Static spin-3/2 perturbations of two-black hole system

International Nuclear Information System (INIS)

Embacher, F.; Aichelburg, P.C.

1984-01-01

We construct the most general static regular, non-gauge spin-3/2 perturbations on the Majumdar-Papapetrou background for two black holes. The construction applies a limiting procedure by combining Killing spinors and spacetime perturbations. The supercharge associated with the spin-3/2 field is proportional to the difference of the mass parameters, implying that a system of two equal black holes has zero supercharge. (Author)

No firewalls or information problem for black holes entangled with large systems

Science.gov (United States)

Stoltenberg, Henry; Albrecht, Andreas

2015-01-01

We discuss how under certain conditions the black hole information puzzle and the (related) arguments that firewalls are a typical feature of black holes can break down. We first review the arguments of Almheiri, Marolf, Polchinski and Sully favoring firewalls, focusing on entanglements in a simple toy model for a black hole and the Hawking radiation. By introducing a large and inaccessible system entangled with the black hole (representing perhaps a de Sitter stretched horizon or inaccessible part of a landscape), we show complementarity can be restored and firewalls can be avoided throughout the black hole's evolution. Under these conditions black holes do not have an "information problem." We point out flaws in some of our earlier arguments that such entanglement might be generically present in some cosmological scenarios and call out certain ways our picture may still be realized.

Pothole Detection System Using a Black-box Camera

Directory of Open Access Journals (Sweden)

Youngtae Jo

2015-11-01

Full Text Available Aging roads and poor road-maintenance systems result a large number of potholes, whose numbers increase over time. Potholes jeopardize road safety and transportation efficiency. Moreover, they are often a contributing factor to car accidents. To address the problems associated with potholes, the locations and size of potholes must be determined quickly. Sophisticated road-maintenance strategies can be developed using a pothole database, which requires a specific pothole-detection system that can collect pothole information at low cost and over a wide area. However, pothole repair has long relied on manual detection efforts. Recent automatic detection systems, such as those based on vibrations or laser scanning, are insufficient to detect potholes correctly and inexpensively owing to the unstable detection of vibration-based methods and high costs of laser scanning-based methods. Thus, in this paper, we introduce a new pothole-detection system using a commercial black-box camera. The proposed system detects potholes over a wide area and at low cost. We have developed a novel pothole-detection algorithm specifically designed to work with the embedded computing environments of black-box cameras. Experimental results are presented with our proposed system, showing that potholes can be detected accurately in real-time.

Black hole astrophysics

International Nuclear Information System (INIS)

Blandford, R.D.; Thorne, K.S.

1979-01-01

Following an introductory section, the subject is discussed under the headings: on the character of research in black hole astrophysics; isolated holes produced by collapse of normal stars; black holes in binary systems; black holes in globular clusters; black holes in quasars and active galactic nuclei; primordial black holes; concluding remarks on the present state of research in black hole astrophysics. (U.K.)

Measuring the spin of black holes in binary systems using gravitational waves.

Science.gov (United States)

Vitale, Salvatore; Lynch, Ryan; Veitch, John; Raymond, Vivien; Sturani, Riccardo

2014-06-27

Compact binary coalescences are the most promising sources of gravitational waves (GWs) for ground-based detectors. Binary systems containing one or two spinning black holes are particularly interesting due to spin-orbit (and eventual spin-spin) interactions and the opportunity of measuring spins directly through GW observations. In this Letter, we analyze simulated signals emitted by spinning binaries with several values of masses, spins, orientations, and signal-to-noise ratios, as detected by an advanced LIGO-Virgo network. We find that for moderate or high signal-to-noise ratio the spin magnitudes can be estimated with errors of a few percent (5%-30%) for neutron star-black hole (black hole-black hole) systems. Spins' tilt angle can be estimated with errors of 0.04 rad in the best cases, but typical values will be above 0.1 rad. Errors will be larger for signals barely above the threshold for detection. The difference in the azimuth angles of the spins, which may be used to check if spins are locked into resonant configurations, cannot be constrained. We observe that the best performances are obtained when the line of sight is perpendicular to the system's total angular momentum and that a sudden change of behavior occurs when a system is observed from angles such that the plane of the orbit can be seen both from above and below during the time the signal is in band. This study suggests that direct measurement of black hole spin by means of GWs can be as precise as what can be obtained from x-ray binaries.

Lidov–Kozai Cycles with Gravitational Radiation: Merging Black Holes in Isolated Triple Systems

International Nuclear Information System (INIS)

Silsbee, Kedron; Tremaine, Scott

2017-01-01

We show that a black-hole binary with an external companion can undergo Lidov–Kozai cycles that cause a close pericenter passage, leading to a rapid merger due to gravitational-wave emission. This scenario occurs most often for systems in which the companion has a mass comparable to the reduced mass of the binary and the companion orbit has a semimajor axis within a factor of ∼10 of the binary semimajor axis. Using a simple population-synthesis model and three-body simulations, we estimate the rate of mergers in triple black-hole systems in the field to be about six per Gpc 3 per year in the absence of natal kicks during black-hole formation. This value is within the low end of the 90% credible interval for the total black hole–black hole merger rate inferred from the current LIGO results. There are many uncertainties in these calculations, the largest of which is the unknown distribution of natal kicks. Even modest natal kicks of 40 km s −1 will reduce the merger rate by a factor of 40. A few percent of these systems will have eccentricity greater than 0.999 when they first enter the frequency band detectable by aLIGO (above 10 Hz).

Lidov–Kozai Cycles with Gravitational Radiation: Merging Black Holes in Isolated Triple Systems

Energy Technology Data Exchange (ETDEWEB)

Silsbee, Kedron [Department of Astrophysical Sciences, Princeton University, Ivy Lane, Princeton, NJ 08544 (United States); Tremaine, Scott, E-mail: ksilsbee@astro.princeton.edu, E-mail: tremaine@ias.edu [Institute for Advanced Study, 1 Einstein Drive Princeton, NJ 08540 (United States)

2017-02-10

We show that a black-hole binary with an external companion can undergo Lidov–Kozai cycles that cause a close pericenter passage, leading to a rapid merger due to gravitational-wave emission. This scenario occurs most often for systems in which the companion has a mass comparable to the reduced mass of the binary and the companion orbit has a semimajor axis within a factor of ∼10 of the binary semimajor axis. Using a simple population-synthesis model and three-body simulations, we estimate the rate of mergers in triple black-hole systems in the field to be about six per Gpc{sup 3} per year in the absence of natal kicks during black-hole formation. This value is within the low end of the 90% credible interval for the total black hole–black hole merger rate inferred from the current LIGO results. There are many uncertainties in these calculations, the largest of which is the unknown distribution of natal kicks. Even modest natal kicks of 40 km s{sup −1} will reduce the merger rate by a factor of 40. A few percent of these systems will have eccentricity greater than 0.999 when they first enter the frequency band detectable by aLIGO (above 10 Hz).

Hawking radiation from astrophysical black holes to analogous systems in lab

CERN Document Server

Belgiorno, Francesco D

2018-01-01

The aim of this book is to provide the reader with a guide to Hawking radiation through a dual approach to the problem. In the first part of the book, we summarize some basic knowledge about black holes and quantum field theory in curved spacetime. In the second part, we present a survey of methods for deriving and studying Hawking radiation from astrophysical black holes, from the original calculation by S W Hawking to the most recent contributions involving gravitational anomalies and tunneling. In the third part, we introduce analogue gravity models, with particular attention to dielectric black hole systems, to which the studies of the present authors are devoted. The mutual interchange of knowledge between the aforementioned parts is addressed to render a more comprehensive picture of this very fascinating quantum phenomenon associated with black holes.

Black Holes

OpenAIRE

Townsend, P. K.

1997-01-01

This paper is concerned with several not-quantum aspects of black holes, with emphasis on theoretical and mathematical issues related to numerical modeling of black hole space-times. Part of the material has a review character, but some new results or proposals are also presented. We review the experimental evidence for existence of black holes. We propose a definition of black hole region for any theory governed by a symmetric hyperbolic system of equations. Our definition reproduces the usu...

System analysis of dry black liquor gasification based synthetic gas production comparing oxygen and air blown gasification systems

International Nuclear Information System (INIS)

Naqvi, Muhammad; Yan, Jinyue; Dahlquist, Erik

2013-01-01

Highlights: ► Circulating fluidized bed system for black liquor gasification with direct causticization. ► Effects of gasifying medium i.e. oxygen or air, on gasification are studied. ► Direct causticization eliminates energy intensive limekiln reducing biomass use. ► Results show 10% higher SNG production from O 2 blown system than air blown system. ► SNG production is higher in O 2 blown system than air blown system. - Abstract: The black liquor gasification based bio-fuel production at chemical pulp mill is an attractive option to replace conventional recovery boilers increasing system energy efficiency. The present paper studies circulating fluidized bed system with direct causticization using TiO 2 for the gasification of the black liquor to the synthesis gas. The advantage of using direct causticization is the elimination of energy-intensive lime kiln which is an integral part of the conventional black liquor recovery system. The study evaluates the effects of gasifying medium i.e. oxygen or air, on the fluidized bed gasification system, the synthesis gas composition, and the downstream processes for the synthesis gas conversion to the synthetic natural gas (SNG). The results showed higher synthetic natural gas production potential with about 10% higher energy efficiency using oxygen blown gasification system than the air blown system. From the pulp mill integration perspective, the material and energy balance results in better integration of air blown system than the oxygen blown system, e.g. less steam required to be generated in the power boiler, less electricity import, and less additional biomass requirement. However, the air blown system still requires a significant amount of energy in terms of the synthesis gas handling and gas upgrading using the nitrogen rejection system

myBlackBox: Blackbox Mobile Cloud Systems for Personalized Unusual Event Detection

Directory of Open Access Journals (Sweden)

Junho Ahn

2016-05-01

Full Text Available We demonstrate the feasibility of constructing a novel and practical real-world mobile cloud system, called myBlackBox, that efficiently fuses multimodal smartphone sensor data to identify and log unusual personal events in mobile users’ daily lives. The system incorporates a hybrid architectural design that combines unsupervised classification of audio, accelerometer and location data with supervised joint fusion classification to achieve high accuracy, customization, convenience and scalability. We show the feasibility of myBlackBox by implementing and evaluating this end-to-end system that combines Android smartphones with cloud servers, deployed for 15 users over a one-month period.

Mapping Violence, Naming Life: A History of Anti-Black Oppression in the Higher Education System

Science.gov (United States)

Mustaffa, Jalil Bishop

2017-01-01

The article will provide a historical overview of anti-Black violence in the higher education system across three time periods: Colonial Era, Post-Civil War, and the mid-to-late twentieth century. Mapping violence demands a focus on how higher education historically has practiced anti-Black oppression coupled with how Black people have practiced…

Search for black holes

International Nuclear Information System (INIS)

Cherepashchuk, Anatolii M

2003-01-01

Methods and results of searching for stellar mass black holes in binary systems and for supermassive black holes in galactic nuclei of different types are described. As of now (June 2002), a total of 100 black hole candidates are known. All the necessary conditions Einstein's General Relativity imposes on the observational properties of black holes are satisfied for candidate objects available, thus further assuring the existence of black holes in the Universe. Prospects for obtaining sufficient criteria for reliably distinguishing candidate black holes from real black holes are discussed. (reviews of topical problems)

A massive binary black-hole system in OJ 287 and a test of general relativity.

Science.gov (United States)

Valtonen, M J; Lehto, H J; Nilsson, K; Heidt, J; Takalo, L O; Sillanpää, A; Villforth, C; Kidger, M; Poyner, G; Pursimo, T; Zola, S; Wu, J-H; Zhou, X; Sadakane, K; Drozdz, M; Koziel, D; Marchev, D; Ogloza, W; Porowski, C; Siwak, M; Stachowski, G; Winiarski, M; Hentunen, V-P; Nissinen, M; Liakos, A; Dogru, S

2008-04-17

Tests of Einstein's general theory of relativity have mostly been carried out in weak gravitational fields where the space-time curvature effects are first-order deviations from Newton's theory. Binary pulsars provide a means of probing the strong gravitational field around a neutron star, but strong-field effects may be best tested in systems containing black holes. Here we report such a test in a close binary system of two candidate black holes in the quasar OJ 287. This quasar shows quasi-periodic optical outbursts at 12-year intervals, with two outburst peaks per interval. The latest outburst occurred in September 2007, within a day of the time predicted by the binary black-hole model and general relativity. The observations confirm the binary nature of the system and also provide evidence for the loss of orbital energy in agreement (within 10 per cent) with the emission of gravitational waves from the system. In the absence of gravitational wave emission the outburst would have happened 20 days later.

Black Writers' Views of America.

Science.gov (United States)

Hairston, Loyle

1979-01-01

This article argues that the stagnation, pessimism, and self-pity evident in recent Black writing results in part from the alienation of Black writers from the mainstream of Black life, and in part from the illusions that they share with other Blacks who have embraced the American value system. (Author/EB)

Modelling anaerobic digestion of concentrated black water and faecal matter in accumulation system

NARCIS (Netherlands)

Elmitwalli, T.; Zeeman, G.; Otterpohl, R.

2011-01-01

A dynamic mathematical model based on anaerobic digestion model no. 1 (ADM1) was developed for accumulation (AC) system treating concentrated black water and faecal matter at different temperatures. The AC system was investigated for the treatment of waste(water) produced from the following systems:

Black to Black

DEFF Research Database (Denmark)

Langkjær, Michael Alexander

2012-01-01

Pop musicians performing in black stage costume take advantage of cultural traditions relating to matters black. Stylistically, black is a paradoxical color: although a symbol of melancholy, pessimism, and renunciation, black also expresses minimalist modernity and signifies exclusivity (as is hi...

Statistical physics of black holes as quantum-mechanical systems

OpenAIRE

Giddings, Steven B.

2013-01-01

Some basic features of black-hole statistical mechanics are investigated, assuming that black holes respect the principles of quantum mechanics. Care is needed in defining an entropy S_bh corresponding to the number of microstates of a black hole, given that the black hole interacts with its surroundings. An open question is then the relationship between this entropy and the Bekenstein-Hawking entropy S_BH. For a wide class of models with interactions needed to ensure unitary quantum evolutio...

Biomass in monospecific and mixed stands of eucalyptus and black wattle and corn in an agroforestry system

Directory of Open Access Journals (Sweden)

Márcio Viera

2011-06-01

Full Text Available This study aimed at quantifying the production and distribution of aboveground biomass from the plants in monospecific and mixed stands of eucalyptus (hybrid E. urophylla x E. grandis and black wattle (Acacia mearnsii and, of corn (Zea mays in agrosilvicultural systems. The biomass evaluation (leaf, branch, bark and wood from the forest species at 6 and 18 months of age were performed at the treatments: 100E (100% of eucalyptus + corn; - 100A (100% of black wattle + corn; - 50E:50A (50% of eucalyptus + 50% of black wattle + corn. The corn biomass evaluation (stem, leaves, straw, cob and grains was performed at treatments 100E; 100A; 50E:50A; 75E:25A (75% of eucalyptus + 25% of black wattle + corn; and - 25E:75A (25% of eucalyptus + 75% of black wattle + corn. The biomass production from eucalyptus and from the black wattle, in both monospecific and mixed planting, did not differ in any of the assessed ages but, when evaluated by plants compartments, it was verified an interspecific competitive interaction from the eucalyptus on the black wattle, reducing the formation of crown biomass. The total production of corn biomass in agrosilvicutural systems with eucalyptus and with black wattle in monospecific or mixed plantings did not differ in the studied treatments.

Black Hole Area Quantization rule from Black Hole Mass Fluctuations

OpenAIRE

Schiffer, Marcelo

2016-01-01

We calculate the black hole mass distribution function that follows from the random emission of quanta by Hawking radiation and with this function we calculate the black hole mass fluctuation. From a complete different perspective we regard the black hole as quantum mechanical system with a quantized event horizon area and transition probabilities among the various energy levels and then calculate the mass dispersion. It turns out that there is a perfect agreement between the statistical and ...

A Dancing Black Hole

Science.gov (United States)

Shoemaker, Deirdre; Smith, Kenneth; Schnetter, Erik; Fiske, David; Laguna, Pablo; Pullin, Jorge

2002-04-01

Recently, stationary black holes have been successfully simulated for up to times of approximately 600-1000M, where M is the mass of the black hole. Considering that the expected burst of gravitational radiation from a binary black hole merger would last approximately 200-500M, black hole codes are approaching the point where simulations of mergers may be feasible. We will present two types of simulations of single black holes obtained with a code based on the Baumgarte-Shapiro-Shibata-Nakamura formulation of the Einstein evolution equations. One type of simulations addresses the stability properties of stationary black hole evolutions. The second type of simulations demonstrates the ability of our code to move a black hole through the computational domain. This is accomplished by shifting the stationary black hole solution to a coordinate system in which the location of the black hole is time dependent.

H I OBSERVATIONS OF THE SUPERMASSIVE BINARY BLACK HOLE SYSTEM IN 0402+379

International Nuclear Information System (INIS)

Rodriguez, C.; Taylor, G. B.; Pihlstroem, Y. M.; Zavala, R. T.; Peck, A. B.

2009-01-01

We have recently discovered a supermassive binary black hole system with a projected separation between the two black holes of 7.3 pc in the radio galaxy 0402+379 (Rodriguez et al. 2006). This is the most compact supermassive binary black hole pair yet imaged by more than two orders of magnitude. We present Global VLBI observations at 1.3464 GHz of this radio galaxy, taken to improve the quality of the H I data. Two absorption lines are found toward the southern jet of the source, one redshifted by 370 ± 10 km s -1 and the other blueshifted by 700 ± 10 km s -1 with respect to the systemic velocity of the source, which, along with the results obtained for the opacity distribution over the source, suggests the presence of two mass clumps rotating around the central region of the source. We propose a model consisting of a geometrically thick disk, of which we only see a couple of clumps, that reproduces the velocities measured from the H I absorption profiles. These clumps rotate in circular Keplerian orbits around an axis that crosses one of the supermassive black holes of the binary system in 0402+379. We find an upper limit for the inclination angle of the twin jets of the source to the line of sight of θ = 66 deg., which, according to the proposed model, implies a lower limit on the central mass of ∼7 x 10 8 M sun and a lower limit for the scale height of the thick disk of ∼12 pc.

A Universal Scaling for the Energetics of Relativistic Jets From Black Hole Systems

Science.gov (United States)

Nemmen, R. S.; Georganopoulos, M.; Guiriec, S.; Meyer, E. T.; Gehrels, N.; Sambruna, R. M.

2013-01-01

Black holes generate collimated, relativistic jets which have been observed in gamma-ray bursts (GRBs), microquasars, and at the center of some galaxies (active galactic nuclei; AGN). How jet physics scales from stellar black holes in GRBs to the supermassive ones in AGNs is still unknown. Here we show that jets produced by AGNs and GRBs exhibit the same correlation between the kinetic power carried by accelerated particles and the gamma-ray luminosity, with AGNs and GRBs lying at the low and high-luminosity ends, respectively, of the correlation. This result implies that the efficiency of energy dissipation in jets produced in black hole systems is similar over 10 orders of magnitude in jet power, establishing a physical analogy between AGN and GRBs.

The search for black holes

International Nuclear Information System (INIS)

Torn, K.

1976-01-01

Conceivable experimental investigations to prove the existence of black holes are discussed. Double system with a black hole turning around a star-satellite are in the spotlight. X-radiation emmited by such systems and resulting from accretion of the stellar gas by a black hole, and the gas heating when falling on the black hole might prove the model suggested. A source of strong X-radiation observed in the Cygnus star cluster and referred to as Cygnus X-1 may be thus identified as a black hole. Direct registration of short X-ray pulses with msec intervals might prove the suggestion. The lack of appropriate astrophysic facilities is pointed out to be the major difficulty on the way of experimental verifications

Black holes are hot

International Nuclear Information System (INIS)

Gibbons, G.

1976-01-01

Recent work, which has been investigating the use of the concept of entropy with respect to gravitating systems, black holes and the universe as a whole, is discussed. The resulting theory of black holes assigns a finite temperature to them -about 10 -7 K for ordinary black holes of stellar mass -which is in complete agreement with thermodynamical concepts. It is also shown that black holes must continuously emit particles just like ordinary bodies which have a certain temperature. (U.K.)

Comparison of Refractory Performance in Black Liquor Gasifiers and a Smelt Test System

International Nuclear Information System (INIS)

Peascoe, RA

2001-01-01

Prior laboratory corrosion studies along with experience at the black liquor gasifier in New Bern, North Carolina, clearly demonstrate that serious material problems exist with the gasifier's refractory lining. Mullite-based and alumina-based refractories used at the New Bern facility suffered significant degradation even though they reportedly performed adequately in smaller scale systems. Oak Ridge National Laboratory's involvement in the failure analysis, and the initial exploration of suitable replacement materials, led to the realization that a simple and reliable, complementary method for refractory screening was needed. The development of a laboratory test system and its suitability for simulating the environment of black liquor gasifiers was undertaken. Identification and characterization of corrosion products were used to evaluate the test system as a rapid screening tool for refractory performance and as a predictor of refractory lifetime. Results from the test systems and pl ants were qualitatively similar

Notes on Phase Transition of Nonsingular Black Hole

International Nuclear Information System (INIS)

Ma Meng-Sen; Zhao Ren

2015-01-01

On the belief that a black hole is a thermodynamic system, we study the phase transition of nonsingular black holes. If the black hole entropy takes the form of the Bekenstein—Hawking area law, the black hole mass M is no longer the internal energy of the black hole thermodynamic system. Using the thermodynamic quantities, we calculate the heat capacity, thermodynamic curvature and free energy. It is shown that there will be a larger black hole/smaller black hole phase transition for the nonsingular black hole. At the critical point, the second-order phase transition appears. (paper)

Gravitational Waveforms in the Early Inspiral of Binary Black Hole Systems

Science.gov (United States)

Barkett, Kevin; Kumar, Prayush; Bhagwat, Swetha; Brown, Duncan; Scheel, Mark; Szilagyi, Bela; Simulating eXtreme Spacetimes Collaboration

2015-04-01

The inspiral, merger and ringdown of compact object binaries are important targets for gravitational wave detection by aLIGO. Detection and parameter estimation will require long, accurate waveforms for comparison. There are a number of analytical models for generating gravitational waveforms for these systems, but the only way to ensure their consistency and correctness is by comparing with numerical relativity simulations that cover many inspiral orbits. We've simulated a number of binary black hole systems with mass ratio 7 and a moderate, aligned spin on the larger black hole. We have attached these numerical waveforms to analytical waveform models to generate long hybrid gravitational waveforms that span the entire aLIGO frequency band. We analyze the robustness of these hybrid waveforms and measure the faithfulness of different hybrids with each other to obtain an estimate on how long future numerical simulations need to be in order to ensure that waveforms are accurate enough for use by aLIGO.

Black holes and everyday physics

International Nuclear Information System (INIS)

Bekenstein, J.D.

1982-01-01

Black holes have piqued much curiosity. But thus far they have been important only in ''remote'' subjects like astrophysics and quantum gravity. It is shown that the situation can be improved. By a judicious application of black hole physics, one can obtain new results in ''everyday physics''. For example, black holes yield a quantum universal upper bound on the entropy-to-energy ratio for ordinary thermodynamical systems which was unknown earlier. It can be checked, albeit with much labor, by ordinary statistical methods. Black holes set a limitation on the number of species of elementary particles-quarks, leptons, neutrinos - which may exist. And black holes lead to a fundamental limitation on the rate at which information can be transferred for given message energy by any communication system. (author)

Black holes escaping from domain walls

International Nuclear Information System (INIS)

Flachi, Antonino; Sasaki, Misao; Pujolas, Oriol; Tanaka, Takahiro

2006-01-01

Previous studies concerning the interaction of branes and black holes suggested that a small black hole intersecting a brane may escape via a mechanism of reconnection. Here we consider this problem by studying the interaction of a small black hole and a domain wall composed of a scalar field and simulate the evolution of this system when the black hole acquires an initial recoil velocity. We test and confirm previous results, however, unlike the cases previously studied, in the more general set-up considered here, we are able to follow the evolution of the system also during the separation, and completely illustrate how the escape of the black hole takes place

Black hole hair removal

International Nuclear Information System (INIS)

Banerjee, Nabamita; Mandal, Ipsita; Sen, Ashoke

2009-01-01

Macroscopic entropy of an extremal black hole is expected to be determined completely by its near horizon geometry. Thus two black holes with identical near horizon geometries should have identical macroscopic entropy, and the expected equality between macroscopic and microscopic entropies will then imply that they have identical degeneracies of microstates. An apparent counterexample is provided by the 4D-5D lift relating BMPV black hole to a four dimensional black hole. The two black holes have identical near horizon geometries but different microscopic spectrum. We suggest that this discrepancy can be accounted for by black hole hair - degrees of freedom living outside the horizon and contributing to the degeneracies. We identify these degrees of freedom for both the four and the five dimensional black holes and show that after their contributions are removed from the microscopic degeneracies of the respective systems, the result for the four and five dimensional black holes match exactly.

Estimation of Theaflavins (TF) and Thearubigins (TR) Ratio in Black Tea Liquor Using Electronic Vision System

Science.gov (United States)

Akuli, Amitava; Pal, Abhra; Ghosh, Arunangshu; Bhattacharyya, Nabarun; Bandhopadhyya, Rajib; Tamuly, Pradip; Gogoi, Nagen

2011-09-01

Quality of black tea is generally assessed using organoleptic tests by professional tea tasters. They determine the quality of black tea based on its appearance (in dry condition and during liquor formation), aroma and taste. Variation in the above parameters is actually contributed by a number of chemical compounds like, Theaflavins (TF), Thearubigins (TR), Caffeine, Linalool, Geraniol etc. Among the above, TF and TR are the most important chemical compounds, which actually contribute to the formation of taste, colour and brightness in tea liquor. Estimation of TF and TR in black tea is generally done using a spectrophotometer instrument. But, the analysis technique undergoes a rigorous and time consuming effort for sample preparation; also the operation of costly spectrophotometer requires expert manpower. To overcome above problems an Electronic Vision System based on digital image processing technique has been developed. The system is faster, low cost, repeatable and can estimate the amount of TF and TR ratio for black tea liquor with accuracy. The data analysis is done using Principal Component Analysis (PCA), Multiple Linear Regression (MLR) and Multiple Discriminate Analysis (MDA). A correlation has been established between colour of tea liquor images and TF, TR ratio. This paper describes the newly developed E-Vision system, experimental methods, data analysis algorithms and finally, the performance of the E-Vision System as compared to the results of traditional spectrophotometer.

Entropy and black-hole thermodynamics

International Nuclear Information System (INIS)

Wald, R.M.

1979-01-01

The concept of entropy is examined with an eye toward gaining insight into the nature of black-hole thermodynamics. Definitions of entropy are given for ordinary classical and quantum-mechanical systems which lead to plausibility arguments for the ordinary laws of thermodynamics. The treatment of entropy for a classical system is in the spirit of the information-theory viewpoint, but by explicitly incorporating the coarse-grained observable into the definition of entropy, we eliminate any nonobjective features. The definition of entropy for a quantum-mechanical system is new, but directly parallels the classical treatment. We then apply these ideas to a self-gravitating quantum system which contains a black hole. Under some assumptions: which, although nontrivial, are by no means exotic: about the nature of such a system, it is seen that the same plausibility arguments which lead to the ordinary laws of thermodynamics for ordinary systems now lead to the laws of black-hole mechanics, including the generalized second law of thermodynamics. Thus, it appears perfectly plausible that black-hole thermodynamics is nothing more than ordinary thermodynamics applied to a self-gravitating quantum system

Gravitational waves from the Papaloizou-Pringle instability in black-hole-torus systems.

Science.gov (United States)

Kiuchi, Kenta; Shibata, Masaru; Montero, Pedro J; Font, José A

2011-06-24

Black hole (BH)-torus systems are promising candidates for the central engine of γ-ray bursts (GRBs), and also possible outcomes of the collapse of supermassive stars to supermassive black holes (SMBHs). By three-dimensional general relativistic numerical simulations, we show that an m = 1 nonaxisymmetric instability grows for a wide range of self-gravitating tori orbiting BHs. The resulting nonaxisymmetric structure persists for a time scale much longer than the dynamical one, becoming a strong emitter of large amplitude, quasiperiodic gravitational waves. Our results indicate that both, the central engine of GRBs and newly formed SMBHs, can be strong gravitational wave sources observable by forthcoming ground-based and spacecraft detectors.

Black Political Socialization and Political Change: The Black Panther Party Platform as a "Model" of Radical Political Socialization

Science.gov (United States)

McLemore, Leslie Burl

1975-01-01

Considers the potential impact of black revolutionary nationalism--cultural and military--upon the social patterns of black people, arguing that a racial, cultural, and military approach through black organizations with a highly developed system of communications holds the key to black salvation in America. (Author/JM)

Black-hole bomb and superradiant instabilities

International Nuclear Information System (INIS)

Cardoso, Vitor; Dias, Oscar J.C.; Lemos, Jose P.S.; Yoshida, Shijun

2004-01-01

A wave impinging on a Kerr black hole can be amplified as it scatters off the hole if certain conditions are satisfied, giving rise to superradiant scattering. By placing a mirror around the black hole one can make the system unstable. This is the black-hole bomb of Press and Teukolsky. We investigate in detail this process and compute the growing time scales and oscillation frequencies as a function of the mirror's location. It is found that in order for the system black hole plus mirror to become unstable there is a minimum distance at which the mirror must be located. We also give an explicit example showing that such a bomb can be built. In addition, our arguments enable us to justify why large Kerr-AdS black holes are stable and small Kerr-AdS black holes should be unstable

Boosting jet power in black hole spacetimes.

Science.gov (United States)

Neilsen, David; Lehner, Luis; Palenzuela, Carlos; Hirschmann, Eric W; Liebling, Steven L; Motl, Patrick M; Garrett, Travis

2011-08-02

The extraction of rotational energy from a spinning black hole via the Blandford-Znajek mechanism has long been understood as an important component in models to explain energetic jets from compact astrophysical sources. Here we show more generally that the kinetic energy of the black hole, both rotational and translational, can be tapped, thereby producing even more luminous jets powered by the interaction of the black hole with its surrounding plasma. We study the resulting Poynting jet that arises from single boosted black holes and binary black hole systems. In the latter case, we find that increasing the orbital angular momenta of the system and/or the spins of the individual black holes results in an enhanced Poynting flux.

System aspects of black liquor gasification - Consequences for both industry and society

Energy Technology Data Exchange (ETDEWEB)

NONE

2002-02-01

The pulp and paper industry consumes large quantities of biofuels (mainly bark and black liquor) to satisfy process requirements. Biomass is however a limited resource, and biofuel usage should therefore be as effective as possible. Modern pulp mills and integrated pulp and paper mills have excess fuel compared to the amounts needed to satisfy the process steam demand. The excess fuel is often used for cogeneration of electric power in CHP units. For integrated pulp and paper mills, this usually requires import of supplementary fuel to the plant. For market pulp mills, the excess internal biofuel quantities are sufficient to also allow electric power generation in condensing power plant units. If biofuel availability at a reasonable price is limited, import/export to, from a mill changes the amount of such biofuel available to alternative users. The goal of this thesis is to compare different mill powerhouse technologies and CHP plant configurations (including conventional recovery boiler technology and black liquor gasification technology) in order to identify the technology and CHP plant configuration that can produce the most electric power output from a given fuel resource for a given process steam demand. Different process steam demand levels for different representative mill types are considered. The comparison accounts for increased/decreased electricity production in an alternative energy system when biofuel is imported/exported to/from from the mill. The alternative energy system considered includes a district heating system with CHP capacity and natural gas fired combined cycle power plant capacity. The results show that black liquor gasification is in all cases considered an attractive powerhouse recovery cycle technology compared to conventional recovery boiler technology. If the marginal electric power generation efficiency for biofuel exported to the reference alternative energy system is 49%, excess mill internal biofuel should be used on mill

Non-Existence of Black Hole Solutionsfor a Spherically Symmetric, Static Einstein-Dirac-Maxwell System

Science.gov (United States)

Finster, Felix; Smoller, Joel; Yau, Shing-Tung

We consider for j=1/2, 3/2,... a spherically symmetric, static system of (2j+1) Dirac particles, each having total angular momentum j. The Dirac particles interact via a classical gravitational and electromagnetic field. The Einstein-Dirac-Maxwell equations for this system are derived. It is shown that, under weak regularity conditions on the form of the horizon, the only black hole solutions of the EDM equations are the Reissner-Nordstrom solutions. In other words, the spinors must vanish identically. Applied to the gravitational collapse of a "cloud" of spin-1/2-particles to a black hole, our result indicates that the Dirac particles must eventually disappear inside the event horizon.

Statistical mechanics of black holes

International Nuclear Information System (INIS)

Harms, B.; Leblanc, Y.

1992-01-01

We analyze the statistical mechanics of a gas of neutral and charged black holes. The microcanonical ensemble is the only possible approach to this system, and the equilibrium configuration is the one for which most of the energy is carried by a single black hole. Schwarzschild black holes are found to obey the statistical bootstrap condition. In all cases, the microcanonical temperature is identical to the Hawking temperature of the most massive black hole in the gas. U(1) charges in general break the bootstrap property. The problems of black-hole decay and of quantum coherence are also addressed

Young, Black, and Sentenced To Die: Black Males and the Death Penalty.

Science.gov (United States)

Joseph, Janice

1996-01-01

Explores the death penalty as imposed on young black males in the United States and examines the disparity in death penalty rates for homicides with black offenders and white victims. States continue to impose the death penalty rather than viewing youth violence as a failure of the social system. (SLD)

Universality in the relaxation dynamics of the composed black-hole-charged-massive-scalar-field system: The role of quantum Schwinger discharge

Directory of Open Access Journals (Sweden)

Shahar Hod

2015-07-01

Full Text Available The quasinormal resonance spectrum {ωn(μ,q,M,Q}n=0n=∞ of charged massive scalar fields in the charged Reissner–Nordström black-hole spacetime is studied analytically in the large-coupling regime qQ≫Mμ (here {μ,q} are respectively the mass and charge coupling constant of the field, and {M,Q} are respectively the mass and electric charge of the black hole. This physical system provides a striking illustration for the validity of the universal relaxation bound τ×T≥ħ/π in black-hole physics (here τ≡1/ℑω0 is the characteristic relaxation time of the composed black-hole-scalar-field system, and T is the Bekenstein–Hawking temperature of the black hole. In particular, it is shown that the relaxation dynamics of charged massive scalar fields in the charged Reissner–Nordström black-hole spacetime may saturate this quantum time-times-temperature inequality. Interestingly, we prove that potential violations of the bound by light scalar fields are excluded by the Schwinger-type pair-production mechanism (a vacuum polarization effect, a quantum phenomenon which restricts the physical parameters of the composed black-hole-charged-field system to the regime qQ≪M2μ2/ħ.

The Phase Transition of Higher Dimensional Charged Black Holes

International Nuclear Information System (INIS)

Li, Huaifan; Zhao, Ren; Zhang, Lichun; Guo, Xiongying

2016-01-01

We have studied phase transitions of higher dimensional charge black hole with spherical symmetry. We calculated the local energy and local temperature and find that these state parameters satisfy the first law of thermodynamics. We analyze the critical behavior of black hole thermodynamic system by taking state parameters (Q,Φ) of black hole thermodynamic system, in accordance with considering the state parameters (P,V) of van der Waals system, respectively. We obtain the critical point of black hole thermodynamic system and find that the critical point is independent of the dual independent variables we selected. This result for asymptotically flat space is consistent with that for AdS spacetime and is intrinsic property of black hole thermodynamic system.

Black hole Berry phase

NARCIS (Netherlands)

de Boer, J.; Papadodimas, K.; Verlinde, E.

2009-01-01

Supersymmetric black holes are characterized by a large number of degenerate ground states. We argue that these black holes, like other quantum mechanical systems with such a degeneracy, are subject to a phenomenon which is called the geometric or Berry’s phase: under adiabatic variations of the

Bounding the Role of Black Carbon in the Climate System: a Scientific Assessment

Science.gov (United States)

Bond, T. C.; Doherty, S. J.; Fahey, D. W.; Forster, P. M.; Bernsten, T.; DeAngelo, B. J.; Flanner, M. G.; Ghan, S.; Karcher, B.; Koch, D.;

Bounding the Role of Black Carbon in the Climate System: A Scientific Assessment

Energy Technology Data Exchange (ETDEWEB)

Bond, Tami C.; Doherty, Sarah J.; Fahey, D. W.; Forster, Piers; Berntsen, T.; DeAngelo, B. J.; Flanner, M. G.; Ghan, Steven J.; Karcher, B.; Koch, Dorothy; Kinne, Stefan; Kondo, Yutaka; Quinn, P. K.; Sarofim, Marcus; Schultz, Martin; Schulz, M.; Venkataraman, C.; Zhang, Hua; Zhang, Shiqiu; Bellouin, N.; Guttikunda, S. K.; Hopke, P. K.; Jacobson, M. Z.; Kaiser, J. W.; Klimont, Z.; Lohmann, U.; Schwarz, Joshua P.; Shindell, Drew; Storelvmo, Trude; Warren, Stephen G.; Zender, C. S.

2013-06-06

Black carbon aerosol plays a unique and important role in Earth’s climate system. Black carbon is a type of carbonaceous material with a unique combination of physical properties. Predominant sources are combustion related; namely, fossil fuels for transportation, solid fuels for industrial and residential uses, and open burning of biomass. Total global emissions of black carbon using bottom-up inventory methods are 7500 Gg yr-1 in the year 2000 with an uncertainty range of 2000 to 29000. This assessment provides an evaluation of black-carbon climate forcing that is comprehensive in its inclusion of all known and relevant processes and that is quantitative in providing best estimates and uncertainties of the main forcing terms: direct solar absorption, influence on liquid, mixed-phase, and ice clouds, and deposition on snow and ice. These effects are calculated with models, but when possible, they are evaluated with both microphysical measurements and field observations. Global atmospheric absorption attributable to black carbon is too low in many models, and should be increased by about about 60%. After this scaling, the best estimate for the industrial-era (1750 to 2005) direct radiative forcing of black carbon is +0.43 W m-2 with 90% uncertainty bounds of (+0.17, +0.68) W m-2. Total direct forcing by all black carbon sources in the present day is estimated as +0.49 (+0.20, +0.76) W m-2. Direct radiative forcing alone does not capture important rapid adjustment mechanisms. A framework is described and used for quantifying climate forcings and their rapid responses and feedbacks. The best estimate of industrial-era (1750 to 2005) climate forcing of black carbon through all forcing mechanisms is +0.77 W m-2 with 90% uncertainty bounds of +-0.06 to +1.53 W m-2. Thus, there is a 96% probability that black carbon emissions, independent of co-emitted species, have a positive forcing and warm the climate. With a value of +0.77 W m-2, black carbon is likely the second

Looking for the invisible universe - Black matter, black energy, black holes

International Nuclear Information System (INIS)

Elbaz, David

2016-01-01

As the discovery of the expansion of the universe and of black holes put the study of cosmology into question again because it now refers to invisible things such as black holes, black energy and black matter, the author proposes an other view on the universe within such a context. He first discusses these three enigmas of black matter, black energy and black holes. In a second part, he addresses, discusses and comments five illusions: the Uranian illusion (questions of the existence of an anti-world, of black matter temperature), the Mercurian illusion (quantum gravity, the string theory), the Martian illusion (a patchwork universe, the illusion of the infinite), the cosmic Maya (the John Wheeler's cup, the holographic universe), and the narcissistic illusion

Stage separation study of Nike-Black Brant V Sounding Rocket System

Science.gov (United States)

Ferragut, N. J.

1976-01-01

A new Sounding Rocket System has been developed. It consists of a Nike Booster and a Black Brant V Sustainer with slanted fins which extend beyond its nozzle exit plane. A cursory look was taken at different factors which must be considered when studying a passive separation system. That is, one separation system without mechanical constraints in the axial direction and which will allow separation due to drag differential accelerations between the Booster and the Sustainer. The equations of motion were derived for rigid body motions and exact solutions were obtained. The analysis developed could be applied to any other staging problem of a Sounding Rocket System.

Spin One Hawking Radiation from Dirty Black Holes

OpenAIRE

Petarpa Boonserm; Tritos Ngampitipan; Matt Visser

2013-01-01

A “clean” black hole is a black hole in vacuum such as the Schwarzschild black hole. However in real physical systems, there are matter fields around a black hole. Such a black hole is called a “dirty black hole”. In this paper, the effect of matter fields on the black hole and the greybody factor is investigated. The results show that matter fields make a black hole smaller. They can increase the potential energy to a black hole to obstruct Hawking radiation to propagate. This causes the gre...

The Crisis in Black and Black.

Science.gov (United States)

Hutchinson, Earl Ofari

These essays explore why the historic conflict between blacks and whites in the United States has become a crisis that divides many African Americans. The changing racial dynamic is not marked by conflicts. between the black middle class and the poor, black men and women, the black intellectual elite and rappers, black politicians and the urban…

Statistical black-hole thermodynamics

International Nuclear Information System (INIS)

Bekenstein, J.D.

1975-01-01

Traditional methods from statistical thermodynamics, with appropriate modifications, are used to study several problems in black-hole thermodynamics. Jaynes's maximum-uncertainty method for computing probabilities is used to show that the earlier-formulated generalized second law is respected in statistically averaged form in the process of spontaneous radiation by a Kerr black hole discovered by Hawking, and also in the case of a Schwarzschild hole immersed in a bath of black-body radiation, however cold. The generalized second law is used to motivate a maximum-entropy principle for determining the equilibrium probability distribution for a system containing a black hole. As an application we derive the distribution for the radiation in equilibrium with a Kerr hole (it is found to agree with what would be expected from Hawking's results) and the form of the associated distribution among Kerr black-hole solution states of definite mass. The same results are shown to follow from a statistical interpretation of the concept of black-hole entropy as the natural logarithm of the number of possible interior configurations that are compatible with the given exterior black-hole state. We also formulate a Jaynes-type maximum-uncertainty principle for black holes, and apply it to obtain the probability distribution among Kerr solution states for an isolated radiating Kerr hole

Nonlinear evolutions of bosonic clouds around black holes

International Nuclear Information System (INIS)

Okawa, Hirotada

2015-01-01

Black holes are a laboratory not only for testing the theory of gravity but also for exploring the properties of fundamental fields. Fundamental fields around a supermassive black hole give rise to extremely long-lived quasi-bound states which can in principle extract the energy and angular momentum from the black hole. To investigate the final state of such a system, the backreaction onto the spacetime becomes important because of the nonlinearity of the Einstein equation. In this paper, we review the numerical method to trace the evolution of massive scalar fields in the vicinity of black holes, how such a system originates from scalar clouds initially in the absence of black holes or from the capture of scalar clouds by a black hole, and the evolution of quasi-bound states around both a non-rotating black hole and a rotating black hole including the backreaction. (paper)

Relativistic three-body effects in black hole coalescence

International Nuclear Information System (INIS)

Campanelli, Manuela; Dettwyler, Miranda; Lousto, Carlos O.; Hannam, Mark

2006-01-01

Three-body interactions are expected to be common in globular clusters and in galactic cores hosting supermassive black holes. We consider an equal-mass binary black hole system in the presence of a third black hole. Using numerically generated binary black hole initial data sets, and first and second-order post-Newtonian (1PN and 2PN) techniques, we find that the presence of the third black hole has non-negligible relativistic effects on the location of the binary's innermost stable circular orbit (ISCO), and that these effects arise at 2PN order. For a stellar-mass black hole binary in orbit about a supermassive black hole, the massive black hole has stabilizing effects on the orbiting binary, leading to an increase in merger time and a decrease of the terminal orbital frequency, and an amplification of the gravitational radiation emitted from the binary system by up to 6%

Black hole dynamics in Einstein-Maxwell-dilaton theory

Science.gov (United States)

Hirschmann, Eric W.; Lehner, Luis; Liebling, Steven L.; Palenzuela, Carlos

2018-03-01

We consider the properties and dynamics of black holes within a family of alternative theories of gravity, namely Einstein-Maxwell-dilaton theory. We analyze the dynamical evolution of individual black holes as well as the merger of binary black hole systems. We do this for a wide range of parameter values for the family of Einstein-Maxwell-dilaton theories, investigating, in the process, the stability of these black holes. We examine radiative degrees of freedom, explore the impact of the scalar field on the dynamics of merger, and compare with other scalar-tensor theories. We argue that the dilaton can largely be discounted in understanding merging binary systems and that the end states essentially interpolate between charged and uncharged, rotating black holes. For the relatively small charge values considered here, we conclude that these black hole systems will be difficult to distinguish from their analogs within General Relativity.

The fluoride in the groundwater of Guarani Aquifer System: the origin associated with black shales of Paraná Basin

Science.gov (United States)

Kern, M. L.; Vieiro, A. P.; Machado, G.

