Evolution Of Holes Research Articles

Constraints on redshifts of blazars from extragalactic background light attenuation using Fermi-LAT data

ABSTRACT The extragalactic high-energy γ-ray sky is dominated by blazars, which are active galactic nuclei with their jets pointing towards us. Distance measurements are of fundamental importance yet for some of these sources are challenging because any spectral signature from the host galaxy may be outshone by the non-thermal emission from the jet. In this paper, we present a method to constrain redshifts for these sources that relies only on data from the Large Area Telescope on board the Fermi Gamma-ray Space Telescope. This method takes advantage of the signatures that the pair-production interaction between photons with energies larger than approximately 10 GeV and the extragalactic background light leaves on γ-ray spectra. We find upper limits for the distances of 303 γ-ray blazars, classified as 157 BL Lacertae objects, 145 of uncertain class, and 1 flat-spectrum-radio quasar, whose redshifts are otherwise unknown. These derivations can be useful for planning observations with imaging atmospheric Cherenkov telescopes and also for testing theories of supermassive black hole evolution. Our results are applied to estimate the detectability of these blazars with the future Cherenkov Telescope Array, finding that at least 21 of them could be studied in a reasonable exposure of 20 h.

Disentangling the evolution of electrons and holes in photoexcited ZnO nanoparticles.

The evolution of charge carriers in photoexcited room temperature ZnO nanoparticles in solution is investigated using ultrafast ultraviolet photoluminescence spectroscopy, ultrafast Zn K-edge absorption spectroscopy, and ab initio molecular dynamics (MD) simulations. The photoluminescence is excited at 4.66 eV, well above the band edge, and shows that electron cooling in the conduction band and exciton formation occur in <500 fs, in excellent agreement with theoretical predictions. The x-ray absorption measurements, obtained upon excitation close to the band edge at 3.49 eV, are sensitive to the migration and trapping of holes. They reveal that the 2 ps transient largely reproduces the previously reported transient obtained at 100 ps time delay in synchrotron studies. In addition, the x-ray absorption signal is found to rise in ∼1.4 ps, which we attribute to the diffusion of holes through the lattice prior to their trapping at singly charged oxygen vacancies. Indeed, the MD simulations show that impulsive trapping of holes induces an ultrafast expansion of the cage of Zn atoms in <200 fs, followed by an oscillatory response at a frequency of ∼100 cm-1, which corresponds to a phonon mode of the system involving the Zn sub-lattice.

Dynamics and kinetics of phase transition for regular AdS black holes in general relativity coupled to nonlinear electrodynamics

We study the stochastic dynamics and kinetics of the phase transition of the regular black holes in Anti-de Sitter spacetime by employing the free energy landscape. Our investigation focuses on two important classes of regular black hole solutions, namely the Hayward and Bardeen, which can be obtained from coupling of non-linear electrodynamics. The dynamics of the phase transition is described by the Fokker–Planck equation, using which, we investigate the probabilistic evolution of regular AdS black holes. We solve this equation numerically by imposing both reflecting and absorbing boundary conditions and appropriate initial conditions. In this context, the on-shell Gibbs free energy is treated as a function of the event horizon radius, where the difference of the event horizon radii in different phases serves as the order parameter for the phase transition. The study allows us to probe the dynamic process of transitioning between coexisting small and large black hole phases due to thermal fluctuations, as quantified by the calculation of the first passage time. Furthermore, we explore the influence of temperature on this dynamic process. This research contributes to a deeper understanding of the microstructures of regular AdS black holes.

Simulating supermassive black hole mass measurements for a sample of ultramassive galaxies using ELT/HARMONI high-spatial-resolution integral-field stellar kinematics

