Types Of Black Holes Research Articles

Minimal massive gravity: Conserved charges, excitations, and the chiral gravity limit

We find the excitations and construct the conserved charges ( mass and angular momentum) of the recently found Minimal Massive Gravity (MMG) in 2+1 dimensions in asymptotically Anti-de Sitter (AdS) spacetimes. The field equation of the theory does not come from an action and hence lacks the required Bianchi Identity needed to define conserved charges. But the theory, which also provides a healthy extension of the Topologically Massive Gravity in the bulk and boundary of spacetime, does admit conserved charges for metric that are solutions. Our construction is based on background Killing vectors and imperative to provide physical meaning to the integration constants in the black hole type metrics. We also study the chiral gravity limit of MMG.

ON LOCAL IONIZATION EQUILIBRIUM AND DISK WINDS IN QSOs

We present theoretical C iv λλ1548,1550 absorption line profiles for QSOs calculated assuming the accretion disk wind (ADW) scenario. The results suggest that the multiple absorption troughs seen in many QSOs may be due to the discontinuities in the ion balance of the wind (caused by X-rays), rather than discontinuities in the density/velocity structure. The profiles are calculated from a 2.5-dimensional time-dependent hydrodynamic simulation of a line-driven disk wind for a typical QSO black hole mass, a typical QSO luminosity, and for a standard Shakura–Sunyaev disk. We include the effects of ionizing X-rays originating from within the inner disk radius by assuming that the wind is shielded from the X-rays from a certain viewing angle up to 90° ("edge on"). In the shielded region, we assume constant ionization equilibrium, and thus constant line-force parameters. In the non-shielded region, we assume that both the line-force and the C iv populations are nonexistent. The model can account for P-Cygni absorption troughs (produced at edge on viewing angles), multiple absorption troughs (produced at viewing angles close to the angle that separates the shielded region and the non-shielded region), and for detached absorption troughs (produced at an angle in between the first two absorption line types); that is, the model can account for the general types of broad absorption lines seen in QSOs as a viewing angle effect. The steady nature of ADWs, in turn, may account for the steady nature of the absorption structure observed in multiple-trough broad absorption line QSOs. The model parameters are Mbh = 109 M☉ and Ldisk = 1047 erg s−1.

Real projective connections, V. I. Smirnov’s approach, and black-hole-type solutions of the Liouville equation

We consider real projective connections on Riemann surfaces and their corresponding solutions of the Liouville equation. We show that these solutions have singularities of a special type (a black-hole type) on a finite number of simple analytic contours. We analyze the case of the Riemann sphere with four real punctures, considered in V. I. Smirnov’s thesis (Petrograd, 1918) in detail.

Absorption and Scattering Cross Section of Regular Black Holes

By using the partial wave method, we investigate the absorption of massless scalar wave from regular black hole. We numerically carry out the absorption cross section and find that the larger angular momentum quantum number l is, the smaller the corresponding maximum value of partial absorption cross section is. Comparing with Schwarzschild case, the absorption cross section of regular black holes is strengthened in both low and high frequency regions, and the absorption cross section oscillates around the geometric optical value in the high frequency region. Generally speaking, the scattering flux is strengthened and its scattering width becomes narrower in the forward direction. There are obvious contrast of scattering properties of different type of regular black hole.

Solutions in the scalar-tensor theory with nonminimal derivative coupling

We present black hole type solutions in the scalar-tensor theory with nonminimal derivative coupling to the Einstein tensor. The effects of the nonminimal derivative coupling appear in the large scales, while the solutions approach those in the Einstein gravity in the small scales. For the particular coupling constant tuned to the inverse of the cosmological constant, the scalar field becomes trivial and the solutions in the Einstein gravity are recovered. For the other coupling constant, more general solutions can be obtained. If the two-dimensional maximally symmetric space is a two-sphere, the spacetime structure approaches anti-de Sitter spacetime in the large scales. On the other hand, if the two-dimensional space is a two-hyperboloid, the spacetime approaches de Sitter (AdS) spacetime. If it is a flat space, the cosmological constant affects only the amplitude of the scalar field. The extension to the higher-dimensional case is also straightforward. For a certain range of the negative cosmological constant, thermodynamic properties of a black hole are very similar to those of the Schwarzschild-AdS black hole in the Einstein gravity.