2008-09-01

This work presents petrological and geochemical results of the black shales interval from Permian and Devonian strata of the Paraná Basin, Brazil and its relationships with fluoride of groundwater from Guarani Aquifer System. The Guarani Aquifer, located in South Brazil, Uruguay, Paraguay and Argentine, presents contents of fluoride higher than the Brazilian accepted potability limits. Several hypotheses have been presented for the origin of the fluoride in the groundwater of the Guarani Aquifer. Microcrystalline fluorite was registered in black shales of Ponta Grossa and Irati formations from Paraná Basin. The results shown in this work suggest that fluoride present in groundwater of Guarani Aquifer can be originated in deeper groundwater that circulates in Ponta Grossa and Irati formations. The interaction of the groundwater coming from deeper black shales with the groundwater-bearing Aquifer Guarani System occurs through regional fragile structures (faults and fractures) that constitute excellent hydraulic connectors between the two sedimentary packages. The microcrystalline fluorite registered in Ponta Grossa and Irati Formations can be dissolved promoting fluoride enrichment in groundwater of these black shales and Guarani Aquifer System.

Hypercompact Stellar Systems Around Recoiling Supermassive Black Holes

Science.gov (United States)

Merritt, David; Schnittman, Jeremy D.; Komossa, S.

2009-07-01

A supermassive black hole ejected from the center of a galaxy by gravitational-wave recoil carries a retinue of bound stars—a "hypercompact stellar system" (HCSS). The numbers and properties of HCSSs contain information about the merger histories of galaxies, the late evolution of binary black holes, and the distribution of gravitational-wave kicks. We relate the structural properties (size, mass, density profile) of HCSSs to the properties of their host galaxies and to the size of the kick in two regimes: collisional (M BH lsim 107 M sun), i.e., short nuclear relaxation times, and collisionless (M BH gsim 107 M sun), i.e., long nuclear relaxation times. HCSSs are expected to be similar in size and luminosity to globular clusters, but in extreme cases (large galaxies, kicks just above escape velocity) their stellar mass can approach that of ultracompact dwarf galaxies. However, they differ from all other classes of compact stellar system in having very high internal velocities. We show that the kick velocity is encoded in the velocity dispersion of the bound stars. Given a large enough sample of HCSSs, the distribution of gravitational-wave kicks can therefore be empirically determined. We combine a hierarchical merger algorithm with stellar population models to compute the rate of production of HCSSs over time and the probability of observing HCSSs in the local universe as a function of their apparent magnitude, color, size, and velocity dispersion, under two different assumptions about the star formation history prior to the kick. We predict that ~102 HCSSs should be detectable within 2 Mpc of the center of the Virgo cluster, and that many of these should be bright enough that their kick velocities (i.e., velocity dispersions) could be measured with reasonable exposure times. We discuss other strategies for detecting HCSSs and speculate on some exotic manifestations.

Bio-refinery system of DME or CH4 production from black liquor gasification in pulp mills.

Science.gov (United States)

Naqvi, M; Yan, J; Fröling, M

2010-02-01

There is great interest in developing black liquor gasification technology over recent years for efficient recovery of bio-based residues in chemical pulp mills. Two potential technologies of producing dimethyl ether (DME) and methane (CH(4)) as alternative fuels from black liquor gasification integrated with the pulp mill have been studied and compared in this paper. System performance is evaluated based on: (i) comparison with the reference pulp mill, (ii) fuel to product efficiency (FTPE) and (iii) biofuel production potential (BPP). The comparison with the reference mill shows that black liquor to biofuel route will add a highly significant new revenue stream to the pulp industry. The results indicate a large potential of DME and CH(4) production globally in terms of black liquor availability. BPP and FTPE of CH(4) production is higher than DME due to more optimized integration with the pulping process and elimination of evaporation unit in the pulp mill.

Black hole final state conspiracies

International Nuclear Information System (INIS)

McInnes, Brett

2009-01-01

The principle that unitarity must be preserved in all processes, no matter how exotic, has led to deep insights into boundary conditions in cosmology and black hole theory. In the case of black hole evaporation, Horowitz and Maldacena were led to propose that unitarity preservation can be understood in terms of a restriction imposed on the wave function at the singularity. Gottesman and Preskill showed that this natural idea only works if one postulates the presence of 'conspiracies' between systems just inside the event horizon and states at much later times, near the singularity. We argue that some AdS black holes have unusual internal thermodynamics, and that this may permit the required 'conspiracies' if real black holes are described by some kind of sum over all AdS black holes having the same entropy

Thermodynamic theory of black holes

Energy Technology Data Exchange (ETDEWEB)

Davies, P C.W. [King' s Coll., London (UK). Dept. of Mathematics

1977-04-21

The thermodynamic theory underlying black hole processes is developed in detail and applied to model systems. It is found that Kerr-Newman black holes undergo a phase transition at a = 0.68M or Q = 0.86M, where the heat capacity has an infinite discontinuity. Above the transition values the specific heat is positive, permitting isothermal equilibrium with a surrounding heat bath. Simple processes and stability criteria for various black hole situations are investigated. The limits for entropically favoured black hole formation are found. The Nernst conditions for the third law of thermodynamics are not satisfied fully for black holes. There is no obvious thermodynamic reason why a black hole may not be cooled down below absolute zero and converted into a naked singularity. Quantum energy-momentum tensor calculations for uncharged black holes are extended to the Reissner-Nordstrom case, and found to be fully consistent with the thermodynamic picture for Q < M. For Q < M the model predicts that 'naked' collapse also produces radiation, with such intensity that the collapsing matter is entirely evaporated away before a naked singularity can form.

Universality of black hole quantum computing

Energy Technology Data Exchange (ETDEWEB)

Dvali, Gia [Muenchen Univ. (Germany). Arnold Sommerfeld Center for Theoretical Physics; Max-Planck-Institut fuer Physik, Muenchen (Germany); New York Univ., NY (United States). Center for Cosmology and Particle Physics; Gomez, Cesar [Muenchen Univ. (Germany). Arnold Sommerfeld Center for Theoretical Physics; Univ. Autonoma de Madrid (Spain). Inst. de Fisica Teorica UAM-CSIC; Luest, Dieter [Muenchen Univ. (Germany). Arnold Sommerfeld Center for Theoretical Physics; Max-Planck-Institut fuer Physik, Muenchen (Germany); Omar, Yasser [Instituto de Telecomunicacoes (Portugal). Physics of Information and Quantum Technologies Group; Lisboa Univ. (Portugal). Inst. Superior Tecnico; Richter, Benedikt [Muenchen Univ. (Germany). Arnold Sommerfeld Center for Theoretical Physics; Instituto de Telecomunicacoes (Portugal). Physics of Information and Quantum Technologies Group; Lisboa Univ. (Portugal). Inst. Superior Tecnico

2017-01-15

By analyzing the key properties of black holes from the point of view of quantum information, we derive a model-independent picture of black hole quantum computing. It has been noticed that this picture exhibits striking similarities with quantum critical condensates, allowing the use of a common language to describe quantum computing in both systems. We analyze such quantum computing by allowing coupling to external modes, under the condition that the external influence must be soft-enough in order not to offset the basic properties of the system. We derive model-independent bounds on some crucial time-scales, such as the times of gate operation, decoherence, maximal entanglement and total scrambling. We show that for black hole type quantum computers all these time-scales are of the order of the black hole half-life time. Furthermore, we construct explicitly a set of Hamiltonians that generates a universal set of quantum gates for the black hole type computer. We find that the gates work at maximal energy efficiency. Furthermore, we establish a fundamental bound on the complexity of quantum circuits encoded on these systems, and characterize the unitary operations that are implementable. It becomes apparent that the computational power is very limited due to the fact that the black hole life-time is of the same order of the gate operation time. As a consequence, it is impossible to retrieve its information, within the life-time of a black hole, by externally coupling to the black hole qubits. However, we show that, in principle, coupling to some of the internal degrees of freedom allows acquiring knowledge about the micro-state. Still, due to the trivial complexity of operations that can be performed, there is no time advantage over the collection of Hawking radiation and subsequent decoding. (copyright 2016 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

CYG X-3: A GALACTIC DOUBLE BLACK HOLE OR BLACK-HOLE-NEUTRON-STAR PROGENITOR

Energy Technology Data Exchange (ETDEWEB)

Belczynski, Krzysztof; Bulik, Tomasz [Astronomical Observatory, University of Warsaw, Al. Ujazdowskie 4, 00-478 Warsaw (Poland); Mandel, Ilya [School of Physics and Astronomy, University of Birmingham, Edgbaston B15 2TT (United Kingdom); Sathyaprakash, B. S. [School of Physics and Astronomy, Cardiff University, 5, The Parade, Cardiff CF24 3YB (United Kingdom); Zdziarski, Andrzej A.; Mikolajewska, Joanna [Centrum Astronomiczne im. M. Kopernika, Bartycka 18, PL-00-716 Warszawa (Poland)

2013-02-10

There are no known stellar-origin double black hole (BH-BH) or black-hole-neutron-star (BH-NS) systems. We argue that Cyg X-3 is a very likely BH-BH or BH-NS progenitor. This Galactic X-ray binary consists of a compact object, wind-fed by a Wolf-Rayet (W-R) type companion. Based on a comprehensive analysis of observational data, it was recently argued that Cyg X-3 harbors a 2-4.5 M {sub Sun} black hole (BH) and a 7.5-14.2 M {sub Sun} W-R companion. We find that the fate of such a binary leads to the prompt ({approx}< 1 Myr) formation of a close BH-BH system for the high end of the allowed W-R mass (M {sub W-R} {approx}> 13 M {sub Sun }). For the low- to mid-mass range of the W-R star (M {sub W-R} {approx} 7-10 M {sub Sun }) Cyg X-3 is most likely (probability 70%) disrupted when W-R ends up as a supernova. However, with smaller probability, it may form a wide (15%) or a close (15%) BH-NS system. The advanced LIGO/VIRGO detection rate for mergers of BH-BH systems from the Cyg X-3 formation channel is {approx}10 yr{sup -1}, while it drops down to {approx}0.1 yr{sup -1} for BH-NS systems. If Cyg X-3 in fact hosts a low-mass black hole and massive W-R star, it lends additional support for the existence of BH-BH/BH-NS systems.

Will Integration Hurt My Black Son's Education?

Science.gov (United States)

Latimer, Leah Y.

1987-01-01

In integrated schools, the educational system is slow to encourage black youngsters to participate at all levels of school life. Black participation is also inhibited by an insidious peer pressure and immature code of racial pride that defines blackness in terms that often exclude excellence in efforts beyond music, dance, and sports. (PS)

Nibelung-Kaoline-Black band fluit clay - the new key-horizon in the carboniferous system of the Ruhr coal field

Energy Technology Data Exchange (ETDEWEB)

Burger, K.; Otte, M.U. (Bergbau A.G. Lippe, Gelsenkirchen (Germany, F.R.). Abt. Markscheidewesen); Pfisterer, W. (Bergbau A.G. Lippe, Herne (Germany, F.R.). Hauptlaboratorium)

1979-10-01

Based upon the stratigraphic distribution of the kaoline-black-band flint clay in the carbon strata of the Ruhr, the Nibelung-Kaoline-black-band flint clay found in the upper Westphal C (Dorsten strata) is defined to be the new keyhorizon. The position of the discoveries of the kaoline-black-band flint clay, its stratigraphic positions as well as its macroscopic and microscopic characteristics together with the chemical composition are given. Investigations of the structure and minerals content show that the Nibelung-Kaolin-black-band flint clay is a new keyhorizon and is of great importance for the stratigraphy of the upper Westfal C. Its position within the system is represented by strata sections.

Supersymmetric black holes from Toda theories

International Nuclear Information System (INIS)

Delduc, F.; Saveliev, M.V.; Gervais, J.L.

1992-07-01

By the example of nonabelian Toda type theory associated with the Lie superalgebra osp(2/4) it is shown that this integrable dynamical system is relevant to a black hole background metric in the corresponding target space. In the even sector the model under consideration reduces to the exactly solvable conformal theory (nonabelian B 2 Toda system) in the presence of a black hole. (author) 6 refs

Black powder in gas pipelines

Energy Technology Data Exchange (ETDEWEB)

Sherik, Abdelmounam [Saudi Aramco, Dhahran (Saudi Arabia)

2009-07-01

Despite its common occurrence in the gas industry, black powder is a problem that is not well understood across the industry, in terms of its chemical and physical properties, source, formation, prevention or management of its impacts. In order to prevent or effectively manage the impacts of black powder, it is essential to have knowledge of its chemical and physical properties, formation mechanisms and sources. The present paper is divided into three parts. The first part of this paper is a synopsis of published literature. The second part reviews the recent laboratory and field work conducted at Saudi Aramco Research and Development Center to determine the compositions, properties, sources and formation mechanisms of black powder in gas transmission systems. Microhardness, nano-indentation, X-ray Diffraction (XRD), X-ray Fluorescence (XRF) and Scanning Electron Microscopy (SEM) techniques were used to analyze a large number of black powder samples collected from the field. Our findings showed that black powder is generated inside pipelines due to internal corrosion and that the composition of black powder is dependent on the composition of transported gas. The final part presents a summary and brief discussion of various black powder management methods. (author)

Energy level diagrams for black hole orbits

Science.gov (United States)

Levin, Janna

2009-12-01

A spinning black hole with a much smaller black hole companion forms a fundamental gravitational system, like a colossal classical analog to an atom. In an appealing if imperfect analogy with atomic physics, this gravitational atom can be understood through a discrete spectrum of periodic orbits. Exploiting a correspondence between the set of periodic orbits and the set of rational numbers, we are able to construct periodic tables of orbits and energy level diagrams of the accessible states around black holes. We also present a closed-form expression for the rational q, thereby quantifying zoom-whirl behavior in terms of spin, energy and angular momentum. The black hole atom is not just a theoretical construct, but corresponds to extant astrophysical systems detectable by future gravitational wave observatories.

Energy level diagrams for black hole orbits

International Nuclear Information System (INIS)

Levin, Janna

2009-01-01

A spinning black hole with a much smaller black hole companion forms a fundamental gravitational system, like a colossal classical analog to an atom. In an appealing if imperfect analogy with atomic physics, this gravitational atom can be understood through a discrete spectrum of periodic orbits. Exploiting a correspondence between the set of periodic orbits and the set of rational numbers, we are able to construct periodic tables of orbits and energy level diagrams of the accessible states around black holes. We also present a closed-form expression for the rational q, thereby quantifying zoom-whirl behavior in terms of spin, energy and angular momentum. The black hole atom is not just a theoretical construct, but corresponds to extant astrophysical systems detectable by future gravitational wave observatories.

System of the Wind Wave Operational Forecast by the Black Sea Marine Forecast Center

Directory of Open Access Journals (Sweden)

Yu.B. Ratner

2017-10-01

Full Text Available System of the wind wave operational forecast in the Black Sea based on the SWAN (Simulating Waves Nearshore numerical spectral model is represented. In the course of the system development the SWAN model was adapted to take into account the features of its operation at the Black Sea Marine Forecast Center. The model input-output is agreed with the applied nomenclature and the data representation formats. The user interface for rapid access to simulation results was developed. The model adapted to wave forecast in the Black Sea in a quasi-operational mode, is validated for 2012–2015. Validation of the calculation results was carried out for all five forecasting terms based on the analysis of two-dimensional graphs of the wave height distribution derived from the data of prognostic calculations and remote measurements obtained with the altimeter installed on the Jason-2 satellite. Calculation of the statistical characteristics of the deviations between the wave height prognostic values and the data of their measurements from the Jason-2 satellite, as well as a regression analysis of the relationship between the forecasted and measured wave heights was additionally carried out. A comparison of the results obtained with the similar results reported in the works of other authors published in 2009–2016 showed their satisfactory compliance with each other. The forecasts carried out by the authors for the Black Sea as well as those obtained for the other World Ocean regions show that the current level of numerical methods for sea wave forecasting is in full compliance with the requirements of specialists engaged in studying and modeling the state of the ocean and the atmosphere, as well as the experts using these results for solving applied problems.

Quantum mechanics of black holes.

Science.gov (United States)

Witten, Edward

2012-08-03

The popular conception of black holes reflects the behavior of the massive black holes found by astronomers and described by classical general relativity. These objects swallow up whatever comes near and emit nothing. Physicists who have tried to understand the behavior of black holes from a quantum mechanical point of view, however, have arrived at quite a different picture. The difference is analogous to the difference between thermodynamics and statistical mechanics. The thermodynamic description is a good approximation for a macroscopic system, but statistical mechanics describes what one will see if one looks more closely.

Black-swan events in animal populations

OpenAIRE

Anderson, Sean C.; Branch, Trevor A.; Cooper, Andrew B.; Dulvy, Nicholas K.

2017-01-01

Black swans?statistically improbable events with profound consequences?happen more often than expected in financial, social, and natural systems. Our work demonstrates the rare but systematic presence of black-swan events in animal populations around the world (mostly birds, mammals, and insects). These events are predominantly downward, implying that unexpected population crashes occur more frequently than increases. Black-swan events are not driven by life history (e.g., lifespan) but by ex...

Dual jets from binary black holes.

Science.gov (United States)

Palenzuela, Carlos; Lehner, Luis; Liebling, Steven L

2010-08-20

The coalescence of supermassive black holes--a natural outcome when galaxies merge--should produce gravitational waves and would likely be associated with energetic electromagnetic events. We have studied the coalescence of such binary black holes within an external magnetic field produced by the expected circumbinary disk surrounding them. Solving the Einstein equations to describe black holes interacting with surrounding plasma, we present numerical evidence for possible jets driven by these systems. Extending the process described by Blandford and Znajek for a single, spinning black hole, the picture that emerges suggests that the electromagnetic field extracts energy from the orbiting black holes, which ultimately merge and settle into the standard Blandford-Znajek scenario. Emissions along these jets could potentially be observable at large distances.

Black Silicon Solar Cells with Black Ribbons

DEFF Research Database (Denmark)

Davidsen, Rasmus Schmidt; Tang, Peter Torben; Mizushima, Io

2016-01-01

We present the combination of mask-less reactive ion etch (RIE) texturing and blackened interconnecting ribbons as a method for obtaining all-black solar panels, while using conventional, front-contacted solar cells. Black silicon made by mask-less reactive ion etching has total, average...... in the range 15.7-16.3%. The KOH-textured reference cell had an efficiency of 17.9%. The combination of black Si and black interconnecting ribbons may result in aesthetic, all-black panels based on conventional, front-contacted silicon solar cells....... reflectance below 0.5% across a 156x156 mm2 silicon (Si) wafer. Black interconnecting ribbons were realized by oxidizing copper resulting in reflectance below 3% in the visible wavelength range. Screen-printed Si solar cells were realized on 156x156 mm2 black Si substrates with resulting efficiencies...

Intellectual Classification of Black and White Children in Special Education Programs Using the WISC-III and the Cognitive Assessment System.

Science.gov (United States)

Naglieri, Jack A.; Rojahn, Johannes

2001-01-01

Comparison of the Wechsler Intelligence Scale for Children (Third Edition) and the Cognitive Assessment System (CAS) with 78 special education students found that the WISC-III identified more children, especially more black children, as having mental retardation. Results imply that the problem of disproportionate identification of black children…

Binary black hole in a double magnetic monopole field

Science.gov (United States)

Rodriguez, Maria J.

2018-01-01

Ambient magnetic fields are thought to play a critical role in black hole jet formation. Furthermore, dual electromagnetic signals could be produced during the inspiral and merger of binary black hole systems. In this paper, we derive the exact solution for the electromagnetic field occurring when a static, axisymmetric binary black hole system is placed in the field of two magnetic or electric monopoles. As a by-product of this derivation, we also find the exact solution of the binary black hole configuration in a magnetic or electric dipole field. The presence of conical singularities in the static black hole binaries represent the gravitational attraction between the black holes that also drag the external two monopole field. We show that these off-balance configurations generate no energy outflows.

Binary black hole in a double magnetic monopole field

Energy Technology Data Exchange (ETDEWEB)

Rodriguez, Maria J. [Utah State University, Department of Physics, Logan, UT (United States); Max Planck Institute for Gravitational Physics, Potsdam (Germany)

2018-01-15

Ambient magnetic fields are thought to play a critical role in black hole jet formation. Furthermore, dual electromagnetic signals could be produced during the inspiral and merger of binary black hole systems. In this paper, we derive the exact solution for the electromagnetic field occurring when a static, axisymmetric binary black hole system is placed in the field of two magnetic or electric monopoles. As a by-product of this derivation, we also find the exact solution of the binary black hole configuration in a magnetic or electric dipole field. The presence of conical singularities in the static black hole binaries represent the gravitational attraction between the black holes that also drag the external two monopole field. We show that these off-balance configurations generate no energy outflows. (orig.)

Evaluation of sowing patterns and weed control on mung bean (Vigna radiate L. Wilczek - black cumin (Nigella sativa L. intercropping system

Directory of Open Access Journals (Sweden)

parviz Rezvani Moghadam

2016-04-01

Full Text Available In order to study different arrangements and weed controls effects on mung bean (Vigna radiate L. Wilczek – black cumin (Nigella sativa L. intercropping an experiment was conducted at the Research Station of Faculty of Agriculture, Ferdowsi University of Mashhad, Iran, during growing season 2005 – 2006. Sixteen treatments comprising combinations of eight sowing patterns [A1: Sole black cumin, A2: Sole mung bean, A3: 3 rows black cumin– 2 rows mung bean, A4: 3 rows black cumin – 2 rows mung bean, A5: 2 rows black cumin – 1 rows mung bean, A6: 1 row black cumin – 2 rows mung bean, A7: 3 rows black cumin – 3 rows mung bean (Striped, A8: 1 row black cumin – 1 row mung bean (alternative rows] and two weed controls [V1: unweeded, V2: completely hand weeding] were arranged in a factorial experiment based on randomized complete block design with three replications. Results showed that in intercropping systems leaf area index (LAI of mung bean reduced but in the case of black cumin increased. Mung bean total dry matter in intercropping system did not differ comparing with sole crop but total dry matter in black cumin increased. All yield components in both crops affected by sowing patterns and weed control treatments. Number of branches/plant, number of pods or follicules/plant and number of seed/pods or follicules increased in A8, A4, A5 and A3 sowing patterns in mung bean and A3, A5 and A7 sowing patterns in black cumin compared with other arrangements. By increasing mung bean ratio in rows, the number of weed species, weed density, dry weight of weeds and abundance of weed species decreased. In unweeded treatment, number of branches/plant, number of pods or follicules/plant and number of seed/pods or follicules decreased in both crops. Land equivalent ratio (LER was more than 1.00 in all sowing patterns.

Erratic Black Hole Regulates Itself

Science.gov (United States)

2009-03-01

New results from NASA's Chandra X-ray Observatory have made a major advance in explaining how a special class of black holes may shut off the high-speed jets they produce. These results suggest that these black holes have a mechanism for regulating the rate at which they grow. Black holes come in many sizes: the supermassive ones, including those in quasars, which weigh in at millions to billions of times the mass of the Sun, and the much smaller stellar-mass black holes which have measured masses in the range of about 7 to 25 times the Sun's mass. Some stellar-mass black holes launch powerful jets of particles and radiation, like seen in quasars, and are called "micro-quasars". The new study looks at a famous micro-quasar in our own Galaxy, and regions close to its event horizon, or point of no return. This system, GRS 1915+105 (GRS 1915 for short), contains a black hole about 14 times the mass of the Sun that is feeding off material from a nearby companion star. As the material swirls toward the black hole, an accretion disk forms. This system shows remarkably unpredictable and complicated variability ranging from timescales of seconds to months, including 14 different patterns of variation. These variations are caused by a poorly understood connection between the disk and the radio jet seen in GRS 1915. Chandra, with its spectrograph, has observed GRS 1915 eleven times since its launch in 1999. These studies reveal that the jet in GRS 1915 may be periodically choked off when a hot wind, seen in X-rays, is driven off the accretion disk around the black hole. The wind is believed to shut down the jet by depriving it of matter that would have otherwise fueled it. Conversely, once the wind dies down, the jet can re-emerge. "We think the jet and wind around this black hole are in a sort of tug of war," said Joseph Neilsen, Harvard graduate student and lead author of the paper appearing in the journal Nature. "Sometimes one is winning and then, for reasons we don

A study of the anthropic activities impact on the Black Sea eco-system (Romanian coast area) using nuclear methods

International Nuclear Information System (INIS)

Timofte, L.

1997-01-01

This research represents a first step in the direction of a real evaluation of the Black Sea - Romanian Coast pollution level. A continental closed sea, with a special chemism and a specific dynamic regime of its waters, the Black Sea is seriously affected by pollution today, its eco - systems suffering deep restructuring, many of these with an irreversible character and an alarming degradation of the marine life quality. Starting with 1996, a systematic sampling of the principal systemic parts of the Black Sea Eco - System (Romanian Coast Area) was initiated at NIPNE - HH Bucharest. The samples are prepared and analysed by high precision nuclear methods such as: neutron activation analysis, atomic absorption spectrometry, inductively coupled plasma mass spectrometry and others. The results are presented as distribution maps and profiles of different elements (radioactive elements, heavy metals, trace elements etc.) in the investigated parts of the marine environment (water, sediments, vegetation and fauna). The research methodology and the obtained results offer a useful and efficient tool for the followup and permanent evaluation of the eco - system of the Black Sea. Monitoring this eco - system using a network and an efficient programme allows the storage of valuable data which are further used to make short - term and long - term prognosis referring to its evaluation. The results fit into the newest research programmes initiated by the international scientific community in the line of environment surveillance (The Programme of the International Board for Scientific Exploration of the Mediterranean supported by the European Community and US). (author)

Reversible Carnot cycle outside a black hole

International Nuclear Information System (INIS)

Xi-Hao, Deng; Si-Jie, Gao

2009-01-01

A Carnot cycle outside a Schwarzschild black hole is investigated in detail. We propose a reversible Carnot cycle with a black hole being the cold reservoir. In our model, a Carnot engine operates between a hot reservoir with temperature T 1 and a black hole with Hawking temperature T H . By naturally extending the ordinary Carnot cycle to the black hole system, we show that the thermal efficiency for a reversible process can reach the maximal efficiency 1 – T H /T 1 . Consequently, black holes can be used to determine the thermodynamic temperature by means of the Carnot cycle. The role of the atmosphere around the black hole is discussed. We show that the thermal atmosphere provides a necessary mechanism to make the process reversible. (general)

Super-horizon primordial black holes

International Nuclear Information System (INIS)

Harada, Tomohiro; Carr, B.J.

2005-01-01

We discuss a new class of solutions to the Einstein equations which describe a primordial black hole (PBH) in a flat Friedmann background. Such solutions arise if a Schwarzschild black hole is patched onto a Friedmann background via a transition region. They are possible providing the black hole event horizon is larger than the cosmological apparent horizon. Such solutions have a number of strange features. In particular, one has to define the black hole and cosmological horizons carefully and one then finds that the mass contained within the black hole event horizon decreases when the black hole is larger than the Friedmann cosmological apparent horizon, although its area always increases. These solutions involve two distinct future null infinities and are interpreted as the conversion of a white hole into a black hole. Although such solutions may not form from gravitational collapse in the same way as standard PBHs, there is nothing unphysical about them, since all energy and causality conditions are satisfied. Their conformal diagram is a natural amalgamation of the Kruskal diagram for the extended Schwarzschild solution and the conformal diagram for a black hole in a flat Friedmann background. In this paper, such solutions are obtained numerically for a spherically symmetric universe containing a massless scalar field, but it is likely that they exist for more general matter fields and less symmetric systems

The Lagrange Points in a Binary Black Hole System: Applications to Electromagnetic Signatures

Science.gov (United States)

Schnittman, Jeremy

2010-01-01

We study the stability and evolution of the Lagrange points L_4 and L-5 in a black hole (BH) binary system, including gravitational radiation. We find that gas and stars can be shepherded in with the BH system until the final moments before merger, providing the fuel for a bright electromagnetic counterpart to a gravitational wave signal. Other astrophysical signatures include the ejection of hyper-velocity stars, gravitational collapse of globular clusters, and the periodic shift of narrow emission lines in AGN.

Lung clearance of inhaled particles after exposure to carbon black generated from a resuspension system

International Nuclear Information System (INIS)

Lee, P.S.; Gorski, R.A.; Hering, W.E.; Chan, T.L.

1987-01-01

A system to resuspend carbon black particles for providing submicron aerosols for inhalation exposure studies has been developed. The effect of continuous exposure to carbonaceous material (as a surrogate for the carbonaceous particles in diesel exhaust) on the pulmonary clearance of inhaled diesel tracer particles was studied in male Fischer 344 rats. Submicron carbon black particles with a mass median aerodynamic diameter (MMAD) of 0.22 micron and a size distribution similar to that of exhaust particles from a GM 5.7-liter diesel engine were successfully generated and administered to test animals at a nominal concentration of 6 mg/m3 for 20 hr/day, 7 days/week, for periods lasting 1 to 11 weeks. Immediately after the carbon black exposure, test animals were administered 14 C-tagged diesel particles for 45 min in a nose-only chamber. The pulmonary retention of inhaled radioactive tracer particles was determined at preselected time intervals. Based upon the data collected up to 1 year postexposure, prolonged exposure to carbon black particles exhibits a similar inhibitory effect on pulmonary clearance as does prolonged exposure to diesel exhaust with a comparable particulate dose. This observation indicates that the excessive accumulation of carbonaceous material may be the predominant factor affecting lung clearance

Black holes

International Nuclear Information System (INIS)

Feast, M.W.

1981-01-01

This article deals with two questions, namely whether it is possible for black holes to exist, and if the answer is yes, whether we have found any yet. In deciding whether black holes can exist or not the central role in the shaping of our universe played by the forse of gravity is discussed, and in deciding whether we are likely to find black holes in the universe the author looks at the way stars evolve, as well as white dwarfs and neutron stars. He also discusses the problem how to detect a black hole, possible black holes, a southern black hole, massive black holes, as well as why black holes are studied

Black Lives Matter: A Call to Action for Counseling Psychology Leaders.

Science.gov (United States)

Crowell, Candice; Mosley, Della; Falconer, Jameca; Faloughi, Reuben; Singh, Anneliese; Stevens-Watkins, Danelle; Cokley, Kevin

2017-08-01

Police brutality and widespread systemic racism represent historical and current sources of trauma in Black communities. Both the Black Lives Matter movement and counseling psychology propose to confront these realities at multiple levels. Black Lives Matter seeks to increase awareness about systemic racism and promote resilience among Black people. Counseling psychology states values of multiculturalism, social justice, and advocacy. Executive leadership in counseling psychology may seek to promote racial justice, yet struggle with how to participate in Black Lives Matter movements and address racial discrimination within larger systems spontaneously and consistently. However, counseling psychology trainees and professionals are actively involved in the Black Lives Matter movement, leading the way forward. Through the framework of spontaneity in social movements, this manuscript highlights what counseling psychologists are currently contributing to Black Lives Matter and makes recommendations that build on the opportunity counseling psychologists have for further involvement in the movement.

Black silicon with black bus-bar strings

DEFF Research Database (Denmark)

Davidsen, Rasmus Schmidt; Tang, Peter Torben; Mizushima, Io

2016-01-01

We present the combination of black silicon texturing and blackened bus-bar strings as a potential method for obtaining all-black solar panels, while using conventional, front-contacted solar cells. Black silicon was realized by mask-less reactive ion etching resulting in total, average reflectance...... below 0.5% across a 156x156 mm2 silicon wafer. Black bus-bars were realized by oxidized copper resulting in reflectance below 3% in the entire visible wavelength range. The combination of these two technologies may result in aesthetic, all-black panels based on conventional, front-contacted solar cells...

Mass accretion rate fluctuations in black hole X-ray binaries

NARCIS (Netherlands)

Rapisarda, S.

2017-01-01

This thesis is about the first systematic and quantitative application of propagating mass accretion rate fluctuations models to black hole X-ray binaries. Black hole X-ray binaries are systems consisting of a solar mass star orbiting around a stellar mass black hole. Eventually, the black hole

Black hole based tests of general relativity

International Nuclear Information System (INIS)

Yagi, Kent; Stein, Leo C

2016-01-01

General relativity has passed all solar system experiments and neutron star based tests, such as binary pulsar observations, with flying colors. A more exotic arena for testing general relativity is in systems that contain one or more black holes. Black holes are the most compact objects in the Universe, providing probes of the strongest-possible gravitational fields. We are motivated to study strong-field gravity since many theories give large deviations from general relativity only at large field strengths, while recovering the weak-field behavior. In this article, we review how one can probe general relativity and various alternative theories of gravity by using electromagnetic waves from a black hole with an accretion disk, and gravitational waves from black hole binaries. We first review model-independent ways of testing gravity with electromagnetic/gravitational waves from a black hole system. We then focus on selected examples of theories that extend general relativity in rather simple ways. Some important characteristics of general relativity include (but are not limited to) (i) only tensor gravitational degrees of freedom, (ii) the graviton is massless, (iii) no quadratic or higher curvatures in the action, and (iv) the theory is four-dimensional. Altering a characteristic leads to a different extension of general relativity: (i) scalar–tensor theories, (ii) massive gravity theories, (iii) quadratic gravity, and (iv) theories with large extra dimensions. Within each theory, we describe black hole solutions, their properties, and current and projected constraints on each theory using black hole based tests of gravity. We close this review by listing some of the open problems in model-independent tests and within each specific theory. (paper)

Black-hole driven winds

International Nuclear Information System (INIS)

Punsly, B.M.

1988-01-01

This dissertation is a study of the physical mechanism that allows a large scale magnetic field to torque a rapidly rotating, supermassive black hole. This is an interesting problem as it has been conjectured that rapidly rotating black holes are the central engines that power the observed extragalactic double radio sources. Axisymmetric solutions of the curved space-time version of Maxwell's equations in the vacuum do not torque black holes. Plasma must be introduced for the hole to mechanically couple to the field. The dynamical aspect of rotating black holes that couples the magnetic field to the hole is the following. A rotating black hole forces the external geometry of space-time to rotate (the dragging of inertial frames). Inside of the stationary limit surface, the ergosphere, all physical particle trajectories must appear to rotate in the same direction as the black hole as viewed by the stationary observers at asymptotic infinity. In the text, it is demonstrated how plasma that is created on field lines that thread both the ergosphere and the equatorial plane will be pulled by gravity toward the equator. By the aforementioned properties of the ergosphere, the disk must rotate. Consequently, the disk acts like a unipolar generator. It drives a global current system that supports the toroidal magnetic field in an outgoing, magnetically dominated wind. This wind carries energy (mainly in the form of Poynting flux) and angular momentum towards infinity. The spin down of the black hole is the ultimate source of this energy and angular momentum flux

Stochastic Gravitational-Wave Background due to Primordial Binary Black Hole Mergers.

Science.gov (United States)

Mandic, Vuk; Bird, Simeon; Cholis, Ilias

2016-11-11

Recent Advanced LIGO detections of binary black hole mergers have prompted multiple studies investigating the possibility that the heavy GW150914 binary system was of primordial origin, and hence could be evidence for dark matter in the form of black holes. We compute the stochastic background arising from the incoherent superposition of such primordial binary black hole systems in the Universe and compare it to the similar background spectrum due to binary black hole systems of stellar origin. We investigate the possibility of detecting this background with future gravitational-wave detectors, and conclude that constraining the dark matter component in the form of black holes using stochastic gravitational-wave background measurements will be very challenging.

Rotating black holes in dilatonic Einstein-Gauss-Bonnet theory.

Science.gov (United States)

Kleihaus, Burkhard; Kunz, Jutta; Radu, Eugen

2011-04-15

We construct generalizations of the Kerr black holes by including higher-curvature corrections in the form of the Gauss-Bonnet density coupled to the dilaton. We show that the domain of existence of these Einstein-Gauss-Bonnet-dilaton (EGBD) black holes is bounded by the Kerr black holes, the critical EGBD black holes, and the singular extremal EGBD solutions. The angular momentum of the EGBD black holes can exceed the Kerr bound. The EGBD black holes satisfy a generalized Smarr relation. We also compare their innermost stable circular orbits with those of the Kerr black holes and show the existence of differences which might be observable in astrophysical systems.

Black rings

International Nuclear Information System (INIS)

Emparan, Roberto; Reall, Harvey S

2006-01-01

A black ring is a five-dimensional black hole with an event horizon of topology S 1 x S 2 . We provide an introduction to the description of black rings in general relativity and string theory. Novel aspects of the presentation include a new approach to constructing black ring coordinates and a critical review of black ring microscopics. (topical review)

Quantum chaos and the black hole horizon

CERN Multimedia

CERN. Geneva

2016-01-01

Thanks to AdS/CFT, the analogy between black holes and thermal systems has become a practical tool, shedding light on thermalization, transport, and entanglement dynamics. Continuing in this vein, recent work has shown how chaos in the boundary CFT can be analyzed in terms of high energy scattering right on the horizon of the dual black hole. The analysis revolves around certain out-of-time-order correlation functions, which are simple diagnostics of the butterfly effect. We will review this work, along with a general bound on these functions that implies black holes are the most chaotic systems in quantum mechanics. (NB Room Change to Main Auditorium)

"Black Like Me": Reframing Blackness for Decolonial Politics

Science.gov (United States)

Dei, George J. Sefa

2018-01-01

From a particular vantage point, as an African-born scholar with a politics to affirm my Black subjectivity and Indigeneity in a diasporic context, my article engages a (re)theorization of Blackness for decolonial politics. Building on existing works of how Black scholars, themselves, have theorized Blackness, and recognizing the fluid,…

The Use of Simulation to Reduce the Domain of "Black Swans" with Application to Hurricane Impacts to Power Systems.

Science.gov (United States)

Berner, Christine L; Staid, Andrea; Flage, Roger; Guikema, Seth D

2017-10-01

Recently, the concept of black swans has gained increased attention in the fields of risk assessment and risk management. Different types of black swans have been suggested, distinguishing between unknown unknowns (nothing in the past can convincingly point to its occurrence), unknown knowns (known to some, but not to relevant analysts), or known knowns where the probability of occurrence is judged as negligible. Traditional risk assessments have been questioned, as their standard probabilistic methods may not be capable of predicting or even identifying these rare and extreme events, thus creating a source of possible black swans. In this article, we show how a simulation model can be used to identify previously unknown potentially extreme events that if not identified and treated could occur as black swans. We show that by manipulating a verified and validated model used to predict the impacts of hazards on a system of interest, we can identify hazard conditions not previously experienced that could lead to impacts much larger than any previous level of impact. This makes these potential black swan events known and allows risk managers to more fully consider them. We demonstrate this method using a model developed to evaluate the effect of hurricanes on energy systems in the United States; we identify hurricanes with potentially extreme impacts, storms well beyond what the historic record suggests is possible in terms of impacts. © 2016 Society for Risk Analysis.

Shaping Globular Clusters with Black Holes

Science.gov (United States)

Kohler, Susanna

2018-03-01

How many black holes lurk within the dense environments of globular clusters, and how do these powerful objects shape the properties of the cluster around them? One such cluster, NGC 3201, is now helping us to answer these questions.Hunting Stellar-Mass Black HolesSince the detection of merging black-hole binaries by the Laser Interferometer Gravitational-Wave Observatory (LIGO), the dense environments of globular clusters have received increasing attention as potential birthplaces of these compact binary systems.The central region of the globular star cluster NGC 3201, as viewed by Hubble. The black hole is in orbit with the star marked by the blue circle. [NASA/ESA]In addition, more and more stellar-mass black-hole candidates have been observed within globular clusters, lurking in binary pairs with luminous, non-compact companions. The most recent of these detections, found in the globular cluster NGC 3201, stands alone as the first stellar-mass black hole candidate discovered via radial velocity observations: the black holes main-sequence companion gave away its presence via a telltale wobble.Now a team of scientists led by Kyle Kremer (CIERA and Northwestern University) is using models of this system to better understand the impact that black holes might have on their host clusters.A Model ClusterThe relationship between black holes and their host clusters is complicated. Though the cluster environment can determine the dynamical evolution of the black holes, the retention rate of black holes in a globular cluster (i.e., how many remain in the cluster when they are born as supernovae, rather than being kicked out during the explosion) influences how the host cluster evolves.Kremer and collaborators track this complex relationship by modeling the evolution of a cluster similar to NGC 3201 with a Monte Carlo code. The code incorporates physics relevant to the evolution of black holes and black-hole binaries in globular clusters, such as two-body relaxation

Management of high blood pressure in Blacks: an update of the International Society on Hypertension in Blacks consensus statement.

Science.gov (United States)

Flack, John M; Sica, Domenic A; Bakris, George; Brown, Angela L; Ferdinand, Keith C; Grimm, Richard H; Hall, W Dallas; Jones, Wendell E; Kountz, David S; Lea, Janice P; Nasser, Samar; Nesbitt, Shawna D; Saunders, Elijah; Scisney-Matlock, Margaret; Jamerson, Kenneth A

2010-11-01

Since the first International Society on Hypertension in Blacks consensus statement on the "Management of High Blood Pressure in African American" in 2003, data from additional clinical trials have become available. We reviewed hypertension and cardiovascular disease prevention and treatment guidelines, pharmacological hypertension clinical end point trials, and blood pressure-lowering trials in blacks. Selected trials without significant black representation were considered. In this update, blacks with hypertension are divided into 2 risk strata, primary prevention, where elevated blood pressure without target organ damage, preclinical cardiovascular disease, or overt cardiovascular disease for whom blood pressure consistently secondary prevention, where elevated blood pressure with target organ damage, preclinical cardiovascular disease, and/or a history of cardiovascular disease, for whom blood pressure consistently blood pressure is ≤10 mm Hg above target levels, monotherapy with a diuretic or calcium channel blocker is preferred. When blood pressure is >15/10 mm Hg above target, 2-drug therapy is recommended, with either a calcium channel blocker plus a renin-angiotensin system blocker or, alternatively, in edematous and/or volume-overload states, with a thiazide diuretic plus a renin-angiotensin system blocker. Effective multidrug therapeutic combinations through 4 drugs are described. Comprehensive lifestyle modifications should be initiated in blacks when blood pressure is ≥115/75 mm Hg. The updated International Society on Hypertension in Blacks consensus statement on hypertension management in blacks lowers the minimum target blood pressure level for the lowest-risk blacks, emphasizes effective multidrug regimens, and de-emphasizes monotherapy.

Onset of superradiant instabilities in the composed Kerr-black-hole–mirror bomb

Directory of Open Access Journals (Sweden)

Shahar Hod

2014-09-01

Full Text Available It was first pointed out by Press and Teukolsky that a system composed of a spinning Kerr black hole surrounded by a reflecting mirror may develop instabilities. The physical mechanism responsible for the development of these exponentially growing instabilities is the superradiant amplification of bosonic fields confined between the black hole and the mirror. A remarkable feature of this composed black-hole–mirror-field system is the existence of a critical mirror radius, rmstat, which supports stationary (marginally-stable field configurations. This critical (‘stationary’ mirror radius marks the boundary between stable and unstable black-hole–mirror-field configurations: composed systems whose confining mirror is situated in the region rmrmstat are unstable (that is, there are confined field modes which grow exponentially over time. In the present paper we explore this critical (marginally-stable boundary between stable and explosive black-hole–mirror-field configurations. It is shown that the innermost (smallest radius of the confining mirror which allows the extraction of rotational energy from a spinning Kerr black hole approaches the black-hole horizon radius in the extremal limit of rapidly-rotating black holes. We find, in particular, that this critical mirror radius (which marks the onset of superradiant instabilities in the composed system scales linearly with the black-hole temperature.

Additivity of the entropies of black holes and matter

International Nuclear Information System (INIS)

Martinez, E.A.; York, J.W. Jr.

1989-01-01

The principal object of this work is to address two related questions about thermodynamic equilibrium between black holes and matter: is there gravitational entropy other than that for black holes? In particular, is there gravitational entropy associated with matter in addition to its usual thermodynamic entropy? The authors treat here the case when the black hole and matter are minimally coupled and in equilibrium; nonequilibrium creation of entropy will not be considered and if black holes and matter are in thermal equilibrium, in what sense are their entropies additive? In order to answer these questions, the authors present a model in which a black hole is surrounded by a thin shell of matter and construct the thermodynamics of the system based on the current approach to black hole thermodynamics. The authors review the essential aspects of this approach and then apply it to the present example. Finally, some further thermodynamical properties of the system are presented

Chaos and order in models of black hole pairs

International Nuclear Information System (INIS)

Levin, Janna

2006-01-01

Chaos in the orbits of black hole pairs has by now been confirmed by several independent groups. While the chaotic behavior of binary black hole orbits is no longer argued, it remains difficult to quantify the importance of chaos to the evolutionary dynamics of a pair of comparable mass black holes. None of our existing approximations are robust enough to offer convincing quantitative conclusions in the most highly nonlinear regime. It is intriguing to note that, in three different approximations to a black hole pair built of a spinning black hole and a nonspinning companion, two approximations exhibit chaos and one approximation does not. The fully relativistic scenario of a spinning test mass around a Schwarzschild black hole shows chaos, as does the post-Newtonian Lagrangian approximation. However, the approximately equivalent post-Newtonian Hamiltonian approximation does not show chaos when only one body spins. It is well known in dynamical systems theory that one system can be regular while an approximately related system is chaotic, so there is no formal conflict. However, the physical question remains: Is there chaos for comparable mass binaries when only one object spins? We are unable to answer this question given the poor convergence of the post-Newtonian approximation to the fully relativistic system. A resolution awaits better approximations that can be trusted in the highly nonlinear regime

Dynamical black rings with a positive cosmological constant

International Nuclear Information System (INIS)

Kimura, Masashi

2009-01-01

We construct dynamical black ring solutions in the five-dimensional Einstein-Maxwell system with a positive cosmological constant and investigate the geometrical structure. The solutions describe the physical process such that a thin black ring at early time shrinks and changes into a single black hole as time increases. We also discuss the multiblack rings and the coalescence of them.

