abstract We show the significance of the super-Eddington accretion for the cosmic growth of supermassive black holes (SMBHs) with a semianalytical model for galaxy and black hole evolution. The model explains various observed properties of galaxies and active galactic nuclei at a wide redshift range. By tracing the growth history of individual SMBHs, we find that the fraction of the SMBH mass acquired during the super-Eddington accretion phases to the total SMBH mass becomes larger for less massive black holes and at higher redshift. Even at z ∼ 0, SMBHs with have acquired more than 50% of their mass by super-Eddington accretions, which is apparently inconsistent with the classical Sołtan argument. However, the mass-weighted radiation efficiency of SMBHs with obtained with our model, is about 0.08 at z ∼ 0, which is consistent with Sołtan’s argument within the observational uncertainties. We, therefore, conclude that Sołtan’s argument cannot reject the possibility that SMBHs are grown mainly by super-Eddington accretions.

Evolution of binary black holes in AGN accretion discs: Disc-binary interaction and gravitational wave emission

Binary black hole (BBH) mergers are the primary sources of gravitational wave (GW) events detected by LIGO/Virgo. Binary black holes embedded in the accretion discs of active galactic nuclei (AGN) are possible candidates for such GW events. We have developed an idealised analytic model for the orbital evolution of BBHs in AGN accretion discs by combining the evolution equations of disc-binary interaction and GW inspiral. We investigated the coupled “disc+GW”-driven evolution of BBHs transitioning from the disc-driven regime at large orbital separations into the GW-driven regime at small separations. In this evolution channel, BBH mergers are accelerated by a combination of orbital decay and orbital eccentricity growth in the disc-dominated regime. We provide a quantification of the resulting merger timescale τmerger, and analyse its dependence on both the accretion disc and binary orbital parameters. By computing the evolution of the orbital eccentricity as a function of the GW frequency, we predict that most binaries in AGN discs should have significant residual eccentricities (e ∼ 0.01 − 0.1), potentially detectable by LISA. We further discuss the potentials and caveats of this particular BBH-in-AGN channel in the framework of binary evolutionary paths.

Interacting Holographic Dark Energy, the Present Accelerated Expansion and Black Holes

We study the evolution of the universe by assuming an integrated model, which involves interacting dark energy and holographic principle with Hubble scale as IR cutoff. First we determined the interaction rate at which matter is converting to dark energy. In the next step, we evaluated the equation of state parameter which describes the nature of dark energy. Our result predicts that the present state of the universe is dominated by quintessence type dark energy and it will become phantom dominated in near future. Again our analysis successfully addresses the problem of present accelerated expansion of the universe and softens the coincidence problem. We also found that the universe was previously undergoing a decelerated phase of expansion and transition from deceleration to acceleration would occur at a time $t_{q=0}=0.732 t_0$, where $t_0$ is the present age of the universe. Finally, we discuss the evolution of Black Holes in this environment.