Competing p-wave orders

We construct electrically charged, asymptotically AdS5 black hole solutions that are dual to d = 4 CFTs in a superfluid phase with either p-wave or (p + ip)-wave order. The two types of black holes have non-vanishing charged two-form in the bulk and appear at the same critical temperature in the unbroken phase. Both the p-wave and the (p + ip)-wave phase can be thermodynamically preferred, depending on the mass and charge of the two-form, and there can also be first order transitions between them. The p-wave black holes have a helical structure and some of them exhibit the phenomenon of pitch inversion as the temperature is decreased. Both the p-wave and the (p + ip)-wave black holes have zero entropy density ground states at zero temperature and we identify some new ground states which exhibit scaling symmetry, including a novel scenario for the emergence of conformal symmetry in the IR.

Violations of the Equivalence Principle by a Nonlocally Reconstructed Vacuum at the Black Hole Horizon

If information escapes from an evaporating black hole, then field modes just outside the horizon must be thermally entangled with distant Hawking radiation. But for an infalling observer to find empty space at the horizon, the same modes would have to be entangled with the black hole interior. Thus, unitarity appears to require a "firewall" at the horizon. Identifying the interior with the distant radiation promises to resolve the entanglement conflict and restore the vacuum. But the map must adjust for any interactions, or else the firewall will reappear if the Hawking radiation scatters off the cosmic microwave background. Such a map produces a "frozen vacuum," a phenomenon that is arguably worse than a firewall. An infalling observer is unable to excite the vacuum near the horizon. This allows the horizon to be locally detected and so violates the equivalence principle.

Correspondence of phase transition points and singularities of thermodynamic geometry of black holes

We explore a formulation of thermodynamic geometry of black holes and prove that the divergent points of the specific heat correspond exactly to the singularities of the thermodynamic curvature. We investigate this correspondence for different types of black holes. This formulation can also be applied to an arbitrary thermodynamic system.

POPULATION OF BLACK HOLES IN THE MILKY WAY AND IN THE MAGELLANIC CLOUDS

In this review, I will briefly discuss the different types of black hole (BH) populations (supermassive, intermediate mass and stellar mass BHs) both in the Galaxy and in the Magellanic Clouds and compare them with each other.

Baryons in the relativistic jets of the stellar-mass black-hole candidate 4U 1630-47

Accreting black holes are known to power relativistic jets, both in stellar-mass binary systems and at the centres of galaxies. The power carried away by the jets, and, hence, the feedback they provide to their surroundings, depends strongly on their composition. Jets containing a baryonic component should carry significantly more energy than electron-positron jets. Energetic considerations and circular-polarization measurements have provided conflicting circumstantial evidence for the presence or absence of baryons in jets, and the only system in which they have been unequivocally detected is the peculiar X-ray binary SS 433 (refs 4, 5). Here we report the detection of Doppler-shifted X-ray emission lines from a more typical black-hole candidate X-ray binary, 4U 1630-47, coincident with the reappearance of radio emission from the jets of the source. We argue that these lines arise from baryonic matter in a jet travelling at approximately two-thirds the speed of light, thereby establishing the presence of baryons in the jet. Such baryonic jets are more likely to be powered by the accretion disk than by the spin of the black hole, and if the baryons can be accelerated to relativistic speeds, the jets should be strong sources of γ-rays and neutrino emission.

A transition mass for black holes to show broad emission lines

Although the super-massive (AGN) and stellar mass (XRBs) black holes have many properties in common, the broad emission lines (BELs) are exclusively signatures of the AGN. Based on the detection of these lines from SDSS data bases, there seems to be no AGN with mass M_BH \lesssim 10^5 M_sun. In this paper we investigate if such low mass black holes are really non-existent or they are undetected because the BELs in them are not produced efficiently. Using the ionizing spectral energy distribution for a wide range of black hole mass, 10 - 10^9 M_sun, spanning XRBs to AGN, we calculate the equivalent widths (EWs) of ultraviolet and optical lines Ly\alpha 1216 \AA, H\beta 4861 \AA, CIV 1549 \AA and MgII 2798 \AA. The LOC (locally optimally emitting cloud) model has been used to describe the broad emission line region (BELR) for the calculations. We find that the hardening of the SED shape with decreasing mass do not decrease the BEL EWs. However, finite size of the BELR, as measured by the line widths, which is controlled by the mass of the black hole, regulates the production of these emission lines. There seems to be a peak in the EWs of the emission lines for typical AGN black holes of ~ 10^8 M_sun, below which the lines become intrinsically fainter with a sharp fall-off below ~ 10^6 M_sun. This may be the cause of the absence of low mass AGN in SDSS.