Black Alcoholism.

Science.gov (United States)

Watts, Thomas D.; Wright, Roosevelt

1988-01-01

Examines some aspects of the problem of alcoholism among Blacks, asserting that Black alcoholism can best be considered in an ecological, environmental, sociocultural, and public health context. Notes need for further research on alcoholism among Blacks and for action to reduce the problem of Black alcoholism. (NB)

Black holes as lumps of fluid

International Nuclear Information System (INIS)

Caldarelli, Marco M.; Dias, Oscar J.C.; Emparan, Roberto; Klemm, Dietmar

2009-01-01

The old suggestive observation that black holes often resemble lumps of fluid has recently been taken beyond the level of an analogy to a precise duality. We investigate aspects of this duality, and in particular clarify the relation between area minimization of the fluid vs. area maximization of the black hole horizon, and the connection between surface tension and curvature of the fluid, and surface gravity of the black hole. We also argue that the Rayleigh-Plateau instability in a fluid tube is the holographic dual of the Gregory-Laflamme instability of a black string. Associated with this fluid instability there is a rich variety of phases of fluid solutions that we study in detail, including in particular the effects of rotation. We compare them against the known results for asymptotically flat black holes finding remarkable agreement. Furthermore, we use our fluid results to discuss the unknown features of the gravitational system. Finally, we make some observations that suggest that asymptotically flat black holes may admit a fluid description in the limit of large number of dimensions.

Tracking black holes in numerical relativity

International Nuclear Information System (INIS)

Caveny, Scott A.; Anderson, Matthew; Matzner, Richard A.

2003-01-01

This work addresses the problem of generically tracking black hole event horizons in computational simulation of black hole interactions. Solutions of the hyperbolic eikonal equation, solved on a curved spacetime manifold containing black hole sources, are employed in development of a robust tracking method capable of continuously monitoring arbitrary changes of topology in the event horizon as well as arbitrary numbers of gravitational sources. The method makes use of continuous families of level set viscosity solutions of the eikonal equation with identification of the black hole event horizon obtained by the signature feature of discontinuity formation in the eikonal's solution. The method is employed in the analysis of the event horizon for the asymmetric merger in a binary black hole system. In this first such three dimensional analysis, we establish both qualitative and quantitative evidence for our method and its application to the asymmetric problem. We focus attention on (1) the topology of the throat connecting the holes following merger, (2) the time of merger, and (3) continuing to account for the surface of section areas of the black hole sources

The Black Holes in the Hearts of Galaxies

Science.gov (United States)

Rigby, Jane

2010-01-01

In the past 20 years, astronomers have discovered that almost every galaxy contains a black hole at its center. These black holes outweigh our sun by a factor of a million to a billion. Surprisingly, there's a very tight connection between the size of the galaxy and its central black hole -- the bigger the galaxy, the bigger the black hole. We don't know why this relationship exists -- how can a black hole, with a sphere of influence the size of our solar system, know what kind of galaxy it inhabits? What processes create this relationship? I'll explore these topics, and show how new space telescopes are helping us discover thousands of black holes and explore how they evolve with time.

The Properties of SBR/ENR50 Blend Containing Nanoclay/Carbon Black Dual Filler System Cured by Electron Beam

Directory of Open Access Journals (Sweden)

Sima Ahmadi-Shooli

2017-05-01

Full Text Available Nanocomposites based on an SBR/ENR50 rubber blend with the blend ratio of 50/50 using Cloisite 15A nanoclay (5 and 10 phr and carbon black (20 phr were prepared by melt mixing process. The rubber compounds were crosslinked by electron beam irradiation process at 50 and 100 kGy doses. A reference sample containing carbon black at 35 phr was prepared using a conventional sulphur curing system. The gel content of the samples was specified using gel fraction measurement. The results showed the maximum gel content for the sample having 5 phr nanoclay and 20 phr carbon black. The dynamic mechanical properties, including the storage modulus, loss modulus, and loss factor, of the nanocomposites were evaluated using dynamic mechanical analysis (DMA tests. The results indicated that, in spite of a well dispersed nanoclay in samples containing 10 phr nanoclay and 20 phr carbon black, a minimum loss factor was observed in the sample containing 5 phr nanoclay and 20 phr carbon black at 100 kGy. On the other hand, the storage modulus of the reference sample was found to be higher than that of the sample with 5 phr nanoclay and 20 phr carbon black. The mechanical properties, including the tensile strength, stress at 100%, 200%, and 300% elongation and the percentage of elongation were measured by a tensile machine. The results showed an increase in tensile strength and the stress at different elongations for a sample with 5 phr nanoclay and 20 phr carbon black compared to the reference sample. In the corresponding SEM images of the samples having nanoclay and carbon black irradiated at 100 kGy a significantly higher surface roughness was observed.

Special data base of Informational - Computational System 'INM RAS - Black Sea' for solving inverse and data assimilation problems

Science.gov (United States)

Zakharova, Natalia; Piskovatsky, Nicolay; Gusev, Anatoly

2014-05-01

Development of Informational-Computational Systems (ICS) for data assimilation procedures is one of multidisciplinary problems. To study and solve these problems one needs to apply modern results from different disciplines and recent developments in: mathematical modeling; theory of adjoint equations and optimal control; inverse problems; numerical methods theory; numerical algebra and scientific computing. The above problems are studied in the Institute of Numerical Mathematics of the Russian Academy of Science (INM RAS) in ICS for personal computers. In this work the results on the Special data base development for ICS "INM RAS - Black Sea" are presented. In the presentation the input information for ICS is discussed, some special data processing procedures are described. In this work the results of forecast using ICS "INM RAS - Black Sea" with operational observation data assimilation are presented. This study was supported by the Russian Foundation for Basic Research (project No 13-01-00753) and by Presidium Program of Russian Academy of Sciences (project P-23 "Black sea as an imitational ocean model"). References 1. V.I. Agoshkov, M.V. Assovskii, S.A. Lebedev, Numerical simulation of Black Sea hydrothermodynamics taking into account tide-forming forces. Russ. J. Numer. Anal. Math. Modelling (2012) 27, No.1, pp. 5-31. 2. E.I. Parmuzin, V.I. Agoshkov, Numerical solution of the variational assimilation problem for sea surface temperature in the model of the Black Sea dynamics. Russ. J. Numer. Anal. Math. Modelling (2012) 27, No.1, pp. 69-94. 3. V.B. Zalesny, N.A. Diansky, V.V. Fomin, S.N. Moshonkin, S.G. Demyshev, Numerical model of the circulation of Black Sea and Sea of Azov. Russ. J. Numer. Anal. Math. Modelling (2012) 27, No.1, pp. 95-111. 4. Agoshkov V.I.,Assovsky M.B., Giniatulin S. V., Zakharova N.B., Kuimov G.V., Parmuzin E.I., Fomin V.V. Informational Computational system of variational assimilation of observation data "INM RAS - Black sea"// Ecological

On the many saddle points description of quantum black holes

Energy Technology Data Exchange (ETDEWEB)

Germani, Cristiano, E-mail: cristiano.germani@physik.uni-muenchen.de

2014-06-02

Considering two dimensional gravity coupled to a CFT, we show that a semiclassical black hole can be described in terms of two Liouville theories matched at the horizon. The black hole exterior corresponds to a space-like while the interior to a time-like Liouville theory. This matching automatically implies that a semiclassical black hole has an infinite entropy. The path integral description of the time-like Liouville theory (the Black Hole interior) is studied and it is found that the correlation functions of the coupled CFT-gravity system are dominated by two (complex) saddle points, even in the semiclassical limit. We argue that this system can be interpreted as two interacting Bose–Einstein condensates constructed out of two degenerate quantum states. In AdS/CFT context, the same system is mapped into two interacting strings intersecting inside a three-dimensional BTZ black hole.

Novel platinum black electroplating technique improving mechanical stability.

Science.gov (United States)

Kim, Raeyoung; Nam, Yoonkey

2013-01-01

Platinum black microelectrodes are widely used as an effective neural signal recording sensor. The simple fabrication process, high quality signal recording and proper biocompatibility are the main advantages of platinum black microelectrodes. When microelectrodes are exposed to actual biological system, various physical stimuli are applied. However, the porous structure of platinum black is vulnerable to external stimuli and destroyed easily. The impedance level of the microelectrode increases when the microelectrodes are damaged resulting in decreased recording performance. In this study, we developed mechanically stable platinum black microelectrodes by adding polydopamine. The polydopamine layer was added between the platinum black structures by electrodeposition method. The initial impedance level of platinum black only microelectrodes and polydopamine added microelectrodes were similar but after applying ultrasonication the impedance value dramatically increased for platinum black only microelectrodes, whereas polydopamine added microelectrodes showed little increase which were nearly retained initial values. Polydopamine added platinum black microelectrodes are expected to extend the availability as neural sensors.

Black holes, qubits and octonions

International Nuclear Information System (INIS)

Borsten, L.; Dahanayake, D.; Duff, M.J.; Ebrahim, H.; Rubens, W.

2009-01-01

We review the recently established relationships between black hole entropy in string theory and the quantum entanglement of qubits and qutrits in quantum information theory. The first example is provided by the measure of the tripartite entanglement of three qubits (Alice, Bob and Charlie), known as the 3-tangle, and the entropy of the 8-charge STU black hole of N=2 supergravity, both of which are given by the [SL(2)] 3 invariant hyperdeterminant, a quantity first introduced by Cayley in 1845. Moreover the classification of three-qubit entanglements is related to the classification of N=2 supersymmetric STU black holes. There are further relationships between the attractor mechanism and local distillation protocols and between supersymmetry and the suppression of bit flip errors. At the microscopic level, the black holes are described by intersecting D3-branes whose wrapping around the six compact dimensions T 6 provides the string-theoretic interpretation of the charges and we associate the three-qubit basis vectors, |ABC>(A,B,C=0 or 1), with the corresponding 8 wrapping cycles. The black hole/qubit correspondence extends to the 56 charge N=8 black holes and the tripartite entanglement of seven qubits where the measure is provided by Cartan's E 7 contains [SL(2)] 7 invariant. The qubits are naturally described by the seven vertices ABCDEFG of the Fano plane, which provides the multiplication table of the seven imaginary octonions, reflecting the fact that E 7 has a natural structure of an O-graded algebra. This in turn provides a novel imaginary octonionic interpretation of the 56=7x8 charges of N=8: the 24=3x8 NS-NS charges correspond to the three imaginary quaternions and the 32=4x8 R-R to the four complementary imaginary octonions. We contrast this approach with that based on Jordan algebras and the Freudenthal triple system. N=8 black holes (or black strings) in five dimensions are also related to the bipartite entanglement of three qutrits (3-state systems

How bees distinguish black from white

Directory of Open Access Journals (Sweden)

Horridge A

2014-10-01

Full Text Available Adrian Horridge Biological Sciences, Australian National University, Canberra, ACT, AustraliaAbstract: Bee eyes have photoreceptors for ultraviolet, green, and blue wavelengths that are excited by reflected white but not by black. With ultraviolet reflections excluded by the apparatus, bees can learn to distinguish between black, gray, and white, but theories of color vision are clearly of no help in explaining how they succeed. Human vision sidesteps the issue by constructing black and white in the brain. Bees have quite different and accessible mechanisms. As revealed by extensive tests of trained bees, bees learned two strong signals displayed on either target. The first input was the position and a measure of the green receptor modulation at the vertical edges of a black area, which included a measure of the angular width between the edges of black. They also learned the average position and total amount of blue reflected from white areas. These two inputs were sufficient to help decide which of two targets held the reward of sugar solution, but the bees cared nothing for the black or white as colors, or the direction of contrast at black/white edges. These findings provide a small step toward understanding, modeling, and implementing in silicon the anti-intuitive visual system of the honeybee, in feeding behavior. Keywords: vision, detectors, black/white, color, visual processing

Magnetohydrodynamic Simulations of Black Hole Accretion

Science.gov (United States)

Avara, Mark J.

Black holes embody one of the few, simple, solutions to the Einstein field equations that describe our modern understanding of gravitation. In isolation they are small, dark, and elusive. However, when a gas cloud or star wanders too close, they light up our universe in a way no other cosmic object can. The processes of magnetohydrodynamics which describe the accretion inflow and outflows of plasma around black holes are highly coupled and nonlinear and so require numerical experiments for elucidation. These processes are at the heart of astrophysics since black holes, once they somehow reach super-massive status, influence the evolution of the largest structures in the universe. It has been my goal, with the body of work comprising this thesis, to explore the ways in which the influence of black holes on their surroundings differs from the predictions of standard accretion models. I have especially focused on how magnetization of the greater black hole environment can impact accretion systems.

Better Physician's 'Black Bags'

Science.gov (United States)

1976-01-01

The "black bag" is outgrowth of astronaut monitoring technology from NASA's Johnson Space Center. Technically known as the portable medical status system, a highly advanced physician's "black bag" weighs less than 30 pounds, yet contains equipment for monitoring and recording vital signs, electrocardiograms, and electroencephalograms. Liquid crystal displays are used to present 15 digits of data simultaneously for long periods of time without excessive use of battery power. Single printed circuit card contains all circuitry required to measure and display vital signs such as heart and respiration rate, temperature, and blood pressure.

The theory of optical black hole lasers

Energy Technology Data Exchange (ETDEWEB)

Gaona-Reyes, José L., E-mail: jgaona@fis.cinvestav.mx; Bermudez, David, E-mail: dbermudez@fis.cinvestav.mx

2017-05-15

The event horizon of black holes and white holes can be achieved in the context of analogue gravity. It was proven for a sonic case that if these two horizons are close to each other their dynamics resemble a laser, a black hole laser, where the analogue of Hawking radiation is trapped and amplified. Optical analogues are also very successful and a similar system can be achieved there. In this work we develop the theory of optical black hole lasers and prove that the amplification is also possible. Then, we study the optical system by determining the forward propagation of modes, obtaining an approximation for the phase difference which governs the amplification, and performing numerical simulations of the pulse propagation of our system. - Highlights: • We develop the conditions to obtain the kinematics of the optical black hole laser. • We prove the amplification of Hawking radiation for the optical case. • We derive the forward propagation of modes and check the result of the backward case. • A model is proposed to calculate the phase difference and the amplification rate. • We perform numerical simulations of a pulse between two solitons forming a cavity.

Black holes

OpenAIRE

Brügmann, B.; Ghez, A. M.; Greiner, J.

2001-01-01

Recent progress in black hole research is illustrated by three examples. We discuss the observational challenges that were met to show that a supermassive black hole exists at the center of our galaxy. Stellar-size black holes have been studied in x-ray binaries and microquasars. Finally, numerical simulations have become possible for the merger of black hole binaries.

Black Hole Hunters Set New Distance Record

Science.gov (United States)

2010-01-01

around each other in a diabolic waltz, with a period of about 32 hours. The astronomers also found that the black hole is stripping matter away from the star as they orbit each other. "This is indeed a very 'intimate' couple," notes collaborator Robin Barnard. "How such a tightly bound system has been formed is still a mystery." Only one other system of this type has previously been seen, but other systems comprising a black hole and a companion star are not unknown to astronomers. Based on these systems, the astronomers see a connection between black hole mass and galactic chemistry. "We have noticed that the most massive black holes tend to be found in smaller galaxies that contain less 'heavy' chemical elements," says Crowther [2]. "Bigger galaxies that are richer in heavy elements, such as the Milky Way, only succeed in producing black holes with smaller masses." Astronomers believe that a higher concentration of heavy chemical elements influences how a massive star evolves, increasing how much matter it sheds, resulting in a smaller black hole when the remnant finally collapses. In less than a million years, it will be the Wolf-Rayet star's turn to go supernova and become a black hole. "If the system survives this second explosion, the two black holes will merge, emitting copious amounts of energy in the form of gravitational waves as they combine [3]," concludes Crowther. However, it will take some few billion years until the actual merger, far longer than human timescales. "Our study does however show that such systems might exist, and those that have already evolved into a binary black hole might be detected by probes of gravitational waves, such as LIGO or Virgo [4]." Notes [1] Stellar-mass black holes are the extremely dense, final remnants of the collapse of very massive stars. These black holes have masses up to around twenty times the mass of the Sun, as opposed to supermassive black holes, found in the centre of most galaxies, which can weigh a million to a

The phase structure of higher-dimensional black rings and black holes

International Nuclear Information System (INIS)

Emparan, Roberto; Harmark, Troels; Niarchos, Vasilis; Obers, Niels A.; RodrIguez, Maria J.

2007-01-01

We construct an approximate solution for an asymptotically flat, neutral, thin rotating black ring in any dimension D ≥ 5 by matching the near-horizon solution for a bent boosted black string, to a linearized gravity solution away from the horizon. The rotating black ring solution has a regular horizon of topology S 1 x S D-3 and incorporates the balancing condition of the ring as a zero-tension condition. For D = 5 our method reproduces the thin ring limit of the exact black ring solution. For D ≥ 6 we show that the black ring has a higher entropy than the Myers-Perry black hole in the ultra-spinning regime. By exploiting the correspondence between ultra-spinning black holes and black membranes on a two-torus, we take steps towards qualitatively completing the phase diagram of rotating blackfolds with a single angular momentum. We are led to propose a connection between MP black holes and black rings, and between MP black holes and black Saturns, through merger transitions involving two kinds of 'pinched' black holes. More generally, the analogy suggests an infinite number of pinched black holes of spherical topology leading to a complicated pattern of connections and mergers between phases

On the Charter Question: Black Marxism and Black Nationalism

Science.gov (United States)

Stern, Mark; Hussain, Khuram

2015-01-01

This article brings two black intellectual traditions to bear on the question of charter schools: black Marxism and black nationalism. The authors examine the theoretical and rhetorical devices used to talk about charters schools by focusing on how notions of "black liberation" are deployed by the charter movement, and to what end. The…

Stationary Black Holes: Uniqueness and Beyond

Directory of Open Access Journals (Sweden)

Heusler Markus

1998-01-01

Full Text Available The spectrum of known black hole solutions to the stationary Einstein equations has increased in an unexpected way during the last decade. In particular, it has turned out that not all black hole equilibrium configurations are characterized by their mass, angular momentum and global charges. Moreover, the high degree of symmetry displayed by vacuum and electro-vacuum black hole space-times ceases to exist in self-gravitating non-linear field theories. This text aims to review some of the recent developments and to discuss them in the light of the uniqueness theorem for the Einstein-Maxwell system.

Stationary Black Holes: Uniqueness and Beyond

Directory of Open Access Journals (Sweden)

Piotr T. Chruściel

2012-05-01

Full Text Available The spectrum of known black-hole solutions to the stationary Einstein equations has been steadily increasing, sometimes in unexpected ways. In particular, it has turned out that not all black-hole-equilibrium configurations are characterized by their mass, angular momentum and global charges. Moreover, the high degree of symmetry displayed by vacuum and electro vacuum black-hole spacetimes ceases to exist in self-gravitating non-linear field theories. This text aims to review some developments in the subject and to discuss them in light of the uniqueness theorem for the Einstein-Maxwell system.

"Be Real Black for Me": Imagining BlackCrit in Education

Science.gov (United States)

Dumas, Michael J.; ross, kihana miraya

2016-01-01

The authors put forward a theorization of a Black Critical Theory, or what might be called BlackCrit, within, and in response to, Critical Race Theory, and then outline ways that BlackCrit in education helps us to more incisively analyze how the specificity of (anti)blackness matters in explaining how Black bodies become marginalized, disregarded,…

Cardiovascular benefits of black cumin (Nigella sativa).

Science.gov (United States)

Shabana, Adel; El-Menyar, Ayman; Asim, Mohammad; Al-Azzeh, Hiba; Al Thani, Hassan

2013-03-01

Black Cumin (Nigella sativa), which belongs to the botanical family of Ranunculaceae, commonly grows in Eastern Europe, the Middle East, and Western Asia. Its ripe fruit contains tiny black seeds, known as "Al-Habba Al-Sauda" and "Al-Habba Al-Barakah" in Arabic and black seed or black cumin in English. Seeds of Nigella sativa are frequently used in folk medicine in the Middle East and some Asian countries for the promotion of good health and the treatment of many ailments. However, data for the cardiovascular benefits of black cumin are not well-established. We reviewed the literature from 1960 to March 2012 by using the following key words: "Nigella sativa," "black seeds," and "thymoquinone." Herein, we discussed the most relevant articles to find out the role of Nigella sativa in the cardiovascular diseases spectrum especially when there is a paucity of information and need of further studies in human to establish the utility of Nigella sativa in cardiovascular system protection.

Onset of superradiant instabilities in the composed Kerr-black-hole–mirror bomb

Energy Technology Data Exchange (ETDEWEB)

Hod, Shahar [The Ruppin Academic Center, Emeq Hefer 40250 (Israel); The Hadassah Institute, Jerusalem 91010 (Israel)

2014-09-07

It was first pointed out by Press and Teukolsky that a system composed of a spinning Kerr black hole surrounded by a reflecting mirror may develop instabilities. The physical mechanism responsible for the development of these exponentially growing instabilities is the superradiant amplification of bosonic fields confined between the black hole and the mirror. A remarkable feature of this composed black-hole–mirror-field system is the existence of a critical mirror radius, r{sub m}{sup stat}, which supports stationary (marginally-stable) field configurations. This critical (‘stationary’) mirror radius marks the boundary between stable and unstable black-hole–mirror-field configurations: composed systems whose confining mirror is situated in the region r{sub m}systems whose confining mirror is situated in the region r{sub m}>r{sub m}{sup stat} are unstable (that is, there are confined field modes which grow exponentially over time). In the present paper we explore this critical (marginally-stable) boundary between stable and explosive black-hole–mirror-field configurations. It is shown that the innermost (smallest) radius of the confining mirror which allows the extraction of rotational energy from a spinning Kerr black hole approaches the black-hole horizon radius in the extremal limit of rapidly-rotating black holes. We find, in particular, that this critical mirror radius (which marks the onset of superradiant instabilities in the composed system) scales linearly with the black-hole temperature.

Planck absolute entropy of a rotating BTZ black hole

Science.gov (United States)

Riaz, S. M. Jawwad

2018-04-01

In this paper, the Planck absolute entropy and the Bekenstein-Smarr formula of the rotating Banados-Teitelboim-Zanelli (BTZ) black hole are presented via a complex thermodynamical system contributed by its inner and outer horizons. The redefined entropy approaches zero as the temperature of the rotating BTZ black hole tends to absolute zero, satisfying the Nernst formulation of a black hole. Hence, it can be regarded as the Planck absolute entropy of the rotating BTZ black hole.

Criteria for retrograde rotation of accreting black holes

Science.gov (United States)

Mikhailov, A. G.; Piotrovich, M. Yu; Gnedin, Yu N.; Natsvlishvili, T. M.; Buliga, S. D.

2018-06-01

Rotating supermassive black holes produce jets and their origin is connected to the magnetic field that is generated by accreting matter flow. There is a point of view that electromagnetic fields around rotating black holes are brought to the hole by accretion. In this situation the prograde accreting discs produce weaker large-scale black hole threading magnetic fields, implying weaker jets than in retrograde regimes. The basic goal of this paper is to find the best candidates for retrograde accreting systems in observed active galactic nuclei. We show that active galactic nuclei with low Eddington ratio are really the best candidates for retrograde systems. This conclusion is obtained for kinetically dominated Fanaroff-Riley class II radio galaxies, flat-spectrum radio-loud narrow-line Seyfert I galaxies and a number of nearby galaxies. Our conclusion is that the best candidates for retrograde systems are the noticeable population of active galactic nuclei in the Universe. This result corresponds to the conclusion that in the merging process the interaction of merging black holes with a retrograde circumbinary disc is considerably more effective for shrinking the binary system.

Black holes: the membrane paradigm

International Nuclear Information System (INIS)

Thorne, K.S.; Price, R.H.; Macdonald, D.A.

1986-01-01

The physics of black holes is explored in terms of a membrane paradigm which treats the event horizon as a two-dimensional membrane embedded in three-dimensional space. A 3+1 formalism is used to split Schwarzschild space-time and the laws of physics outside a nonrotating hole, which permits treatment of the atmosphere in terms of the physical properties of thin slices. The model is applied to perturbed slowly or rapidly rotating and nonrotating holes, and to quantify the electric and magnetic fields and eddy currents passing through a membrane surface which represents a stretched horizon. Features of tidal gravitational fields in the vicinity of the horizon, quasars and active galalctic nuclei, the alignment of jets perpendicular to accretion disks, and the effects of black holes at the center of ellipsoidal star clusters are investigated. Attention is also given to a black hole in a binary system and the interactions of black holes with matter that is either near or very far from the event horizon. Finally, a statistical mechanics treatment is used to derive a second law of thermodynamics for a perfectly thermal atmosphere of a black hole

Einstein's Gift: Stellar Mass Black Holes in the LIGO Era

Science.gov (United States)

Cadonati, Laura; Georgia Institute of Technology, LIGO-Virgo Collaboration

2017-01-01

The discovery of gravitational waves from the coalescence of black hole binary systems in LIGO has provided the first evidence for heavy stellar mass black holes. In this talk, I will review the observational evidence for black holes in LIGO data, its astrophysical implications and the plans for the near and long term future of ground based gravitational wave detection of black hole binary coalescences.

Spatial consideration of black rainfall region using geographical information system and based on witness of A-bomb survivors and newspaper articles

International Nuclear Information System (INIS)

Sato, Yuya; Satoh, Kenichi; Shimamoto; Kawano, Noriyuki

2012-01-01

The black rainfall area after the A-bomb explosion was investigated using informational materials in the title because orographic precipitate is important for radioactive substances to spread. Witnesses were collected from questionnaires about exposure done by Asahi Newspapers (Apr., 2005) and by Japan Confederation of A- and H-Bomb Sufferers Organizations (Nov., 1985-Mar., 1986); from Newspaper Data Base in Hiroshima University about articles concerning A-bomb, exposure and black rain; and about geography, from National Digital Cartographic Data Base of Geographical Survey Institute. Geographical Information System was used for identifying the valley and ridge to plot the keywords about the above exposure, black rain and so on. It was found that black rain was experienced in Hiroshima City alone whereas witness of seeing the mushroom cloud was obtained at many places nearby around the City, suggesting the biased black rainfall region within the City. Particularly, when the black rain witnesses in the City were summing up for each region, they were found biased in the west to northern west areas of the hypocenter, that were downwind of the first ridge from the explosion site. Thus the black rainfall was found localized western to northern western from the hypocenter, which was thought to be further confirmed by other evidence like soil analysis. (T.T.)

Black holes as critical point of quantum phase transition.

Science.gov (United States)

Dvali, Gia; Gomez, Cesar

We reformulate the quantum black hole portrait in the language of modern condensed matter physics. We show that black holes can be understood as a graviton Bose-Einstein condensate at the critical point of a quantum phase transition, identical to what has been observed in systems of cold atoms. The Bogoliubov modes that become degenerate and nearly gapless at this point are the holographic quantum degrees of freedom responsible for the black hole entropy and the information storage. They have no (semi)classical counterparts and become inaccessible in this limit. These findings indicate a deep connection between the seemingly remote systems and suggest a new quantum foundation of holography. They also open an intriguing possibility of simulating black hole information processing in table-top labs.

A Systems Approach for Ameliorating Possible Prima Facie Denial of Hispanic/Black Students' Rights Through Disproportionate Enrollment in Special Education.

Science.gov (United States)

McDonnell, James R.

The paper discusses the issue of educational equity, principles of systems analysis, systems approaches in the educational milieu, the evaluation aspect of the systems approach, and application of the systems approach to preventing disproportionate enrollment of Hispanics and Blacks in special education classes in Holyoke, Massachusetts. The…

Magnetic field decay in black widow pulsars

Science.gov (United States)

Mendes, Camile; de Avellar, Marcio G. B.; Horvath, J. E.; Souza, Rodrigo A. de; Benvenuto, O. G.; De Vito, M. A.

2018-04-01

We study in this work the evolution of the magnetic field in `redback-black widow' pulsars. Evolutionary calculations of these `spider' systems suggest that first the accretion operates in the redback stage, and later the companion star ablates matter due to winds from the recycled pulsar. It is generally believed that mass accretion by the pulsar results in a rapid decay of the magnetic field when compared to the rate of an isolated neutron star. We study the evolution of the magnetic field in black widow pulsars by solving numerically the induction equation using the modified Crank-Nicolson method with intermittent episodes of mass accretion on to the neutron star. Our results show that the magnetic field does not fall below a minimum value (`bottom field') in spite of the long evolution time of the black widow systems, extending the previous conclusions for much younger low-mass X-ray binary systems. We find that in this scenario, the magnetic field decay is dominated by the accretion rate, and that the existence of a bottom field is likely related to the fact that the surface temperature of the pulsar does not decay as predicted by the current cooling models. We also observe that the impurity of the pulsar crust is not a dominant factor in the decay of magnetic field for the long evolution time of black widow systems.

Black-boxing and cause-effect power

Science.gov (United States)

Albantakis, Larissa; Tononi, Giulio

2018-01-01

Reductionism assumes that causation in the physical world occurs at the micro level, excluding the emergence of macro-level causation. We challenge this reductionist assumption by employing a principled, well-defined measure of intrinsic cause-effect power–integrated information (Φ), and showing that, according to this measure, it is possible for a macro level to “beat” the micro level. Simple systems were evaluated for Φ across different spatial and temporal scales by systematically considering all possible black boxes. These are macro elements that consist of one or more micro elements over one or more micro updates. Cause-effect power was evaluated based on the inputs and outputs of the black boxes, ignoring the internal micro elements that support their input-output function. We show how black-box elements can have more common inputs and outputs than the corresponding micro elements, revealing the emergence of high-order mechanisms and joint constraints that are not apparent at the micro level. As a consequence, a macro, black-box system can have higher Φ than its micro constituents by having more mechanisms (higher composition) that are more interconnected (higher integration). We also show that, for a given micro system, one can identify local maxima of Φ across several spatiotemporal scales. The framework is demonstrated on a simple biological system, the Boolean network model of the fission-yeast cell-cycle, for which we identify stable local maxima during the course of its simulated biological function. These local maxima correspond to macro levels of organization at which emergent cause-effect properties of physical systems come into focus, and provide a natural vantage point for scientific inquiries. PMID:29684020

Black-boxing and cause-effect power.

Directory of Open Access Journals (Sweden)

William Marshall

2018-04-01

Full Text Available Reductionism assumes that causation in the physical world occurs at the micro level, excluding the emergence of macro-level causation. We challenge this reductionist assumption by employing a principled, well-defined measure of intrinsic cause-effect power-integrated information (Φ, and showing that, according to this measure, it is possible for a macro level to "beat" the micro level. Simple systems were evaluated for Φ across different spatial and temporal scales by systematically considering all possible black boxes. These are macro elements that consist of one or more micro elements over one or more micro updates. Cause-effect power was evaluated based on the inputs and outputs of the black boxes, ignoring the internal micro elements that support their input-output function. We show how black-box elements can have more common inputs and outputs than the corresponding micro elements, revealing the emergence of high-order mechanisms and joint constraints that are not apparent at the micro level. As a consequence, a macro, black-box system can have higher Φ than its micro constituents by having more mechanisms (higher composition that are more interconnected (higher integration. We also show that, for a given micro system, one can identify local maxima of Φ across several spatiotemporal scales. The framework is demonstrated on a simple biological system, the Boolean network model of the fission-yeast cell-cycle, for which we identify stable local maxima during the course of its simulated biological function. These local maxima correspond to macro levels of organization at which emergent cause-effect properties of physical systems come into focus, and provide a natural vantage point for scientific inquiries.

Bio-refinery system of DME or CH4 production from black liquor gasification in pulp mills

Energy Technology Data Exchange (ETDEWEB)

Raza, M.; Jinyue Yan (Dept. of Chemical Engineering and Technology/Energy Processes, Royal Institute of Technology, Stockholm (Sweden)). e-mail: rnaqvi@kth.se; Froeling, Morgan (Dept. of Chemical and Biological Engineering, Chalmers Univ. of Technology, Goeteborg (Sweden))

2009-07-01

The consumption of fossil fuels is rapidly increasing and there is an urgent need to develop technologies for renewable fuel production not only as alternatives but also as additional fuels. Efficient polygeneration of transportation fuels with heat and electricity is one of the innovative technologies which have potential to replace fossil fuels and mitigate climate change. Two potential technologies of producing dimethyl ether (DME) and methane (CH4) as alternative fuels integrated with black liquor gasification have been studied and compared in this paper. System performance is evaluated based on: (i) Comparison with the reference pulp mill, (ii) Fuel to product efficiency (FTPE) and (iii) Biofuel Production Potential (BPP). The comparison with the reference mill shows that black liquor to biofuel route will add a highly significant new revenue stream to the pulp industry. The results indicate a large potential of DME and CH4 production globally in terms of black liquor availability. BPP and FTPE of CH4 production is higher than DME due to more optimized integration with the pulping process and elimination of evaporation unit in the pulp mill

Binary black holes on a budget: simulations using workstations

International Nuclear Information System (INIS)

Marronetti, Pedro; Tichy, Wolfgang; Bruegmann, Bernd; Gonzalez, Jose; Hannam, Mark; Husa, Sascha; Sperhake, Ulrich

2007-01-01

Binary black hole simulations have traditionally been computationally very expensive: current simulations are performed in supercomputers involving dozens if not hundreds of processors, thus systematic studies of the parameter space of binary black hole encounters still seem prohibitive with current technology. Here we show how the multi-layered refinement level code BAM can be used on dual processor workstations to simulate certain binary black hole systems. BAM, based on the moving punctures method, provides grid structures composed of boxes of increasing resolution near the centre of the grid. In the case of binaries, the highest resolution boxes are placed around each black hole and they track them in their orbits until the final merger when a single set of levels surrounds the black hole remnant. This is particularly useful when simulating spinning black holes since the gravitational fields gradients are larger. We present simulations of binaries with equal mass black holes with spins parallel to the binary axis and intrinsic magnitude of S/m 2 = 0.75. Our results compare favourably to those of previous simulations of this particular system. We show that the moving punctures method produces stable simulations at maximum spatial resolutions up to M/160 and for durations of up to the equivalent of 20 orbital periods

Contemporary Black Theatre.

Science.gov (United States)

Thomas, Pearl

The distinguishable black theatre in America, mirroring a distinguishable black experience, is an artistic product which demands audience involvement. Both the Afro-American oral tradition and the art of gesture are integral aspects of black theatre. In addition, the tragedy found black theatre is not tragedy in the classic sense, as blacks feel…

Phosphate and organic fertilizer recovery from black water

NARCIS (Netherlands)

Tervahauta, T.H.

2014-01-01

In this thesis the integration of treatment systems for black and grey water was investigated to improve resource recovery within source-separated sanitation concepts. Special focus was set on phosphate and organic fertilizer recovery from vacuum collected black water. Currently, the soil

Prospects for Probing Strong Gravity with a Pulsar-Black Hole System

Science.gov (United States)

Wex, N.; Liu, K.; Eatough, R. P.; Kramer, M.; Cordes, J. M.; Lazio, T. J. W.

2012-01-01

The discovery of a pulsar (PSR) in orbit around a black hole (BH) is expected to provide a superb new probe of relativistic gravity and BH properties. Apart from a precise mass measurement for the BH, one could expect a clean verification of the dragging of space-time caused by the BH spin. In order to measure the quadrupole moment of the BH for testing the no-hair theorem of general relativity (GR), one has to hope for a sufficiently massive BH. In this respect, a PSR orbiting the super-massive BH in the center of our Galaxy would be the ultimate laboratory for gravity tests with PSRs. But even for gravity theories that predict the same properties for BHs as GR, a PSR-BH system would constitute an excellent test system, due to the high grade of asymmetry in the strong field properties of these two components. Here we highlight some of the potential gravity tests that one could expect from different PSR-BH systems.

Caged black holes: Black holes in compactified spacetimes. I. Theory

International Nuclear Information System (INIS)

Kol, Barak; Sorkin, Evgeny; Piran, Tsvi

2004-01-01

In backgrounds with compact dimensions there may exist several phases of black objects including a black hole and a black string. The phase transition between them raises questions and touches on fundamental issues such as topology change, uniqueness, and cosmic censorship. No analytic solution is known for the black hole, and moreover one can expect approximate solutions only for very small black holes, while phase transition physics happens when the black hole is large. Hence we turn to numerical solutions. Here some theoretical background to the numerical analysis is given, while the results will appear in a subsequent paper. The goals for a numerical analysis are set. The scalar charge and tension along the compact dimension are defined and used as improved order parameters which put both the black hole and the black string at finite values on the phase diagram. The predictions for small black holes are presented. The differential and the integrated forms of the first law are derived, and the latter (Smarr's formula) can be used to estimate the 'overall numerical error'. Field asymptotics and expressions for physical quantities in terms of the numerical values are supplied. The techniques include the 'method of equivalent charges', free energy, dimensional reduction, and analytic perturbation for small black holes

Primary black holes

International Nuclear Information System (INIS)

Novikov, I.; Polnarev, A.

1981-01-01

Proves are searched for of the formation of the so-called primary black holes at the very origin of the universe. The black holes would weigh less than 10 13 kg. The formation of a primary black hole is conditional on strong fluctuations of the gravitational field corresponding roughly to a half of the fluctuation maximally permissible by the general relativity theory. Only big fluctuations of the gravitational field can overcome the forces of the hot gas pressure and compress the originally expanding matter into a black hole. Low-mass black holes have a temperature exceeding that of the black holes formed from stars. A quantum process of particle formation, the so-called evaporation takes place in the strong gravitational field of a black hole. The lower the mass of the black hole, the shorter the evaporation time. The analyses of processes taking place during the evaporation of low-mass primary black holes show that only a very small proportion of the total mass of the matter in the universe could turn into primary black holes. (M.D.)

Heaviest Stellar Black Hole Discovered in Nearby Galaxy

Science.gov (United States)

2007-10-01

Astronomers have located an exceptionally massive black hole in orbit around a huge companion star. This result has intriguing implications for the evolution and ultimate fate of massive stars. The black hole is part of a binary system in M33, a nearby galaxy about 3 million light years from Earth. By combining data from NASA's Chandra X-ray Observatory and the Gemini telescope on Mauna Kea, Hawaii, the mass of the black hole, known as M33 X-7, was determined to be 15.7 times that of the Sun. This makes M33 X-7 the most massive stellar black hole known. A stellar black hole is formed from the collapse of the core of a massive star at the end of its life. Chandra X-ray Image of M33 X-7 Chandra X-ray Image of M33 X-7 "This discovery raises all sorts of questions about how such a big black hole could have been formed," said Jerome Orosz of San Diego State University, lead author of the paper appearing in the October 18th issue of the journal Nature. M33 X-7 orbits a companion star that eclipses the black hole every three and a half days. The companion star also has an unusually large mass, 70 times that of the Sun. This makes it the most massive companion star in a binary system containing a black hole. Hubble Optical Image of M33 X-7 Hubble Optical Image of M33 X-7 "This is a huge star that is partnered with a huge black hole," said coauthor Jeffrey McClintock of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass. "Eventually, the companion will also go supernova and then we'll have a pair of black holes." The properties of the M33 X-7 binary system - a massive black hole in a close orbit around a massive companion star - are difficult to explain using conventional models for the evolution of massive stars. The parent star for the black hole must have had a mass greater than the existing companion in order to have formed a black hole before the companion star. Gemini Optical Image of M33 X-7 Gemini Optical Image of M33 X-7 Such a massive star would

Two separate outflows in the dual supermassive black hole system NGC 6240.

Science.gov (United States)

Müller-Sánchez, F; Nevin, R; Comerford, J M; Davies, R I; Privon, G C; Treister, E

2018-04-01

Theoretical models and numerical simulations have established a framework of galaxy evolution in which galaxies merge and create dual supermassive black holes (with separations of one to ten kiloparsecs), which eventually sink into the centre of the merger remnant, emit gravitational waves and coalesce. The merger also triggers star formation and supermassive black hole growth, and gas outflows regulate the stellar content 1-3 . Although this theoretical picture is supported by recent observations of starburst-driven and supermassive black hole-driven outflows 4-6 , it remains unclear how these outflows interact with the interstellar medium. Furthermore, the relative contributions of star formation and black hole activity to galactic feedback remain unknown 7-9 . Here we report observations of dual outflows in the central region of the prototypical merger NGC 6240. We find a black-hole-driven outflow of [O III] to the northeast and a starburst-driven outflow of Hα to the northwest. The orientations and positions of the outflows allow us to isolate them spatially and study their properties independently. We estimate mass outflow rates of 10 and 75 solar masses per year for the Hα bubble and the [O III] cone, respectively. Their combined mass outflow is comparable to the star formation rate 10 , suggesting that negative feedback on star formation is occurring.

In situ characterization of the black pigment from parietal art of the Rouffignac Cave with a portable XRF system

International Nuclear Information System (INIS)

Sanoit, J. de; Chambellan, D.; Plassard, F.

2005-01-01

The Rouffignac cave in Dordogne (France) is a palaeolithic site which contains, among others, an important patrimony of cave art realized with black pigment (mammoths, bisons, woolly rhinoceros, horses, ibexes). Although no direct dating has ever been realized to date, the graphic works of this cave are generally connected to the Magdalenian age by cross-dating (stylistic comparison). For the first time, in situ non destructive analyses of this pigment were able to be made due to the use of a portable XRF system (X-Ray Fluorescence). The experimental set-up is mainly constituted with a small X-ray generator (Bullet TM 40 kV, Moxtek), a SDD detector (silicon drift detector, Rontec 1102) cooled by a Peltier cryostat and an optical system, the whole being connected to a portable system for acquisition of spectrometric data. The experimental spectra obtained on the three rhinoceros frieze, the horse over the flint nodule, the ten mammoths frieze and some animals of the Grand Plafond showed a systematic presence of manganese in all figures. This hypothesis had been already suggested by Graziosi in 1956 in the review 'La Nature' after a destructive analysis of a sample taken on one of the horses of the Grand Plafond. A Monte-Carlo simulation allowed a first quantitative approach in the analysis of the black pigment of the drawings. We can assess that the used manganese ore does not only result from a unique source because variable ratios of manganese, barium and iron were probed in the black pigment. None of the studied drawing was executed exclusively with black charcoal that would have made the selection of a sample suitable for radiocarbon dating less complicated. Additional non destructive in situ analysis using a portable PIXE set-up (Particles Induced X-ray Emission) equipped with a 210 Po as radiation source can be foreseen to allow the detection of elements with atomic numbers (Z) between 11 and 16 in the first layers of the black pigment, there where the XRF

77 FR 70423 - Black Bear Hydro Partners, LLC and Black Bear Development Holdings, LLC and Black Bear SO, LLC...

Science.gov (United States)

2012-11-26

... Bear Hydro Partners, LLC and Black Bear Development Holdings, LLC and Black Bear SO, LLC; Notice of..., 2012, Black Bear Hydro Partners, LLC, sole licensee (transferor) and Black Bear Development Holdings, LLC and Black Bear SO, LLC (transferees) filed an application for the partial the transfer of licenses...

Dancing with Black Holes

Science.gov (United States)

Aarseth, S. J.

2008-05-01

We describe efforts over the last six years to implement regularization methods suitable for studying one or more interacting black holes by direct N-body simulations. Three different methods have been adapted to large-N systems: (i) Time-Transformed Leapfrog, (ii) Wheel-Spoke, and (iii) Algorithmic Regularization. These methods have been tried out with some success on GRAPE-type computers. Special emphasis has also been devoted to including post-Newtonian terms, with application to moderately massive black holes in stellar clusters. Some examples of simulations leading to coalescence by gravitational radiation will be presented to illustrate the practical usefulness of such methods.

Coalescence of rotating black holes on Eguchi-Hanson space

International Nuclear Information System (INIS)

Matsuno, Ken; Ishihara, Hideki; Kimura, Masashi; Tomizawa, Shinya

2007-01-01

We obtain new charged rotating multi-black hole solutions on the Eguchi-Hanson space in the five-dimensional Einstein-Maxwell system with a Chern-Simons term and a positive cosmological constant. In the two-black holes case, these solutions describe the coalescence of two rotating black holes with the horizon topologies of S 3 into a single rotating black hole with the horizon topology of the lens space L(2;1)=S 3 /Z 2 . We discuss the differences in the horizon areas between our solutions and the two-centered Klemm-Sabra solutions which describe the coalescence of two rotating black holes with the horizon topologies of S 3 into a single rotating black hole with the horizon topology of S 3

Phase transition for black holes with scalar hair and topological black holes

International Nuclear Information System (INIS)

Myung, Yun Soo

2008-01-01

We study phase transitions between black holes with scalar hair and topological black holes in asymptotically anti-de Sitter spacetimes. As the ground state solutions, we introduce the non-rotating BTZ black hole in three dimensions and topological black hole with hyperbolic horizon in four dimensions. For the temperature matching only, we show that the phase transition between black hole with scalar hair (Martinez-Troncoso-Zanelli black hole) and topological black hole is second-order by using differences between two free energies. However, we do not identify what order of the phase transition between scalar and non-rotating BTZ black holes occurs in three dimensions, although there exists a possible decay of scalar black hole to non-rotating BTZ black hole

Gelationous Organism (Macrozooplankton in the Black Sea and Effects

Directory of Open Access Journals (Sweden)

Zekiye BİRİNCİ ÖZDEMİR

2017-06-01

Full Text Available It is important problem as ecological, invasion of the marine systems by the gelatinous organism that distributed natural balance. Black Sea ecosystem has been changed critical level by the some causes such as marine pollution, eutrophication, climate change, overfishing, invasive gelatinous organisms. Effect in the ecosystem of gelatinous organisms occurred especially with collapsed of Black Sea anchovy (Engraulis encrasicolus stock and fishery production. In the study, gelatinous organism species, important for Black sea, and its effects in the Black sea ecosystem were presented.