ABSTRACT As the earliest relics of star formation episodes of the Universe, the most massive galaxies are the key to our understanding of the stellar population, cosmic structure, and supermassive black hole (SMBH) evolution. However, the details of their formation histories remain uncertain. We address these problems by planning a large survey sample of 101 ultramassive galaxies (z ≤ 0.3, |δ + 24°| &amp;lt; 45°, |b| &amp;gt; 8°), including 76 per cent ellipticals, 17 per cent lenticulars, and 7 per cent spirals brighter than MK ≤ −27 mag (stellar mass 2 × 1012 ≲ M⋆ ≲ 5 × 1012 M⊙) with ELT/HARMONI. Our sample comprises diverse galaxy environments ranging from isolated to dense-cluster galaxies. The primary goals of the project are to (1) explore the stellar dynamics inside galaxy nuclei and weigh SMBHs, (2) constrain the black hole scaling relations at the highest mass, and (3) probe the late-time assembly of these most massive galaxies through the stellar population and kinematical gradients. We describe the survey, discuss the distinct demographics and environmental properties of the sample, and simulate their HARMONI Iz-, Iz + J-, and H + K-band observations by combining the inferred stellar-mass models from Pan-STARRS observations, an assumed synthetic spectrum of stars, and SMBHs with masses estimated based on different black hole scaling relations. Our simulations produce excellent state-of-the-art integral field spectrography and stellar kinematics (ΔVrms ≲ 1.5 per cent) in a relatively short exposure time. We use these stellar kinematics in combination with the Jeans anisotropic model to reconstruct the SMBH mass and its error using a Markov chain Monte Carlo simulation. Thus, these simulations and modellings can be benchmarks to evaluate the instrument models and pipelines dedicated to HARMONI to exploit the unprecedented capabilities of ELT.

Massive black hole growth using the star gulping mechanism

"The evolution of merging black holes (BHs) and their associated processes will be the center-piece study for the upcoming gravitational waves (GWs) observatories, including the LISA Space Mission from ESA. We ran simulations specifically for studying the BH growth, in order to provide estimates regarding the detection rates for the future GW laboratories. Here, we describe the results of our investigations for a new implementation regarding the BH growth, star gulping (SG), in which stars are absorbed by BHs. The current scientific literature emphasizes two main mechanisms for the growth of BHs: accretion of surrounding material and merging with another BH. By taking into account both methods, one can begin to model the growth processes of the most massive BHs (MBHs) from the moment of their origin to current observations. Our previous work showed that even if you consider these processes at their maximum, it is very difficult to grow BHs to the masses and concentrations that we measure today. Therefore, we performed detailed simulations in order to study another growth mechanism, star gulping (SG), that has the potential to add more mass to BHs."

Semiclassical dynamics of Hawking radiation

We consider gravity in 3+1 spacetime dimensions coupled to N scalar matter fields in a semiclassical limit where . The dynamical evolution of a black hole including the back-reaction of the Hawking radiation on the metric is formulated as an initial-value problem. The quantum stress-energy tensor is evaluated using a point-splitting regularization along spacelike geodesics. To account for the quantum entanglement of the matter fields, they are treated as a set of bilocal collective fields defined on spacelike hypersurfaces. The resulting semiclassical field equations include terms up to fourth order in derivatives that can be treated in a perturbative expansion. The formulation we arrive at should be amenable to numerical simulation of time-dependent semiclassical spacetime.

Non-isometric codes for the black hole interior from fundamental and effective dynamics

We introduce a new holographic map for encoding black hole interiors by including both fundamental and effective dynamics. This holographic map is constructed by evolving a state in the effective, semiclassical gravity description of the interior backwards in time to pull the degrees of freedom outside the black hole, before evolving forwards in time in the fundamental description. We show this “backwards-forwards” map is equivalent to a post-selection map of the type introduced by Akers, Engelhardt, Harlow, Penington, and Vardhan, and in the case of trivial effective interactions reduces to their model, while providing a suitable generalization when those interactions are nontrivial. We show the map is equivariant with respect to time evolution, and independent of any interactions outside the black hole. This construction includes interactions with an infaller in a way that preserves the unitarity of black hole evolution exactly and does not allow for superpolynomial computational complexity.