NS2-Based Black Hole Attack Modeling and Simulation of Ad Hoc Network

Taking the AODV protocol as an example, the attack characteristics of different types of black holes are analyzed. Then, an attack model of black hole is established. Finally, the effects of black hole attacks to network performance are analyzed by simulations in different types and intensities. The simulation results show that this model can accurately simulate the impact of black hole attack on network performance and can provide reference and corresponding simulation environment for the security research of Ad Hoc network.

Gauge-Gravity Duality and the Black Hole Interior

We present a further argument that typical black holes with field theory duals have firewalls at the horizon. This argument makes no reference to entanglement between the black hole and any distant system, and so is not evaded by identifying degrees of freedom inside the black hole with those outside. We also address the Einstein-Rosen=Einstein-Podolsky-Rosen conjecture of Maldacena and Susskind, arguing that the correlations in generic highly entangled states cannot be geometrized as a smooth wormhole.

Solutions and Thermodynamics of Charged Rotating Black Holes in a Fuzzy Space

We investigate the effect of fuzzy space on black hole and its thermodynamic Properties; we also present our results in different types of black holes according to the parameters and representing electric and magnetic charges.

THE NOT-SO-MASSIVE BLACK HOLE IN THE MICROQUASAR GRS1915+105

We present a new dynamical study of the black hole X-ray transient GRS1915+105 making use of near-infrared spectroscopy obtained with X-shooter at the VLT. We detect a large number of donor star absorption features across a wide range of wavelengths spanning the H and K bands. Our 24 epochs covering a baseline of over 1 year permit us to determine a new binary ephemeris including a refined orbital period of P=33.85 +/- 0.16 d. The donor star radial velocity curves deliver a significantly improved determination of the donor semi-amplitude which is both accurate (K_2=126 +/- 1 km/s) and robust against choice of donor star template and spectral features used. We furthermore constrain the donor star's rotational broadening to vsini=21 +/-4 km/s, delivering a binary mass ratio of q=0.042 +/- 0.024. If we combine these new constraints with distance and inclination estimates derived from modelling the radio emission, a black hole mass of M_BH=10.1 +/- 0.6 M_sun is inferred, paired with an evolved mass donor of M_2=0.47 +/- 0.27 M_sun. Our analysis suggests a more typical black hole mass for GRS1915+105 rather than the unusually high values derived in the pioneering dynamical study by Greiner et al. (2001). Our data demonstrate that high-resolution infrared spectroscopy of obscured accreting binaries can deliver dynamical mass determinations with a precision on par with optical studies.

Black hole mass estimate for a sample of radio-loud narrow-line Seyfert 1 galaxies

We discuss the relationship between a standard Shakura & Sunyaev accretion disc model and the big blue bump (BBB) observed in Type 1 active galactic nuclei. Given the similarity between the BBB and the predicted disc spectrum, we propose a new method to estimate black hole masses which relies on the modelling of both optical and UV data with a Shakura & Sunyaev disc spectrum. We apply this method to a sample of 23 radio-loud narrow-line Seyfert 1 (RL-NLS1) galaxies, using data from Wide-field Infrared Survey Explorer, SDSS and GALEX. Our black hole mass estimates are at least a factor of ∼6 above previous results based on single epoch virial methods, while the Eddington ratios are correspondingly lower. Hence, the black hole masses of RL-NLS1 galaxies are typically above 108 M⊙, in agreement with the typical black hole mass of blazars.

LOCAL LUMINOUS INFRARED GALAXIES. III. CO-EVOLUTION OF BLACK HOLE GROWTH AND STAR FORMATION ACTIVITY?

Local luminous infrared (IR) galaxies (LIRGs) have both high star formation rates (SFR) and a high AGN (Seyfert and AGN/starburst composite) incidence. Therefore, they are ideal candidates to explore the co-evolution of black hole (BH) growth and star formation (SF) activity, not necessarily associated with major mergers. Here, we use Spitzer/IRS spectroscopy of a complete volume-limited sample of local LIRGs (distances of <78Mpc). We estimate typical BH masses of 3x10^7 M_sun using [NeIII]15.56micron and optical [OIII]5007A gas velocity dispersions and literature stellar velocity dispersions. We find that in a large fraction of local LIRGs the current SFR is taking place not only in the inner nuclear ~1.5kpc region, as estimated from the nuclear 11.3micron PAH luminosities, but also in the host galaxy. We next use the ratios between the SFRs and BH accretion rates (BHAR) to study whether the SF activity and BH growth are contemporaneous in local LIRGs. On average, local LIRGs have SFR to BHAR ratios higher than those of optically selected Seyferts of similar AGN luminosities. However, the majority of the IR-bright galaxies in the RSA Seyfert sample behave like local LIRGs. Moreover, the AGN incidence tends to be higher in local LIRGs with the lowest SFRs. All this suggests that in local LIRGs there is a distinct IR-bright star forming phase taking place prior to the bulk of the current BH growth (i.e., AGN phase). The latter is reflected first as a composite and then as a Seyfert, and later as a non-LIRG optically identified Seyfert nucleus with moderate SF in its host galaxy.