Surface geometry of 5D black holes and black rings

International Nuclear Information System (INIS)

Frolov, Valeri P.; Goswami, Rituparno

2007-01-01

We discuss geometrical properties of the horizon surface of five-dimensional rotating black holes and black rings. Geometrical invariants characterizing these 3D geometries are calculated. We obtain a global embedding of the 5D rotating black horizon surface into a flat space. We also describe the Kaluza-Klein reduction of the black ring solution (along the direction of its rotation) which, though it is nakedly singular, relates this solution to the 4D metric of a static black hole distorted by the presence of external scalar (dilaton) and vector ('electromagnetic') fields. The properties of the reduced black hole horizon and its embedding in E 3 are briefly discussed

Ruppeiner theory of black hole thermodynamics

International Nuclear Information System (INIS)

Aman, Jan E; Bedford, James; Grumiller, Daniel; Pidokrajt, Narit; Ward, John

2007-01-01

The Ruppeiner metric as determined by the Hessian of the Gibbs surface provides a geometric description of thermodynamic systems in equilibrium. An interesting example is a black hole in equilibrium with its own Hawking radiation. In this article, we present results from the Ruppeiner study of various black hole families from different gravity theories e.g. 2D dilaton gravity, BTZ, general relativity and higher-dimensional Einstein-Maxwell gravity

Black silicon solar cells with black bus-bar strings

DEFF Research Database (Denmark)

Davidsen, Rasmus Schmidt; Tang, Peter Torben; Mizushima, Io

2016-01-01

We present the combination of black silicon texturing and blackened bus-bar strings as a potential method for obtaining all-black solar panels, while using conventional, front-contacted solar cells. Black silicon was realized by maskless reactive ion etching resulting in total, average reflectance...... below 0.5% across a 156x156 mm2 silicon wafer. Four different methods to obtain blackened bus-bar strings were compared with respect to reflectance, and two of these methods (i.e., oxidized copper and etched solder) were used to fabricate functional allblack solar 9-cell panels. The black bus-bars (e.......g., by oxidized copper) have a reflectance below 3% in the entire visible wavelength range. The combination of black silicon cells and blackened bus-bars results in aesthetic, all-black panels based on conventional, front-contacted solar cells without compromising efficiency....

Micro black holes and the democratic transition

International Nuclear Information System (INIS)

Dvali, Gia; Pujolas, Oriol

2009-01-01

Unitarity implies that the evaporation of microscopic quasiclassical black holes cannot be universal in different particle species. This creates a puzzle, since it conflicts with the thermal nature of quasiclassical black holes, according to which all of the species should see the same horizon and be produced with the same Hawking temperatures. We resolve this puzzle by showing that for the microscopic black holes, on top of the usual quantum evaporation time, there is a new time scale which characterizes a purely classical process during which the black hole loses the ability to differentiate among the species and becomes democratic. We demonstrate this phenomenon in a well-understood framework of large extra dimensions, with a number of parallel branes. An initially nondemocratic black hole is the one localized on one of the branes, with its high-dimensional Schwarzschild radius being much shorter than the interbrane distance. Such a black hole seemingly cannot evaporate into the species localized on the other branes that are beyond its reach. We demonstrate that in reality the system evolves classically in time, in such a way that the black hole accretes the neighboring branes. The end result is a completely democratic static configuration, in which all of the branes share the same black hole and all of the species are produced with the same Hawking temperature. Thus, just like their macroscopic counterparts, the microscopic black holes are universal bridges to the hidden sector physics.

Holographic complexity of cold hyperbolic black holes

International Nuclear Information System (INIS)

Barbón, José L.F.; Martín-García, Javier

2015-01-01

AdS black holes with hyperbolic horizons provide strong-coupling descriptions of thermal CFT states on hyperboloids. The low-temperature limit of these systems is peculiar. In this note we show that, in addition to a large ground state degeneracy, these states also have an anomalously large holographic complexity, scaling logarithmically with the temperature. We speculate on whether this fact generalizes to other systems whose extreme infrared regime is formally controlled by Conformal Quantum Mechanics, such as various instances of near-extremal charged black holes.

Stability of black holes based on horizon thermodynamics

Directory of Open Access Journals (Sweden)

Meng-Sen Ma

2015-12-01

Full Text Available On the basis of horizon thermodynamics we study the thermodynamic stability of black holes constructed in general relativity and Gauss–Bonnet gravity. In the framework of horizon thermodynamics there are only five thermodynamic variables E, P, V, T, S. It is not necessary to consider concrete matter fields, which may contribute to the pressure of black hole thermodynamic system. In non-vacuum cases, we can derive the equation of state, P=P(V,T. According to the requirements of stable equilibrium in conventional thermodynamics, we start from these thermodynamic variables to calculate the heat capacity at constant pressure and Gibbs free energy and analyze the local and global thermodynamic stability of black holes. It is shown that P>0 is the necessary condition for black holes in general relativity to be thermodynamically stable, however this condition cannot be satisfied by many black holes in general relativity. For black hole in Gauss–Bonnet gravity negative pressure can be feasible, but only local stable black hole exists in this case.

Exp(1076) Shades of Black: Aspects of Black Hole Microstates

Science.gov (United States)

Vasilakis, Orestis

In this thesis we examine smooth supergravity solutions known as "microstate geometries". These solutions have neither a horizon, nor a singularity, yet they have the same asymptotic structure and conserved charges as black holes. Specifically we study supersymmetric and extremal non-supersymmetric solutions. The goal of this program is to construct enough microstates to account for the correct scaling behavior of the black hole entropy with respect to the charges within the supergravity approximation. For supersymmetric systems that are ⅛-BPS, microstate geometries account so far only for Q5/4 of the total entropy S ˜ Q3/2, while for non-supersymmetric systems the known microstate geometries are sporadic. For the supersymmetric case we construct solutions with three and four charges. Five-dimensional systems with three and four charges are ⅛-BPS. Thus they admit macroscopic horizons making the supergravity approximation valid. For the three-charge case we present some steps towards the construction of the superstratum, a microstate geometry depending on arbitrary functions of two variables, which is expected to provide the necessary entropy for this class of solutions. Specifically we construct multiple concentric solutions with three electric and two dipole magnetic charges which depend on arbitrary functions of two variables and examine their properties. These solutions have no KKM charge and thus are singular. For the four-charge case we construct microstate geometries by extending results available in the literature for three charges. We find smooth solutions in terms of bubbled geometries with ambipolar Gibbons-Hawking base space and by constructing the relevant supertubes. In the non-supersymmetric case we work with a three-charge system of extremal black holes known as almost-BPS, which provides a controlled way of breaking sypersymmetry. By using supertubes we construct the first systematic example of a family of almost-BPS microstate geometries and

Formation of the black-hole binary M33 X-7 through mass exchange in a tight massive system.

Science.gov (United States)

Valsecchi, Francesca; Glebbeek, Evert; Farr, Will M; Fragos, Tassos; Willems, Bart; Orosz, Jerome A; Liu, Jifeng; Kalogera, Vassiliki

2010-11-04

The X-ray source M33 X-7 in the nearby galaxy Messier 33 is among the most massive X-ray binary stellar systems known, hosting a rapidly spinning, 15.65M(⊙) black hole orbiting an underluminous, 70M(⊙) main-sequence companion in a slightly eccentric 3.45-day orbit (M(⊙), solar mass). Although post-main-sequence mass transfer explains the masses and tight orbit, it leaves unexplained the observed X-ray luminosity, the star's underluminosity, the black hole's spin and the orbital eccentricity. A common envelope phase, or rotational mixing, could explain the orbit, but the former would lead to a merger and the latter to an overluminous companion. A merger would also ensue if mass transfer to the black hole were invoked for its spin-up. Here we report simulations of evolutionary tracks which reveal that if M33 X-7 started as a primary body of 85M(⊙)-99M(⊙) and a secondary body of 28M(⊙)-32M(⊙), in a 2.8-3.1-d orbit, its observed properties can be consistently explained. In this model, the main-sequence primary transfers part of its envelope to the secondary and loses the rest in a wind; it ends its life as a ∼16M(⊙) helium star with an iron-nickel core that collapses to a black hole (with or without an accompanying supernova). The release of binding energy, and possibly collapse asymmetries, 'kick' the nascent black hole into an eccentric orbit. Wind accretion explains the X-ray luminosity, and the black-hole spin can be natal.

Distortion of Schwarzschild-anti-de Sitter black holes to black strings

International Nuclear Information System (INIS)

Tomimatsu, Akira

2005-01-01

Motivated by the existence of black holes with various topologies in four-dimensional spacetimes with a negative cosmological constant, we study axisymmetric static solutions describing any large distortions of Schwarzschild-anti-de Sitter black holes parametrized by the mass m. Under the approximation such that m is much larger than the anti-de Sitter radius, it is found that a cylindrically symmetric black string is obtained as a special limit of distorted spherical black holes. Such a prolonged distortion of the event horizon connecting a Schwarzschild-anti-de Sitter black hole to a black string is allowed without violating both the usual black hole thermodynamics and the hoop conjecture for the horizon circumference

An Integrative Database System of Agro-Ecology for the Black Soil Region of China

Directory of Open Access Journals (Sweden)

Cuiping Ge

2007-12-01

Full Text Available The comprehensive database system of the Northeast agro-ecology of black soil (CSDB_BL is user-friendly software designed to store and manage large amounts of data on agriculture. The data was collected in an efficient and systematic way by long-term experiments and observations of black land and statistics information. It is based on the ORACLE database management system and the interface is written in PB language. The database has the following main facilities:(1 runs on Windows platforms; (2 facilitates data entry from *.dbf to ORACLE or creates ORACLE tables directly; (3has a metadata facility that describes the methods used in the laboratory or in the observations; (4 data can be transferred to an expert system for simulation analysis and estimates made by Visual C++ and Visual Basic; (5 can be connected with GIS, so it is easy to analyze changes in land use ; and (6 allows metadata and data entity to be shared on the internet. The following datasets are included in CSDB_BL: long-term experiments and observations of water, soil, climate, biology, special research projects, and a natural resource survey of Hailun County in the 1980s; images from remote sensing, graphs of vectors and grids, and statistics from Northeast of China. CSDB_BL can be used in the research and evaluation of agricultural sustainability nationally, regionally, or locally. Also, it can be used as a tool to assist the government in planning for agricultural development. Expert systems connected with CSDB_BL can give farmers directions for farm planting management.

Low-mass black holes as the remnants of primordial black hole formation.

Science.gov (United States)

Greene, Jenny E

2012-01-01

Bridging the gap between the approximately ten solar mass 'stellar mass' black holes and the 'supermassive' black holes of millions to billions of solar masses are the elusive 'intermediate-mass' black holes. Their discovery is key to understanding whether supermassive black holes can grow from stellar-mass black holes or whether a more exotic process accelerated their growth soon after the Big Bang. Currently, tentative evidence suggests that the progenitors of supermassive black holes were formed as ∼10(4)-10(5) M(⊙) black holes via the direct collapse of gas. Ongoing searches for intermediate-mass black holes at galaxy centres will help shed light on this formation mechanism.

Gauge-Gravity Duality and the Black Hole Interior

Science.gov (United States)

Marolf, Donald; Polchinski, Joseph

2013-10-01

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.

Teaching Celia in the Age of Black Lives Matter

Directory of Open Access Journals (Sweden)

Brandon R. Byrd

2016-11-01

Full Text Available The emergence of Black Lives Matter has introduced a language of black liberation to a new generation of students. In doing so, it has provided an opportunity for historical study. Teacher-scholars can and should take advantage of the renewed interest in systemic threats to black life in the United States when teaching about past victims of state-sanctioned violence including Celia, an enslaved teenager executed for killing her master after years of sexual abuse. In doing so, they can not only draw useful connections between the past and present but also lay the foundations for a more meaningful study of black radicalism and black resistance in the United States.

A cellphone based system for large-scale monitoring of black carbon

Science.gov (United States)

Ramanathan, N.; Lukac, M.; Ahmed, T.; Kar, A.; Praveen, P. S.; Honles, T.; Leong, I.; Rehman, I. H.; Schauer, J. J.; Ramanathan, V.

2011-08-01

Black carbon aerosols are a major component of soot and are also a major contributor to global and regional climate change. Reliable and cost-effective systems to measure near-surface black carbon (BC) mass concentrations (hereafter denoted as [BC]) globally are necessary to validate air pollution and climate models and to evaluate the effectiveness of BC mitigation actions. Toward this goal we describe a new wireless, low-cost, ultra low-power, BC cellphone based monitoring system (BC_CBM). BC_CBM integrates a Miniaturized Aerosol filter Sampler (MAS) with a cellphone for filter image collection, transmission and image analysis for determining [BC] in real time. The BC aerosols in the air accumulate on the MAS quartz filter, resulting in a coloration of the filter. A photograph of the filter is captured by the cellphone camera and transmitted by the cellphone to the analytics component of BC_CBM. The analytics component compares the image with a calibrated reference scale (also included in the photograph) to estimate [BC]. We demonstrate with field data collected from vastly differing environments, ranging from southern California to rural regions in the Indo-Gangetic plains of Northern India, that the total BC deposited on the filter is directly and uniquely related to the reflectance of the filter in the red wavelength, irrespective of its source or how the particles were deposited. [BC] varied from 0.1 to 1 μg m -3 in Southern California and from 10 to 200 μg m -3 in rural India in our field studies. In spite of the 3 orders of magnitude variation in [BC], the BC_CBM system was able to determine the [BC] well within the experimental error of two independent reference instruments for both indoor air and outdoor ambient air. Accurate, global-scale measurements of [BC] in urban and remote rural locations, enabled by the wireless, low-cost, ultra low-power operation of BC_CBM, will make it possible to better capture the large spatial and temporal variations in

Dance of Two Monster Black Holes

Science.gov (United States)

Kohler, Susanna

2016-03-01

than two dozen ground-based optical telescopes and the Swift/XRT satellite to observe OJ 287 in this time frame. The outburst occurred right on schedule, peaking on 5 December 2015, and the results of the observing campaign are now presented in a study led by Mauri Valtonen (University of Turku).Optical photometry of OJ 287 from October to December 2015, showing the outburst that resulted from the secondary black hole crossing the disk. [Valtonen et al. 2016]Because the secondary black holes orbit is affected by the spin of the primary black hole, Valtonen and collaborators were able to use the timing of the outburst to measure the spin of OJ 287s primary black hole to remarkably high precision. They find that its Kerr parameter is 0.313 0.01 which means its spinning at about a third of the maximum rate allowed by general relativity.The outburst timing also confirmed several general-relativistic properties of the system, including its loss of energy to gravitational waves. Remarkably, the energy lost as the secondary black hole punches through the accretion disk is still ten thousand times smaller than the amount of energy it loses through gravitational waves!The observations from this outburst have provided important black-hole measurements and tests of general relativity which are especially relevant in this new era of gravitational wave detections. And we may be able to perform still more tests on the secondarys next pass through the disk, which should occur in 2019.BonusCheck out this awesome animation of the orbits in a system similar to OJ 287! The secondarys orbit precesses around the primary due to general-relativistic effects. The sound you hearis an audio representation of the increasing frequency as the two black holes inspiral. You can find more information about this animation here. [Steve Drasco Curt Cutler]CitationM. J. Valtonen et al 2016 ApJ 819 L37. doi:10.3847/2041-8205/819/2/L37

Biodecolorization of Reactive Black 5 by laccasemediator system ...

African Journals Online (AJOL)

Reactive azo dyes are widely used as textile colorants, typically for cotton dyeing, due to their variety of color shades, and minimal energy consumption. In the present study, commercial laccase from Trametes versicolor was used for the biodecolorization of Reactive Black 5 (RB-5) dye using different redox mediators viz, ...

THE MASS DISTRIBUTION OF STELLAR-MASS BLACK HOLES

International Nuclear Information System (INIS)

Farr, Will M.; Sravan, Niharika; Kalogera, Vicky; Cantrell, Andrew; Kreidberg, Laura; Bailyn, Charles D.; Mandel, Ilya

2011-01-01

We perform a Bayesian analysis of the mass distribution of stellar-mass black holes using the observed masses of 15 low-mass X-ray binary systems undergoing Roche lobe overflow and 5 high-mass, wind-fed X-ray binary systems. Using Markov Chain Monte Carlo calculations, we model the mass distribution both parametrically—as a power law, exponential, Gaussian, combination of two Gaussians, or log-normal distribution—and non-parametrically—as histograms with varying numbers of bins. We provide confidence bounds on the shape of the mass distribution in the context of each model and compare the models with each other by calculating their relative Bayesian evidence as supported by the measurements, taking into account the number of degrees of freedom of each model. The mass distribution of the low-mass systems is best fit by a power law, while the distribution of the combined sample is best fit by the exponential model. This difference indicates that the low-mass subsample is not consistent with being drawn from the distribution of the combined population. We examine the existence of a 'gap' between the most massive neutron stars and the least massive black holes by considering the value, M 1% , of the 1% quantile from each black hole mass distribution as the lower bound of black hole masses. Our analysis generates posterior distributions for M 1% ; the best model (the power law) fitted to the low-mass systems has a distribution of lower bounds with M 1% >4.3 M sun with 90% confidence, while the best model (the exponential) fitted to all 20 systems has M 1% >4.5 M sun with 90% confidence. We conclude that our sample of black hole masses provides strong evidence of a gap between the maximum neutron star mass and the lower bound on black hole masses. Our results on the low-mass sample are in qualitative agreement with those of Ozel et al., although our broad model selection analysis more reliably reveals the best-fit quantitative description of the underlying mass

Characterizing Black Hole Mergers

Science.gov (United States)

Baker, John; Boggs, William Darian; Kelly, Bernard

2010-01-01

Binary black hole mergers are a promising source of gravitational waves for interferometric gravitational wave detectors. Recent advances in numerical relativity have revealed the predictions of General Relativity for the strong burst of radiation generated in the final moments of binary coalescence. We explore features in the merger radiation which characterize the final moments of merger and ringdown. Interpreting the waveforms in terms of an rotating implicit radiation source allows a unified phenomenological description of the system from inspiral through ringdown. Common features in the waveforms allow quantitative description of the merger signal which may provide insights for observations large-mass black hole binaries.

Black Culture

Directory of Open Access Journals (Sweden)

Angela Khristin Brown

2013-07-01

Full Text Available The migration of blacks in North America through slavery became united.  The population of blacks past downs a tradition of artist through art to native born citizens. The art tradition involved telling stories to each generation in black families. The black culture elevated by tradition created hope to determine their personal freedom to escape from poverty of enslavement and to establish a way of life through tradition. A way of personal freedoms was through getting a good education that lead to a better foundation and a better way of life.

Black Holes Versus Firewalls and Thermo-Field Dynamics

Science.gov (United States)

Chowdhury, Borun D.

2013-09-01

In this paper, we examine the implications of the ongoing black holes versus firewalls debate for the thermo-field dynamics of black holes by analyzing a conformal field theory (CFT) in a thermal state in the context of anti-de Sitter/CFT. We argue that the thermo-field doubled copy of the thermal CFT should be thought of not as a fictitious system, but as the image of the CFT in the heat bath. In case of strong coupling between the CFT and the heat bath, this image allows for free infall through the horizon and the system is described by a black hole. Conversely, firewalls are the appropriate dual description in case of weak interaction of the CFT with its heat bath.

Energy flux through the horizon in the black hole-domain wall systems

International Nuclear Information System (INIS)

Stojkovic, Dejan

2004-01-01

We study various configurations in which a domain wall (or cosmic string), described by the Nambu-Goto action, is embedded in a background space-time of a black hole in (3+1) and higher dimensional models. We calculate energy fluxes through the black hole horizon. In the simplest case, when a static domain wall enters the horizon of a static black hole perpendicularly, the energy flux is zero. In more complicated situations, where parameters which describe the domain wall surface are time and position dependent, the flux is non-vanishing is principle. These results are of importance in various conventional cosmological models which accommodate the existence of domain walls and strings and also in brane world scenarios. (author)

Magnetized black holes and black rings in the higher dimensional dilaton gravity

International Nuclear Information System (INIS)

Yazadjiev, Stoytcho S.

2006-01-01

In this paper we consider magnetized black holes and black rings in the higher dimensional dilaton gravity. Our study is based on exact solutions generated by applying a Harrison transformation to known asymptotically flat black hole and black ring solutions in higher dimensional spacetimes. The explicit solutions include the magnetized version of the higher dimensional Schwarzschild-Tangherlini black holes, Myers-Perry black holes, and five-dimensional (dipole) black rings. The basic physical quantities of the magnetized objects are calculated. We also discuss some properties of the solutions and their thermodynamics. The ultrarelativistic limits of the magnetized solutions are briefly discussed and an explicit example is given for the D-dimensional magnetized Schwarzschild-Tangherlini black holes

Black Hole Horizons and Bose-Einstein Condensation

CERN Document Server

Ferrari, Frank

2016-01-01

Consider a particle sitting at a fixed position outside of a stable black hole. If the system is heated up, the black hole horizon grows and there should exist a critical temperature above which the particle enters the black hole interior. We solve a simple model describing exactly this situation: a large N matrix quantum mechanics modeling a fixed D-particle in a black hole background. We show that indeed a striking phenomenon occurs: above some critical temperature, there is a non-perturbative Bose-Einstein condensation of massless strings. The transition, even though precisely defined by the presence of the condensate, cannot be sharply detected by measurements made in a finite amount of time. The order parameter is fundamentally non-local in time and corresponds to infinite-time correlations.

Orbit classification in an equal-mass non-spinning binary black hole pseudo-Newtonian system

Science.gov (United States)

Zotos, Euaggelos E.; Dubeibe, F. L.; González, Guillermo A.

2018-04-01

The dynamics of a test particle in a non-spinning binary black hole system of equal masses is numerically investigated. The binary system is modeled in the context of the pseudo-Newtonian circular restricted three-body problem, such that the primaries are separated by a fixed distance and move in a circular orbit around each other. In particular, the Paczyński-Wiita potential is used for describing the gravitational field of the two non-Newtonian primaries. The orbital properties of the test particle are determined through the classification of the initial conditions of the orbits, using several values of the Jacobi constant, in the Hill's regions of possible motion. The initial conditions are classified into three main categories: (i) bounded, (ii) escaping and (iii) displaying close encounters. Using the smaller alignment index (SALI) chaos indicator, we further classify bounded orbits into regular, sticky or chaotic. To gain a complete view of the dynamics of the system, we define grids of initial conditions on different types of two-dimensional planes. The orbital structure of the configuration plane, along with the corresponding distributions of the escape and collision/close encounter times, allow us to observe the transition from the classical Newtonian to the pseudo-Newtonian regime. Our numerical results reveal a strong dependence of the properties of the considered basins with the Jacobi constant as well as with the Schwarzschild radius of the black holes.

No-Hair Theorem for Black Holes in Astrophysical Environments

Science.gov (United States)

Gürlebeck, Norman

2015-04-01

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.

No-hair theorem for black holes in astrophysical environments.

Science.gov (United States)

Gürlebeck, Norman

2015-04-17

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.

Distinguishing spin-aligned and isotropic black hole populations with gravitational waves.

Science.gov (United States)

Farr, Will M; Stevenson, Simon; Miller, M Coleman; Mandel, Ilya; Farr, Ben; Vecchio, Alberto

2017-08-23

The direct detection of gravitational waves from merging binary black holes opens up a window into the environments in which binary black holes form. One signature of such environments is the angular distribution of the black hole spins. Binary systems that formed through dynamical interactions between already-compact objects are expected to have isotropic spin orientations (that is, the spins of the black holes are randomly oriented with respect to the orbit of the binary system), whereas those that formed from pairs of stars born together are more likely to have spins that are preferentially aligned with the orbit. The best-measured combination of spin parameters for each of the four likely binary black hole detections GW150914, LVT151012, GW151226 and GW170104 is the 'effective' spin. Here we report that, if the magnitudes of the black hole spins are allowed to extend to high values, the effective spins for these systems indicate a 0.015 odds ratio against an aligned angular distribution compared to an isotropic one. When considering the effect of ten additional detections, this odds ratio decreases to 2.9 × 10 -7 against alignment. The existing preference for either an isotropic spin distribution or low spin magnitudes for the observed systems will be confirmed (or overturned) confidently in the near future.

Black hole based quantum computing in labs and in the sky

Energy Technology Data Exchange (ETDEWEB)

Dvali, Gia [Arnold Sommerfeld Center for Theoretical Physics, Department fuer Physik, Ludwig-Maximilians-Universitaet Muenchen (Germany); Max-Planck-Institut fuer Physik, Muenchen (Germany); Center for Cosmology and Particle Physics, Department of Physics, New York University, New York, NY (United States); Panchenko, Mischa [Arnold Sommerfeld Center for Theoretical Physics, Department fuer Physik, Ludwig-Maximilians-Universitaet Muenchen (Germany)

2016-08-15

Analyzing some well established facts, we give a model-independent parameterization of black hole quantum computing in terms of a set of macro and micro quantities and their relations. These include the relations between the extraordinarily-small energy gap of black hole qubits and important time-scales of information-processing, such as, scrambling time and Page's time. We then show, confirming and extending previous results, that other systems of nature with identical quantum informatics features are attractive Bose-Einstein systems at the critical point of quantum phase transition. Here we establish a complete isomorphy between the quantum computational properties of these two systems. In particular, we show that the quantum hair of a critical condensate is strikingly similar to the quantum hair of a black hole. Irrespectively whether one takes the similarity between the two systems as a remarkable coincidence or as a sign of a deeper underlying connection, the following is evident. Black holes are not unique in their way of quantum information processing and we can manufacture black hole based quantum computers in labs by taking advantage of quantum criticality. (copyright 2016 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Black hole based quantum computing in labs and in the sky

International Nuclear Information System (INIS)

Dvali, Gia; Panchenko, Mischa

2016-01-01

Analyzing some well established facts, we give a model-independent parameterization of black hole quantum computing in terms of a set of macro and micro quantities and their relations. These include the relations between the extraordinarily-small energy gap of black hole qubits and important time-scales of information-processing, such as, scrambling time and Page's time. We then show, confirming and extending previous results, that other systems of nature with identical quantum informatics features are attractive Bose-Einstein systems at the critical point of quantum phase transition. Here we establish a complete isomorphy between the quantum computational properties of these two systems. In particular, we show that the quantum hair of a critical condensate is strikingly similar to the quantum hair of a black hole. Irrespectively whether one takes the similarity between the two systems as a remarkable coincidence or as a sign of a deeper underlying connection, the following is evident. Black holes are not unique in their way of quantum information processing and we can manufacture black hole based quantum computers in labs by taking advantage of quantum criticality. (copyright 2016 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Black Holes and Galactic Density Cusps III From Black Hole to Bulge

CERN Document Server

Henriksen, Richard N; Macmillan, Joseph D

2011-01-01

Aims. In this paper we continue our study of density cusps that may contain central black holes. Methods. We recall our attempts to use distribution functions with a memory of self-similar relaxation, but mostly they apply only in restricted regions of the global system. We are forced to consider related distribution functions that are steady but not self-similar. Results. One remarkably simple distribution function that has a filled loss cone describes a bulge that transits from a near black hole domain to an outer 'zero flux' regime where$\\rho\\propto r^{-7/4}$. The transition passes from an initial inverse square profile through a region having a 1/r density profile. The structure is likely to be developed at an early stage in the growth of a galaxy. A central black hole is shown to grow exponentially in this background with an e-folding time of a few million years. Conclusions. We derive our results from first principles, using only the angular momentum integral in spherical symmetry. The initial relaxatio...

The Geometry of Black Hole Singularities

Directory of Open Access Journals (Sweden)

Ovidiu Cristinel Stoica

2014-01-01

Full Text Available Recent results show that important singularities in General Relativity can be naturally described in terms of finite and invariant canonical geometric objects. Consequently, one can write field equations which are equivalent to Einstein's at nonsingular points but, in addition remain well-defined and smooth at singularities. The black hole singularities appear to be less undesirable than it was thought, especially after we remove the part of the singularity due to the coordinate system. Black hole singularities are then compatible with global hyperbolicity and do not make the evolution equations break down, when these are expressed in terms of the appropriate variables. The charged black holes turn out to have smooth potential and electromagnetic fields in the new atlas. Classical charged particles can be modeled, in General Relativity, as charged black hole solutions. Since black hole singularities are accompanied by dimensional reduction, this should affect Feynman's path integrals. Therefore, it is expected that singularities induce dimensional reduction effects in Quantum Gravity. These dimensional reduction effects are very similar to those postulated in some approaches to make Quantum Gravity perturbatively renormalizable. This may provide a way to test indirectly the effects of singularities, otherwise inaccessible.

Topological transport from a black hole

Directory of Open Access Journals (Sweden)

Dmitry Melnikov

2018-03-01

Full Text Available In this paper the low temperature zero-frequency transport in a 2+1-dimensional theory dual to a dyonic black hole is discussed. It is shown that transport exhibits topological features: the transverse electric and heat conductivities satisfy the Wiedemann–Franz law of free electrons; the direct heat conductivity is measured in units of the central charge of CFT2+1, while the direct electric conductivity vanishes; the thermoelectric conductivity is non-zero at vanishing temperature, while the O(T behavior, controlled by the Mott relation, is subleading. Provided that the entropy of the black hole, and the dual system, is non-vanishing at T=0, the observations indicate that the dyonic black hole describes a ħ→0 limit of a highly degenerate topological state, in which the black hole charge measures the density of excited non-abelian quasiparticles. The holographic description gives further evidence that non-abelian nature of quasiparticles can be determined by the low temperature behavior of the thermoelectric transport.

Hawking temperatures of Myers-Perry black holes from tunneling

International Nuclear Information System (INIS)

Ma Zhengze

2009-01-01

Using the tunneling method of Parikh and Wilczek, we derive the Hawking temperature of a general higher-dimensional rotating black hole which is equal to its surface gravity on the horizon divided by 2π. In order to eliminate the motion on the rotating degrees of freedom of a tunneling particle from a higher-dimensional rotating black hole, we choose a reference system that is co-rotating with the black hole horizon. Then, we apply the obtained result to the Myers-Perry higher-dimensional asymptotically flat black holes and reproduce their Hawking temperatures using the tunneling approach.

Microscopic origin of black hole reentrant phase transitions

Science.gov (United States)

Zangeneh, M. Kord; Dehyadegari, A.; Sheykhi, A.; Mann, R. B.

2018-04-01

Understanding the microscopic behavior of the black hole ingredients has been one of the important challenges in black hole physics during the past decades. In order to shed some light on the microscopic structure of black holes, in this paper, we explore a recently observed phenomenon for black holes namely reentrant phase transition, by employing the Ruppeiner geometry. Interestingly enough, we observe two properties for the phase behavior of small black holes that leads to reentrant phase transition. They are correlated and they are of the interaction type. For the range of pressure in which the system underlies reentrant phase transition, it transits from the large black holes phase to the small one which possesses higher correlation than the other ranges of pressures. On the other hand, the type of interaction between small black holes near the large/small transition line differs for usual and reentrant phase transitions. Indeed, for the usual case, the dominant interaction is repulsive whereas for the reentrant case we encounter an attractive interaction. We show that in the reentrant phase transition case, the small black holes behave like a bosonic gas whereas in the usual phase transition case, they behave like a quantum anyon gas.

Stellar-mass black holes and ultraluminous x-ray sources.

Science.gov (United States)

Fender, Rob; Belloni, Tomaso

2012-08-03

We review the likely population, observational properties, and broad implications of stellar-mass black holes and ultraluminous x-ray sources. We focus on the clear empirical rules connecting accretion and outflow that have been established for stellar-mass black holes in binary systems in the past decade and a half. These patterns of behavior are probably the keys that will allow us to understand black hole feedback on the largest scales over cosmological time scales.

Difference Principle and Black-hole Thermodynamics

OpenAIRE

Martin, Pete

2009-01-01

The heuristic principle that constructive dynamics may arise wherever there exists a difference, or gradient, is discussed. Consideration of black-hole entropy appears to provide a clue for setting a lower bound on any extensive measure of such collective system difference, or potential to give rise to constructive dynamics. It is seen that the second-power dependence of black-hole entropy on mass is consistent with the difference principle, while consideration of Hawking radiation forces one...

The Black Lives Matter Movement and Historically Black Colleges and Universities

Science.gov (United States)

Gasman, Marybeth

2017-01-01

This article looks at the Black Lives Matter Movement and Historically Black Colleges and Universities. Historically Black Colleges and Universities (HBCUs) continue to play an important role in society. However, what the Black Lives Matter movement shows consistently is that predominantly White institutions need to change, to step up and embrace…

Black holes in a box: Toward the numerical evolution of black holes in AdS space-times

International Nuclear Information System (INIS)

Witek, Helvi; Nerozzi, Andrea; Cardoso, Vitor; Herdeiro, Carlos; Sperhake, Ulrich; Zilhao, Miguel

2010-01-01

The evolution of black holes in ''confining boxes'' is interesting for a number of reasons, particularly because it mimics the global structure of anti-de Sitter geometries. These are nonglobally hyperbolic space-times and the Cauchy problem may only be well defined if the initial data are supplemented by boundary conditions at the timelike conformal boundary. Here, we explore the active role that boundary conditions play in the evolution of a bulk black hole system, by imprisoning a black hole binary in a box with mirrorlike boundary conditions. We are able to follow the post-merger dynamics for up to two reflections off the boundary of the gravitational radiation produced in the merger. We estimate that about 15% of the radiation energy is absorbed by the black hole per interaction, whereas transfer of angular momentum from the radiation to the black hole is observed only in the first interaction. We discuss the possible role of superradiant scattering for this result. Unlike the studies with outgoing boundary conditions, both of the Newman-Penrose scalars Ψ 4 and Ψ 0 are nontrivial in our setup, and we show that the numerical data verifies the expected relations between them.

The superradiant instability regime of the spinning Kerr black hole

Science.gov (United States)

Hod, Shahar

2016-07-01

Spinning Kerr black holes are known to be superradiantly unstable to massive scalar perturbations. We here prove that the instability regime of the composed Kerr-black-hole-massive-scalar-field system is bounded from above by the dimensionless inequality Mμ r+ is the dimensionless ratio between the horizon radii of the black hole. It is further shown that this analytically derived upper bound on the superradiant instability regime of the spinning Kerr black hole agrees with recent numerical computations of the instability resonance spectrum.

VBSM: VCC-Based Black Box Service Model with Enhanced Data Integrity

OpenAIRE

Kang, Won; Lee, Jae; Park, Jong

2014-01-01

Recently, intelligent transport systems have been applied to vehicle cloud environments. Such technology is especially useful for the systematic management of road traffic. Moreover, automobiles are increasingly equipped with a black box for accident prevention and preservation of evidence. Vehicle black boxes have become mandatory because black box images and voice data have served as forensic evidence in courts. However, the data from black boxes can be forged or modified by man-in-the-midd...

Black hole levitron

International Nuclear Information System (INIS)

Arsiwalla, Xerxes D.; Verlinde, Erik P.

2010-01-01

We study the problem of spatially stabilizing four dimensional extremal black holes in background electric/magnetic fields. Whilst looking for stationary stable solutions describing black holes placed in external fields we find that taking a continuum limit of Denef et al.'s multicenter supersymmetric black hole solutions provides a supergravity description of such backgrounds within which a black hole can be trapped within a confined volume. This construction is realized by solving for a levitating black hole over a magnetic dipole base. We comment on how such a construction is akin to a mechanical levitron.

Black Holes

OpenAIRE

Horowitz, Gary T.; Teukolsky, Saul A.

1998-01-01

Black holes are among the most intriguing objects in modern physics. Their influence ranges from powering quasars and other active galactic nuclei, to providing key insights into quantum gravity. We review the observational evidence for black holes, and briefly discuss some of their properties. We also describe some recent developments involving cosmic censorship and the statistical origin of black hole entropy.

Astrophysical flows near f(T) gravity black holes

Energy Technology Data Exchange (ETDEWEB)

Ahmed, Ayyesha K.; Jamil, Mubasher [National University of Sciences and Technology (NUST), Department of Mathematics, School of Natural Sciences (SNS), Islamabad (Pakistan); Azreg-Ainou, Mustapha [Baskent University, Baglica Campus, Engineering Faculty, Ankara (Turkey); Bahamonde, Sebastian [University College London, Department of Mathematics, London (United Kingdom); Capozziello, Salvatore [Universita di Napoli ' ' Federico II' ' , Dipartimento di Fisica, Naples (Italy); Gran Sasso Science Institute (INFN), L' Aquila (Italy); INFN Sezione di Napoli, Naples (Italy)

2016-05-15

In this paper, we study the accretion process for fluids flowing near a black hole in the context of f(T) teleparallel gravity. Specifically, by performing a dynamical analysis by a Hamiltonian system, we are able to find the sonic points. After that, we consider different isothermal test fluids in order to study the accretion process when they are falling onto the black hole. We find that these flows can be classified according to the equation of state and the black hole features. Results are compared in f(T) and f(R) gravity. (orig.)

Relativistic hydrodynamic evolutions with black hole excision

International Nuclear Information System (INIS)

Duez, Matthew D.; Shapiro, Stuart L.; Yo, H.-J.

2004-01-01

We present a numerical code designed to study astrophysical phenomena involving dynamical spacetimes containing black holes in the presence of relativistic hydrodynamic matter. We present evolutions of the collapse of a fluid star from the onset of collapse to the settling of the resulting black hole to a final stationary state. In order to evolve stably after the black hole forms, we excise a region inside the hole before a singularity is encountered. This excision region is introduced after the appearance of an apparent horizon, but while a significant amount of matter remains outside the hole. We test our code by evolving accurately a vacuum Schwarzschild black hole, a relativistic Bondi accretion flow onto a black hole, Oppenheimer-Snyder dust collapse, and the collapse of nonrotating and rotating stars. These systems are tracked reliably for hundreds of M following excision, where M is the mass of the black hole. We perform these tests both in axisymmetry and in full 3+1 dimensions. We then apply our code to study the effect of the stellar spin parameter J/M 2 on the final outcome of gravitational collapse of rapidly rotating n=1 polytropes. We find that a black hole forms only if J/M 2 2 >1, the collapsing star forms a torus which fragments into nonaxisymmetric clumps, capable of generating appreciable 'splash' gravitational radiation

A unitary model of the black hole evaporation

Science.gov (United States)

Feng, Yu-Lei; Chen, Yi-Xin

2014-12-01

A unitary effective field model of the black hole evaporation is proposed to satisfy almost the four postulates of the black hole complementarity (BHC). In this model, we enlarge a black hole-scalar field system by adding an extra radiation detector that couples with the scalar field. After performing a partial trace over the scalar field space, we obtain an effective entanglement between the black hole and the detector (or radiation in it). As the whole system evolves, the S-matrix formula can be constructed formally step by step. Without local quantum measurements, the paradoxes of the information loss and AMPS's firewall can be resolved. However, the information can be lost due to quantum decoherence, as long as some local measurement has been performed on the detector to acquire the information of the radiation in it. But unlike Hawking's completely thermal spectrum, some residual correlations can be found in the radiations. All these considerations can be simplified in a qubit model that provides a modified quantum teleportation to transfer the information via an EPR pairs.

Noncommutative black holes

Energy Technology Data Exchange (ETDEWEB)

Lopez-DomInguez, J C [Instituto de Fisica de la Universidad de Guanajuato PO Box E-143, 37150 Leoen Gto. (Mexico); Obregon, O [Instituto de Fisica de la Universidad de Guanajuato PO Box E-143, 37150 Leoen Gto. (Mexico); RamIrez, C [Facultad de Ciencias FIsico Matematicas, Universidad Autonoma de Puebla, PO Box 1364, 72000 Puebla (Mexico); Sabido, M [Instituto de Fisica de la Universidad de Guanajuato PO Box E-143, 37150 Leoen Gto. (Mexico)

2007-11-15

We study noncommutative black holes, by using a diffeomorphism between the Schwarzschild black hole and the Kantowski-Sachs cosmological model, which is generalized to noncommutative minisuperspace. Through the use of the Feynman-Hibbs procedure we are able to study the thermodynamics of the black hole, in particular, we calculate Hawking's temperature and entropy for the 'noncommutative' Schwarzschild black hole.

Configurational entropy of anti-de Sitter black holes

International Nuclear Information System (INIS)

Braga, Nelson R.F.; Rocha, Roldão da

2017-01-01

Recent studies indicate that the configurational entropy is an useful tool to investigate the stability and (or) the relative dominance of states for diverse physical systems. Recent examples comprise the connection between the variation of this quantity and the relative fraction of light mesons and glueballs observed in hadronic processes. Here we develop a technique for defining a configurational entropy for an AdS-Schwarzschild black hole. The achieved result corroborates consistency with the Hawking–Page phase transition. Namely, the dominance of the black hole configurational entropy will be shown to increase with the temperature. In order to verify the consistency of the new procedure developed here, we also consider the case of black holes in flat space-time. For such a black hole, it is known that evaporation leads to instability. The configurational entropy obtained for the flat space case is thoroughly consistent with the physical expectation. In fact, we show that the smaller the black holes, the more unstable they are. So, the configurational entropy furnishes a reliable measure for stability of black holes.

Configurational entropy of anti-de Sitter black holes

Energy Technology Data Exchange (ETDEWEB)

Braga, Nelson R.F., E-mail: braga@if.ufrj.br [Instituto de Física, Universidade Federal do Rio de Janeiro, Caixa Postal 68528, RJ 21941-972 (Brazil); Rocha, Roldão da, E-mail: roldao.rocha@ufabc.edu.br [Centro de Matemática, Computação e Cognição, Universidade Federal do ABC – UFABC, 09210-580, Santo André (Brazil)

2017-04-10

Recent studies indicate that the configurational entropy is an useful tool to investigate the stability and (or) the relative dominance of states for diverse physical systems. Recent examples comprise the connection between the variation of this quantity and the relative fraction of light mesons and glueballs observed in hadronic processes. Here we develop a technique for defining a configurational entropy for an AdS-Schwarzschild black hole. The achieved result corroborates consistency with the Hawking–Page phase transition. Namely, the dominance of the black hole configurational entropy will be shown to increase with the temperature. In order to verify the consistency of the new procedure developed here, we also consider the case of black holes in flat space-time. For such a black hole, it is known that evaporation leads to instability. The configurational entropy obtained for the flat space case is thoroughly consistent with the physical expectation. In fact, we show that the smaller the black holes, the more unstable they are. So, the configurational entropy furnishes a reliable measure for stability of black holes.

Black hole critical phenomena without black holes

Indian Academy of Sciences (India)

large values of Ф, black holes do form and for small values the scalar field ... on the near side of the ridge ultimately evolve to form black holes while those configu- ... The inset shows a bird's eye view looking down on the saddle point.

Optimization of degradation of Reactive Black 5 (RB5) and electricity generation in solar photocatalytic fuel cell system.

Science.gov (United States)

Khalik, Wan Fadhilah; Ho, Li-Ngee; Ong, Soon-An; Voon, Chun-Hong; Wong, Yee-Shian; Yusoff, NikAthirah; Lee, Sin-Li; Yusuf, Sara Yasina

2017-10-01

The photocatalytic fuel cell (PFC) system was developed in order to study the effect of several operating parameters in degradation of Reactive Black 5 (RB5) and its electricity generation. Light irradiation, initial dye concentration, aeration, pH and cathode electrode are the operating parameters that might give contribution in the efficiency of PFC system. The degradation of RB5 depends on the presence of light irradiation and solar light gives better performance to degrade the azo dye. The azo dye with low initial concentration decolorizes faster compared to higher initial concentration and presence of aeration in PFC system would enhance its performance. Reactive Black 5 rapidly decreased at higher pH due to the higher amount of OH generated at higher pH and Pt-loaded carbon (Pt/C) was more suitable to be used as cathode in PFC system compared to Cu foil and Fe foil. The rapid decolorization of RB5 would increase their voltage output and in addition, it would also increase their V oc , J sc and P max . The breakage of azo bond and aromatic rings was confirmed through UV-Vis spectrum and COD analysis. Copyright © 2017 Elsevier Ltd. All rights reserved.

Black widow spider

Science.gov (United States)

... medlineplus.gov/ency/article/002858.htm Black widow spider To use the sharing features on this page, please enable JavaScript. The black widow spider (Latrodectus) has a shiny black body with a ...

Quasinormal modes and classical wave propagation in analogue black holes

International Nuclear Information System (INIS)

Berti, Emanuele; Cardoso, Vitor; Lemos, Jose P.S.