Large-scale Evolution of Seconds-long Relativistic Jets from Black Hole–Neutron Star Mergers

We present the first numerical simulations that track the evolution of a black hole–neutron star (BH–NS) merger from premerger to r ≳ 1011 cm. The disk that forms after a merger of mass ratio q = 2 ejects massive disk winds (3–5 × 10−2 M ⊙). We introduce various postmerger magnetic configurations and find that initial poloidal fields lead to jet launching shortly after the merger. The jet maintains a constant power due to the constancy of the large-scale BH magnetic flux until the disk becomes magnetically arrested (MAD), where the jet power falls off as L j ∼ t −2. All jets inevitably exhibit either excessive luminosity due to rapid MAD activation when the accretion rate is high or excessive duration due to delayed MAD activation compared to typical short gamma-ray bursts (sGRBs). This provides a natural explanation for long sGRBs such as GRB 211211A but also raises a fundamental challenge to our understanding of jet formation in binary mergers. One possible implication is the necessity of higher binary mass ratios or moderate BH spins to launch typical sGRB jets. For postmerger disks with a toroidal magnetic field, dynamo processes delay jet launching such that the jets break out of the disk winds after several seconds. We show for the first time that sGRB jets with initial magnetization σ 0 > 100 retain significant magnetization (σ ≫ 1) at r > 1010 cm, emphasizing the importance of magnetic processes in the prompt emission. The jet–wind interaction leads to a power-law angular energy distribution by inflating an energetic cocoon whose emission is studied in a companion paper.

Recipes for Jet Feedback and Spin Evolution of Black Holes with Strongly Magnetized Super-Eddington Accretion Disks

A spinning black hole (BH) accreting from a disk of strongly magnetized plasma via a magnetically arrested disk is known to produce an efficient electromagnetic jet powered by the BH’s spin energy. We present general relativistic radiative magnetohydrodynamic simulations of magnetically arrested systems covering a range of sub- to super-Eddington accretion rates. Using the numerical results from these simulations, we develop formulae to describe the magnetization, jet efficiency, and spin evolution of an accreting BH as a function of its spin and accretion rate. A BH with near-Eddington accretion experiences a mild degree of spin-down because of angular momentum loss through the jet, leading to an equilibrium spin of 0.8 rather than 1.0 at the Eddington limit. As the accretion rate increases above Eddington, the spin-down effect becomes progressively stronger, ultimately converging on previous predictions based on nonradiative simulations. In particular, spin evolution drives highly super-Eddington systems toward a BH spin near zero. The formulae developed in this letter may be applied to galaxy- and cosmological-scale simulations that include BHs. If magnetically arrested disk accretion is common among supermassive BHs, the present results have broad implications for active galactic nucleus feedback and cosmological spin evolution.

Using ANNs to predict the evolution of spectrum occupancy in cognitive-radio systems

This paper analyzes the use of Artificial Neural Networks (ANNs) to identify and predict the evolution of vacant portions or frequency holes of the radio spectrum in Cognitive Radio (CR) systems. The operating frequency of CR transceivers can be modified over the air according to the information provided by the ANN in order to establish the communication in the least occupied band. To this end, ANNs are trained with time-series datasets sensed from the electromagnetic environment. Several network architectures are considered in the study, including Convolutional Neural Networks (CNNs), Long Short-Term Memory (LSTM) networks and hybrid combinations of them. These ANNs are modeled and compared in terms of their complexity, speed and accuracy of the prediction. Both simulations and experimental results are shown to validate the approach presented in this work.

A connection between regular black holes and horizonless ultracompact stars

We illustrate that regular black holes and horizonless stars, typically considered as quite distinct families of black hole mimickers, are intimately intertwined. We show that any spherically symmetric regular black hole can be continuously deformed into a horizonless star under the mild conditions of non-negativity of gravitational energy (Misner-Sharp quasi-local mass), and an assumed linear relation between the latter and the Arnowitt-Deser-Misner (ADM) mass. We illustrate this general result by considering the family of geometries proposed by Hayward as the description of regular black holes, and we also describe the properties of the corresponding horizonless stars. The form of the associated effective stress-energy tensor shows that these horizonless stars can be identified as anisotropic gravastars with a soft surface and inner/outer light rings. We also construct dynamical geometries that could describe the evolution of regular black holes towards horizonless stars, and show that it is plausible that the effective stress-energy tensor in the first stages of evolution is generated by semiclassical effects, in agreement with independent works analyzing semiclassical backreaction.