TUNNELING OF DIRAC PARTICLES FROM PHANTOM REISSNER NORDSTROM ADS BLACK HOLE

We study the Hawking radiation of Dirac particles from Phantom Reissner Nordstrom ADS black hole by tunneling method. We use charge relativistic Dirac equation to study the emission of such particles. To solve Dirac equation we use WKB approximation and find the tunneling probability of outgoing particles. Finally we find the Hawking temperature for such type of black holes.

THE DEMOGRAPHICS OF BROAD-LINE QUASARS IN THE MASS-LUMINOSITY PLANE. II. BLACK HOLE MASS AND EDDINGTON RATIO FUNCTIONS

We employ a flexible Bayesian technique to estimate the black hole mass and Eddington ratio functions for Type 1 (i.e., broad line) quasars from a uniformly-selected data set of ~58,000 quasars from the SDSS DR7. We find that the SDSS becomes significantly incomplete at M_{BH} < 3 x 10^8 M_{Sun} or L / L_{Edd} < 0.07, and that the number densities of Type 1 quasars continue to increase down to these limits. Both the mass and Eddington ratio functions show evidence of downsizing, with the most massive and highest Eddington ratio black holes experiencing Type 1 quasar phases first, although the Eddington ratio number densities are flat at z < 2. We estimate the maximum Eddington ratio of Type 1 quasars in the observable Universe to be L / L_{Edd} ~ 3. Consistent with our results in Paper I, we do not find statistical evidence for a so-called "sub-Eddington boundary" in the mass-luminosity plane of broad line quasars, and demonstrate that such an apparent boundary in the observed distribution can be caused by selection effect and errors in virial BH mass estimates. Based on the typical Eddington ratio in a given mass bin, we estimate typical growth times for the black holes in Type 1 quasars and find that they are typically comparable to or longer than the age of the universe, implying an earlier phase of accelerated (i.e., with higher Eddington ratios) and possibly obscured growth. The large masses probed by our sample imply that most of our black holes reside in what are locally early type galaxies, and we interpret our results within the context of models of self-regulated black hole growth.

On the positivity of black hole degeneracies in string theory

Certain helicity trace indices of charged states in N = 4 and N = 8 superstring theory have been computed exactly using their explicit weakly coupled microscopic descrip- tion. These indices are expected to count the exact quantum degeneracies of black holes carrying the same charges. In order for this interpretation to be consistent, these indices should be positive integers. We prove this positivity property for a class of four/five dimen- sional black holes in type II string theory compactified on T 6 /T 5 and on K3 ×T 2 /S 1 . The proof relies on the mock modular properties of the corresponding generating functions. 1. Introduction and statement of results The study of supersymmetric black holes in string theory has been very effective in shedding light on the issue of black hole entropy. The strength of the string theoretic approach lies in the fact that there are two related descriptions of charged black holes. The first (strong string coupling, macroscopic) description is a low energy effective description as general relativity coupled to a set of matter fields. In the second (weak string coupling, microscopic) descrip- tion, a generic state of the theory with the same charges as the black hole is identified as a collection of fundamental objects of string theory namely fundamental strings and branes. The fluctuations of these objects make up the elementary excitations (microstates) of the theory, which can be described by conventional quantum field theoretic methods. The key idea is to identify these two descriptions valid at strong and weak coupling, respectively. At strong coupling, the excitations of the strings and branes exert a gravitational force on each other, and the black hole can be thought of as a quantum mechanical bound state of these microstates. In a class of supersymmetric string theories with sixteen or more unbroken supercharges we now have a practically complete understanding of the spectrum of BPS states (see (27) for a relatively recent review). One can therefore subject the above idea to high precision tests, by comparing the statistical entropy of the ensemble of states and an appropriately defined thermodynamic entropy of the corresponding BPS black hole, beyond a large charge approximation. Since we know the microscopic degeneracies exactly, one can even aim for an