2004-01-01

Many properties of black holes can be studied using acoustic analogues in the laboratory through the propagation of sound waves. We investigate in detail sound wave propagation in a rotating acoustic (2+1)-dimensional black hole, which corresponds to the 'draining bathtub' fluid flow. We compute the quasinormal mode frequencies of this system and discuss late-time power-law tails. Because of the presence of an ergoregion, waves in a rotating acoustic black hole can be superradiantly amplified. We also compute superradiant reflection coefficients and instability time scales for the acoustic black hole bomb, the equivalent of the Press-Teukolsky black hole bomb. Finally we discuss quasinormal modes and late-time tails in a nonrotating canonical acoustic black hole, corresponding to an incompressible, spherically symmetric (3+1)-dimensional fluid flow

Search for Black-Holes: the nature of the Unseen Companions of the Systems HD 152667 and 72754

International Nuclear Information System (INIS)

Freitas Pacheco, J.A. de

1978-01-01

The nature of the unseen companions in the single spectroscopic binary systems HD 152667 and HD 72754 is analysed. In the first system, the secondary is likely to be a normal B4 main sequence star while in HD 72754, the secondary, in spite of being the more massive star, is not detected. We cannot at the present, disregard the possibility that this massive object be associated with a collapsed star - a black-hole [pt

New coordinates for BTZ black hole and Hawking radiation via tunnelling

International Nuclear Information System (INIS)

Liu Wenbiao

2006-01-01

Hawking radiation can usefully be viewed as a semi-classical tunnelling process that originates at the black hole horizon. For the stationary axisymmetric BTZ black hole, a generalized Painleve coordinate system (Painleve-BTZ coordinates) is introduced, and Hawking radiation as tunnelling under the effect of self-gravitation is investigated. The corrected radiation is obtained which is not precise thermal spectrum. The result is consistent with the underlying unitary theory. Moreover, Bekenstein-Hawking entropy of BTZ black hole is not necessarily corrected when we choose appropriate coordinate system to study the tunnelling effect

Insight into the microscopic structure of an AdS black hole from a thermodynamical phase transition.

Science.gov (United States)

Wei, Shao-Wen; Liu, Yu-Xiao

2015-09-11

Comparing with an ordinary thermodynamic system, we investigate the possible microscopic structure of a charged anti-de Sitter black hole completely from the thermodynamic viewpoint. The number density of the black hole molecules is introduced to measure the microscopic degrees of freedom of the black hole. We found that the number density suffers a sudden change accompanied by a latent heat when the black hole system crosses the small-large black hole coexistence curve, while when the system passes the critical point, it encounters a second-order phase transition with a vanishing latent heat due to the continuous change of the number density. Moreover, the thermodynamic scalar curvature suggests that there is a weak attractive interaction between two black hole molecules. These phenomena might cast new insight into the underlying microscopic structure of a charged anti-de Sitter black hole.

Teaching Celia in the Age of Black Lives Matter

OpenAIRE

Brandon R. Byrd

2016-01-01

The emergence of Black Lives Matter has introduced a language of black liberation to a new generation of students. In doing so, it has provided an opportunity for historical study. Teacher-scholars can and should take advantage of the renewed interest in systemic threats to black life in the United States when teaching about past victims of state-sanctioned violence including Celia, an enslaved teenager executed for killing her master after years of sexual abuse. In doing so, they can not onl...

Black Hole Solution of Einstein-Born-Infeld-Yang-Mills Theory

Directory of Open Access Journals (Sweden)

Kun Meng

2017-01-01

Full Text Available A new four-dimensional black hole solution of Einstein-Born-Infeld-Yang-Mills theory is constructed; several degenerated forms of the black hole solution are presented. The related thermodynamical quantities are calculated, with which the first law of thermodynamics is checked to be satisfied. Identifying the cosmological constant as pressure of the system, the phase transition behaviors of the black hole in the extended phase space are studied.

Ultraspinning limits and super-entropic black holes

Energy Technology Data Exchange (ETDEWEB)

Hennigar, Robie A. [Department of Physics and Astronomy, University of Waterloo, Waterloo, Ontario, N2L 3G1 (Canada); Kubizňák, David [Department of Physics and Astronomy, University of Waterloo, Waterloo, Ontario, N2L 3G1 (Canada); Perimeter Institute, 31 Caroline St. N., Waterloo, Ontario, N2L 2Y5 (Canada); Mann, Robert B. [Department of Physics and Astronomy, University of Waterloo, Waterloo, Ontario, N2L 3G1 (Canada); Musoke, Nathan [Perimeter Institute, 31 Caroline St. N., Waterloo, Ontario, N2L 2Y5 (Canada)

2015-06-16

By employing the new ultraspinning limit we construct novel classes of black holes with non-compact event horizons and finite horizon area and study their thermodynamics. Our ultraspinning limit can be understood as a simple generating technique that consists of three steps: i) transforming the known rotating AdS black hole solution to a special coordinate system that rotates (in a given 2-plane) at infinity ii) boosting this rotation to the speed of light iii) compactifying the corresponding azimuthal direction. In so doing we qualitatively change the structure of the spacetime since it is no longer possible to return to a frame that does not rotate at infinity. The obtained black holes have non-compact horizons with topology of a sphere with two punctures. The entropy of some of these exceeds the maximal bound implied by the reverse isoperimetric inequality, such black holes are super-entropic.

Ultraspinning limits and super-entropic black holes

Science.gov (United States)

Hennigar, Robie A.; Kubizňák, David; Mann, Robert B.; Musoke, Nathan

2015-06-01

By employing the new ultraspinning limit we construct novel classes of black holes with non-compact event horizons and finite horizon area and study their thermo-dynamics. Our ultraspinning limit can be understood as a simple generating technique that consists of three steps: i) transforming the known rotating AdS black hole solution to a special coordinate system that rotates (in a given 2-plane) at infinity ii) boosting this rotation to the speed of light iii) compactifying the corresponding azimuthal direction. In so doing we qualitatively change the structure of the spacetime since it is no longer pos-sible to return to a frame that does not rotate at infinity. The obtained black holes have non-compact horizons with topology of a sphere with two punctures. The entropy of some of these exceeds the maximal bound implied by the reverse isoperimetric inequality, such black holes are super-entropic.

Black holes in an expanding universe.

Science.gov (United States)

Gibbons, Gary W; Maeda, Kei-ichi

2010-04-02

An exact solution representing black holes in an expanding universe is found. The black holes are maximally charged and the universe is expanding with arbitrary equation of state (P = w rho with -1 < or = for all w < or = 1). It is an exact solution of the Einstein-scalar-Maxwell system, in which we have two Maxwell-type U(1) fields coupled to the scalar field. The potential of the scalar field is an exponential. We find a regular horizon, which depends on one parameter [the ratio of the energy density of U(1) fields to that of the scalar field]. The horizon is static because of the balance on the horizon between gravitational attractive force and U(1) repulsive force acting on the scalar field. We also calculate the black hole temperature.

Hidden Pair of Supermassive Black Holes

Science.gov (United States)

Kohler, Susanna

2015-08-01

Could a pair of supermassive black holes (SMBHs) be lurking at the center of the galaxy Mrk 231? A recent study finds that this may be the case and the unique spectrum of this galaxy could be the key to discovering more hidden binary SMBH systems.Where Are the Binary Supermassive Black Holes?Its believed that most, if not all, galaxies have an SMBH at their centers. As two galaxies merge, the two SMBHs should evolve into a closely-bound binary system before they eventually merge. Given the abundance of galaxy mergers, we would expect to see the kinematic and visual signatures of these binary SMBHs among observed active galactic nuclei yet such evidence for sub-parsec binary SMBH systems remains scarce and ambiguous. This has led researchers to wonder: is there another way that we might detect these elusive systems?A collaboration led by Chang-Shuo Yan (National Astronomical Observatories, Chinese Academy of Sciences) thinks that there is. The group suggests that these systems might have distinct signatures in their optical-to-UV spectra, and they identify a system that might be just such a candidate: Mrk 231.A Binary CandidateProposed model of Mrk 231. Two supermassive black holes, each with their own mini-disk, orbit each other in the center of a circumbinary disk. The secondary black hole has cleared gap in the circumbinary disk as a result of its orbit around the primary black hole. [Yan et al. 2015]Mrk 231 is a galaxy with a disturbed morphology and tidal tails strong clues that it might be in the final stages of a galactic merger. In addition to these signs, Mrk 231 also has an unusual spectrum for a quasar: its continuum emission displays an unexpected drop in the near-UV band.Yan and her collaborators propose that the odd behavior of Mrk 231s spectrum can be explained if the center of the galaxy houses a pair of SMBHs each with its own mini accretion disk surrounded by a circumbinary accretion disk. As the secondary SMBH orbits the primary SMBH (with a

Before Inflation and after Black Holes

Science.gov (United States)

Stoltenberg, Henry

This dissertation covers work from three research projects relating to the physics before the start of inflation and information after the decay of a black hole. For the first project, we analyze the cosmological role of terminal vacua in the string theory landscape, and point out that existing work on this topic makes very strong assumptions about the properties of the terminal vacua. We explore the implications of relaxing these assumptions (by including "arrival" as well as "departure" terminals) and demonstrate that the results in earlier work are highly sensitive to their assumption of no arrival terminals. We use our discussion to make some general points about tuning and initial conditions in cosmology. The second project is a discussion of the black hole information problem. Under certain conditions the black hole information puzzle and the (related) arguments that firewalls are a typical feature of black holes can break down. We first review the arguments of Almheiri, Marolf, Polchinski and Sully (AMPS) favoring firewalls, focusing on entanglements in a simple toy model for a black hole and the Hawking radiation. By introducing a large and inaccessible system entangled with the black hole (representing perhaps a de Sitter stretched horizon or inaccessible part of a landscape) we show complementarity can be restored and firewalls can be avoided throughout the black hole's evolution. Under these conditions black holes do not have an "information problem". We point out flaws in some of our earlier arguments that such entanglement might be generically present in some cosmological scenarios, and call out certain ways our picture may still be realized. The third project also examines the firewall argument. A fundamental limitation on the behavior of quantum entanglement known as "monogamy" plays a key role in the AMPS argument. Our goal is to study and apply many-body entanglement theory to consider the entanglement among different parts of Hawking radiation and

Multiscalar black holes with contingent primary hair: Mechanics and stability

International Nuclear Information System (INIS)

Mignemi, Salvatore; Wiltshire, David L.

2004-01-01

We generalize a class of magnetically charged black holes nonminimally coupled to two scalar fields previously found by one of us to the case of multiple scalar fields. The black holes possess a novel type of primary scalar hair, which we call a contingent primary hair: although the solutions possess degrees of freedom which are not completely determined by the other charges of the theory, the charges necessarily vanish in the absence of the magnetic monopole. Only one constraint relates the black hole mass to the magnetic charge and scalar charges of the theory. We obtain a Smarr-type thermodynamic relation, and the first law of black hole thermodynamics for the system. We further explicitly show in the two-scalar-field case that, contrary to the case of many other hairy black holes, the black hole solutions are stable to radial perturbations

Powerful jets from accreting black holes: evidence from the optical and infrared

NARCIS (Netherlands)

Russell, D.M.; Fender, R.P.; Wachter, A.D.; Propst, R.J.

2010-01-01

A common consequence of accretion onto black holes is the formation of powerful, relativistic jets that escape the system. In the case of supermassive black holes at the centres of galaxies this has been known for decades, but for stellar-mass black holes residing within galaxies like our own, it

Black holes and random matrices

Energy Technology Data Exchange (ETDEWEB)

Cotler, Jordan S.; Gur-Ari, Guy [Stanford Institute for Theoretical Physics, Stanford University,Stanford, CA 94305 (United States); Hanada, Masanori [Stanford Institute for Theoretical Physics, Stanford University,Stanford, CA 94305 (United States); Yukawa Institute for Theoretical Physics, Kyoto University,Kyoto 606-8502 (Japan); The Hakubi Center for Advanced Research, Kyoto University,Kyoto 606-8502 (Japan); Polchinski, Joseph [Department of Physics, University of California,Santa Barbara, CA 93106 (United States); Kavli Institute for Theoretical Physics, University of California,Santa Barbara, CA 93106 (United States); Saad, Phil; Shenker, Stephen H. [Stanford Institute for Theoretical Physics, Stanford University,Stanford, CA 94305 (United States); Stanford, Douglas [Institute for Advanced Study,Princeton, NJ 08540 (United States); Streicher, Alexandre [Stanford Institute for Theoretical Physics, Stanford University,Stanford, CA 94305 (United States); Department of Physics, University of California,Santa Barbara, CA 93106 (United States); Tezuka, Masaki [Department of Physics, Kyoto University,Kyoto 606-8501 (Japan)

2017-05-22

We argue that the late time behavior of horizon fluctuations in large anti-de Sitter (AdS) black holes is governed by the random matrix dynamics characteristic of quantum chaotic systems. Our main tool is the Sachdev-Ye-Kitaev (SYK) model, which we use as a simple model of a black hole. We use an analytically continued partition function |Z(β+it)|{sup 2} as well as correlation functions as diagnostics. Using numerical techniques we establish random matrix behavior at late times. We determine the early time behavior exactly in a double scaling limit, giving us a plausible estimate for the crossover time to random matrix behavior. We use these ideas to formulate a conjecture about general large AdS black holes, like those dual to 4D super-Yang-Mills theory, giving a provisional estimate of the crossover time. We make some preliminary comments about challenges to understanding the late time dynamics from a bulk point of view.

Astrophysical black holes

CERN Document Server

Gorini, Vittorio; Moschella, Ugo; Treves, Aldo; Colpi, Monica

2016-01-01

Based on graduate school lectures in contemporary relativity and gravitational physics, this book gives a complete and unified picture of the present status of theoretical and observational properties of astrophysical black holes. The chapters are written by internationally recognized specialists. They cover general theoretical aspects of black hole astrophysics, the theory of accretion and ejection of gas and jets, stellar-sized black holes observed in the Milky Way, the formation and evolution of supermassive black holes in galactic centers and quasars as well as their influence on the dynamics in galactic nuclei. The final chapter addresses analytical relativity of black holes supporting theoretical understanding of the coalescence of black holes as well as being of great relevance in identifying gravitational wave signals. With its introductory chapters the book is aimed at advanced graduate and post-graduate students, but it will also be useful for specialists.

Neighbourhood food, physical activity, and educational environments and black/white disparities in obesity: a complex systems simulation analysis.

Science.gov (United States)

Orr, Mark G; Kaplan, George A; Galea, Sandro

2016-09-01

Multiple approaches that can contribute to reducing obesity have been proposed. These policies may share overlapping pathways, and may have unanticipated consequences, creating considerable complexity. Aiming to illuminate the use of agent-based models to explore the consequences of key policies, this paper simulates the effects of increasing neighbourhood availability of good food stores, physical activity infrastructure and higher school quality on the reduction of black/white disparities in body mass index (BMI) in the USA. We used an agent-based model, with parameters derived from the empirical literature, which included individual and neighbourhood characteristics over the life course as determinants of behaviours thought to impact BMI. We systematically varied the strength of the 3 policy interventions, examining the impact of 125 different policy scenarios on black/white BMI disparities. In the absence of any of these policies, black/white BMI disparities generally increased over time. However, we found that some combinations of these policies resulted in reductions in BMI, yielding decreases in the black/white BMI disparity as large as a 90%. Within the structure of relationships captured in this simulation model, there is support for the further use of agent-based simulation models to explore upstream policies as plausible candidates for the reduction of black/white disparities in BMI. These results highlight the potential insights into important public health problems, such as obesity, that can come from uniting the systems science approach with policy analysis. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/

Thermal BEC Black Holes

Directory of Open Access Journals (Sweden)

Roberto Casadio

2015-10-01

Full Text Available We review some features of Bose–Einstein condensate (BEC models of black holes obtained by means of the horizon wave function formalism. We consider the Klein–Gordon equation for a toy graviton field coupled to a static matter current in a spherically-symmetric setup. The classical field reproduces the Newtonian potential generated by the matter source, while the corresponding quantum state is given by a coherent superposition of scalar modes with a continuous occupation number. An attractive self-interaction is needed for bound states to form, the case in which one finds that (approximately one mode is allowed, and the system of N bosons can be self-confined in a volume of the size of the Schwarzschild radius. The horizon wave function formalism is then used to show that the radius of such a system corresponds to a proper horizon. The uncertainty in the size of the horizon is related to the typical energy of Hawking modes: it decreases with the increasing of the black hole mass (larger number of gravitons, resulting in agreement with the semiclassical calculations and which does not hold for a single very massive particle. The spectrum of these systems has two components: a discrete ground state of energy m (the bosons forming the black hole and a continuous spectrum with energy ω > m (representing the Hawking radiation and modeled with a Planckian distribution at the expected Hawking temperature. Assuming the main effect of the internal scatterings is the Hawking radiation, the N-particle state can be collectively described by a single-particle wave-function given by a superposition of a total ground state with energy M = Nm and Entropy 2015, 17 6894 a Planckian distribution for E > M at the same Hawking temperature. This can be used to compute the partition function and to find the usual area law for the entropy, with a logarithmic correction related to the Hawking component. The backreaction of modes with ω > m is also shown to reduce

Thermodynamics of intersecting black branes from interacting elementary branes

Energy Technology Data Exchange (ETDEWEB)

Morita, Takeshi [Department of Physics, Shizuoka University,836 Ohya, Suruga-ku, Shizuoka 422-8529 (Japan); Shiba, Shotaro [Maskawa Institute for Science and Culture, Kyoto Sangyo University,Kamigamo-Motoyama, Kita-ku, Kyoto 603-8555 (Japan)

2015-09-14

If an Einstein-Maxwell-Dilaton system admits the extreme brane solution in which no force works between the parallel branes, the collective motion of nearly parallel branes exhibits the thermodynamical properties which are coincident with those of the corresponding black branes at low energy regime (up to unfixed numerical factors). Hence it may provide the microscopic description of the black branes (p-soup proposal). This fact motivates us to test this proposal in the intersecting black branes which have multiple brane charges and/or momentum along the brane direction. We consider the case that the multiple branes satisfy the intersection rule and feel no force when they are static, and find the agreement to the black hole thermodynamics.

Lumpy AdS5× S5 black holes and black belts

International Nuclear Information System (INIS)

Dias, Óscar J.C.; Santos, Jorge E.; Way, Benson

2015-01-01

Sufficiently small Schwarzschild black holes in global AdS 5 ×S 5 are Gregory-Laflamme unstable. We construct new families of black hole solutions that bifurcate from the onset of this instability and break the full SO(6) symmetry group of the S 5 down to SO(5). These new “lumpy" solutions are labelled by the harmonics ℓ. We find evidence that the ℓ=1 branch never dominates the microcanonical/canonical ensembles and connects through a topology-changing merger to a localised black hole solution with S 8 topology. We argue that these S 8 black holes should become the dominant phase in the microcanonical ensemble for small enough energies, and that the transition to Schwarzschild black holes is first order. Furthermore, we find two branches of solutions with ℓ=2. We expect one of these branches to connect to a solution containing two localised black holes, while the other branch connects to a black hole solution with horizon topology S 4 ×S 4 which we call a “black belt”.

Black holes in binary stars

NARCIS (Netherlands)

Wijers, R.A.M.J.

1996-01-01

Introduction Distinguishing neutron stars and black holes Optical companions and dynamical masses X-ray signatures of the nature of a compact object Structure and evolution of black-hole binaries High-mass black-hole binaries Low-mass black-hole binaries Low-mass black holes Formation of black holes

Turkish Straits System and Southern Black Sea: Exchange. Mixing and Shelf / Canyon Interactions

Science.gov (United States)

Özsoy, Emin; Gürses, Özgür; Tutsak, Ersin

2015-04-01

Based largely on an experiment employing high-resolution measurements carried out in June-July 2013 and re-interpretation of past experiments, the oceanographic variability of the exchange through the Turkish Straits System (TSS) and the interactions with the southern Black Sea are revealed through CTD, ADCP, oxygen and light transmission measurements. The exchange flow is primarily governed by the complex topography spanning two narrow straits, wide continental shelf regions, steep slopes and numerous canyons connecting deep basins. Water properties and currents in the high energy environment depends on the mosaic of fine-scale processes and pathways. The TSS, often approximated as a two-layer system has a hydraulically controlled, upper ocean and straits intensified regime, leading to surface jets and bottom plumes participating in mixing and renewal processes. The exit of the 'Mediterranean effluent' onto the Black Sea past a sill overflow from the Bosphorus passes through two subsequent hydraulic jumps and proceeds along a narrow canyon that veers to the west clear of the greater Bosphorus Canyon finally cascading down the few small canyons. A diffusive spread from the bottom vein of salty water reforms to the east and spills down the Bosphorus Canyon. The suspended particulate signature of the cascade, as well as its influence in hydrography is traced over the shelf and slope waters and through the numerous canyons into deep water where the reformed flow is found to sustain signatures of the past evolution of intrusive waters. An evaluation of the processes is given with reference to model development carried out in parallel to the analyses of the measurements.

Black Interpretation, Black American Literature, and Grey Audiences.

Science.gov (United States)

Washington, Earl M.

1981-01-01

Defines and illustrates language techniques used by Black authors writing to and for Blacks in the 1960s and 1970s. Suggests how language and theme barriers of such literature might be overcome in a contemporary integrated oral interpretation classroom. (PD)

#BlackBabiesMatter: Analyzing Black Religious Media in Conservative and Progressive Evangelical Communities

Directory of Open Access Journals (Sweden)

Monique Moultrie

2017-11-01

Full Text Available This article explores how conservative and progressive black Protestants interrogate the theological theme of the sacrality of black life through digital media. The innovations of religious media in black evangelical communities remain an understudied phenomenon in African American religion, making this an apt arena for further discovery. This current intervention into the study of African American Religion examines digital activism through examples of religious media produced by blacks for black audiences. This article begins its interrogation of the sacrality of black life by juxtaposing those who contend that Black Babies Matter as pro-birth-oriented, religiously motivated activists with those religious opponents asserting Black Lives Matter who present an intersectional pro-life approach. The comparison of views relies on womanist cultural analysis as its main methodology to analyze and interpret digital media and explore its ramifications for African American Religion.

Boundary counterterms and the thermodynamics of 2-D black holes

International Nuclear Information System (INIS)

Davis, Joshua L.; McNees, Robert

2005-01-01

We utilize a novel method to study the thermodynamics of two dimensional type 0A black holes with constant RR flux. Our approach is based on the Hamilton-Jacobi method of deriving boundary counterterms. We demonstrate this approach by recovering the standard results for a well understood example, Witten's black hole. Between this example and the 0A black hole we find universal expressions for the entropy and black hole mass, as well as the infra-red divergence of the partition function. As a non-trivial check of our results we verify the first law of thermodynamics for these systems. Our results for the mass disagree with the predictions of a proposed matrix model dual of the 0A black hole

Drop formation of black liquor spraying; Mustalipeaen pisaroituminen

Energy Technology Data Exchange (ETDEWEB)

Fogelholm, C J; Kankkunen, A; Nieminen, K; Laine, J; Miikkulainen, P [Helsinki Univ. of Technology, Otaniemi (Finland): Lab. of Energy Technology and Environmental Protection

1997-10-01

Black liquor is a spent liquor of the pulp and paper industry. It is burned in kraft recovery boilers for chemical and energy recovery. The high dry solids content and viscosity of black liquor require a high spraying temperature. This affects the performance of the boiler. Kraft recovery boiler deposit formation, emissions and chemical recovery are strongly affected by the drop size and the velocity of the black liquor spray formed by a splashplate nozzle. The sheet breakup mechanism is studied with a system based on a video and image-analysis. The drop size of mill-scale nozzles was measured also with an image-analysis-system. Measurements were carried out in a spray test chamber. The sheet breakup mechanism and drop size tests were carried out both below and over the boiling point of black liquor. Special attention was paid to the effect of flashing on drop formation. Temperature increase normally decreases drop size. In the temperature where the wavy-sheet disintegration changes to perforated-sheet disintegration the drop size increases. Spray velocity rises when the temperature is increased above the boiling point. (orig.)

Scalar hairy black holes and scalarons in the isolated horizons formalism

International Nuclear Information System (INIS)

Corichi, Alejandro; Nucamendi, Ulises; Salgado, Marcelo

2006-01-01

The Isolated Horizons (IH) formalism, together with a simple phenomenological model for colored black holes has been used to predict nontrivial formulas that relate the ADM mass of the solitons and hairy Black Holes of Gravity-Matter system on the one hand, and several horizon properties of the black holes in the other. In this article, the IH formalism is tested numerically for spherically symmetric solutions to an Einstein-Higgs system where hairy black holes were recently found to exist. It is shown that the mass formulas still hold and that, by appropriately extending the current model, one can account for the behavior of the horizon properties of these new solutions. An empirical formula that approximates the ADM mass of hairy solutions is put forward, and some of its properties are analyzed

Nonrotating black hole in a post-Newtonian tidal environment

International Nuclear Information System (INIS)

Taylor, Stephanne; Poisson, Eric

2008-01-01

We examine the motion and tidal dynamics of a nonrotating black hole placed within a post-Newtonian external spacetime. The black hole's gravity is described accurately to all orders in Gm/c 2 r, where m is the black-hole mass and r is the distance to the black hole. The tidal perturbation created by the external environment is treated as a small perturbation. At a large distance from the black hole, the gravitational field of the external distribution of matter is assumed to be sufficiently weak to be adequately described by the (first) post-Newtonian approximation to general relativity. There, the black hole is treated as a monopole contribution to the total gravitational field. There exists an overlap in the domains of validity of each description, and the black-hole and post-Newtonian metrics are matched in the overlap. The matching procedure produces (i) a justification of the statement that a nonrotating black hole is a post-Newtonian monopole; (ii) a complete characterization of the coordinate transformation between the inertial, barycentric frame and the accelerated, black-hole frame; (iii) the equations of motion for the black hole; and (iv) the gravito-electric and gravito-magnetic tidal fields acting on the black hole. We first calculate the equations of motion and tidal fields by making no assumptions regarding the nature of the post-Newtonian environment; this could contain a continuous distribution of matter (so as to model a galactic core) or any number of condensed bodies. We next specialize our discussion to a situation in which the black hole is a member of a post-Newtonian two-body system. As an application of our results, we examine the geometry of the deformed event horizon and calculate the tidal heating of the black hole, the rate at which it acquires mass as a result of its tidal interaction with the companion body.

Black holes. Chapter 6

International Nuclear Information System (INIS)

Penrose, R.

1980-01-01

Conditions for the formation of a black hole are considered, and the properties of black holes. The possibility of Cygnus X-1 as a black hole is discussed. Einstein's theory of general relativity in relation to the formation of black holes is discussed. (U.K.)

Black holes in massive close binaries - observational data and evolutionary status

International Nuclear Information System (INIS)

Tutukov, A.V.; Cherepashchuk, A.M.; Moskovskii Gosudarstvennyi Universitet, Moscow, USSR)

1985-01-01

The available information on the mass of four candidate black holes in X-ray binary systems is summarized; these systems are compared with neutron star binaries with regard to the mass of their components. In mass, the relativistic objects form two distinct groups, neutron stars with masses equal to about 1-2 solar masses and black hole candidates with masses equal to about 10-60 solar masses (there seem to be no intermediate cases), but there is no correlation with the mass of the optical star. Mass exchange between the optical component of a close binary and its neutron star companion would be unlikely to produce a black hole more massive than 5-7 solar masses. Instead, the black holes having masses greater than about 10 solar masses might result from core collapse in stars of initial mass equating 20-100 solar masses through either a rise in the presupernova core mass or weakness of the magnetic field. The (10-30)-fold disparity in the incidence of black holes coupled with OB stars and with radio pulsars could indicate that black holes tend to form in pairs. 36 references

Black ringoids: spinning balanced black objects in d≥5 dimensions — the codimension-two case

International Nuclear Information System (INIS)

Kleihaus, Burkhard; Kunz, Jutta; Radu, Eugen

2015-01-01

We propose a general framework for the study of asymptotically flat black objects with k+1 equal magnitude angular momenta in d≥5 spacetime dimensions (with 0≤k≤[((d−5)/2)]). In this approach, the dependence on all angular coordinates but one is factorized, which leads to a codimension-two problem. This framework can describe black holes with spherical horizon topology, the simplest solutions corresponding to a class of Myers-Perry black holes. A different set of solutions describes balanced black objects with S"n"+"1×S"2"k"+"1 horizon topology. The simplest members of this family are the black rings (k=0). The solutions with k>0 are dubbed black ringoids. Based on the nonperturbative numerical results found for several values of (n,k), we propose a general picture for the properties and the phase diagram of these solutions and the associated black holes with spherical horizon topology: n=1 black ringoids repeat the k=0 pattern of black rings and Myers-Perry black holes in 5 dimensions, whereas n>1 black ringoids follow the pattern of higher dimensional black rings associated with ‘pinched’ black holes and Myers-Perry black holes.

Black theology in South Africa – A theology of human dignity and black identity

Directory of Open Access Journals (Sweden)

Timothy van Aarde

2016-08-01

Full Text Available Black theology in South Africa is still relevant 20 years after the apartheid regime ended. It is a theology that gave to Black South Africans human dignity and a black identity. Black theology in South Africa confronted the imbalances of power and abusive power structures through an affirmation of human dignity and the uniqueness of the identity of black people. The biblical narrative of the Exodus is a definitive narrative in American black theology and liberation theology in overcoming oppression understood as political victimisation. Black theology in South Africa is not primarily about power and economics but also about the rediscovery of human dignity and black identity and to a lesser extent about victimisation. A third generation of black theology in South Africa will gain impetus through a rediscovery of human dignity and identity as its core values instead of a Black American liberation theology of victimisation or a Marxist liberation theology of the eradication of all power or economic imbalances.

[Black urine or black sclera of the eyes? Consider alkaptonuria].

Science.gov (United States)

Gubbels, Nanda P; Sijbrand, Merijn H; Onstenk, Ron

2014-01-01

Alkaptonuria is a rare metabolic disorder due to a defect in the gene for homogentisic acid oxidase. This results in an accumulation of homogentisic acid, which leads to the deposit of pigment in the connective tissue in the body. This causes problems and symptoms in various organ systems, such as early artropathy, dark-coloured urine, black sclerae, dark-coloured aortic valves and an increased risk of kidney stones and gall stones. Various specialists may see patients with this disease. The diagnosis is often missed. We describe a 69-year-old woman who underwent surgery due to joint problems, which showed up black cartilage. It turned out that for many years she had also had eye and heart problems. Not until later in life was she diagnosed with alkaptonuria. There is no curative treatment for alkaptonuria at the moment. Early recognition of the disease can increase the quality of life. Preventative check-ups and guidance are also therefore necessary.

BOOK REVIEW: Introduction to Black Hole Physics Introduction to Black Hole Physics

Science.gov (United States)

Tanaka, Takahiro

2012-07-01

Introduction to Black Hole Physics is a large volume (504 pages), and yet despite this it is still really an introductory text. The book gives an introduction to general relativity, but most of the text is dedicated to attracting the reader's attention to the interesting world of black hole physics. In this sense, the book is very distinct from other textbooks on general relativity. We are told that it was based on the lectures given by Professor Frolov, one of the authors, over the last 30 years. One can obtain the basic ideas about black holes, and also the necessary tips to understand general relativity at a very basic level. For example, in the discussion about particle motion in curved space, the authors start with a brief review on analytical mechanics. The book does not require its readers to have a great deal of knowledge in advance. If you are familiar with such a basic subject, you can simply omit that section. The reason why I especially picked up on this topic as an example is that the book devotes a significant number of pages to geodesic motions in black hole spacetime. One of the main motivations to study black holes is related to how they will actually be observed, once we develop the ability to observe them clearly. The book does explain such discoveries as, for instance, how the motion of a particle is related to a beautiful mathematical structure arising from the hidden symmetry of spacetime, which became transparent via the recent progress in the exploration of black holes in higher dimensions; a concise introduction to this latest topic is deferred to Appendix D, so as not to distract the reader with its mathematical complexities. It should be also mentioned that the book is not limited to general relativistic aspects: quantum fields on a black hole background and Hawking radiation are also covered. Also included are current hot topics, for instance the gravitational waves from a system including black holes, whose first direct detection is

Quasinormal modes of semiclassical electrically charged black holes

Energy Technology Data Exchange (ETDEWEB)

Fernandez Piedra, Owen Pavel [Departamento de Fisica y Quimica, Facultad de Mecanica, Universidad de Cienfuegos, Carretera a Rodas, km 4, Cuatro Caminos, Cienfuegos (Cuba); De Oliveira, Jeferson, E-mail: opavel@ucf.edu.cu, E-mail: jeferson@fma.if.usp.br [Instituto de Fisica, Universidade de Sao Paulo, CP 66318, 05315-970, Sao Paulo (Brazil)

2011-04-21

We report the results concerning the influence of vacuum polarization due to quantum massive vector, scalar and spinor fields on the scalar sector of quasinormal modes in spherically symmetric charged black holes. The vacuum polarization from quantized fields produces a shift in the values of the quasinormal frequencies, and correspondingly the semiclassical system becomes a better oscillator with respect to the classical Reissner-Nordstroem black hole.

Black-hole astrophysics

Energy Technology Data Exchange (ETDEWEB)

Bender, P. [Univ. of Colorado, Boulder, CO (United States); Bloom, E. [Stanford Linear Accelerator Center, Menlo Park, CA (United States); Cominsky, L. [Sonoma State Univ., Rohnert Park, CA (United States). Dept. of Physics and Astronomy] [and others

1995-07-01

Black-hole astrophysics is not just the investigation of yet another, even if extremely remarkable type of celestial body, but a test of the correctness of the understanding of the very properties of space and time in very strong gravitational fields. Physicists` excitement at this new prospect for testing theories of fundamental processes is matched by that of astronomers at the possibility to discover and study a new and dramatically different kind of astronomical object. Here the authors review the currently known ways that black holes can be identified by their effects on their neighborhood--since, of course, the hole itself does not yield any direct evidence of its existence or information about its properties. The two most important empirical considerations are determination of masses, or lower limits thereof, of unseen companions in binary star systems, and measurement of luminosity fluctuations on very short time scales.

Black holes thermodynamics, information, and firewalls

CERN Document Server

Mann, Robert B

2015-01-01

This book reflects the resurgence of interest in the quantum properties of black holes, culminating most recently in controversial discussions about firewalls. On the thermodynamic side, it describes how new developments allowed the inclusion of pressure/volume terms in the first law, leading to a new understanding of black holes as chemical systems, experiencing novel phenomena such as triple points and reentrant phase transitions. On the quantum-information side, the reader learns how basic arguments undergirding quantum complementarity have been shown to be flawed; and how this suggests that a black hole may surround itself with a firewall: a violent and chaotic region of highly excited states. In this thorough and pedagogical treatment, Robert Mann traces these new developments from their roots to our present-day understanding, highlighting their relationships and the challenges they present for quantum gravity.

Affirmative action and the Black women in South Africa.

Science.gov (United States)

Serote, P

1994-02-01

An overview was given of how affirmative action for Blacks and women in South Africa in fact marginalizes Black women. The definition of the problem influences the solution; affirmative action obscures the complex nature of discrimination experienced by Black women by class, role, and culture and focuses only on gender and race. Secondly, the power of White women and Black men supercede the power of Black women. Apartheid benefitted White women over Black men. Affirmative action, as shifting power between groups, would solidify White women's power. The debates have taken place within university and academic contexts, a place where Black women have been excluded and the dominant groups are White men, followed by White women, and then Black men. The debate in the private sector also is devoid of Black women's voices; multinationals began to hire and train Black male managers, and there was criticism that standards were falling. Recruitment of Black women is unknown, but only 1.1% of managers are Black. Visibility within the academic and private sector debates has excluded Black women. In the articulation of ideas, most literature has been written by White men. The intersection of power and privilege belongs to males and White women as part of the larger dominant ideology. Black women's marginalization means their issues will not be addressed. The people who stand to benefit the most from affirmative action are those who are in need of improved living conditions, literacy, and employment, or those excluded from jobs and position in spite of being qualified. Black women without a societal power base have no bargaining power. To insure that Black women benefit, there is need to treat Black women as a distinctive group with priority. There is also a need to examine the myths that have been spun around Black women, their needs, abilities, and controlling images. There is a need to integrate Black womens ideas into the mainstream and recognize that maybe Black women need

Scalar hair around charged black holes in Einstein-Gauss-Bonnet gravity

Science.gov (United States)

Grandi, Nicolás; Landea, Ignacio Salazar

2018-02-01

We explore charged black hole solutions in Einstein-Gauss-Bonnet gravity in five dimensions, with a charged scalar hair. We interpret such hairy black holes as the final state of the superradiant instability previously reported for this system. We explore the relation of the hairy black hole solutions with the nonbackreacting quasibound states and scalar clouds, as well as with the boson star solutions.

Throat quantization of the Schwarzschild–Tangherlini(-AdS) black hole

International Nuclear Information System (INIS)

Kunstatter, Gabor; Maeda, Hideki

2014-01-01

Adopting the throat quantization pioneered by Louko and Mäkelä, we derive the mass and area spectra for the Schwarzschild–Tangherlini black hole and its anti-de Sitter (AdS) generalization in arbitrary dimensions. We find that the system can be quantized exactly in three special cases: the three-dimensional BTZ black hole, toroidal black holes in any dimension, and five-dimensional Schwarzshild–Tangherlini(-AdS) black holes. For the remaining cases the spectra are obtained for large mass using the WKB approximation. For asymptotically flat black holes, the area/entropy has an equally spaced spectrum, as expected from previous work. In the asymptotically AdS case on the other hand, it is the mass spectrum that is equally spaced. Our exact results for the BTZ black hole mass with Dirichlet boundary conditions are consistent with the spectra of the corresponding operators in the dual CFT. (paper)

Astrophysical flows near [Formula: see text] gravity black holes.

Science.gov (United States)

Ahmed, Ayyesha K; Azreg-Aïnou, Mustapha; Bahamonde, Sebastian; Capozziello, Salvatore; Jamil, Mubasher

In this paper, we study the accretion process for fluids flowing near a black hole in the context of f ( T ) teleparallel gravity. Specifically, by performing a dynamical analysis by a Hamiltonian system, we are able to find the sonic points. After that, we consider different isothermal test fluids in order to study the accretion process when they are falling onto the black hole. We find that these flows can be classified according to the equation of state and the black hole features. Results are compared in f ( T ) and f ( R ) gravity.

UH-60M Black Hawk Helicopter (UH-60M Black Hawk)

Science.gov (United States)

2016-12-01

Selected Acquisition Report (SAR) RCS: DD-A&T(Q&A)823-341 UH-60M Black Hawk Helicopter (UH-60M Black Hawk ) As of FY 2017 President’s Budget Defense...Acquisition Management Information Retrieval (DAMIR) March 21, 2016 18:25:45 UNCLASSIFIED UH-60M Black Hawk December 2015 SAR March 21, 2016 18...Operational Requirements Document OSD - Office of the Secretary of Defense O&S - Operating and Support PAUC - Program Acquisition Unit Cost UH-60M Black Hawk

Black American and Nigerian Pentecostalism: A Black Religious ...

African Journals Online (AJOL)

Black American and Nigerian Pentecostalism: A Black Religious Schizophrenia, 1910-2010. ... in American and African Pentecostalism as is related to social crisis, the dislocation of masses brought on by economic deprivation, urbanization, the break up of traditional society and consequence loss of traditional values.

Black Tea

Science.gov (United States)

... mental alertness as well as learning, memory, and information processing skills. It is also used for treating headache; ... of carbamazepine. Since black tea contains caffeine, in theory taking black tea with carbamazepine might decrease the ...

Analogue Hawking radiation from astrophysical black-hole accretion

International Nuclear Information System (INIS)

Das, Tapas K

2004-01-01

We show that spherical accretion onto astrophysical black holes can be considered as a natural example of an analogue system. We provide, for the first time, an exact analytical scheme for calculating the analogue Hawking temperature and surface gravity for general relativistic accretion onto astrophysical black holes. Our calculation may bridge the gap between the theory of transonic astrophysical accretion and the theory of analogue Hawking radiation. We show that the domination of the analogue Hawking temperature over the actual Hawking temperature may be a real astrophysical phenomenon, though observational tests of this fact will at best be difficult and at worst might prove to be impossible. We also discuss the possibilities of the emergence of analogue white holes around astrophysical black holes. Our calculation is general enough to accommodate accreting black holes with any mass

Black hole microstates and attractor without supersymmetry

International Nuclear Information System (INIS)

Dabholkar, Atish; Trivedi, Sandip P.; Sen, Ashoke

2007-01-01

Due to the attractor mechanism, the entropy of an extremal black hole does not vary continuously as we vary the asymptotic values of various moduli fields. Using this fact we argue that the entropy of an extremal black hole in string theory, calculated for a range of values of the asymptotic moduli for which the microscopic theory is strongly coupled, should match the statistical entropy of the same system calculated for a range of values of the asymptotic moduli for which the microscopic theory is weakly coupled. This argument does not rely on supersymmetry and applies equally well to nonsupersymmetric extremal black holes. We discuss several examples which support this argument and also several caveats which could invalidate this argument

Reinvestigation of moving punctured black holes with a new code

International Nuclear Information System (INIS)

Cao Zhoujian; Yo Hweijang; Yu Juiping

2008-01-01

We report on our code, in which the moving puncture method is applied and an adaptive/fixed mesh refinement is implemented, and on its preliminary performance on black hole simulations. Based on the Baumgarte-Sharpiro-Shibata-Nakamura (BSSN) formulation, up-to-date gauge conditions and the modifications of the formulation are also implemented and tested. In this work, we present our primary results about the simulation of a single static black hole, of a moving single black hole, and of the head-on collision of a binary black hole system. For the static punctured black hole simulations, different modifications of the BSSN formulation are applied. It is demonstrated that both the currently used sets of modifications lead to a stable evolution. For cases of a moving punctured black hole with or without spin, we search for viable gauge conditions and study the effect of spin on the black hole evolution. Our results confirm previous results obtained by other research groups. In addition, we find a new gauge condition, which has not yet been adopted by any other researchers, which can also give stable and accurate black hole evolution calculations. We examine the performance of the code for the head-on collision of a binary black hole system, and the agreement of the gravitational waveform it produces with that obtained in other works. In order to understand qualitatively the influence of matter on the binary black hole collisions, we also investigate the same head-on collision scenarios but perturbed by a scalar field. The numerical simulations performed with this code not only give stable and accurate results that are consistent with the works by other numerical relativity groups, but also lead to the discovery of a new viable gauge condition, as well as clarify some ambiguities in the modification of the BSSN formulation. These results demonstrate that this code is reliable and ready to be used in the study of more realistic astrophysical scenarios and of numerical

Chaos in charged AdS black hole extended phase space

Science.gov (United States)

Chabab, M.; El Moumni, H.; Iraoui, S.; Masmar, K.; Zhizeh, S.

2018-06-01

We present an analytical study of chaos in a charged black hole in the extended phase space in the context of the Poincare-Melnikov theory. Along with some background on dynamical systems, we compute the relevant Melnikov function and find its zeros. Then we analyse these zeros either to identify the temporal chaos in the spinodal region, or to observe spatial chaos in the small/large black hole equilibrium configuration. As a byproduct, we derive a constraint on the Black hole' charge required to produce chaotic behaviour. To the best of our knowledge, this is the first endeavour to understand the correlation between chaos and phase picture in black holes.

Poor representation of Blacks, Latinos, and Native Americans in medicine.

Science.gov (United States)

Rodriguez, José E; Campbell, Kendall M; Adelson, Wendi J

2015-04-01

In this article, the authors discuss how various systems in medicine are limiting representation of blacks, Latinos, and Native Americans. Flat and decreasing percentages of Underrepresented Minorities in Medicine (URMM), especially in the black and Native American populations, is concerning for family medicine since members from URMM groups care for minority and underserved populations in greater numbers. Underrepresentation is not only noted in the medical community but also in our medical schools when it comes to numbers of URMM faculty. The changing definition of "disadvantaged" in medical school admissions has also played a part in limiting URMM representation. In addition, the Medical College Admissions Test (MCAT) excludes black, Latino, and Native American students in greater numbers. The authors support these arguments with evidence from the medical literature. Although unintentional, these systems effectively limit representation of blacks, Latinos, and Native Americans in medicine. Effective changes are suggested and can be implemented to ensure that URMM individuals have equal representation in careers in medicine.

Tidal Forces in Dyonic Reissner-Nördstrom Black Hole

Science.gov (United States)

Sharif, M.; Kousar, Lubna

2018-03-01

This paper investigates the tidal as well as magnetic charge effects produced in dyonic Reissner-Nordström black hole. We evaluate Newtonian radial acceleration using radial geodesics for freely falling test particles. We establish system of equations governing radial and angular tidal forces using geodesic deviation equation and discuss their solutions for bodies falling freely towards this black hole. The radial tidal force turns out to be compressing outside the event horizon whereas the angular tidal force changes sign between event and Cauchy horizons unlike Schwarzschild black hole. The radial geodesic component starts decreasing in dyonic Reissner-Nordström black hole unlike Schwarzschild case. We conclude that magnetic charge strongly affects the radial as well as angular components of tidal force.

Black Sea GIS developed in MHI

Science.gov (United States)

Zhuk, E.; Khaliulin, A.; Zodiatis, G.; Nikolaidis, A.; Isaeva, E.

2016-08-01

The work aims at creating the Black Sea geoinformation system (GIS) and complementing it with a model bank. The software for data access and visualization was developed using client server architecture. A map service based on MapServer and MySQL data management system were chosen for the Black Sea GIS. Php-modules and python-scripts are used to provide data access, processing, and exchange between the client application and the server. According to the basic data types, the module structure of GIS was developed. Each type of data is matched to a module which allows selection and visualization of the data. At present, a GIS complement with a model bank (the models build in to the GIS) and users' models (programs launched on users' PCs but receiving and displaying data via GIS) is developed.