Hole-driven dynamics of a three-dimensional gravitational liquid curtain

It is known that the disintegration of vertical liquid curtains (sheets) is affected crucially by the amplification of free edge holes forming inside the curtain. This paper aims to investigate the influence of the hole expansion dynamics, driven by the so-called rim retraction, on the breakup of a liquid curtain, in both supercritical (Weber number $We &gt; 1$ ) and subcritical ( $We &lt; 1$ ) conditions. The analysis is based on three-dimensional direct numerical simulations. For a selected supercritical configuration, the steady flow topology is first analysed. The investigation reveals the classic triangular shape regime of the steady curtain, due to the surface-tension-induced borders retraction towards its centre plane. The unsteady dynamics is then investigated as the curtain response to a hole perturbation introduced artificially in the steady flow configuration. The hole evolution determines a rim retraction phenomenon inside the curtain, which is influenced by both capillary and gravity forces. In supercritical conditions, the hole does not influence the curtain flow dynamics in the long-time limit. By reducing the Weber number slightly under the critical threshold ( $We=1$ ), the initial amplification rate of the hole area increases, due to the stronger retraction effect of surface tension acting on the hole rims. The free hole expansion in fully subcritical conditions ( $We &lt; 1$ ) is investigated finally by simulating an edge-free curtain flow. As $We$ decreases progressively, the hole expands while it is convected downstream by gravity acceleration. In the range $0.4&lt; We&lt;1$ , the subcritical curtain returns to the intact unperturbed configuration after the hole expulsion at the downstream outflow. For $We&lt;0.4$ , the surface tension force becomes strong enough to reverse the gravitational motion of the hole top point, which retracts upstream towards the sheet inlet section while expanding along the lateral directions. This last phenomenon causes finally the breakup of the curtain, which results in a columnar regime strictly resembling similar experimental findings of the literature.

Constant-roll and primordial black holes in f(Q,T) gravity

In this study, we investigate the consequence of the constant-roll condition and examine the role of a chosen form of f(Q,T) gravity, given by f(Q,T)=αQ2+σT, in the cosmological inflation process. We analyze the inflationary scenario by calculating modified Friedmann equations and giving an alternative technique that enables relating modified slow-roll parameters to the constant roll parameter β. Considering both chaotic and hilltop models, we calculate the spectral index and the tensor-to-scalar ratio and compare their compatibility with Planck’s data for different choices of the constant roll parameter β. We examine the evolution of primordial black holes in our chosen modified gravity model taking into account the accretion process and the evaporation due to Hawking radiation. We compute the evaporation and accretion masses rate and provide an analytic estimation of the primordial black holes mass and of the radiation in the f(Q,T) gravity model.

Black hole evolution in the Bondi–Hoyle–Lyttleton accretion model

Black hole evolution in the Bondi–Hoyle–Lyttleton accretion model

Analysis of Galaxy, Black hole and BH-BH mergers based on IllustrisTNG

Contemporarily, one of the most significant current trends in the studies of black holes is the black hole mergers. In this paper, we would present prescriptions for star formation and stellar evolution of black hole, and make comparisons in features of the black holes before and after the merger. Based on Illustris TNG, we collect our data to investigate Galaxy and black hole mergers and utilize the corresponding programming API function on it to visualize the results. Specifically, the relationship between galaxy mass and gas size will be demonstrated with the help of diagrams in part one. Besides, the general relationship between the characteristics of the black holes before the merger and the characteristics of the black hole after the merger will be discussed. The variance and standard division of the data will be calculated to confirm the relationship. These results explore the basic relationship between galaxies and the similarity between black holes before and after the merger, which shed light on further understanding of the corresponding processes.

Co-Evolution vs. Co-existence: The effect of accretion modelling on the evolution of black holes and host galaxies

ABSTRACT We append two additional black hole (BH) accretion models, namely viscous disc and gravitational torque-driven accretion, into the Numerical Investigation of a Hundred Astrophysical Objects (NIHAO) project of galaxy simulations. We show that these accretion models, characterized by a weaker dependence on the BH mass compared to the commonly used Bondi-Hoyle accretion, naturally create a common evolutionary track (co-existence) between the mass of the BH and the stellar mass of the galaxy, even without any direct coupling via feedback (FB). While FB is indeed required to control the final BH and stellar mass of the galaxies, our results suggest that FB might not be the leading driver of the cosmic co-evolution between these two quantities; in these models, co-evolution is simply determined by the shared central gas supply. Conversely, simulations using Bondi-Hoyle accretion show a two-step evolution, with an early growth of stellar mass followed by exponential growth of the central supermassive black hole (SMBH). Our results show that the modelling of BH accretion (sometimes overlooked) is an extremely important part of BH evolution and can improve our understanding of how scaling relations emerge and evolve, and whether SMBH and stellar mass co-exist or co-evolve through cosmic time.