Black holes are warm

International Nuclear Information System (INIS)

Ravndal, F.

1978-01-01

Applying Einstein's theory of gravitation to black holes and their interactions with their surroundings leads to the conclusion that the sum of the surface areas of several black holes can never become less. This is shown to be analogous to entropy in thermodynamics, and the term entropy is also thus applied to black holes. Continuing, expressions are found for the temperature of a black hole and its luminosity. Thermal radiation is shown to lead to explosion of the black hole. Numerical examples are discussed involving the temperature, the mass, the luminosity and the lifetime of black mini-holes. It is pointed out that no explosions corresponding to the prediction have been observed. It is also shown that the principle of conservation of leptons and baryons is broken by hot black holes, but that this need not be a problem. The related concept of instantons is cited. It is thought that understanding of thermal radiation from black holes may be important for the development of a quantified gravitation theory. (JIW)

Is It because I'm Black? A Black Female Research Experience

Science.gov (United States)

Maylor, Uvanney

2009-01-01

This article examines what it means to be a Black female researcher in contemporary Britain. Drawing on Black feminist theory and critical race theory (CRT), this article seeks to highlight some of the experiences and challenges that Black female researchers face when undertaking research, particularly research that has diversity, equality or…

Who Will Make America Great Again? "Black People, of Course…"

Science.gov (United States)

King, Joyce E.

2017-01-01

The author reflects on the relevance of her intellectual journey through the Black consciousness movement in the 1960s to her pedagogy teaching from a Black Studies theoretical perspective on liberating knowledge. This pedagogical approach aims to fortify education students' consciousness regarding a systemic understanding of how racism and…

The stable problem of the black-hole connected region in the Schwarzschild black hole

OpenAIRE

Tian, Guihua

2005-01-01

The stability of the Schwarzschild black hole is studied. Using the Painlev\\'{e} coordinate, our region can be defined as the black-hole-connected region(r>2m, see text) of the Schwarzschild black hole or the white-hole-connected region(r>2m, see text) of the Schwarzschild black hole. We study the stable problems of the black-hole-connected region. The conclusions are: (1) in the black-hole-connected region, the initially regular perturbation fields must have real frequency or complex frequen...

Black hole thermodynamical entropy

International Nuclear Information System (INIS)

Tsallis, Constantino; Cirto, Leonardo J.L.

2013-01-01

As early as 1902, Gibbs pointed out that systems whose partition function diverges, e.g. gravitation, lie outside the validity of the Boltzmann-Gibbs (BG) theory. Consistently, since the pioneering Bekenstein-Hawking results, physically meaningful evidence (e.g., the holographic principle) has accumulated that the BG entropy S BG of a (3+1) black hole is proportional to its area L 2 (L being a characteristic linear length), and not to its volume L 3 . Similarly it exists the area law, so named because, for a wide class of strongly quantum-entangled d-dimensional systems, S BG is proportional to lnL if d=1, and to L d-1 if d>1, instead of being proportional to L d (d ≥ 1). These results violate the extensivity of the thermodynamical entropy of a d-dimensional system. This thermodynamical inconsistency disappears if we realize that the thermodynamical entropy of such nonstandard systems is not to be identified with the BG additive entropy but with appropriately generalized nonadditive entropies. Indeed, the celebrated usefulness of the BG entropy is founded on hypothesis such as relatively weak probabilistic correlations (and their connections to ergodicity, which by no means can be assumed as a general rule of nature). Here we introduce a generalized entropy which, for the Schwarzschild black hole and the area law, can solve the thermodynamic puzzle. (orig.)

Quantum aspects of black holes

CERN Document Server

2015-01-01

Beginning with an overview of the theory of black holes by the editor, this book presents a collection of ten chapters by leading physicists dealing with the variety of quantum mechanical and quantum gravitational effects pertinent to black holes. The contributions address topics such as Hawking radiation, the thermodynamics of black holes, the information paradox and firewalls, Monsters, primordial black holes, self-gravitating Bose-Einstein condensates, the formation of small black holes in high energetic collisions of particles, minimal length effects in black holes and small black holes at the Large Hadron Collider. Viewed as a whole the collection provides stimulating reading for researchers and graduate students seeking a summary of the quantum features of black holes.

Charged black holes in quadratic gravity

International Nuclear Information System (INIS)

Matyjasek, Jerzy; Tryniecki, Dariusz

2004-01-01

Iterative solutions to fourth-order gravity describing static and electrically charged black holes are constructed. The obtained solutions are parametrized by two integration constants which are related to the electric charge and the exact location of the event horizon. Special emphasis is put on the extremal black holes. It is explicitly demonstrated that in the extremal limit the exact location of the (degenerate) event horizon is given by r + =|e|. Similarly to the classical Reissner-Nordstroem solution, the near-horizon geometry of the charged black holes in quadratic gravity, when expanded into the whole manifold, is simply that of Bertotti and Robinson. Similar considerations have been carried out for boundary conditions of the second type which employ the electric charge and the mass of the system as seen by a distant observer. The relations between results obtained within the framework of each method are briefly discussed

Cosmological and black hole apparent horizons

CERN Document Server

Faraoni, Valerio

2015-01-01

This book overviews the extensive literature on apparent cosmological and black hole horizons. In theoretical gravity, dynamical situations such as gravitational collapse, black hole evaporation, and black holes interacting with non-trivial environments, as well as the attempts to model gravitational waves occurring in highly dynamical astrophysical processes, require that the concept of event horizon be generalized. Inequivalent notions of horizon abound in the technical literature and are discussed in this manuscript. The book begins with a quick review of basic material in the first one and a half chapters, establishing a unified notation. Chapter 2 reminds the reader of the basic tools used in the analysis of horizons and reviews the various definitions of horizons appearing in the literature. Cosmological horizons are the playground in which one should take baby steps in understanding horizon physics. Chapter 3 analyzes cosmological horizons, their proposed thermodynamics, and several coordinate systems....

Four-dimensional black holes with scalar hair in nonlinear electrodynamics

International Nuclear Information System (INIS)

Barrientos, Jose; Gonzalez, P.A.; Vasquez, Yerko

2016-01-01

We consider a gravitating system consisting of a scalar field minimally coupled to gravity with a self-interacting potential and a U(1) nonlinear electromagnetic field. Solving analytically and numerically the coupled system for both power-law and Born-Infeld type electrodynamics, we find charged hairy black hole solutions. Then we study the thermodynamics of these solutions and we find that at a low temperature the topological charged black hole with scalar hair is thermodynamically preferred, whereas the topological charged black hole without scalar hair is thermodynamically preferred at a high temperature for power-law electrodynamics. Interestingly enough, these phase transitions occur at a fixed critical temperature and do not depend on the exponent p of the nonlinear electrodynamics. (orig.)

Four-dimensional black holes with scalar hair in nonlinear electrodynamics

Energy Technology Data Exchange (ETDEWEB)

Barrientos, Jose [Universidad de Concepcion, Departamento de Fisica, Concepcion (Chile); Universidad Catolica del Norte, Departamento de Ensenanza de las Ciencias Basicas, Coquimbo (Chile); Gonzalez, P.A. [Universidad Diego Portales, Facultad de Ingenieria, Santiago (Chile); Vasquez, Yerko [Universidad de La Serena, Departamento de Fisica y Astronomia, Facultad de Ciencias, La Serena (Chile)

2016-12-15

We consider a gravitating system consisting of a scalar field minimally coupled to gravity with a self-interacting potential and a U(1) nonlinear electromagnetic field. Solving analytically and numerically the coupled system for both power-law and Born-Infeld type electrodynamics, we find charged hairy black hole solutions. Then we study the thermodynamics of these solutions and we find that at a low temperature the topological charged black hole with scalar hair is thermodynamically preferred, whereas the topological charged black hole without scalar hair is thermodynamically preferred at a high temperature for power-law electrodynamics. Interestingly enough, these phase transitions occur at a fixed critical temperature and do not depend on the exponent p of the nonlinear electrodynamics. (orig.)

Einstein-Yang-Mills-Lorentz black holes

Energy Technology Data Exchange (ETDEWEB)

Cembranos, Jose A.R.; Gigante Valcarcel, Jorge [Universidad Complutense de Madrid, Departamento de Fisica Teorica I, Madrid (Spain)

2017-12-15

Different black hole solutions of the coupled Einstein-Yang-Mills equations have been well known for a long time. They have attracted much attention from mathematicians and physicists since their discovery. In this work, we analyze black holes associated with the gauge Lorentz group. In particular, we study solutions which identify the gauge connection with the spin connection. This ansatz allows one to find exact solutions to the complete system of equations. By using this procedure, we show the equivalence between the Yang-Mills-Lorentz model in curved space-time and a particular set of extended gravitational theories. (orig.)

LIGO Discovers the Merger of Two Black Holes

Science.gov (United States)

Kohler, Susanna

2016-02-01

Big news: the Laser Interferometer Gravitational-Wave Observatory (LIGO) has detected its first gravitational-wave signal! Not only is the detection of this signal a major technical accomplishment and an exciting confirmation of general relativity, but it also has huge implications for black-hole astrophysics.What did LIGO see?LIGO is designed to detect the ripples in space-time created by two massive objects orbiting each other. These waves can reach observable amplitudes when a binary system consisting of two especially massive objects i.e., black holes or neutron stars reach the end of their inspiral and merge.LIGO has been unsuccessfully searching for gravitational waves since its initial operations in 2002, but a recent upgrade in its design has significantly increased its sensitivity and observational range. The first official observing run of Advanced LIGO began 18 September 2015, but the instruments were up and running in engineering mode several weeks before that. And it was in this time frame before official observing even began! that LIGO spotted its first gravitational wave signal: GW150914.One of LIGOs two detection sites, located near Hanford in eastern Washington. [LIGO]The signal, detected on 14 September, 2015, provides astronomers with a remarkable amount of information about the merger that caused it. From the detection, the LIGO team has extracted the masses of the two black holes that merged, 36+5-4 and 29+4-4 solar masses, as well as the mass of the final black hole formed by the merger, ~62 solar masses. The team also determined that the merger happened roughly a billion light-years away (at a redshift of z~0.1), and the direction of the signal was localized to an area of ~600 square degrees (roughly 1% of the sky).Why is this detection a big deal?This is the firstdirect detection of gravitational waves, providing spectacular further confirmation of Einsteins theory of general relativity. But the implications of GW150914 go far beyond this

Black holes and beyond

Energy Technology Data Exchange (ETDEWEB)

NONE

2002-02-01

Belief in the existence of black holes is the ultimate act of faith for a physicist. First suggested by the English clergyman John Michell in the year 1784, the gravitational pull of a black hole is so strong that nothing - not even light - can escape. Gravity might be the weakest of the fundamental forces but black-hole physics is not for the faint-hearted. Black holes present obvious problems for would-be observers because they cannot, by definition, be seen with conventional telescopes - although before the end of the decade gravitational-wave detectors should be able to study collisions between black holes. Until then astronomers can only infer the existence of a black hole from its gravitational influence on other matter, or from the X-rays emitted by gas and dust as they are dragged into the black hole. However, once this material passes through the 'event horizon' that surrounds the black hole, we will never see it again - not even with X-ray specs. Despite these observational problems, most physicists and astronomers believe that black holes do exist. Small black holes a few kilometres across are thought to form when stars weighing more than about two solar masses collapse under the weight of their own gravity, while supermassive black holes weighing millions of solar masses appear to be present at the centre of most galaxies. Moreover, some brave physicists have proposed ways to make black holes - or at least event horizons - in the laboratory. The basic idea behind these 'artificial black holes' is not to compress a large amount of mass into a small volume, but to reduce the speed of light in a moving medium to less than the speed of the medium and so create an event horizon. The parallels with real black holes are not exact but the experiments could shed new light on a variety of phenomena. The first challenge, however, is to get money for the research. One year on from a high-profile meeting on artificial black holes in London, for

Complicated Contradictions Amid Black Feminism and Millennial Black Women Teachers Creating Curriculum for Black Girls

Science.gov (United States)

Nyachae, Tiffany M.

2016-01-01

Millennial Black women teachers wrestle with two simultaneous burdens: disrupting the racist and sexist status quo of schooling through curriculum, and employing tactics to survive school politics among their majority White women colleagues. This article describes how the "Sisters of Promise" (SOP) curriculum aligned with Black feminism…

Grumblings from an Awakening Black Hole

Science.gov (United States)

Kohler, Susanna

2015-11-01

In June of this year, after nearly three decades of sleep, the black hole V404 Cygni woke up and began grumbling. Scientists across the globe scrambled to observe the sudden flaring activity coming from this previously peaceful black hole. And now were getting the first descriptions of what weve learned from V404 Cygs awakening!Sudden OutburstV404 Cyg is a black hole of roughly nine solar masses, and its in a binary system with a low-mass star. The black hole pulls a stream of gas from the star, which then spirals in around the black hole, forming an accretion disk. Sometimes the material simply accumulates in the disk but every two or three decades, the build-up of gas suddenly rushes toward the black hole as if a dam were bursting.The sudden accretion in these events causes outbursts of activity from the black hole, its flaring easily visible to us. The last time V404 Cyg exhibited such activity was in 1989, and its been rather quiet since then. Our telescopes are of course much more powerful and sensitive now, nearly three decades later so when the black hole woke up and began flaring in June, scientists were delighted at the chance to observe it.The high variability of V404 Cyg is evident in this example set of spectra, where time increases from the bottom panel to the top. [King et al. 2015]Led by Ashley King (Einstein Fellow at Stanford University), a team of scientists observed V404 Cyg with the Chandra X-ray Observatory, obtaining spectra of the black hole during its outbursts. The black hole flared so brightly during its activity that the team had to take precautions to protect the CCDs in their detector from radiation damage! Now the group has released the first results from their analysis.Windy DiskThe primary surprise from V404 Cyg is its winds. Many stellar-mass black holes have outflows of mass, either in the form of directed jets emitted from their centers, or in the form of high-energy winds isotropically emitted from their accretion disks. But V404

Black powder removal in a Mexico gas pipeline

Energy Technology Data Exchange (ETDEWEB)

Morrow, John R. [TDW Services, Inc., New Castle, DE (United States); Drysdale, Colin; Warterfield, Bob D. [T.D.Williamson, Inc., Tulsa, OK (United States)

2008-07-01

This paper focuses on the cleaning methodology and operational constrains involved with the removal of black powder in a high pressure natural gas transmission pipeline. In this case, the accumulation of black powder along the pipeline system over the seven year period since it was put into service was creating significant problems in the areas of maintenance, customer relations, and cost to the pipeline operator due to clogging of filters, reduced gas flow, and penalties as result of non-compliant delivery contracts. The pipeline cleaning project consisted of running cleaning pigs or scrappers with batches of cleaning solution through each section of the pipeline while dealing with such factors as three (3) pipeline section lengths in excess of 160 kms (100 miles), gas flow velocity fluctuations, shutdowns, and gas delivery schedule requirements. The cleaning program for the entire pipeline system included the use of chemical and diesel based cleaning solution, running multiple cleaning pigs, liquid injection and separation system, mobile storage tanks, various equipment and personnel for logistical support. Upon completion of the cleaning program, the level of black powder and other solids in all pipeline sections was reduced to approximately 0.5% liquid/solid ratio and the pipeline system returned to normal optimum operation. (author.

A Search for Black Holes and Neutron Stars in the Kepler Field

Science.gov (United States)

Orosz, Jerome; Short, Donald; Welsh, William; Windmiller, Gur; Dabney, David

2018-01-01

Black holes and neutron stars represent the final evolutionary stages of the most massive stars. In addition to their use as probes into the evolution of massive stars, black holes and neutron stars are ideal laboratories to test General Relativity in the strong field limit. The number of neutron stars and black holes in the Milky Way is not precisely known, but there are an estimated one billion neutron stars in the galaxy based on the observed numbers of radio pulsars. The number of black holes is about 100 million, based on the behavior of the Initial Mass Function at high stellar masses.All of the known steller-mass black holes (and a fair number of neutron stars) are in ``X-ray binaries'' that were discovered because of their luminous X-ray emission. The requirement to be in an X-ray-emitting binary places a strong observational bias on the discovery of stellar-mass black holes. Thus the 21 known black hole binaries represent only the very uppermost tip of the population iceberg.We have conducted an optical survey using Kepler data designed to uncover black holes and neutron stars in both ``quiescent'' X-ray binaries and ``pre-contact'' X-ray binaries. We discuss how the search was conducted, including how potentially interesting light curves were classified and the how variability types were identified. Although we did not find any convincing candidate neutron star or black hole systems, we did find a few noteworthy binary systems, including two binaries that contain low-mass stars with unusually low albedos.

A Lifshitz black hole in four dimensional R2 gravity

International Nuclear Information System (INIS)

Cai Ronggen; Liu Yan; Sun Yawen

2009-01-01

We consider a higher derivative gravity theory in four dimensions with a negative cosmological constant and show that vacuum solutions of both Lifshitz type and Schroedinger type with arbitrary dynamical exponent z exist in this system. Then we find an analytic black hole solution which asymptotes to the vacuum Lifshitz solution with z = 3/2 at a specific value of the coupling constant. We analyze the thermodynamic behavior of this black hole and find that the black hole has zero entropy while non-zero temperature, which is very similar to the case of BTZ black holes in new massive gravity at a specific coupling. In addition, we find that the three dimensional Lifshitz black hole recently found by E. Ayon-Beato et al. has a negative entropy and mass when the Newton constant is taken to be positive.

Rotating black holes at future colliders. III. Determination of black hole evolution

International Nuclear Information System (INIS)

Ida, Daisuke; Oda, Kin-ya; Park, Seong Chan

2006-01-01

TeV scale gravity scenario predicts that the black hole production dominates over all other interactions above the scale and that the Large Hadron Collider will be a black hole factory. Such higher-dimensional black holes mainly decay into the standard model fields via the Hawking radiation whose spectrum can be computed from the greybody factor. Here we complete the series of our work by showing the greybody factors and the resultant spectra for the brane-localized spinor and vector field emissions for arbitrary frequencies. Combining these results with the previous works, we determine the complete radiation spectra and the subsequent time evolution of the black hole. We find that, for a typical event, well more than half a black hole mass is emitted when the hole is still highly rotating, confirming our previous claim that it is important to take into account the angular momentum of black holes

Distorted black holes in terms of multipole moments

International Nuclear Information System (INIS)

Suen, W.

1986-01-01

In terms of a multipole-moment formalism previously developed for non-asymptotically-flat systems in general relativity, the metric of a Schwarzschild black hole in an external quadrupolar gravitational field is studied. Among other results, we find that the black hole develops an induced quadrupole moment, which in turn generates a tidal field opposing the applied field. This effect, plus the fact that the horizon cannot expand when a quasistatic tidal force is applied, can be described in terms of effective 2-dimensional elastic moduli for the black-hole horizon. The bulk modulus is kappa = ∞, and the shear modulus is mu = -63/(20πM), where M is the hole's mass

Black hole mass formula in the membrane paradigm

Science.gov (United States)

Lemos, José P. S.; Zaslavskii, Oleg B.

2018-03-01

The membrane paradigm approach adopts a timelike surface, stretched out off the null event horizon, to study several important black hole properties. We use this powerful tool to give a direct derivation of the black hole mass formula in the static and stationary cases without and with electric field. Since here the membrane is a self-gravitating material system, we go beyond the usual applicability on test particles and test fields of the paradigm.

BlackBerry For Dummies

CERN Document Server

Kao, Robert

2010-01-01

Get the most juice out of your BlackBerry handheld!. Feature-rich and complex, the BlackBerry is the number one smartphone in the corporate world is among the most popular handhelds for business users. This new and updated edition includes all the latest and greatest information on new and current BlackBerry mobile devices. Covering a range of valuable how-to topics, this helpful guide explores the BlackBerry's most useful features, techniques for getting the most out of your BlackBerry, and practical information about power usage.: Covers all aspects of the number one smartphone in the corpor

System Aspects of Black Liquor Gasification. A review of existing reports

Energy Technology Data Exchange (ETDEWEB)

Berntsson, Thore [Chalmers Univ. of Technology, Goeteborg (Sweden)

2008-12-15

Black liquor gasification (BLG) is one of the high-prioritized RandD areas in Sweden. Research work is going on in the national program BLG-Programme. The main aims with the present study are to: - Identify larger projects dealing with energy oriented system aspects of BLG - Make a synthesis on system aspects results in these projects - Identify need for further work, e.g. as a part of a second period of the BLG Programme. No new work or calculations have been performed, the aim has been only to compile and draw conclusions from existing information. The focus has been on system studies. Most of the research on BLG has been technically, chemically and component oriented. These areas are not included in this report. In Chapter 2 basics for BLG are presented and in Chapter 3 important system aspects of this technology are discussed. Future opportunities for energy savings in mills are crucial for a BLG system, both technically and economically. Therefore present knowledge for such opportunities is presented in Chapter 4. In section 1.4 the report/projects included in this report are introduced and in Chapter 5-13 Summaries, especially on system aspects, of these reports are given. In order to keep the report at a reasonable size only major projects dealing with system aspects during the last 10 year period have been included. In Chapter 14 a synthesis of system aspects dealt with in the different reports is presented and in Chapter 15 suggestions for further work are given. In Chapter 16 references are given and finally in the Attachment a brief overview of different BLG technologies is presented

Magnonic black holes

OpenAIRE

Roldán-Molina, A.; Nunez, A.S.; Duine, R. A.

2017-01-01

We show that the interaction between spin-polarized current and magnetization dynamics can be used to implement black-hole and white-hole horizons for magnons - the quanta of oscillations in the magnetization direction in magnets. We consider three different systems: easy-plane ferromagnetic metals, isotropic antiferromagnetic metals, and easy-plane magnetic insulators. Based on available experimental data, we estimate that the Hawking temperature can be as large as 1 K. We comment on the imp...

Satellite monitoring of black bear.

Science.gov (United States)

Craighead, J. J.; Craighead, F. C., Jr.; Varney, J. R.; Cote, C. E.

1971-01-01

Description of a feasibility experiment recently performed to test the use of a satellite system for telemetering environmental and physiological data from the winter den of a 'hibernating' black bear, Ursus americanus. The instrumentation procedure and evaluations of the equipment performance and sensory data obtained are discussed in detail.

Thermodynamics of string black hole with hyperscaling violation

International Nuclear Information System (INIS)

Sadeghi, J.; Pourhassan, B.; Asadi, A.

2014-01-01

In this paper, we start with a black brane and construct a specific space-time which violates hyperscaling. To obtain the string solution, we apply the Null-Melvin Twist and KK reduction. Using the difference action method, we study the thermodynamics of the system to obtain a Hawking-Page phase transition. To have hyperscaling violation, we need to consider θ = (d)/(2). In this case, the free energy F is always negative and our solution is thermal radiation without a black hole. Therefore, we find that there is no Hawking-Page transition. Also, we discuss the stability of the system and all thermodynamical quantities. (orig.)

ACCRETION DISKS AROUND KICKED BLACK HOLES: POST-KICK DYNAMICS

International Nuclear Information System (INIS)

Ponce, Marcelo; Faber, Joshua A.; Lombardi, James C.

2012-01-01

Numerical calculations of merging black hole binaries indicate that asymmetric emission of gravitational radiation can kick the merged black hole at up to thousands of km s –1 , and a number of systems have been observed recently whose properties are consistent with an active galactic nucleus containing a supermassive black hole moving with substantial velocity with respect to its broader accretion disk. We study here the effect of an impulsive kick delivered to a black hole on the dynamical evolution of its accretion disk using a smoothed particle hydrodynamics code, focusing attention on the role played by the kick angle with respect to the orbital angular momentum vector of the pre-kicked disk. We find that for more vertical kicks, for which the angle between the kick and the normal vector to the disk θ ∼ 45°, matter rapidly accretes toward the black hole. There is a systematic trend for higher potential luminosities for more oblique kick angles for a given black hole mass, disk mass, and kick velocity, and we find large amplitude oscillations in time in the case of a kick oriented 60° from the vertical.

Advanced infrared optically black baffle materials

International Nuclear Information System (INIS)

Seals, R.D.; Egert, C.M.; Allred, D.D.

1990-01-01

Infrared optically black baffle surfaces are an essential component of many advanced optical systems. All internal surfaces in advanced infrared optical sensors that require stray light management to achieve resolution are of primary concern in baffle design. Current industrial materials need improvements to meet advanced optical sensor systems requirements for optical, survivability, and endurability. Baffles are required to survive and operate in potentially severe environments. Robust diffuse-absorptive black surfaces, which are thermally and mechanically stable to threats of x-ray, launch, and in-flight maneuver conditions, with specific densities to allow an acceptable weight load, handleable during assembly, cleanable, and adaptive to affordable manufacturing, are required as optical baffle materials. In this paper an overview of recently developed advanced infrared optical baffle materials, requirements, manufacturing strategies, and the Optics MODIL (Manufacturing Operations Development and Integration Laboratory) Advanced Baffle Program are discussed

AN INTERACTION MODEL BETWEEN ENVIRONMENTAL FACTORS AND BLACK RICE GROWTH IN IRRIGATED ORGANIC PADDY FIELD

Directory of Open Access Journals (Sweden)

Budiman

2015-02-01

Full Text Available Black rice production in organic farming system does not meet the demand of local customers because of its low productivity. This research aimed to set an interaction model using multivariate analysis via smartPLS to identify environmental factors which simultaneously affects the growth of black rice. The growth of black rice in two irrigated organic paddy field in Malang, Indonesia was observed during planting period from November 2011 to March 2012. In each rice field, the growth was periodically recorded during planting periods: 19-29 days after planting (dap, 41-45 dap, 62-66 dap, 77-81 dap, 90-94 dap and 104-106 dap. Environmental factors such as water quantities, soil conditions, weed communities and cultivation system around the black rice population were also measured. Black rice growth was influenced simultaneously by water quantities, soil, weed communities and cultivating systems with predictive-relevance value reaching 92.83%. Based on the model, water quantities in paddy field is a key factor which directly and indirectly determined the growth and productivity of black rice.

Framing black boys: parent, teacher, and student narratives of the academic lives of black boys.

Science.gov (United States)

Rowley, Stephanie J; Ross, Latisha; Lozada, Fantasy T; Williams, Amber; Gale, Adrian; Kurtz-Costes, Beth

2014-01-01

The discourse on Black boys tends to suggest that Black boys are in complete peril. We begin with evidence that Black boys are excelling in certain contexts (i.e., in certain states, in certain schools, and in certain courses). We then discuss the ways in which the narratives used by parents, teachers, and Black boys themselves may serve to further reinforce views that Black boys are beyond hope. Research on Black parents suggests that they tend to view their sons as vulnerable and have lower expectations for sons than for daughters. Studies of teachers show that they tend to view Black boys as unteachable, as social problems, and as scary. Research on Black boys shows that they are sometimes complicit in supporting these narratives by engaging in negative or ste reotypical behavior. We also include recent research that includes counter-narratives of Black boys. We end with suggestions for future research.

The Black Family as Educator.

Science.gov (United States)

Wallace, Joan

The black family is the primary socializing agent of the black child and, thus, the primary educator. The culture of blacks in America, in which the child is steeped, is unique, complex and rich-the result of a convergence and fusion of African, American, and European influences. In its education of the black child, the black family must deal,…

Monopole Black Hole Skyrmions

OpenAIRE

Moss, Ian G; Shiiki, N; Winstanley, E

2000-01-01

Charged black hole solutions with pion hair are discussed. These can be\\ud used to study monopole black hole catalysis of proton decay.\\ud There also exist\\ud multi-black hole skyrmion solutions with BPS monopole behaviour.

VBSM: VCC-Based Black Box Service Model with Enhanced Data Integrity

Directory of Open Access Journals (Sweden)

Won Min Kang

2014-10-01

Full Text Available Recently, intelligent transport systems have been applied to vehicle cloud environments. Such technology is especially useful for the systematic management of road traffic. Moreover, automobiles are increasingly equipped with a black box for accident prevention and preservation of evidence. Vehicle black boxes have become mandatory because black box images and voice data have served as forensic evidence in courts. However, the data from black boxes can be forged or modified by man-in-the-middle (MITM attacks and message hijacking. In this paper, we propose a vehicle cloud computing-based black box service model that can provide integrity for black box data through digital signatures in vehicle cloud computing (VCC environments. Our proposed model protects against MITM attacks and message hijacking using only a hash value and digital signature. Moreover, a mirroring technique (RAID 1 provides backup and recovery to protect the data from a traffic accident.

Skyrmion black hole hair: Conservation of baryon number by black holes and observable manifestations

Energy Technology Data Exchange (ETDEWEB)

Dvali, Gia [Arnold Sommerfeld Center, Ludwig-Maximilians-Universität, 80333 München (Germany); Max-Planck-Institut für Physik, Werner-Heisenberg-Institut, 80805 München (Germany); Center for Cosmology and Particle Physics, Department of Physics, New York University, 4 Washington Place, New York, NY 10003 (United States); Gußmann, Alexander, E-mail: alexander.gussmann@physik.uni-muenchen.de [Arnold Sommerfeld Center, Ludwig-Maximilians-Universität, 80333 München (Germany)

2016-12-15

We show that the existence of black holes with classical skyrmion hair invalidates standard proofs that global charges, such as the baryon number, cannot be conserved by a black hole. By carefully analyzing the standard arguments based on a Gedankenexperiment in which a black hole is seemingly-unable to return the baryon number that it swallowed, we identify inconsistencies in this reasoning, which does not take into the account neither the existence of skyrmion black holes nor the baryon/skyrmion correspondence. We then perform a refined Gedankenexperiment by incorporating the new knowledge and show that no contradiction with conservation of baryon number takes place at any stage of black hole evolution. Our analysis also indicates no conflict between semi-classical black holes and the existence of baryonic gauge interaction arbitrarily-weaker than gravity. Next, we study classical cross sections of a minimally-coupled massless probe scalar field scattered by a skyrmion black hole. We investigate how the skyrmion hair manifests itself by comparing this cross section with the analogous cross section caused by a Schwarzschild black hole which has the same ADM mass as the skyrmion black hole. Here we find an order-one difference in the positions of the characteristic peaks in the cross sections. The peaks are shifted to smaller scattering angles when the skyrmion hair is present. This comes from the fact that the skyrmion hair changes the near horizon geometry of the black hole when compared to a Schwarzschild black hole with same ADM mass. We keep the study of this second aspect general so that the qualitative results which we obtain can also be applied to black holes with classical hair of different kind.

Microstates of black holes in expanding universe from interacting branes

Energy Technology Data Exchange (ETDEWEB)

Shiba, Shotaro [Theory Center, High Energy Accelerator Research Organization (KEK),1-1 Oho, Tsukuba, Ibaraki 305-0801 (Japan)

2017-05-15

Thermodynamics of the near extremal black p-branes can be described by collective motions of gravitationally interacting branes. This proposal is called the p-soup model. In this paper, we check this proposal in the case of black brane system which is asymptotically Friedmann-Lemaître-Robertson-Walker universe in an infinite distance. As a result, we can show that the gravitationally interacting branes explain free energy, entropy, temperature and other physical quantities in these systems. This implies that the microstates of this kind of brane system can be also understood in the p-soup model.

VLBA Reveals Closest Pair of Supermassive Black Holes

Science.gov (United States)

2006-05-01

black holes," Taylor said. The VLBA is a continent-wide system of ten radio-telescope antennas. It provides the greatest ability to see fine detail, called resolving power, of any telescope in astronomy. "Astronomers have thought for a long time that close pairs of black holes should result from galaxy collisions," Rodriguez said. Still, finding them has proven difficult. Until now, the closest confirmed pairs of supermassive black holes were at least 4,500 light-years apart. Pairs of smaller black holes, each only a few times the mass of the Sun, have been found in our own Milky Way Galaxy, but 0402+379 harbors the pair of supermassive black holes that are the closest to each other yet found. Galactic collisions are common throughout the Universe, and astronomers think that the binary pairs of supermassive black holes that result can have important effects on the subsequent evolution of the galaxies. In a number of predicted scenarios, such giant pairs of black holes will themselves collide, sending gravitational waves out through the Universe. Such gravitational waves could be detected with a proposed joint space mission between NASA and the European Space Agency, the Laser Interferometer Space Antenna. "Such black-hole collisions undoubtedly are important processes, and we need to understand them. Finding ever-closer pairs of supermassive black holes is the first step in that process. Even finding one such system has dramatically changed our expectations, and informed us about what to look for," Taylor said. Taylor and his collaborators are currently using the VLBA to carry out the largest survey of compact radio-emitting objects ever undertaken, in the hope of finding more such pairs. Rodriguez and Taylor worked with Robert Zavala of the U.S. Naval Observatory, Allison Peck of the SubMillimeter Array of the Harvard- Smithsonian Center for Astrophysics, Lindsey Pollack of the University of California at Santa Cruz, and Roger Romani of Stanford University. Their

Bio-refinery system in a pulp mill for methanol production with comparison of pressurized black liquor gasification and dry gasification using direct causticization

International Nuclear Information System (INIS)

Naqvi, Muhammad; Yan, Jinyue; Dahlquist, Erik

2012-01-01

Black liquor gasification (BLG) for bio-fuel or electricity production at the modern pulp mills is a field in continuous evolution and the efforts are considerably driven by the climate change, fuel security, and renewable energy. This paper evaluates and compares two BLG systems for methanol production: (i) oxygen blown pressurized thermal BLG; and (ii) dry BLG with direct causticization, which have been regarded as the most potential technology candidates for the future deployment. A key objective is to assess integration possibilities of BLG technologies with the reference Kraft pulp mill producing 1000 air dried tonnes (ADt) pulp/day replacing conventional recovery cycle. The study was performed to compare the systems’ performance in terms of potential methanol production, energy efficiency, and potential CO 2 reductions. The results indicate larger potential of black liquor conversion to methanol from the pressurized BLG system (about 77 million tonnes/year of methanol) than the dry BLG system (about 30 million tonnes/year of methanol) utilizing identical amount of black liquor available worldwide (220 million tDS/year). The potential CO 2 emissions reduction from the transport sector is substantially higher in pressurized BLG system (117 million tonnes/year CO 2 reductions) as compared to dry BLG system (45 million tonnes/year CO 2 reductions). However, the dry BLG system with direct causticization shows better results when considering consequences of additional biomass import. In addition, comparison of methanol production via BLG with other bio-refinery products, e.g. hydrogen, dimethyl ether (DME) and bio-methane, has also been discussed.

WHEN CAN GRAVITATIONAL-WAVE OBSERVATIONS DISTINGUISH BETWEEN BLACK HOLES AND NEUTRON STARS?

International Nuclear Information System (INIS)

Hannam, Mark; Fairhurst, Stephen; Brown, Duncan A.; Fryer, Chris L.; Harry, Ian W.

2013-01-01

Gravitational-wave observations of compact binaries have the potential to uncover the distribution of masses and spins of black holes and neutron stars in the universe. The binary components' physical parameters can be inferred from their effect on the phasing of the gravitational-wave signal, but a partial degeneracy between the components' mass ratio and their spins limits our ability to measure the individual component masses. At the typical signal amplitudes expected by the Advanced Laser Interferometer Gravitational-wave Observatory (signal-to-noise ratios between 10 and 20), we show that it will in many cases be difficult to distinguish whether the components are neutron stars or black holes. We identify when the masses of the binary components could be unambiguously measured outside the range of current observations: a system with a chirp mass M ≤ 0.871 M ☉ would unambiguously contain the smallest-mass neutron star observed, and a system with M ≥ 2.786 M ☉ must contain a black hole. However, additional information would be needed to distinguish between a binary containing two 1.35 M ☉ neutron stars and an exotic neutron-star-black-hole binary. We also identify those configurations that could be unambiguously identified as black hole binaries, and show how the observation of an electromagnetic counterpart to a neutron-star-black-hole binary could be used to constrain the black hole spin.

The US Army in Kirkuk: Governance Operations on the Fault Lines of Iraqi Society, 2003-2009

Science.gov (United States)

2011-12-01

point 16 repeatedly to the Baathist regime’s de-Kurdification of Kirkuk as prima facie justification for returning control of the city to the Kurds...Americans had a quid pro quo obligation to help them get their land back from the 10,000 squatting Arabs.23 Patrick Clawson of the Middle East Quarterly...beginning of the campaign, US Soldiers were gradu- ally passing these obligations to Iraqi government officials to manage their own internal and external

Black holes without firewalls

Science.gov (United States)

Larjo, Klaus; Lowe, David A.; Thorlacius, Larus

2013-05-01

The postulates of black hole complementarity do not imply a firewall for infalling observers at a black hole horizon. The dynamics of the stretched horizon, that scrambles and reemits information, determines whether infalling observers experience anything out of the ordinary when entering a large black hole. In particular, there is no firewall if the stretched horizon degrees of freedom retain information for a time of the order of the black hole scrambling time.

Thermodynamical stability of the Bardeen black hole

Energy Technology Data Exchange (ETDEWEB)

Bretón, Nora [Dpto. de Física, Centro de Investigación y de Estudios Avanzados del I. P. N., Apdo. 14-740, D.F. (Mexico); Perez Bergliaffa, Santiago E. [Dpto. de Física, U. Estado do Rio de Janeiro (Brazil)

2014-01-14

We analyze the stability of the regular magnetic Bardeen black hole both thermodynamically and dynamically. For the thermodynamical analysis we consider a microcanonical ensemble and apply the turning point method. This method allows to decide a change in stability (or instability) of a system, requiring only the assumption of smoothness of the area functional. The dynamical stability is asserted using criteria based on the signs of the Lagrangian and its derivatives. It turns out from our analysis that the Bardeen black hole is both thermodynamically and dynamically stable.

Horizon quantum mechanics of rotating black holes

Energy Technology Data Exchange (ETDEWEB)

Casadio, Roberto [Universita di Bologna, Dipartimento di Fisica e Astronomia, Bologna (Italy); I.N.F.N., Sezione di Bologna, I.S. FLAG, Bologna (Italy); Giugno, Andrea [Ludwig-Maximilians-Universitaet, Arnold Sommerfeld Center, Munich (Germany); Giusti, Andrea [Universita di Bologna, Dipartimento di Fisica e Astronomia, Bologna (Italy); I.N.F.N., Sezione di Bologna, I.S. FLAG, Bologna (Italy); Ludwig-Maximilians-Universitaet, Arnold Sommerfeld Center, Munich (Germany); Micu, Octavian [Institute of Space Science, Bucharest, P.O. Box MG-23, Bucharest-Magurele (Romania)

2017-05-15

The horizon quantum mechanics is an approach that was previously introduced in order to analyze the gravitational radius of spherically symmetric systems and compute the probability that a given quantum state is a black hole. In this work, we first extend the formalism to general space-times with asymptotic (ADM) mass and angular momentum. We then apply the extended horizon quantum mechanics to a harmonic model of rotating corpuscular black holes. We find that simple configurations of this model naturally suppress the appearance of the inner horizon and seem to disfavor extremal (macroscopic) geometries. (orig.)

Fear of a Black femme: The existential conundrum of embodying a Black femme identity while being a professor of Black, queer, and feminist studies.

Science.gov (United States)

Story, Kaila Adia

2017-10-02

Although a Black femme identity has been defined and embodied by many as an identity with Black feminist roots and revolutionary potentials, Black femmes are still rendered hypervisible and invisible through racist and heteronormative politics. Similarly, embodying a Black femme identity as a professor in academia often engenders these same pretenses of hypervisibility and invisibility. This essay explores what this existential conundrum has been for me as both a Black femme and professor of Black queer and feminist studies, while illuminating the mix of forces within academia that have attempted to stifle my chosen sexual identity and gendered performance.

PLC-controlled cryostats for the BlackGEM and MeerLICHT detectors

Science.gov (United States)

Raskin, Gert; Morren, Johan; Pessemier, Wim; Bloemen, Steven; Klein-Wolt, Marc; Roelfsema, Ronald; Groot, Paul; Aerts, Conny

2016-08-01

BlackGEM is an array of telescopes, currently under development at the Radboud University Nijmegen and at NOVA (Netherlands Research School for Astronomy). It targets the detection of the optical counterparts of gravitational waves. The first three BlackGEM telescopes are planned to be installed in 2018 at the La Silla observatory (Chile). A single prototype telescope, named MeerLICHT, will already be commissioned early 2017 in Sutherland (South Africa) to provide an optical complement for the MeerKAT radio array. The BlackGEM array consists of, initially, a set of three robotic 65-cm wide-field telescopes. Each telescope is equipped with a single STA1600 CCD detector with 10.5k x 10.5k 9-micron pixels that covers a 2.7 square degrees field of view. The cryostats for housing these detectors are developed and built at the KU Leuven University (Belgium). The operational model of BlackGEM requires long periods of reliable hands-off operation. Therefore, we designed the cryostats for long vacuum hold time and we make use of a closed-cycle cooling system, based on Polycold PCC Joule-Thomson coolers. A single programmable logic controller (PLC) controls the cryogenic systems of several BlackGEM telescopes simultaneously, resulting in a highly reliable, cost-efficient and maintenance-friendly system. PLC-based cryostat control offers some distinct advantages, especially for a robotic facility. Apart of temperature monitoring and control, the PLC also monitors the vacuum quality, the power supply and the status of the PCC coolers (compressor power consumption and temperature, pressure in the gas lines, etc.). Furthermore, it provides an alarming system and safe and reproducible procedures for automatic cool down and warm up. The communication between PLC and higher-level software takes place via the OPC-UA protocol, offering a simple to implement, yet very powerful interface. Finally, a touch-panel display on the PLC provides the operator with a user-friendly and robust

Black Lives Matter of Black Identity Extremist? : The FBI, Black Activists and the Struggle for Victimhood

NARCIS (Netherlands)

Mutsaers, Paul

2017-01-01

The question 'who is the victim?' is an important social directive that shapes the struggles for victimhood in which Black Lives Matters, U.S. police forces and their various (counter)publics are currently engaging. This column begins with a controversial FBI report on so-called Black Identity

Cosmic strings and black holes

International Nuclear Information System (INIS)

Aryal, M.; Ford, L.H.; Vilenkin, A.

1986-01-01

The metric for a Schwarzschild black hole with a cosmic string passing through it is discussed. The thermodynamics of such an object is considered, and it is shown that S = (1/4)A, where S is the entropy and A is the horizon area. It is noted that the Schwarzschild mass parameter M, which is the gravitational mass of the system, is no longer identical to its energy. A solution representing a pair of black holes held apart by strings is discussed. It is nearly identical to a static, axially symmetric solution given long ago by Bach and Weyl. It is shown how these solutions, which were formerly a mathematical curiosity, may be given a more physical interpretation in terms of cosmic strings

Dirhinus giffardii (Hymenoptera: Chalcididae, parasitoid affecting Black Soldier Fly production systems in West Africa

Directory of Open Access Journals (Sweden)

Emilie Devic

2015-12-01

Full Text Available Interest for insect farming is currently growing globally. Conditions in West Africa appear suitable for developing such farming systems that can benefit communities by improving livelihoods, food and feed security or sanitation. In Ghana and Mali, the Black Soldier Fly (Hermetia illucens Linnaeus, 1758 is being produced for waste recycling and animal feed. In a two stages process (egg and larvae production, egg production was hampered by a pupal parasitoid, Dirhinus giffardii Silvestri, 1913 (Hymenoptera: Chalcididae, which reduced future broodstock by almost 72%. This is the first time D. giffardii is reported as a parasitoid of H. illucens pupae and one of the first reports of parasitism in this commercially important fly species. The introduction of precautionary measures is highly recommended for the success of H. illucens production systems in West Africa.

Einstein-Gauss-Bonnet metrics: black holes, black strings and a staticity theorem

International Nuclear Information System (INIS)

Bogdanos, C.; Charmousis, C.; Gouteraux, B.; Zegers, R.

2009-01-01

We find the general solution of the 6-dimensional Einstein-Gauss-Bonnet equations in a large class of space and time-dependent warped geometries. Several distinct families of solutions are found, some of which include black string metrics, space and time-dependent solutions and black holes with exotic horizons. Among these, some are shown to verify a Birkhoff type staticity theorem, although here, the usual assumption of maximal symmetry on the horizon is relaxed, allowing exotic horizon geometries. We provide explicit examples of such static exotic black holes, including ones whose horizon geometry is that of a Bergman space. We find that the situation is very different from higher-dimensional general relativity, where Einstein spaces are admissible black hole horizons and the associated black hole potential is not even affected. In Einstein-Gauss-Bonnet theory, on the contrary, the non-trivial Weyl tensor of such exotic horizons is exposed to the bulk dynamics through the higher order Gauss-Bonnet term, severely constraining the allowed horizon geometries and adding a novel charge-like parameter to the black hole potential. The latter is related to the Euler characteristic of the four-dimensional horizon and provides, in some cases, additional black hole horizons.

The Final Merger of Black-Hole Binaries

Science.gov (United States)

Kelly, Bernard J.; Centrealla, Joan; Baker, John G.; Kelly, Bernard J.; vanMeter, James R.

2010-01-01

Recent breakthroughs in the field of numerical relativity have led to dramatic progress in understanding the predictions of General Relativity for the dynamical interactions of two black holes in the regime of very strong gravitational fields. Such black-hole binaries are important astrophysical systems and are a key target of current and developing gravitational-wave detectors. The waveform signature of strong gravitational radiation emitted as the black holes fall together and merge provides a clear observable record of the process. After decades of slow progress / these mergers and the gravitational-wave signals they generate can now be routinely calculated using the methods of numerical relativity. We review recent advances in understanding the predicted physics of events and the consequent radiation, and discuss some of the impacts this new knowledge is having in various areas of astrophysics

Joule-Thomson expansion of the charged AdS black holes

International Nuclear Information System (INIS)

Oekcue, Oezguer; Aydiner, Ekrem

2017-01-01

In this paper, we study Joule-Thomson effects for charged AdS black holes. We obtain inversion temperatures and curves. We investigate similarities and differences between van der Waals fluids and charged AdS black holes for the expansion. We obtain isenthalpic curves for both systems in the T-P plane and determine the cooling-heating regions. (orig.)

Joule-Thomson expansion of the charged AdS black holes

Energy Technology Data Exchange (ETDEWEB)

Oekcue, Oezguer; Aydiner, Ekrem [Istanbul University, Department of Physics, Faculty of Science, Vezneciler, Istanbul (Turkey)

2017-01-15

In this paper, we study Joule-Thomson effects for charged AdS black holes. We obtain inversion temperatures and curves. We investigate similarities and differences between van der Waals fluids and charged AdS black holes for the expansion. We obtain isenthalpic curves for both systems in the T-P plane and determine the cooling-heating regions. (orig.)

Systemic Insecticides Reduce Feeding, Survival and Fecundity of Adult Black Vine Weevils (Coleoptera: Curculionidae) on a Variety of Ornamental Nursery Crops

Science.gov (United States)

A series of bioassays were conducted to test the systemic activity of clothianidin, chlorantraniliprole, dinotefuran, and thiamethoxam against adult black vine weevils (Otiorhynchus sulcatus F.) on Taxus, Heuchera, Astilbe, Sedum, Euonymus, and Rhododendron grown in containers. The insecticides wer...

Rholography, black holes and Scherk-Schwarz

Energy Technology Data Exchange (ETDEWEB)

Gaddam, Nava [Institute for Theoretical Physics and Center for Extreme Matter and Emergent Phenomena,Utrecht University,3508 TD Utrecht (Netherlands); Gnecchi, Alessandra [Institute for Theoretical Physics, KU Leuven,3001 Leuven (Belgium); Vandoren, Stefan [Institute for Theoretical Physics and Center for Extreme Matter and Emergent Phenomena,Utrecht University,3508 TD Utrecht (Netherlands); Varela, Oscar [Center for the Fundamental Laws of Nature, Harvard University, Cambridge, MA 02138 (United States)

2015-06-10

We present a construction of a class of near-extremal asymptotically flat black hole solutions in four (or five) dimensional gauged supergravity with R-symmetry gaugings obtained from Scherk-Schwarz reductions on a circle. The entropy of these black holes is counted holographically by the well known MSW (or D1/D5) system, with certain twisted boundary conditions labeled by a twist parameter ρ. We find that the corresponding (0,4) (or (4,4)) superconformal algebras are exactly those studied by Schwimmer and Seiberg, using a twist on the outer automorphism group. The interplay between R-symmetries, ρ-algebras and holography leads us to name our construction “Rholography'.

Robustness of binary black hole mergers in the presence of spurious radiation

International Nuclear Information System (INIS)

Bode, Tanja; Shoemaker, Deirdre; Herrmann, Frank; Hinder, Ian

2008-01-01

We present an investigation into how sensitive the last orbits and merger of binary black hole systems are to the presence of spurious radiation in the initial data. Our numerical experiments consist of a binary black hole system starting the last couple of orbits before merger with additional spurious radiation centered at the origin and fixed initial angular momentum. As the energy in the added spurious radiation increases, the binary is invariably hardened for the cases we tested; i.e., the merger of the two black holes is hastened. The change in merger time becomes significant when the additional energy provided by the spurious radiation increases the Arnowitt-Deser-Misner mass of the spacetime by about 1%. While the final masses of the black holes increase due to partial absorption of the radiation, the final spins remain constant to within our numerical accuracy. We conjecture that the spurious radiation is primarily increasing the eccentricity of the orbit and secondarily increasing the mass of the black holes while propagating out to infinity

Black molecular adsorber coatings for spaceflight applications

Science.gov (United States)

Abraham, Nithin S.; Hasegawa, Mark M.; Straka, Sharon A.

2014-09-01

The molecular adsorber coating is a new technology that was developed to mitigate the risk of on-orbit molecular contamination on spaceflight missions. The application of this coating would be ideal near highly sensitive, interior surfaces and instruments that are negatively impacted by outgassed molecules from materials, such as plastics, adhesives, lubricants, epoxies, and other similar compounds. This current, sprayable paint technology is comprised of inorganic white materials made from highly porous zeolite. In addition to good adhesion performance, thermal stability, and adsorptive capability, the molecular adsorber coating offers favorable thermal control characteristics. However, low reflectivity properties, which are typically offered by black thermal control coatings, are desired for some spaceflight applications. For example, black coatings are used on interior surfaces, in particular, on instrument baffles for optical stray light control. Similarly, they are also used within light paths between optical systems, such as telescopes, to absorb light. Recent efforts have been made to transform the white molecular adsorber coating into a black coating with similar adsorptive properties. This result is achieved by optimizing the current formulation with black pigments, while still maintaining its adsorption capability for outgassing control. Different binder to pigment ratios, coating thicknesses, and spray application techniques were explored to develop a black version of the molecular adsorber coating. During the development process, coating performance and adsorption characteristics were studied. The preliminary work performed on black molecular adsorber coatings thus far is very promising. Continued development and testing is necessary for its use on future contamination sensitive spaceflight missions.

Accreting Black Holes

OpenAIRE

Begelman, Mitchell C.

2014-01-01

I outline the theory of accretion onto black holes, and its application to observed phenomena such as X-ray binaries, active galactic nuclei, tidal disruption events, and gamma-ray bursts. The dynamics as well as radiative signatures of black hole accretion depend on interactions between the relatively simple black-hole spacetime and complex radiation, plasma and magnetohydrodynamical processes in the surrounding gas. I will show how transient accretion processes could provide clues to these ...

Naked black holes

International Nuclear Information System (INIS)

Horowitz, G.T.; Ross, S.F.

1997-01-01

It is shown that there are large static black holes for which all curvature invariants are small near the event horizon, yet any object which falls in experiences enormous tidal forces outside the horizon. These black holes are charged and near extremality, and exist in a wide class of theories including string theory. The implications for cosmic censorship and the black hole information puzzle are discussed. copyright 1997 The American Physical Society

Black hole evaporation in a heat bath as a nonequilibrium process and its final fate

International Nuclear Information System (INIS)

Saida, Hiromi

2007-01-01

We consider a black hole in a heat bath, and the whole system which consists of the black hole and the heat bath is isolated from outside environments. When the black hole evaporates, the Hawking radiation causes an energy flow from the black hole to the heat bath. Therefore, since no energy flow arises in an equilibrium state, the thermodynamic state of the whole system is not in equilibrium. That is, in a region around the black hole, the matter field of Hawking radiation and that of heat bath should be in a nonequilibrium state due to the energy flow. Using a simple model which reflects the nonequilibrium nature of energy flow, we find the nonequilibrium effect on a black hole evaporation as follows: if the nonequilibrium region around a black hole is not so large, the evaporation time scale of a black hole in a heat bath becomes longer than that in an empty space (a situation without heat bath), because of the incoming energy flow from the heat bath to the black hole. However, if the nonequilibrium region around a black hole is sufficiently large, the evaporation time scale in a heat bath becomes shorter than that in an empty space, because a nonequilibrium effect of the temperature difference between the black hole and heat bath appears as a strong energy extraction from the black hole by the heat bath. Further, a specific nonequilibrium phenomenon is found: a quasi-equilibrium evaporation stage under the nonequilibrium effect proceeds abruptly to a quantum evaporation stage at a semi-classical level (at black hole radius R g > Planck length) within a very short time scale with a strong burst of energy. (Contrarily, when the nonequilibrium effect is not taken into account, a quasi-equilibrium stage proceeds smoothly to a quantum stage at R g < Planck length without so strong an energy burst.) That is, the nonequilibrium effect of energy flow tends to make a black hole evaporation process more dynamical and to accelerate that process. Finally, on the final fate

Star clusters containing massive, central black holes: evolution calculations

International Nuclear Information System (INIS)

Marchant, A.B.

1980-01-01

This dissertation presents a detailed, two-dimensional simulations of star cluster evolution. A Monte-Carlo method is adapted to simulate the development with time of isolated star clusters. Clusters which evolve on relaxation timescales with and without central black holes are treated. The method is flexible and rugged, rather than highly accurate. It treats the boundary conditions of stellar evaporation and tidal disruption by a central black hole in a precise, stochastic fashion. Dynamical cloning and renormalization and the use of a time-step adjustment algorithm enhance the feasibility of the method which simulates systems with wide ranges of intrinsic length and time scales. First, the method is applied to follow the development and core collapse of an initial Plummer-model cluster without a central black hole. Agreement of these results for early times with the results of previous authors serves as a verification of this method. Three calculations of cluster re-expansion, each beginning with the insertion of a black hole at the center of a highly collapsed cluster core is presented. Each case is characterized by a different value of initial black hole mass or black hole accretion efficiency for the consumption of debris from disrupted stars. It is found that for the special cases examined here substantial, but not catastrophic, growth of the central black hole may accompany core re-expansion. Also, the observability of the evolutionary phases associated with core collapse and re-expansion, constraints on x-ray sources which could be associated with growing black holes, and the observable signature of the cusp of stars surrounding a central black hole are discussed

Legitimizing Blacks in Philosophy

Directory of Open Access Journals (Sweden)

Jameliah Shorter-Bourhanou

2017-12-01

Full Text Available In its efforts toward improving diversity, the discipline of philosophy has tended to focus on increasing the number of black philosophers. One crucial issue that has received less attention is the extent to which black philosophers are delegitimized in the discipline because their philosophical contributions challenge the status quo. A systematic problem that bars black philosophers from equal and full participation, this delegitimization precludes the emergence of genuine diversity and reveals the importance of interrogating broader attitudes toward black philosophical contributions. In this essay, I argue for radical systematic changes to disciplinary hallmarks of professionalization such as pedagogy, mentoring, publishing, and hiring practices with the aim of legitimizing black philosophers and their contributions.

The fall of the black hole firewall: natural nonmaximal entanglement for the Page curve

Science.gov (United States)

Hotta, Masahiro; Sugita, Ayumu

2015-12-01

The black hole firewall conjecture is based on the Page curve hypothesis, which claims that entanglement between a black hole and its Hawking radiation is almost maximum. Adopting canonical typicality for nondegenerate systems with nonvanishing Hamiltonians, we show the entanglement becomes nonmaximal, and energetic singularities (firewalls) do not emerge for general systems. An evaporating old black hole must evolve in Gibbs states with exponentially small error probability after the Page time as long as the states are typical. This means that the ordinarily used microcanonical states are far from typical. The heat capacity computed from the Gibbs states should be nonnegative in general. However, the black hole heat capacity is actually negative due to the gravitational instability. Consequently the states are not typical until the last burst. This requires inevitable modification of the Page curve, which is based on the typicality argument. For static thermal pure states of a large AdS black hole and its Hawking radiation, the entanglement entropy equals the thermal entropy of the smaller system.

Using geographical information systems to explore disparities in preterm birth rates among foreign-born and U.S.-born Black mothers.

Science.gov (United States)

Bloch, Joan Rosen

2011-01-01

To examine spatial patterns of neighborhood contextual factors of stress with preterm birth (PTB) and nativity (foreign-born and U.S.-born) among Black mothers. Descriptive geographic-spatial research. Births to Philadelphia residents during 2003-2005 in the context of Philadelphia residential neighborhoods (N = 350) were studied. All data were aggregated to neighborhood levels (census tracts). Maps were created to assess geographic-spatial patterns. A geographic information system (GIS) database was created that imported geo-coded data on births, crime (assaults with guns and domestic abuse), poverty, race, and nativity (foreign-born vs. U.S.-born). Clear visual patterns of "bad" neighborhoods emerged and were significantly associated with higher prevalence of PTB for foreign-born Black and U.S.-born Black mothers (p < .0001). This study demonstrated how GIS visually clarified important spatial patterns of adverse living conditions and PTB prevalence. Nurses can use GIS to better understand living environments of mothers and their families and to target interventions in geographical areas with the greatest service needs. Further research on individual and contextual factors is warranted to address the observed health disparities among the heterogeneous groups of foreign-born Black mothers. Despite limitations of aggregate data, it is clear that where mothers live matters. This has important implications for nursing practice and policy. © 2011 AWHONN, the Association of Women's Health, Obstetric and Neonatal Nurses.

Using Geographical Information Systems to Explore Disparities in Preterm Birth Rates Among Foreign-born and U.S.-born Black Mothers

Science.gov (United States)

Bloch, Joan Rosen

2012-01-01

Objective To examine spatial patterns of neighborhood contextual factors of stress with preterm birth (PTB) and nativity (foreign-born and U.S.-born) among Black mothers. Design Descriptive geographic-spatial research. Setting & Participants Births to Philadelphia residents during 2003–2005 in the context of Philadelphia residential neighborhoods (N = 350) were studied. Methods All data were aggregated to neighborhood levels (census tracts). Maps were created to assess geographic-spatial patterns. A geographic information system (GIS) database was created that imported geo-coded data on births, crime (assaults with guns and domestic abuse), poverty, race, and nativity (foreign-born vs. U.S.-born). Results Clear visual patterns of “bad” neighborhoods emerged and were significantly associated with higher prevalence of PTB for foreign-born Black and U.S.-born Black mothers (p GIS visually clarified important spatial patterns of adverse living conditions and PTB prevalence. Nurses can use GIS to better understand living environments of mothers and their families and to target interventions in geographical areas with the greatest service needs. Further research on individual and contextual factors is warranted to address the observed health disparities among the heterogeneous groups of foreign-born Black mothers. Despite limitations of aggregate data, it is clear that where mothers live matters. This has important implications for nursing practice and policy. PMID:22273411

Black churches and HIV/AIDS: factors influencing congregations’ responsiveness to social issues.

Science.gov (United States)

Fulton, Brad R

2011-01-01

The ambivalent response of many black churches to current social issues has caused some scholars to question the centrality of black churches within African-American communities. Using a nationally representative sample of black congregations, this study engages the debate about the institutional centrality of black churches by focusing on their response to HIV/AIDS. Although many congregational studies treat black churches as a monolithic whole, this analysis identifies heterogeneity among black churches that shapes their responsiveness to social issues. Contrary to prior claims, a congregation's liberal-conservative ideological orientation does not significantly affect its likelihood of having an HIV/AIDS program. Beyond assessing churches’ internal characteristics, this study uses institutional theory to analyze churches as open systems that can be influenced by their surrounding environment. It demonstrates that externally engaged congregations are significantly more likely to have a program. These results indicate that black churches maintain institutional centrality by engaging their external environment.

SSL/TLS Vulnerability Detection Using Black Box Approach

Science.gov (United States)

Gunawan, D.; Sitorus, E. H.; Rahmat, R. F.; Hizriadi, A.

2018-03-01

Socket Secure Layer (SSL) and Transport Layer Security (TLS) are cryptographic protocols that provide data encryption to secure the communication over a network. However, in some cases, there are vulnerability found in the implementation of SSL/TLS because of weak cipher key, certificate validation error or session handling error. One of the most vulnerable SSL/TLS bugs is heartbleed. As the security is essential in data communication, this research aims to build a scanner that detect the SSL/TLS vulnerability by using black box approach. This research will focus on heartbleed case. In addition, this research also gathers information about existing SSL in the server. The black box approach is used to test the output of a system without knowing the process inside the system itself. For testing purpose, this research scanned websites and found that some of the websites still have SSL/TLS vulnerability. Thus, the black box approach can be used to detect the vulnerability without considering the source code and the process inside the application.

Intermediate-Mass Black Holes

Science.gov (United States)

Miller, M. Coleman; Colbert, E. J. M.

2004-01-01

The mathematical simplicity of black holes, combined with their links to some of the most energetic events in the universe, means that black holes are key objects for fundamental physics and astrophysics. Until recently, it was generally believed that black holes in nature appear in two broad mass ranges: stellar-mass (M~3 20 M⊙), which are produced by the core collapse of massive stars, and supermassive (M~106 1010 M⊙), which are found in the centers of galaxies and are produced by a still uncertain combination of processes. In the last few years, however, evidence has accumulated for an intermediate-mass class of black holes, with M~102 104 M⊙. If such objects exist they have important implications for the dynamics of stellar clusters, the formation of supermassive black holes, and the production and detection of gravitational waves. We review the evidence for intermediate-mass black holes and discuss future observational and theoretical work that will help clarify numerous outstanding questions about these objects.

Thermodynamics, stability and Hawking-Page transition of Kerr black holes from Renyi statistics

Energy Technology Data Exchange (ETDEWEB)

Czinner, Viktor G. [University of Lisbon, Multidisciplinary Center for Astrophysics and Department of Physics, Instituto Superior Tecnico, Lisboa (Portugal); HAS Wigner Research Centre for Physics, Budapest (Hungary); Iguchi, Hideo [Nihon University, Laboratory of Physics, College of Science and Technology, Funabashi, Chiba (Japan)

2017-12-15

Thermodynamics of rotating black holes described by the Renyi formula as equilibrium and zeroth law compatible entropy function is investigated. We show that similarly to the standard Boltzmann approach, isolated Kerr black holes are stable with respect to axisymmetric perturbations in the Renyi model. On the other hand, when the black holes are surrounded by a bath of thermal radiation, slowly rotating black holes can also be in stable equilibrium with the heat bath at a fixed temperature, in contrast to the Boltzmann description. For the question of possible phase transitions in the system, we show that a Hawking-Page transition and a first order small black hole/large black hole transition occur, analogous to the picture of rotating black holes in AdS space. These results confirm the similarity between the Renyi-asymptotically flat and Boltzmann-AdS approaches to black hole thermodynamics in the rotating case as well. We derive the relations between the thermodynamic parameters based on this correspondence. (orig.)

The Effect of Black Peers on Black Test Scores

Science.gov (United States)

Armor, David J.; Duck, Stephanie

2007-01-01

Recent studies have used increasingly complex methodologies to estimate the effect of peer characteristics--race, poverty, and ability--on student achievement. A paper by Hanushek, Kain, and Rivkin using Texas state testing data has received particularly wide attention because it found a large negative effect of school percent black on black math…

Black hole multiplicity at particle colliders (Do black holes radiate mainly on the brane?)

International Nuclear Information System (INIS)

Cavaglia, Marco

2003-01-01

If gravity becomes strong at the TeV scale, we may have the chance to produce black holes at particle colliders. In this Letter we revisit some phenomenological signatures of black hole production in TeV-gravity theories. We show that the bulk-to-brane ratio of black hole energy loss during the Hawking evaporation phase depends crucially on the black hole greybody factors and on the particle degrees of freedom. Since the greybody factors have not yet been calculated in the literature, and the particle content at trans-Planckian energies is not known, it is premature to claim that the black hole emits mainly on the brane. We also revisit the decay time and the multiplicity of the decay products of black hole evaporation. We give general formulae for black hole decay time and multiplicity. We find that the number of particles produced during the evaporation phase may be significantly lower than the average multiplicity which has been used in the past literature

Structure analyses of swollen rubber-carbon black systems by contrast variation SANS

International Nuclear Information System (INIS)

Takenaka, Mikihito; Nishitsuji, Shotaro; Fujii, Sumiaki; Amino, Naoya; Ishikawa, Yasuhiro; Yamaguchi, Daisuke; Koizumi, Satoshi

2010-01-01

The polymer layers adsorbed on carbon black (CB) aggregates in rubber/CB systems have been investigated with contrast variation small-angle neutron scattering (SANS) method. Specimens were swollen by toluene/deuterated toluene solvents having various scattering length densities and their scattering intensities were measured with SANS. The contrast variation SANS for the specimens yielded partial scattering functions: the scattering function for polymer-polymer correlation S pp (q), the scattering function for CB- CB correlation S cc (q), and the scattering function for polymer- CB correlation S pc (q). The analyses of the partial scattering functions explored the existence of dense polymer layers around CB aggregates. Several characteristic parameters are estimated from the analyses, such as the size of aggregates, the thickness of layers, and the volume fractions of polymer of layers and matrix. (author)

Understanding the Black Aesthetic Experience.

Science.gov (United States)

Curtis, Marvin V.

1988-01-01

Discussing the importance of the Black aesthetic experience, Curtis examines Black cultural heritage and participatory style, the spiritual, and the creation and recreation of Black music. Advocating multicultural music education in teacher training, he suggests that Black music be studied for its value and contribution to society. Lists five ways…

String-Corrected Black Holes

Energy Technology Data Exchange (ETDEWEB)

Hubeny, V.

2005-01-12

We investigate the geometry of four dimensional black hole solutions in the presence of stringy higher curvature corrections to the low energy effective action. For certain supersymmetric two charge black holes these corrections drastically alter the causal structure of the solution, converting seemingly pathological null singularities into timelike singularities hidden behind a finite area horizon. We establish, analytically and numerically, that the string-corrected two-charge black hole metric has the same Penrose diagram as the extremal four-charge black hole. The higher derivative terms lead to another dramatic effect--the gravitational force exerted by a black hole on an inertial observer is no longer purely attractive. The magnitude of this effect is related to the size of the compactification manifold.

Binary Black Hole Mergers in the First Advanced LIGO Observing Run

Science.gov (United States)

Abbott, B. P.; Abbott, R.; Abbott, T. D.; Abernathy, M. R.; Acernese, F.; Ackley, K.; Adams, C.; Adams, T.; Addesso, F.; Camp, J. B.;

Binary Black Hole Mergers in the First Advanced LIGO Observing Run

Directory of Open Access Journals (Sweden)

2016-10-01

Full Text Available The first observational run of the Advanced LIGO detectors, from September 12, 2015 to January 19, 2016, saw the first detections of gravitational waves from binary black hole mergers. In this paper, we present full results from a search for binary black hole merger signals with total masses up to 100M_{⊙} and detailed implications from our observations of these systems. Our search, based on general-relativistic models of gravitational-wave signals from binary black hole systems, unambiguously identified two signals, GW150914 and GW151226, with a significance of greater than 5σ over the observing period. It also identified a third possible signal, LVT151012, with substantially lower significance and with an 87% probability of being of astrophysical origin. We provide detailed estimates of the parameters of the observed systems. Both GW150914 and GW151226 provide an unprecedented opportunity to study the two-body motion of a compact-object binary in the large velocity, highly nonlinear regime. We do not observe any deviations from general relativity, and we place improved empirical bounds on several high-order post-Newtonian coefficients. From our observations, we infer stellar-mass binary black hole merger rates lying in the range 9–240  Gpc^{-3} yr^{-1}. These observations are beginning to inform astrophysical predictions of binary black hole formation rates and indicate that future observing runs of the Advanced detector network will yield many more gravitational-wave detections.

Failure to detect seasonal changes in the song system nuclei of the black-capped chickadee (Poecile atricapillus).

Science.gov (United States)

Smulders, T V; Lisi, M D; Tricomi, E; Otter, K A; Chruszcz, B; Ratcliffe, L M; DeVoogd, T J

2006-08-01

Most temperate songbird species sing seasonally, and the brain areas involved in producing song (the song system) vary in size alongside the changes in behavior. Black-capped chickadees (Poecile atricapillus) also sing seasonally, and we find that there are changes in the stereotypy and the length of the fee-bee song from the nonbreeding to the breeding season. Yet despite these changes, we fail to find any evidence of seasonal changes in the song system. The song system of males is larger than that of females, as is typical in songbirds, but the ratio between the sexes is small compared to other species. We suggest three hypotheses to explain our failure to find seasonal variation in the chickadee song system.

BlackMax: A black-hole event generator with rotation, recoil, split branes, and brane tension

International Nuclear Information System (INIS)

Dai Dechang; Starkman, Glenn; Stojkovic, Dejan; Issever, Cigdem; Tseng, Jeff; Rizvi, Eram

2008-01-01

We present a comprehensive black-hole event generator, BlackMax, which simulates the experimental signatures of microscopic and Planckian black-hole production and evolution at the LHC in the context of brane world models with low-scale quantum gravity. The generator is based on phenomenologically realistic models free of serious problems that plague low-scale gravity, thus offering more realistic predictions for hadron-hadron colliders. The generator includes all of the black-hole gray-body factors known to date and incorporates the effects of black-hole rotation, splitting between the fermions, nonzero brane tension, and black-hole recoil due to Hawking radiation (although not all simultaneously). The generator can be interfaced with Herwig and Pythia. The main code can be downloaded from http://www-pnp.physics.ox.ac.uk/~issever/BlackMax/blackmax.html.

Jet precession in binary black holes

Science.gov (United States)

Abraham, Zulema

2018-06-01

Supermassive binary black holes are thought to lie at the centres of merging galaxies. The blazar OJ 287 is the poster child of such systems, showing strong and periodic variability across the electromagnetic spectrum. A new study questions the physical origin of this variability.

Internal structure of black holes

International Nuclear Information System (INIS)

Cvetic, Mirjam

2013-01-01

Full text: We review recent progress that sheds light on the internal structure of general black holes. We first summarize properties of general multi-charged rotating black holes both in four and five dimensions. We show that the asymptotic boundary conditions of these general asymptotically flat black holes can be modified such that a conformal symmetry emerges. These subtracted geometries preserve the thermodynamic properties of the original black holes and are of the Lifshitz type, thus describing 'a black hole in the asymptotically conical box'. Recent efforts employ solution generating techniques to construct interpolating geometries between the original black hole and their subtracted geometries. Upon lift to one dimension higher, these geometries lift to AdS 3 times a sphere, and thus provide a microscopic interpretation of the black hole entropy in terms of dual two-dimensional conformal field theory. (author)

Black supernovae and black holes in non-local gravity

Energy Technology Data Exchange (ETDEWEB)

Bambi, Cosimo [Center for Field Theory and Particle Physics and Department of Physics, Fudan University,200433 Shanghai (China); Theoretical Astrophysics, Eberhard-Karls Universität Tübingen,72076 Tübingen (Germany); Malafarina, Daniele [Department of Physics, Nazarbayev University,010000 Astana (Kazakhstan); Modesto, Leonardo [Center for Field Theory and Particle Physics and Department of Physics, Fudan University,200433 Shanghai (China)

2016-04-22

In a previous paper, we studied the interior solution of a collapsing body in a non-local theory of gravity super-renormalizable at the quantum level. We found that the classical singularity is replaced by a bounce, after which the body starts expanding. A black hole, strictly speaking, never forms. The gravitational collapse does not create an event horizon but only an apparent one for a finite time. In this paper, we solve the equations of motion assuming that the exterior solution is static. With such an assumption, we are able to reconstruct the solution in the whole spacetime, namely in both the exterior and interior regions. Now the gravitational collapse creates an event horizon in a finite comoving time, but the central singularity is approached in an infinite time. We argue that these black holes should be unstable, providing a link between the scenarios with and without black holes. Indeed, we find a non catastrophic ghost-instability of the metric in the exterior region. Interestingly, under certain conditions, the lifetime of our black holes exactly scales as the Hawking evaporation time.

On Thermodynamical Relation Between Rotating Charged BTZ Black Holes and Effective String Theory

Institute of Scientific and Technical Information of China (English)

Alexis Larra(~n)aga

2008-01-01

In this paper we study the first law of thermodynamics for the (2+1)-dimensional rotating charged BTZ black hole considering a pair of thermodynamical systems constructed with the two horizons of this solution. We show that these two systems are similar to the right and left movers of string theory and that the temperature associated with the black hole is the harmonic mean of the temperatures associated with these two systems.

Black Sea aerosols

International Nuclear Information System (INIS)

Hacisalihoglu, G.; Eliyakut, F.; Anwari, M.A.; Ataman, O.Y.; Balkas, T.I.; Tuncel, G.; Olmez, I.

1991-01-01

Shipboard, high volume air particulate samples were collected from the Black Sea atmosphere and analyzed by instrumental neutron activation analysis, atomic absorption spectrophotometry and ion chromatography for about 40 elements and ions. Concentrations of elements in the eastern and western parts of the Black Sea are different at the 95% confidence level, with lower concentrations in the eastern Black Sea. Back-trajectories and concentrations of elements in trajectory groups show that Europe accounts for more than 70% of the anthropogenic elements in the atmosphere. The average sulfate concentration was 7 μg/m 3 , which is comparable with rural sulfate levels in western Europe. Fluxes of elements from the atmosphere to the Black Sea are in good agreement with the results of similar flux calculations for other regions

New Directions for Black Women?

Science.gov (United States)

McGuigan, Dorothy, Ed.

1978-01-01

This collection of papers deals with various aspects of the black female experience in America. "The Black Woman in Transition" discusses the effects of sexism and racism on black women with particular reference to employment and education; it is noted that black women, in comparison with other groups in society, suffer a proportionately higher…

AN ENERGETIC AGN OUTBURST POWERED BY A RAPIDLY SPINNING SUPERMASSIVE BLACK HOLE OR AN ACCRETING ULTRAMASSIVE BLACK HOLE

International Nuclear Information System (INIS)

McNamara, B. R.; Kazemzadeh, F.; Kirkpatrick, C. C.; Rafferty, D. A.; Birzan, L.; Nulsen, P. E. J.; Wise, M. W.

2009-01-01

Powering the 10 62 erg nuclear outburst in the MS0735.6+7421 cluster central galaxy by accretion with a 10% mass-to-energy conversion efficiency implies that its putative supermassive black hole (SMBH) grew by ∼6 x 10 8 M sun over the past 100 Myr. Guided by data at several wavelengths, we place upper limits on the amount of cold gas and star formation near the nucleus of 9 M sun and sun yr -1 , respectively. These limits imply that an implausibly large fraction of the preexisting cold gas in the inner several kpc must have been consumed by its SMBH at the rate of ∼3-5 M sun yr -1 during the past 100 Myr while leaving no trace of star formation. Such a high accretion rate would be difficult to maintain by stellar accretion or the Bondi mechanism, unless the black hole mass approaches 10 11 M sun . Furthermore, its feeble nuclear luminosities in the UV, I, and X-ray bands compared to its enormous mechanical power are inconsistent with rapid accretion onto a ∼5 x 10 9 M sun black hole. We suggest instead that the active galactic nucleus (AGN) outburst is powered by angular momentum released from a rapidly spinning black hole. The rotational energy and power available from a spinning black hole are consistent with the cavity and shock energetics inferred from X-ray observations. A maximally spinning 10 9 M sun black hole contains enough rotational energy, ∼10 62 erg, to quench a cooling flow over its lifetime and to contribute significantly to the excess entropy found in the hot atmospheres of groups and clusters. Two modes of AGN feedback may be quenching star formation in elliptical galaxies centered in cooling halos at late times. An accretion mode that operates in gas-rich systems, and a spin mode operating at modest accretion rates. The spin conjecture may be avoided in MS0735 by appealing to Bondi accretion onto a central black hole whose mass greatly exceeds 10 10 M sun . The host galaxy's unusually large 3.8 kpc stellar core radius (light deficit) may

Small hairy black holes in AdS(5) x S-5

NARCIS (Netherlands)

Bhattacharyya, Sayantani; Minwalla, Shiraz; Papadodimas, Kyriakos

2011-01-01

We study small hairy black holes in a consistent truncation of N = 8 gauged supergravity that consists of a single charged scalar field interacting with the metric and a U(1) gauge field. Small very near extremal RNAdS black holes in this system are unstable to decay by superradiant emission. The

Small hairy black holes in AdS(5) x S-5

NARCIS (Netherlands)

Bhattacharyya, Sayantani; Minwalla, Shiraz; Papadodimas, Kyriakos

We study small hairy black holes in a consistent truncation of N = 8 gauged supergravity that consists of a single charged scalar field interacting with the metric and a U(1) gauge field. Small very near extremal RNAdS black holes in this system are unstable to decay by superradiant emission. The

Featured Image: Making a Rapidly Rotating Black Hole

Science.gov (United States)

Kohler, Susanna

2017-10-01

These stills from a simulation show the evolution (from left to right and top to bottom) of a high-mass X-ray binary over 1.1 days, starting after the star on the right fails to explode as a supernova and then collapses into a black hole. Many high-mass X-ray binaries like the well-known Cygnus X-1, the first source widely accepted to be a black hole host rapidly spinning black holes. Despite our observations of these systems, however, were still not sure how these objects end up with such high rotation speeds. Using simulations like that shown above, a team of scientists led by Aldo Batta (UC Santa Cruz) has demonstrated how a failed supernova explosion can result in such a rapidly spinning black hole. The authors work shows that in a binary where one star attempts to explode as a supernova and fails it doesnt succeed in unbinding the star the large amount of fallback material can interact with the companion star and then accrete onto the black hole, spinning it up in the process. You can read more about the authors simulations and conclusions in the paper below.CitationAldo Batta et al 2017 ApJL 846 L15. doi:10.3847/2041-8213/aa8506

Black-spot poison ivy.

Science.gov (United States)

Schram, Sarah E; Willey, Andrea; Lee, Peter K; Bohjanen, Kimberly A; Warshaw, Erin M

2008-01-01

In black-spot poison ivy dermatitis, a black lacquerlike substance forms on the skin when poison ivy resin is exposed to air. Although the Toxicodendron group of plants is estimated to be the most common cause of allergic contact dermatitis in the United States, black-spot poison ivy dermatitis is relatively rare.

What is black hole?

Indian Academy of Sciences (India)

First page Back Continue Last page Overview Graphics. What is black hole? Possible end phase of a star: A star is a massive, luminous ball of plasma having continuous nuclear burning. Star exhausts nuclear fuel →. White Dwarf, Neutron Star, Black Hole. Black hole's gravitational field is so powerful that even ...

Genocide and Black Ecology

Science.gov (United States)

Sinnette, Calvin H.

1972-01-01

Contends that the survival of black people is in serious jeopardy as is evidenced in contemporary discussions on the worldwide plight of black people, and that an exhaustive study of the problem in its many dimensions is seriously lacking; the moral and ethical issues of genocide require examination from a black perspective. (JW)

Quantum effects in black holes

International Nuclear Information System (INIS)

Frolov, V.P.

1979-01-01

A strict definition of black holes is presented and some properties with regard to their mass are enumerated. The Hawking quantum effect - the effect of vacuum instability in the black hole gravitational field, as a result of shich the black hole radiates as a heated body is analyzed. It is shown that in order to obtain results on the black hole radiation it is sufficient to predetermine the in-vacuum state at a time moment in the past, when the collapsing body has a large size, and its gravitational field can be neglected. The causes and the place of particle production by the black hole, and also the space-time inside the black hole, are considered

Black hole binary OJ287 as a testing platform for general relativity

International Nuclear Information System (INIS)

Valtonen, M J; Gopakumar, A; Mikkola, S; Wiik, K; Lehto, H J

2014-01-01

The blazar OJ287 is the most promising (and the only) case for an extragalactic binary black hole system inspiralling under the action of gravitational radiation reaction. At present, though it is not possible to directly observe the binary components, it is possible to observe the jet emanating from the primary black hole. We have argued that the orbital motion of the secondary black hole is reflected in the wobble of the jet, and demonstrated that the wobble is orbital position dependent. The erratic wobble of the jet is analyzed by taking into account the binary nature of the system, and we have found that the erratic component of jet wobble is very small

Reconceptualizing successful aging among black women and the relevance of the strong black woman archetype.

Science.gov (United States)

Baker, Tamara A; Buchanan, NiCole T; Mingo, Chivon A; Roker, Rosalyn; Brown, Candace S

2015-02-01

Although there are multiple pathways to successful aging, little is known of what it means to age successfully among black women. There is a growing body of literature suggesting that black women experience a number of social challenges (sexism and racism) that may present as barriers to aging successfully. Applying aspects of the Strong Black Women ideal, into theoretical concepts of successful aging, may be particularly relevant in understanding which factors impair or promote the ability of black women to age successfully. The Strong Black Women archetype is a culturally salient ideal prescribing that black women render a guise of self-reliance, selflessness, and psychological, emotional, and physical strength. Although this ideal has received considerable attention in the behavioral sciences, it has been largely absent within the gerontology field. Nevertheless, understanding the dynamics of this cultural ideal may enhance our knowledge while developing an appreciation of the black woman's ability to age successfully. Rather than summarize the social, physical, and mental health literature focusing on health outcomes of black women, this conceptual review examines the Strong Black Women archetype and its application to the lived experiences of black women and contributions to current theories of successful aging. Focusing on successful aging exclusively among black women enhances our understanding of this group by considering their identity as women of color while recognizing factors that dictate their ability to age successfully. © The Author 2014. Published by Oxford University Press on behalf of The Gerontological Society of America. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

The spinning Kerr-black-hole-mirror bomb: A lower bound on the radius of the reflecting mirror

Science.gov (United States)

Hod, Shahar

2016-10-01

The intriguing superradiant amplification phenomenon allows an orbiting scalar field to extract rotational energy from a spinning Kerr black hole. Interestingly, the energy extraction rate can grow exponentially in time if the black-hole-field system is placed inside a reflecting mirror which prevents the field from radiating its energy to infinity. This composed Kerr-black-hole-scalar-field-mirror system, first designed by Press and Teukolsky, has attracted the attention of physicists over the last four decades. Previous numerical studies of this spinning black-hole bomb have revealed the interesting fact that the superradiant instability shuts down if the reflecting mirror is placed too close to the black-hole horizon. In the present study we use analytical techniques to explore the superradiant instability regime of this composed Kerr-black-hole-linearized-scalar-field-mirror system. In particular, it is proved that the lower bound rm/r+ >1/2 (√{ 1 +8M/r- } - 1) provides a necessary condition for the development of the exponentially growing superradiant instabilities in this composed physical system, where rm is the radius of the confining mirror and r± are the horizon radii of the spinning Kerr black hole. We further show that, in the linearized regime, this analytically derived lower bound on the radius of the confining mirror agrees with direct numerical computations of the superradiant instability spectrum which characterizes the spinning black-hole-mirror bomb.

Carbon black vs. black carbon and other airborne materials containing elemental carbon: Physical and chemical distinctions

International Nuclear Information System (INIS)

Long, Christopher M.; Nascarella, Marc A.; Valberg, Peter A.

2013-01-01

Airborne particles containing elemental carbon (EC) are currently at the forefront of scientific and regulatory scrutiny, including black carbon, carbon black, and engineered carbon-based nanomaterials, e.g., carbon nanotubes, fullerenes, and graphene. Scientists and regulators sometimes group these EC-containing particles together, for example, interchangeably using the terms carbon black and black carbon despite one being a manufactured product with well-controlled properties and the other being an undesired, incomplete-combustion byproduct with diverse properties. In this critical review, we synthesize information on the contrasting properties of EC-containing particles in order to highlight significant differences that can affect hazard potential. We demonstrate why carbon black should not be considered a model particle representative of either combustion soots or engineered carbon-based nanomaterials. Overall, scientific studies need to distinguish these highly different EC-containing particles with care and precision so as to forestall unwarranted extrapolation of properties, hazard potential, and study conclusions from one material to another. -- Highlights: •Major classes of elemental carbon-containing particles have distinct properties. •Despite similar names, carbon black should not be confused with black carbon. •Carbon black is distinguished by a high EC content and well-controlled properties. •Black carbon particles are characterized by their heterogenous properties. •Carbon black is not a model particle representative of engineered nanomaterials. -- This review demonstrates the significant physical and chemical distinctions between elemental carbon-containing particles e.g., carbon black, black carbon, and engineered nanomaterials

Unmodeled search for black hole binary systems in the NINJA project

International Nuclear Information System (INIS)

Cadonati, Laura; Fischetti, Sebastian; Mohapatra, Satyanarayan R P; Chatterji, Shourov; Guidi, Gianluca; Sturani, Riccardo; Vicere, Andrea

2009-01-01

The gravitational-wave signature from binary black hole coalescences is an important target for ground-based interferometric detectors such as LIGO and Virgo. The Numerical INJection Analysis (NINJA) project brought together the numerical relativity and gravitational wave data analysis communities, with the goal to optimize the detectability of these events. In its first instantiation, the NINJA project produced a simulated data set with numerical waveforms from binary black hole coalescences of various morphologies (spin, mass ratio, initial conditions), superimposed to Gaussian colored noise at the design sensitivity for initial LIGO and Virgo. We analyzed the NINJA simulated data set with the Q-pipeline algorithm, designed for the all-sky detection of gravitational-wave bursts with minimal assumptions on the shape of the waveform. The algorithm filters the data with a bank of sine-Gaussians, sinusoids with Gaussian envelope, to identify significant excess power in the time-frequency domain. We compared the performance of this burst search algorithm with lalapps r ing, which match-filters data with a bank of ring-down templates to specifically target the final stage of a coalescence of black holes. A comparison of the output of the two algorithms on NINJA data in a single detector analysis yielded qualitatively consistent results; however, due to the low simulation statistics in the first NINJA project, it is premature to draw quantitative conclusions at this stage, and further studies with higher statistics and real detector noise will be needed.

Examining African self-consciousness and Black racial identity as predictors of Black men's psychological well-being.

Science.gov (United States)

Pierre, Martin R; Mahalik, James R

2005-02-01

This study investigated African self-consciousness and Black racial identity as predictors of psychological distress and self-esteem for Black men. One hundred thirty Black men from a college and community sample completed the African Self-Consciousness Scale, the Racial Identity Attitude Scale-B, the Symptom Checklist 90-Revised, and the Coopersmith Self-Esteem Inventory. Canonical correlation analysis found 2 significant roots with the 1st root indicating that Black men whose attitudes reflected Preencounter and Immersion racial identity attitudes and who do not resist against anti-African/Black forces reported greater psychological distress and less esteem. Results from the 2nd root suggested that Black men whose attitudes reflect greater Internalization racial identity attitudes, greater resistance to anti-African/Black forces, and less identification with Blacks reported greater self-esteem. ((c) 2005 APA, all rights reserved).

Quantum and thermodynamic aspects of Black Holes

International Nuclear Information System (INIS)

Sande e Lemos, J.P. de; Videira, A.L.L.

1983-01-01

The main results originating from the attempts of trying to incorporate quantum and thermodynamic properties and concepts to the gravitational system black hole, essentially the Hawking effect and the four laws of thermodynamics are reviewed. (Author) [pt

The angry black woman: the impact of pejorative stereotypes on psychotherapy with black women.

Science.gov (United States)

Ashley, Wendy

2014-01-01

In the aftermath of slavery and the resulting social, economic, and political effects, Black women have become the victims of negative stereotyping in mainstream American culture. Such stereotypes include the myth of the angry Black woman that characterizes these women as aggressive, ill tempered, illogical, overbearing, hostile, and ignorant without provocation. Symptoms presented by Black women during mental health treatment may reinforce this myth. However, many of the negative characteristics of the angry Black woman developed in response to external stressors and historical factors. Black women also have a unique experience with and expressions of anger that shape the presenting symptoms interpreted by the mental health clinician. This myth and corresponding negative stereotypes significantly affect Black women intrapsychically, interpersonally, and are likely to influence the efficacy of mental health treatment. Understanding and treatment of Black women in a mental health context should be influenced by the cultural norms and sociopolitical dynamics affecting these clients. Successful mental health treatment requires cultural competence and clinicians who are well prepared to navigate the inherent complexities of culture with clients. Awareness of the angry Black woman mythology, including its genesis, manifestations, and the unique experiences of Black women, may raise the standards of cultural competence for clinicians and provide more successful treatment outcomes in working with this population. A case example illustrates the assiduity essential to practicing in a culturally competent manner. A client is presented from a traditional psychotherapeutic perspective and then viewed through a lens that integrates psychotherapeutic practice with conscious awareness of the mythology and stereotypes impacting Black women. Implications for culturally relevant practice are discussed.

Blackness: faith, culture, ideology and discourse*

African Journals Online (AJOL)

Crowther, West Africa's first black bishop, who grovelled before his white missionary .... African-American profane discourse is the Signifying Monkey, then "Tar Baby is as ... racism and sexism, systems described by Christian as "societal and psychological... ..... When the inner conflict and tension occasioned by culture theo-.

Over spinning a black hole?

Energy Technology Data Exchange (ETDEWEB)

Bouhmadi-Lopez, Mariam; Cardoso, Vitor; Nerozzi, Andrea; Rocha, Jorge V, E-mail: mariam.bouhmadi@ist.utl.pt, E-mail: vitor.cardoso@ist.utl.pt, E-mail: andrea.nerozzi@ist.utl.pt, E-mail: jorge.v.rocha@ist.utl.pt [CENTRA, Department de Fisica, Instituto Superior Tecnico, Av. Rovisco Pais 1, 1049 Lisboa (Portugal)

2011-09-22

A possible process to destroy a black hole consists on throwing point particles with sufficiently large angular momentum into the black hole. In the case of Kerr black holes, it was shown by Wald that particles with dangerously large angular momentum are simply not captured by the hole, and thus the event horizon is not destroyed. Here we reconsider this gedanken experiment for black holes in higher dimensions. We show that this particular way of destroying a black hole does not succeed and that Cosmic Censorship is preserved.

Masculinity Identity Development and Its Relevance to Supporting Talented Black Males

Science.gov (United States)

Henfield, Malik S.