Triple and quadruple black holes in the ASTRID simulation at z ∼ 2

ABSTRACT We use the ASTRID cosmological hydrodynamic simulation to investigate the properties and evolution of triple and quadruple massive black hole (MBH) systems at z = 2–3. Only a handful of MBH tuple systems have been detected to date. In ASTRID, we find 4 per cent of the $M_{\rm BH}\gt 10^7\, M_\odot$ are in tuples with $\Delta r_{\rm max} \lt 200\, {\rm kpc}$. The tuple systems span a range of separations with the majority of the observable AGN systems at Δr ∼ 50–100 kpc. They include some of the most massive BHs (up to $10^{10} \, M_\odot$) but with at least one of the components of $M_{\rm BH} \sim 10^7 \, {\rm M}_{\odot }$. Tuples’ host galaxies are typically massive with $M_* \sim 10^{10-11} \, M_\odot$. We find that $\gt 10~{{\ \rm per\ cent}}$ massive haloes with Mhalo &amp;gt; 1013 M⊙ host MBH tuples. Following the subsequent interactions between MBHs in tuples, we found that in $\sim 5~{{\ \rm per\ cent}}$ of the triplets all three MBHs merge within a Gyr, and 15 per cent go through one merger. As a by-product of the complex multigalaxy interaction of these systems, we also find that up to $\sim 5~{{\ \rm per\ cent}}$ of tuples lead to runaway MBHs. In ASTRID, virtually all of the ultramassive black holes ($\gt 10^{10} \, M_\odot$) have undergone a triple quasar phase, while for BHs with $M_{\rm BH} \sim 10^9 \, M_\odot$, this fraction drops to 50 per cent.

The holographic map of an evaporating black hole

We construct a holographic map that takes the semi-classical state of an evaporating black hole and its Hawking radiation to a microscopic model that reflects the scrambling dynamics of the black hole. The microscopic model is given by a nested sequence of random unitaries, each one implementing a scrambling time step of the black hole evolution. Differently from other models, energy conservation and the thermal nature of the Hawking radiation are taken into account. We show that the QES formula follows for the entropy of multiple subsets of the radiation and black hole. We further show that a version of entanglement wedge reconstruction can be proved by computing suitable trace norms and quantum fidelities involving the action of a unitary on a subset of Hawking partners. If the Hawking partner is in an island, its unitary can be reconstructed by a unitary on the radiation. We also adopt a similar setup and analyse reconstruction of unitaries acting on an infalling system.

QUANTUM BLACK HOLES IN THE EXPANDING UNIVERSE

In the expanding Universe, the evolution of quantum black holes with the modified Schwarzschild and Reissner–Nordström geometries is considered. All quantum black holes at definite moments of the cosmological time lose event horizons and are transformed to gravitating objects with masses M.

Femtosecond laser drilling of film cooling holes: Quantitative analysis and real-time monitoring

The damage to opposite wall caused by excessive ablation will severely affect the performance of the turbine blade in femtosecond laser drilling of film cooling holes. Real-time monitoring and control of drilling stage is regarded as one of the most effective methods for solving the excessive ablation problem. However, due to the complexity of femtosecond laser drilling process, it is difficult to model the relationship between drilling state and machining phenomenon physically. In this paper, the quantitative analysis of femtosecond laser drilling and an intelligent methodology for real-time monitoring and control of drilling stage were developed. The laser drilling was comprehensively analyzed and four drilling stage was firstly divided automatically based on the hole evolution process and the optical emission signal detected in drilling process. And the correlation between signal and drilling stages was established through the analysis of the optical emission signal. Furthermore, this paper proposed a data-driven method to build the classification model of different drilling stages. The periodicity and pulse characteristics of signal and corresponding time-domain features were extracted for further modelling. Finally, the classification model was established via AdaBoost method, which achieves a classification accuracy of 95.22 %. And the generalization performance for real-monitoring of drilling stage was further verified. This study presented a set of processes for real-time monitoring and process control in laser drilling process, which provides a new insight to solve the excessive ablation problem.