2012-01-01

The purpose of the article is to provide a brief introduction to Black male masculine identity development and relate it to the field of gifted education. It will begin with information related to identity development that is applicable to Black males. Next, the phenomenological variant of ecological systems theory (PVEST) will be explored and…

Massive Black Hole Mergers: Can We "See" what LISA will "Hear"?

Science.gov (United States)

Centrella, Joan

2010-01-01

The final merger of massive black holes produces strong gravitational radiation that can be detected by the space-borne LISA. If the black hole merger takes place in the presence of gas and magnetic fields, various types of electromagnetic signals may also be produced. Modeling such electromagnetic counterparts of the final merger requires evolving the behavior of both gas and fields in the strong-field regions around the black holes. We will review current efforts to simulate these systems, and discuss possibilities for observing the electromagnetic signals they produce.

Polarised Black Holes in AdS

CERN Document Server

Costa, Miguel S.; Oliveira, Miguel; Penedones, João; Santos, Jorge E.

2016-05-03

We consider solutions in Einstein-Maxwell theory with a negative cosmological constant that asymptote to global $AdS_{4}$ with conformal boundary $S^{2}\\times\\mathbb{R}_{t}$. At the sphere at infinity we turn on a space-dependent electrostatic potential, which does not destroy the asymptotic $AdS$ behaviour. For simplicity we focus on the case of a dipolar electrostatic potential. We find two new geometries: (i) an $AdS$ soliton that includes the full backreaction of the electric field on the $AdS$ geometry; (ii) a polarised neutral black hole that is deformed by the electric field, accumulating opposite charges in each hemisphere. For both geometries we study boundary data such as the charge density and the stress tensor. For the black hole we also study the horizon charge density and area, and further verify a Smarr formula. Then we consider this system at finite temperature and compute the Gibbs free energy for both $AdS$ soliton and black hole phases. The corresponding phase diagram generalizes the Hawkin...

Adaptability of black walnut, black cherry, and Northern red oak to Northern California

Science.gov (United States)

Philip M. McDonald

1987-01-01

When planted in sheltered sites in northern California, only 49% of black walnut (Juglans nigra L.) and 58% of black cherry (Prunus serotina Ehrh.) survived for 15 years, and 20% of northern red oak (Quercus rubra L.) survived for 10 years. The black walnut trees averaged 0.6 inches diameter at breast...

Continuous phase transition and critical behaviors of 3D black hole with torsion

International Nuclear Information System (INIS)

Ma, Meng-Sen; Liu, Fang; Zhao, Ren

2014-01-01

We study the phase transition and the critical behavior of the BTZ black hole with torsion obtained in (1 + 2)-dimensional Poincaré gauge theory. According to Ehrenfest’s classification, when the parameters in the theory are arranged properly, the BTZ black hole with torsion may possess the second-order phase transition which is also a smaller mass/larger mass black hole phase transition. Nevertheless, the critical behavior is different from the one in the van der Waals liquid/gas system. We also calculated the critical exponents of the relevant thermodynamic quantities, which are the same as the ones obtained in the Hořava-Lifshitz black hole and the Born–Infeld black hole. (paper)

Reconciling White-Box and Black-Box Perspectives on Behavioral Self-adaptation

DEFF Research Database (Denmark)

Bruni, Roberto; Corradini, Andrea; Gadducci, Fabio

2015-01-01

This paper proposes to reconcile two perspectives on behavioral adaptation commonly taken at different stages of the engineering of autonomic computing systems. Requirements engineering activities often take a black-box perspective: A system is considered to be adaptive with respect to an environ......This paper proposes to reconcile two perspectives on behavioral adaptation commonly taken at different stages of the engineering of autonomic computing systems. Requirements engineering activities often take a black-box perspective: A system is considered to be adaptive with respect...... to an environment whenever the system is able to satisfy its goals irrespectively of the environment perturbations. Modeling and programming engineering activities often take a white-box perspective: A system is equipped with suitable adaptation mechanisms and its behavior is classified as adaptive depending...

Black Holes in Higher Dimensions

Directory of Open Access Journals (Sweden)

Reall Harvey S.

2008-09-01

Full Text Available We review black-hole solutions of higher-dimensional vacuum gravity and higher-dimensional supergravity theories. The discussion of vacuum gravity is pedagogical, with detailed reviews of Myers–Perry solutions, black rings, and solution-generating techniques. We discuss black-hole solutions of maximal supergravity theories, including black holes in anti-de Sitter space. General results and open problems are discussed throughout.

Black Hole Accretion in Gamma Ray Bursts

Directory of Open Access Journals (Sweden)

Agnieszka Janiuk

2017-02-01

Full Text Available We study the structure and evolution of the hyperaccreting disks and outflows in the gamma ray bursts central engines. The torus around a stellar mass black hole is composed of free nucleons, Helium, electron-positron pairs, and is cooled by neutrino emission. Accretion of matter powers the relativistic jets, responsible for the gamma ray prompt emission. The significant number density of neutrons in the disk and outflowing material will cause subsequent formation of heavier nuclei. We study the process of nucleosynthesis and its possible observational consequences. We also apply our scenario to the recent observation of the gravitational wave signal, detected on 14 September 2015 by the two Advanced LIGO detectors, and related to an inspiral and merger of a binary black hole system. A gamma ray burst that could possibly be related with the GW150914 event was observed by the Fermi satellite. It had a duration of about 1 s and appeared about 0.4 s after the gravitational-wave signal. We propose that a collapsing massive star and a black hole in a close binary could lead to the event. The gamma ray burst was powered by a weak neutrino flux produced in the star remnant’s matter. Low spin and kick velocity of the merged black hole are reproduced in our simulations. Coincident gravitational-wave emission originates from the merger of the collapsed core and the companion black hole.

submitter Study of Backgrounds to Black Hole Events in the ATLAS Detector

CERN Document Server

Han, Sang Hee

large extra dimension model with black hole mass MBH = sˆ, where sˆ is the parton-parton Centre of Momentum System (CMS) energy squared. In the large extra dimension model, quantum gravity can become strong at a TeV energy scale in the bulk space-time, and could lead to microscopic black holes being produced and observed by the LHC experiments. Once black holes are produced in the collider, they will decay to the SM particles by Hawking evaporation. Under this scenario, an analysis was carried out to determine the significance of black hole signals above some SM backgrounds in the ATLAS detector. Five event selection criteria were app...

Black hole decay as geodesic motion

International Nuclear Information System (INIS)

Gupta, Kumar S.; Sen, Siddhartha

2003-01-01

We show that a formalism for analyzing the near-horizon conformal symmetry of Schwarzschild black holes using a scalar field probe is capable of describing black hole decay. The equation governing black hole decay can be identified as the geodesic equation in the space of black hole masses. This provides a novel geometric interpretation for the decay of black holes. Moreover, this approach predicts a precise correction term to the usual expression for the decay rate of black holes

The Black Atlantic as reversal: A reappraisal of African and black theology

Directory of Open Access Journals (Sweden)

Hans Engdahl

2017-09-01

Full Text Available In this article, I will try to do three things. Firstly, pay attention to the notion of Black Atlantic as coined by Paul Gilroy, which in effect could signify a reversal of colonialism and slavery. Secondly, revisit the 1970s and the debate about the relevance of Black theology vis-à-vis African theology, using John Mbiti’s article ‘An African Views American Black Theology’ as entry point. Here, I will discuss contributions also made by Desmond Tutu and James Cone. Thirdly, starting with the premise that both theologies are relevant and soul mates today, which would (probably be confirmed by all the above mentioned at this point in time, an assessment of current voices will be made, that is, Tinyiko Maluleke and Vuyani Vellem on black and African ecclesiologies from a South African perspective, and Lawrence Burnley on the fate of the Black Church in the United States.

Black carbon in aerosol during BIBLE B

Science.gov (United States)

Liley, J. Ben; Baumgardner, D.; Kondo, Y.; Kita, K.; Blake, D. R.; Koike, M.; Machida, T.; Takegawa, N.; Kawakami, S.; Shirai, T.; Ogawa, T.

2003-02-01

The Biomass Burning and Lightning Experiment (BIBLE) A and B campaigns over the tropical western Pacific during springtime deployed a Gulfstream-II aircraft with systems to measure ozone and numerous precursor species. Aerosol measuring systems included a MASP optical particle counter, a condensation nucleus (CN) counter, and an absorption spectrometer for black carbon. Aerosol volume was very low in the middle and upper troposphere during both campaigns, and during BIBLE A, there was little aerosol enhancement in the boundary layer away from urban areas. In BIBLE B, there was marked aerosol enhancement in the lowest 3 km of the atmosphere. Mixing ratios of CN in cloud-free conditions in the upper troposphere were in general higher than in the boundary layer, indicating new particle formation from gaseous precursors. High concentrations of black carbon were observed during BIBLE B, with mass loadings up to 40 μg m-3 representing as much as one quarter of total aerosol mass. Strong correlations with hydrocarbon enhancement allow the determination of a black carbon emission ratio for the fires at that time. Expressed as elemental carbon, it is about 0.5% of carbon dioxide and 6% of carbon monoxide emissions from the same fires, comparable to methane production, and greater than that of other hydrocarbons.

Charge loss (or the lack thereof) for AdS black holes

International Nuclear Information System (INIS)

Ong, Yen Chin; Chen, Pisin

2014-01-01

The evolution of evaporating charged black holes is complicated to model in general, but is nevertheless important since the hints to the Information Loss Paradox and its recent firewall incarnation may lie in understanding more generic geometries than that of Schwarzschild spacetime. Fortunately, for sufficiently large asymptotically flat Reissner-Nordström black holes, the evaporation process can be modeled via a system of coupled linear ordinary differential equations, with charge loss rate governed by Schwinger pair-production process. The same model can be generalized to study the evaporation of AdS Reissner-Nordström black holes with flat horizon. It was recently found that such black holes always evolve towards extremality since charge loss is inefficient. This property is completely opposite to the asymptotically flat case in which the black hole eventually loses its charges and tends towards Schwarzschild limit. We clarify the underlying reason for this different behavior.

Black report up-date

International Nuclear Information System (INIS)

1988-12-01

In 1984, the Black Report published its results on the incidence of cancer and leukaemia in under 25-year olds in the village of Seascale and the surrounding area near the Sellafield nuclear reprocessing plant. Since then the pressure group core, as a result of their own independent research, has discovered ten additional cases of childhood cancer which should have been included in the Black Report and a Further two cases since the Black Report was written. This represents an additional 31% over the initial numbers considered and a review of the Black Report is sought. (UK)

Lifshitz topological black holes

International Nuclear Information System (INIS)

Mann, R.B.

2009-01-01

I find a class of black hole solutions to a (3+1) dimensional theory gravity coupled to abelian gauge fields with negative cosmological constant that has been proposed as the dual theory to a Lifshitz theory describing critical phenomena in (2+1) dimensions. These black holes are all asymptotic to a Lifshitz fixed point geometry and depend on a single parameter that determines both their area (or size) and their charge. Most of the solutions are obtained numerically, but an exact solution is also obtained for a particular value of this parameter. The thermodynamic behaviour of large black holes is almost the same regardless of genus, but differs considerably for small black holes. Screening behaviour is exhibited in the dual theory for any genus, but the critical length at which it sets in is genus-dependent for small black holes.

Neutron scattering analysis of rubber carbon black composite structure

International Nuclear Information System (INIS)

Hjelm, R.P. Jr.; Wampler, W.A.; Gerspacher, M.

1994-01-01

We explore the uses of small-angle neutron scattering to dissect component form, structure and distribution in carbon black-reinforced rubber by varying the contrast of the system relative to some fluid by changing the fluid scattering-length density. This is the method of contrast variation. Contrast variation allows us to separate scattering contributions from the different components. Here, we extend our studies on high surface area (HSA) carbon black suspended in cyclohexane/deuterocyclohexane to HSA mixed with polyisoprene as a gel of ''bound'' rubber swollen with the same solvent mixtures. Contrast variation of swollen composite gels shows that there are two length scales in the gel structure. Above 1 nm fluctuations in the carbon black predominate. Interactions with elastomer hold the HSA aggregates appart. Below 1 nm the scattering is largely from the elastomer. The smooth surface structure of the carbon black is unaltered by the interactions with elastomer and appears smooth over length scales above about 1 nm. These results show that contrast variation can provide information on composite structure that is not available by other means. This information relates to the reinforcement mechanism of elastomers by carbon blacks

Is black-hole ringdown a memory of its progenitor?

Science.gov (United States)

Kamaretsos, Ioannis; Hannam, Mark; Sathyaprakash, B S

2012-10-05

We perform an extensive numerical study of coalescing black-hole binaries to understand the gravitational-wave spectrum of quasinormal modes excited in the merged black hole. Remarkably, we find that the masses and spins of the progenitor are clearly encoded in the mode spectrum of the ringdown signal. Some of the mode amplitudes carry the signature of the binary's mass ratio, while others depend critically on the spins. Simulations of precessing binaries suggest that our results carry over to generic systems. Using Bayesian inference, we demonstrate that it is possible to accurately measure the mass ratio and a proper combination of spins even when the binary is itself invisible to a detector. Using a mapping of the binary masses and spins to the final black-hole spin allows us to further extract the spin components of the progenitor. Our results could have tremendous implications for gravitational astronomy by facilitating novel tests of general relativity using merging black holes.

Gravitational entropy of nonstationary black holes and spherical shells

International Nuclear Information System (INIS)

Hiscock, W.A.

1989-01-01

The problem of defining the gravitational entropy of a nonstationary black hole is considered in a simple model consisting of a spherical shell which collapses into a preexisting black hole. The second law of black-hole mechanics strongly suggests identifying one-quarter of the area of the event horizon as the gravitational entropy of the system. It is, however, impossible to accurately locate the position of the global event horizon using only local measurements. In order to maintain a local thermodynamics, it is suggested that the entropy of the black hole be identified with one-quarter the area of the apparent horizon. The difference between the event-horizon entropy (to the extent it can be determined) and the apparent-horizon entropy may then be interpreted as the gravitational entropy of the collapsing shell. The total (event-horizon) gravitational entropy evolves in a smooth (C 0 ) fashion, even in the presence of δ-functional shells of matter

Fake Superpotential for Large and Small Extremal Black Holes

CERN Document Server

Andrianopoli, L; Ferrara, S; Trigiante, M

2010-01-01

We consider the fist order, gradient-flow, description of the scalar fields coupled to spherically symmetric, asymptotically flat black holes in extended supergravities. Using the identification of the fake superpotential with Hamilton's characteristic function we clarify some of its general properties, showing in particular (besides reviewing the issue of its duality invariance) that W has the properties of a Liapunov's function, which implies that its extrema (associated with the horizon of extremal black holes) are asymptotically stable equilibrium points of the corresponding first order dynamical system (in the sense of Liapunov). Moreover, we show that the fake superpotential W has, along the entire radial flow, the same flat directions which exist at the attractor point. This allows to study properties of the ADM mass also for small black holes where in fact W has no critical points at finite distance in moduli space. In particular the W function for small non-BPS black holes can always be computed anal...

Black Hole Paradox Solved By NASA's Chandra

Science.gov (United States)

2006-06-01

Black holes are lighting up the Universe, and now astronomers may finally know how. New data from NASA's Chandra X-ray Observatory show for the first time that powerful magnetic fields are the key to these brilliant and startling light shows. It is estimated that up to a quarter of the total radiation in the Universe emitted since the Big Bang comes from material falling towards supermassive black holes, including those powering quasars, the brightest known objects. For decades, scientists have struggled to understand how black holes, the darkest objects in the Universe, can be responsible for such prodigious amounts of radiation. Animation of a Black Hole Pulling Matter from Companion Star Animation of a Black Hole Pulling Matter from Companion Star New X-ray data from Chandra give the first clear explanation for what drives this process: magnetic fields. Chandra observed a black hole system in our galaxy, known as GRO J1655-40 (J1655, for short), where a black hole was pulling material from a companion star into a disk. "By intergalactic standards J1655 is in our backyard, so we can use it as a scale model to understand how all black holes work, including the monsters found in quasars," said Jon M. Miller of the University of Michigan, Ann Arbor, whose paper on these results appears in this week's issue of Nature. Gravity alone is not enough to cause gas in a disk around a black hole to lose energy and fall onto the black hole at the rates required by observations. The gas must lose some of its orbital angular momentum, either through friction or a wind, before it can spiral inward. Without such effects, matter could remain in orbit around a black hole for a very long time. Illustration of Magnetic Fields in GRO J1655-40 Illustration of Magnetic Fields in GRO J1655-40 Scientists have long thought that magnetic turbulence could generate friction in a gaseous disk and drive a wind from the disk that carries angular momentum outward allowing the gas to fall inward

Q ‑ Φ criticality and microstructure of charged AdS black holes in f(R) gravity

Science.gov (United States)

Deng, Gao-Ming; Huang, Yong-Chang

2017-12-01

The phase transition and critical behaviors of charged AdS black holes in f(R) gravity with a conformally invariant Maxwell (CIM) source and constant curvature are further investigated. As a highlight, this research is carried out by employing new state parameters (T,Q, Φ) and contributes to deeper understanding of the thermodynamics and phase structure of black holes. Our analyses manifest that the charged f(R)-CIM AdS black hole undergoes a first-order small-large black hole phase transition, and the critical behaviors qualitatively behave like a Van der Waals liquid-vapor system. However, differing from the case in Einstein’s gravity, phase structures of the black holes in f(R) theory exhibit an interesting dependence on gravity modification parameters. Moreover, we adopt the thermodynamic geometry to probe the black hole microscopic properties. The results show that, on the one hand, both the Ruppeiner curvature and heat capacity diverge exactly at the critical point, on the other hand, the f(R)-CIM AdS black hole possesses the property as ideal Fermi gases. Of special interest, we discover a microscopic similarity between the black holes and a Van der Waals liquid-vapor system.

Acceleration of black hole universe

Science.gov (United States)

Zhang, T. X.; Frederick, C.

2014-01-01

Recently, Zhang slightly modified the standard big bang theory and developed a new cosmological model called black hole universe, which is consistent with Mach's principle, governed by Einstein's general theory of relativity, and able to explain all observations of the universe. Previous studies accounted for the origin, structure, evolution, expansion, and cosmic microwave background radiation of the black hole universe, which grew from a star-like black hole with several solar masses through a supermassive black hole with billions of solar masses to the present state with hundred billion-trillions of solar masses by accreting ambient matter and merging with other black holes. This paper investigates acceleration of the black hole universe and provides an alternative explanation for the redshift and luminosity distance measurements of type Ia supernovae. The results indicate that the black hole universe accelerates its expansion when it accretes the ambient matter in an increasing rate. In other words, i.e., when the second-order derivative of the mass of the black hole universe with respect to the time is positive . For a constant deceleration parameter , we can perfectly explain the type Ia supernova measurements with the reduced chi-square to be very close to unity, χ red˜1.0012. The expansion and acceleration of black hole universe are driven by external energy.

Racial residential segregation, socioeconomic disparities, and the White-Black survival gap

Science.gov (United States)

Duffy, Erin; Mendelsohn, Joshua; Escarce, José J.

2018-01-01

Objective To evaluate the association between racial residential segregation, a prominent manifestation of systemic racism, and the White-Black survival gap in a contemporary cohort of adults, and to assess the extent to which socioeconomic inequality explains this association. Design This was a cross sectional study of White and Black men and women aged 35–75 living in 102 large US Core Based Statistical Areas. The main outcome was the White-Black survival gap. We used 2009–2013 CDC mortality data for Black and White men and women to calculate age-, sex- and race adjusted White and Black mortality rates. We measured segregation using the Dissimilarity index, obtained from the Manhattan Institute. We used the 2009–2013 American Community Survey to define indicators of socioeconomic inequality. We estimated the CBSA-level White–Black gap in probability of survival using sequential linear regression models accounting for the CBSA dissimilarity index and race-specific socioeconomic indicators. Results Black men and women had a 14% and 9% lower probability of survival from age 35 to 75 than their white counterparts. Residential segregation was strongly associated with the survival gap, and this relationship was partly, but not fully, explained by socioeconomic inequality. At the lowest observed level of segregation, and with the Black socioeconomic status (SES) assumed to be at the White SES level scenario, the survival gap is essentially eliminated. Conclusion White-Black differences in survival remain wide notwithstanding public health efforts to improve life expectancy and initiatives to reduce health disparities. Eliminating racial residential segregation and bringing Black socioeconomic status (SES) to White SES levels would eliminate the White-Black survival gap. PMID:29474451

Racial residential segregation, socioeconomic disparities, and the White-Black survival gap.

Directory of Open Access Journals (Sweden)

Ioana Popescu

Full Text Available To evaluate the association between racial residential segregation, a prominent manifestation of systemic racism, and the White-Black survival gap in a contemporary cohort of adults, and to assess the extent to which socioeconomic inequality explains this association.This was a cross sectional study of White and Black men and women aged 35-75 living in 102 large US Core Based Statistical Areas. The main outcome was the White-Black survival gap. We used 2009-2013 CDC mortality data for Black and White men and women to calculate age-, sex- and race adjusted White and Black mortality rates. We measured segregation using the Dissimilarity index, obtained from the Manhattan Institute. We used the 2009-2013 American Community Survey to define indicators of socioeconomic inequality. We estimated the CBSA-level White-Black gap in probability of survival using sequential linear regression models accounting for the CBSA dissimilarity index and race-specific socioeconomic indicators.Black men and women had a 14% and 9% lower probability of survival from age 35 to 75 than their white counterparts. Residential segregation was strongly associated with the survival gap, and this relationship was partly, but not fully, explained by socioeconomic inequality. At the lowest observed level of segregation, and with the Black socioeconomic status (SES assumed to be at the White SES level scenario, the survival gap is essentially eliminated.White-Black differences in survival remain wide notwithstanding public health efforts to improve life expectancy and initiatives to reduce health disparities. Eliminating racial residential segregation and bringing Black socioeconomic status (SES to White SES levels would eliminate the White-Black survival gap.

Why Blue-Collar Blacks Help Less

OpenAIRE

Smith, Sandra Susan; Young, Kara Alexis

2013-01-01

Why are blue-collar blacks less likely to help jobseekers than jobholders from other ethnoracial groups or even than more affluent blacks? Drawing from in-depth, semi-structured interviews with 97 black and Latino workers at one large, public sector employer, we find that blue-collar black workers both helped less proactively and rejected more requests for assistance than did blue-collar Latino and white-collar black workers. We attribute blue-collar blacks’ more passive engagement to their...

Curvature invariant characterization of event horizons of four-dimensional black holes conformal to stationary black holes

Science.gov (United States)

McNutt, David D.

2017-11-01

We introduce three approaches to generate curvature invariants that transform covariantly under a conformal transformation of a four-dimensional spacetime. For any black hole conformally related to a stationary black hole, we show how a set of conformally covariant invariants can be combined to produce a conformally covariant invariant that detects the event horizon of the conformally related black hole. As an application we consider the rotating dynamical black holes conformally related to the Kerr-Newman-Unti-Tamburino-(anti)-de Sitter spacetimes and construct an invariant that detects the conformal Killing horizon along with a second invariant that detects the conformal stationary limit surface. In addition, we present necessary conditions for a dynamical black hole to be conformally related to a stationary black hole and apply these conditions to the ingoing Kerr-Vaidya and Vaidya black hole solutions to determine if they are conformally related to stationary black holes for particular choices of the mass function. While two of the three approaches cannot be generalized to higher dimensions, we discuss the existence of a conformally covariant invariant that will detect the event horizon for any higher dimensional black hole conformally related to a stationary black hole which admits at least two conformally covariant invariants, including all vacuum spacetimes.

A review of the microscopic modeling of the 5-dim. black hole of IIB

Indian Academy of Sciences (India)

We review the theory of the microscopic modeling of the 5-dim. black hole of type IIB string theory in terms of the 1-5 brane system. A detailed discussion of the low energy effective Lagrangian of the brane system is presented and the black hole micro-states are identified. These considerations are valid in the strong ...

New geometries for black hole horizons

Energy Technology Data Exchange (ETDEWEB)

Armas, Jay [Physique Théorique et Mathématique,Université Libre de Bruxelles and International Solvay Institutes, ULB-Campus Plaine CP231, B-1050 Brussels (Belgium); Blau, Matthias [Albert Einstein Center for Fundamental Physics, University of Bern,Sidlerstrasse 5, 3012 Bern (Switzerland)

2015-07-10

We construct several classes of worldvolume effective actions for black holes by integrating out spatial sections of the worldvolume geometry of asymptotically flat black branes. This provides a generalisation of the blackfold approach for higher-dimensional black holes and yields a map between different effective theories, which we exploit by obtaining new hydrodynamic and elastic transport coefficients via simple integrations. Using Euclidean minimal surfaces in order to decouple the fluid dynamics on different sections of the worldvolume, we obtain local effective theories for ultraspinning Myers-Perry branes and helicoidal black branes, described in terms of a stress-energy tensor, particle currents and non-trivial boost vectors. We then study in detail and present novel compact and non-compact geometries for black hole horizons in higher-dimensional asymptotically flat space-time. These include doubly-spinning black rings, black helicoids and helicoidal p-branes as well as helicoidal black rings and helicoidal black tori in D≥6.

Few-layer black phosphorus nanoparticles.

Science.gov (United States)

Sofer, Zdenek; Bouša, Daniel; Luxa, Jan; Mazanek, Vlastimil; Pumera, Martin

2016-01-28

Herein, black phosphorus quantum dots and nanoparticles of a few layer thickness were prepared and characterized using STEM, AFM, dynamic light scattering, X-ray photoelectron spectroscopy, X-ray diffraction, Raman spectroscopy and photoluminescence. Impact electrochemistry of the induvidual black phosphorus nanoparticles allows their size determination. The centrifugation of colloidal black phosphorus nanoparticles allowed separation of quantum dots with sizes up to 15 nm. These black phosphorus nanoparticles exhibit a large band gap and are expected to find a wide range of applications from semiconductors to biomolecule tags. The use of black phosphorus nanoparticles for vapour sensing was successfully demonstrated.

Black Silicon formation using dry etching for solar cells applications

International Nuclear Information System (INIS)

Murias, D.; Reyes-Betanzo, C.; Moreno, M.; Torres, A.; Itzmoyotl, A.; Ambrosio, R.; Soriano, M.; Lucas, J.; Cabarrocas, P. Roca i

2012-01-01

A study on the formation of Black Silicon on crystalline silicon surface using SF 6 /O 2 and SF 6 /O 2 /CH 4 based plasmas in a reactive ion etching (RIE) system is presented. The effect of the RF power, chamber pressure, process time, gas flow rates, and gas mixtures on the texture of silicon surface has been analyzed. Completely Black Silicon surfaces containing pyramid like structures have been obtained, using an optimized mask-free plasma process. Moreover, the Black Silicon surfaces have demonstrated average values of 1% and 4% for specular and diffuse reflectance respectively, feature that is suitable for the fabrication of low cost solar cells.

Quasi-bound state resonances of charged massive scalar fields in the near-extremal Reissner-Nordstroem black-hole spacetime

Energy Technology Data Exchange (ETDEWEB)

Hod, Shahar [The Ruppin Academic Center, Emeq Hefer (Israel); The Hadassah Academic College, Jerusalem (Israel)

2017-05-15

The quasi-bound states of charged massive scalar fields in the near-extremal charged Reissner-Nordstroem black-hole spacetime are studied analytically. These discrete resonant modes of the composed black-hole-field system are characterized by the physically motivated boundary condition of ingoing waves at the black-hole horizon and exponentially decaying (bounded) radial eigenfunctions at spatial infinity. Solving the Klein-Gordon wave equation for the linearized scalar fields in the black-hole spacetime, we derive a remarkably compact analytical formula for the complex frequency spectrum which characterizes the quasi-bound state resonances of the composed Reissner-Nordstroem-black-hole-charged-massive-scalar-field system. (orig.)

Critical behavior and microscopic structure of charged AdS black holes via an alternative phase space

Directory of Open Access Journals (Sweden)

Amin Dehyadegari

2017-05-01

Full Text Available It has been argued that charged Anti-de Sitter (AdS black holes have similar thermodynamic behavior as the Van der Waals fluid system, provided one treats the cosmological constant as a thermodynamic variable (pressure in an extended phase space. In this paper, we disclose the deep connection between charged AdS black holes and Van der Waals fluid system from an alternative point of view. We consider the mass of an AdS black hole as a function of square of the charge Q2 instead of the standard Q, i.e. M=M(S,Q2,P. We first justify such a change of view mathematically and then ask if a phase transition can occur as a function of Q2 for fixed P. Therefore, we write the equation of state as Q2=Q2(T,Ψ where Ψ (conjugate of Q2 is the inverse of the specific volume, Ψ=1/v. This allows us to complete the analogy of charged AdS black holes with Van der Waals fluid system and derive the phase transition as well as critical exponents of the system. We identify a thermodynamic instability in this new picture with real analogy to Van der Waals fluid with physically relevant Maxwell construction. We therefore study the critical behavior of isotherms in Q2–Ψ diagram and deduce all the critical exponents of the system and determine that the system exhibits a small–large black hole phase transition at the critical point (Tc,Qc2,Ψc. This alternative view is important as one can imagine such a change for a given single black hole i.e. acquiring charge which induces the phase transition. Finally, we disclose the microscopic properties of charged AdS black holes by using thermodynamic geometry. Interestingly, we find that scalar curvature has a gap between small and large black holes, and this gap becomes exceedingly large as one moves away from the critical point along the transition line. Therefore, we are able to attribute the sudden enlargement of the black hole to the strong repulsive nature of the internal constituents at the phase transition.

Regular black hole in three dimensions

OpenAIRE

Myung, Yun Soo; Yoon, Myungseok

2008-01-01

We find a new black hole in three dimensional anti-de Sitter space by introducing an anisotropic perfect fluid inspired by the noncommutative black hole. This is a regular black hole with two horizons. We compare thermodynamics of this black hole with that of non-rotating BTZ black hole. The first-law of thermodynamics is not compatible with the Bekenstein-Hawking entropy.

ON THE HIGH-FREQUENCY QUASI-PERIODIC OSCILLATIONS FROM BLACK HOLES

International Nuclear Information System (INIS)

Erkut, M. Hakan

2011-01-01

We apply the global mode analysis, which has been recently developed for the modeling of kHz quasi-periodic oscillations (QPOs) from neutron stars, to the inner region of an accretion disk around a rotating black hole. Within a pseudo-Newtonian approach that keeps the ratio of the radial epicyclic frequency κ to the orbital frequency Ω the same as the corresponding ratio for a Kerr black hole, we determine the innermost disk region where the hydrodynamic modes grow in amplitude. We find that the radiation flux emerging from the inner disk has the highest values within the same region. Using the flux-weighted averages of the frequency bands over this region we identify the growing modes with highest frequency branches Ω + κ and Ω to be the plausible candidates for the high-frequency QPO pairs observed in black hole systems. The observed frequency ratio around 1.5 can therefore be understood naturally in terms of the global free oscillations in the innermost region of a viscous accretion disk around a black hole without invoking a particular resonance to produce black hole QPOs. Although the frequency ratio (Ω + κ)/(Ω) is found to be not sensitive to the black hole's spin which is good for explaining the high-frequency QPOs, it may work as a limited diagnostic of the spin parameter to distinguish black holes with very large spin from the slowly rotating ones. Within our model we estimate the frequency ratio of a high-frequency QPO pair to be greater than 1.5 if the black hole is a slow rotator. For fast rotating black holes, we expect the same ratio to be less than 1.5.

Beyond opening up the black box: Investigating the role of algorithmic systems in Wikipedian organizational culture

Directory of Open Access Journals (Sweden)

R Stuart Geiger

2017-09-01

Full Text Available Scholars and practitioners across domains are increasingly concerned with algorithmic transparency and opacity, interrogating the values and assumptions embedded in automated, black-boxed systems, particularly in user-generated content platforms. I report from an ethnography of infrastructure in Wikipedia to discuss an often understudied aspect of this topic: the local, contextual, learned expertise involved in participating in a highly automated social–technical environment. Today, the organizational culture of Wikipedia is deeply intertwined with various data-driven algorithmic systems, which Wikipedians rely on to help manage and govern the “anyone can edit” encyclopedia at a massive scale. These bots, scripts, tools, plugins, and dashboards make Wikipedia more efficient for those who know how to work with them, but like all organizational culture, newcomers must learn them if they want to fully participate. I illustrate how cultural and organizational expertise is enacted around algorithmic agents by discussing two autoethnographic vignettes, which relate my personal experience as a veteran in Wikipedia. I present thick descriptions of how governance and gatekeeping practices are articulated through and in alignment with these automated infrastructures. Over the past 15 years, Wikipedian veterans and administrators have made specific decisions to support administrative and editorial workflows with automation in particular ways and not others. I use these cases of Wikipedia’s bot-supported bureaucracy to discuss several issues in the fields of critical algorithms studies; critical data studies; and fairness, accountability, and transparency in machine learning—most principally arguing that scholarship and practice must go beyond trying to “open up the black box” of such systems and also examine sociocultural processes like newcomer socialization.

Boosted quantum black hole and black string in M-theory, and quantum correction to Gregory-Laflamme instability

Energy Technology Data Exchange (ETDEWEB)

Hyakutake, Yoshifumi [Faculty of Science, Ibaraki University,Bunkyo 2-1-1, Mito, Ibaraki, 310-8512 (Japan)

2015-09-11

We take into account higher derivative R{sup 4} corrections in M-theory and construct quantum black hole and black string solutions in 11 dimensions up to the next leading order. The quantum black string is stretching along the 11th direction and the Gregory-Laflamme instability is examined at the quantum level. Thermodynamics of the boosted quantum black hole and black string are also discussed. Especially we take the near horizon limit of the quantum black string and investigate its instability quantitatively.

Stationary black holes: large D analysis

International Nuclear Information System (INIS)

Suzuki, Ryotaku; Tanabe, Kentaro

2015-01-01

We consider the effective theory of large D stationary black holes. By solving the Einstein equations with a cosmological constant using the 1/D expansion in near zone of the black hole we obtain the effective equation for the stationary black hole. The effective equation describes the Myers-Perry black hole, bumpy black holes and, possibly, the black ring solution as its solutions. In this effective theory the black hole is represented as an embedded membrane in the background, e.g., Minkowski or Anti-de Sitter spacetime and its mean curvature is given by the surface gravity redshifted by the background gravitational field and the local Lorentz boost. The local Lorentz boost property of the effective equation is observed also in the metric itself. In fact we show that the leading order metric of the Einstein equation in the 1/D expansion is generically regarded as a Lorentz boosted Schwarzschild black hole. We apply this Lorentz boost property of the stationary black hole solution to solve perturbation equations. As a result we obtain an analytic formula for quasinormal modes of the singly rotating Myers-Perry black hole in the 1/D expansion.

Development of a Web-based GIS monitoring and environmental assessment system for the Black Sea: application in the Danube Delta area.

Science.gov (United States)

Tziavos, Ilias N; Alexandridis, Thomas K; Aleksandrov, Borys; Andrianopoulos, Agamemnon; Doukas, Ioannis D; Grigoras, Ion; Grigoriadis, Vassilios N; Papadopoulou, Ioanna D; Savvaidis, Paraskevas; Stergioudis, Argyrios; Teodorof, Liliana; Vergos, Georgios S; Vorobyova, Lyudmila; Zalidis, Georgios C

2016-08-01

In this paper, the development of a Web-based GIS system for the monitoring and assessment of the Black Sea is presented. The integrated multilevel system is based on the combination of terrestrial and satellite Earth observation data through the technological assets provided by innovative information tools and facilities. The key component of the system is a unified, easy to update geodatabase including a wide range of appropriately selected environmental parameters. The collection procedure of current and historical data along with the methods employed for their processing in three test areas of the current study are extensively discussed, and special attention is given to the overall design and structure of the developed geodatabase. Furthermore, the information system includes a decision support component (DSC) which allows assessment and effective management of a wide range of heterogeneous data and environmental parameters within an appropriately designed and well-tested methodology. The DSC provides simplified and straightforward results based on a classification procedure, thus contributing to a monitoring system not only for experts but for auxiliary staff as well. The examples of the system's functionality that are presented highlight its usability as well as the assistance that is provided to the decision maker. The given examples emphasize on the Danube Delta area; however, the information layers of the integrated system can be expanded in the future to cover other regions, thus contributing to the development of an environmental monitoring system for the entire Black Sea.

MAIN FEATURES OF BALNEOLOGICAL AND MUD RESORTS NETWORK OF THE BLACK SEA COUNTRIES

OpenAIRE

Молодецький, А. Е.; Пишна, Г. О.

2016-01-01

Purpose. The aim of the article is the characteristics of geographical (natural and socio-economic) prerequisites for the development of coastal resorts of Black Sea region countries, with emphasis on balneological and mud-bath of recreational resources systems. Six European and Asian countries – Ukraine, Russia, Georgia, Turkey, Bulgaria and Romania have a diverse and significant resort and recreational resources of the Black Sea coast. However, for many decades the Black Sea resorts of thes...

Jets, black holes and disks in blazars

Directory of Open Access Journals (Sweden)

Ghisellini Gabriele

2013-12-01

Full Text Available The Fermi and Swift satellites, together with ground based Cherenkov telescopes, has greatly improved our knowledge of blazars, namely Flat Spectrum Radio Quasars and BL Lac objects, since all but the most powerful emit most of their electro–magnetic output at γ–ray energies, while the very powerful blazars emit mostly in the hard X–ray region of the spectrum. Often they show coordinated variability at different frequencies, suggesting that in these cases the same population of electrons is at work, in a single zone of the jet. The location of this region along the jet is a matter of debate. The jet power correlates with the mass accretion rate, with jets existing at all values of disk luminosities, measured in Eddington units, sampled so far. The most powerful blazars show clear evidence of the emission from their disks, and this has revived methods of finding the black hole mass and accretion rate by modelling a disk spectrum to the data. Being so luminous, blazars can be detected also at very high redshift, and therefore are a useful tool to explore the far universe. One interesting line of research concerns how heavy are their black holes at high redshifts. If we associate the presence of a relativistic jets with a fastly spinning black hole, then we naively expect that the accretion efficiency is larger than for non–spinning holes. As a consequence, the black hole mass in jetted systems should grow at a slower rate. In turn, this would imply that, at high redshifts, the heaviest black holes should be in radio–quiet quasars. We instead have evidences of the opposite, challenging our simple ideas of how a black hole grows.

A Black Hole Spectral Signature

Science.gov (United States)

Titarchuk, Lev; Laurent, Philippe

2000-03-01

An accreting black hole is, by definition, characterized by the drain. Namely, the matter falls into a black hole much the same way as water disappears down a drain matter goes in and nothing comes out. As this can only happen in a black hole, it provides a way to see ``a black hole'', an unique observational signature. The accretion proceeds almost in a free-fall manner close to the black hole horizon, where the strong gravitational field dominates the pressure forces. In this paper we present analytical calculations and Monte-Carlo simulations of the specific features of X-ray spectra formed as a result of upscattering of the soft (disk) photons in the converging inflow (CI) into the black hole. The full relativistic treatment has been implemented to reproduce these spectra. We show that spectra in the soft state of black hole systems (BHS) can be described as the sum of a thermal (disk) component and the convolution of some fraction of this component with the CI upscattering spread (Greens) function. The latter boosted photon component is seen as an extended power-law at energies much higher than the characteristic energy of the soft photons. We demonstrate the stability of the power spectral index over a wide range of the plasma temperature 0 - 10 keV and mass accretion rates (higher than 2 in Eddington units). We also demonstrate that the sharp high energy cutoff occurs at energies of 200-400 keV which are related to the average energy of electrons mec2 impinging upon the event horizon. The spectrum is practically identical to the standard thermal Comptonization spectrum when the CI plasma temperature is getting of order of 50 keV (the typical ones for the hard state of BHS). In this case one can see the effect of the bulk motion only at high energies where there is an excess in the CI spectrum with respect to the pure thermal one. Furthermore we demonstrate that the change of spectral shapes from the soft X-ray state to the hard X-ray state is clearly to be

Modeling Lolium perenne L. roots in the presence of empirical black holes

Science.gov (United States)

Plant root models are designed for understanding structural or functional aspects of root systems. When a process is not thoroughly understood, a black box object is used. However, when a process exists but empirical data do not indicate its existence, you have a black hole. The object of this re...

Black branes as piezoelectrics.

Science.gov (United States)

Armas, Jay; Gath, Jakob; Obers, Niels A

2012-12-14

We find a realization of linear electroelasticity theory in gravitational physics by uncovering a new response coefficient of charged black branes, exhibiting their piezoelectric behavior. Taking charged dilatonic black strings as an example and using the blackfold approach we measure their elastic and piezolectric moduli. We also use our results to draw predictions about the equilibrium condition of charged dilatonic black rings in dimensions higher than six.

Black hole levitron

NARCIS (Netherlands)

Arsiwalla, X.D.; Verlinde, E.P.

2010-01-01

We study the problem of spatially stabilizing four dimensional extremal black holes in background electric/magnetic fields. Whilst looking for stationary stable solutions describing black holes placed in external fields we find that taking a continuum limit of Denef et al.’s multicenter

Black-hole bremsstrahlung and the efficiency of mass-energy radiative transfer

International Nuclear Information System (INIS)

Oliveira, H. P. de; Soares, I. Damiao; Tonini, E. V.

2008-01-01

We present results from numerical evolution of a boosted black hole, perturbed nonlinearly by an axisymmetric distribution of matter in the realm of Robinson-Trautman spacetimes. Characteristic initial data for the system were constructed and the Robinson-Trautmann equation was integrated for these data using a numerical code based on the Galerkin-collocation method. The emission of gravitational waves by the system is typical of bremsstrahlung at early times, a consequence of the deceleration of the black hole as it interacts with the perturbation; part of the perturbation is radiated away and another part is absorbed into the hole. The angular pattern evolves to the quadrupole form for later times. The final configuration is a black hole in motion with larger (Bondi) rest mass and smaller boost parameter. The efficiency Δ of mass-energy extraction by gravitational wave emission was also computed. The relation of Δ to the mass of the remnant black hole satisfies a nonextensive thermostatistics distribution with entropic index q≅1/2. The result extends analytical evaluations based on the linearized theory of gravitational wave emission. For each initial boost parameter, there always exists a (large) value of the perturbation parameter A 0 for which the momentum of the remnant black hole has opposite sign to that of the unperturbed black hole, due to the strong deceleration during the process of gravitational wave emission. The temporal wave form is that of an initial burst and we evaluate that for a large range of A 0 the process corresponds to a high power output in the initial dominant pulse.

Black Hole Grabs Starry Snack

Science.gov (United States)

2006-01-01

[figure removed for brevity, see original site] Poster Version This artist's concept shows a supermassive black hole at the center of a remote galaxy digesting the remnants of a star. NASA's Galaxy Evolution Explorer had a 'ringside' seat for this feeding frenzy, using its ultraviolet eyes to study the process from beginning to end. The artist's concept chronicles the star being ripped apart and swallowed by the cosmic beast over time. First, the intact sun-like star (left) ventures too close to the black hole, and its own self-gravity is overwhelmed by the black hole's gravity. The star then stretches apart (middle yellow blob) and eventually breaks into stellar crumbs, some of which swirl into the black hole (cloudy ring at right). This doomed material heats up and radiates light, including ultraviolet light, before disappearing forever into the black hole. The Galaxy Evolution Explorer was able to watch this process unfold by observing changes in ultraviolet light. The area around the black hole appears warped because the gravity of the black hole acts like a lens, twisting and distorting light.

A nonsingular rotating black hole

International Nuclear Information System (INIS)

Ghosh, Sushant G.

2015-01-01

The spacetime singularities in classical general relativity are inevitable, as predicated by the celebrated singularity theorems. However, it is a general belief that singularities do not exist in Nature and that they are the limitations of the general relativity. In the absence of a welldefined quantum gravity, models of regular black holes have been studied. We employ a probability distribution inspired mass function m(r) to replace the Kerr black hole mass M to represent a nonsingular rotating black hole that is identified asymptotically (r >> k, k > 0 constant) exactly as the Kerr-Newman black hole, and as the Kerr black hole when k = 0. The radiating counterpart renders a nonsingular generalization of Carmeli's spacetime as well as Vaidya's spacetime, in the appropriate limits. The exponential correction factor changing the geometry of the classical black hole to remove the curvature singularity can also be motivated by quantum arguments. The regular rotating spacetime can also be understood as a black hole of general relativity coupled to nonlinear electrodynamics. (orig.)

Entropy of Kerr-de Sitter black hole

Science.gov (United States)

Li, Huai-Fan; Ma, Meng-Sen; Zhang, Li-Chun; Zhao, Ren

2017-07-01

Based on the consideration that the black hole horizon and the cosmological horizon of Kerr-de Sitter black hole are not independent of each other, we conjecture the total entropy of the system should have an extra term contributed from the correlations between the two horizons, except for the sum of the two horizon entropies. By employing globally effective first law and effective thermodynamic quantities, we obtain the corrected total entropy and find that the region of stable state for Kerr-de Sitter is related to the angular velocity parameter a, i.e., the region of stable state becomes bigger as the rotating parameters a is increases.

ILLUMINATING BLACK HOLE BINARY FORMATION CHANNELS WITH SPINS IN ADVANCED LIGO

Energy Technology Data Exchange (ETDEWEB)

Rodriguez, Carl L. [MIT-Kavli Institute for Astrophysics and Space Research, 77 Massachusetts Avenue, 37-664H, Cambridge, MA 02139 (United States); Zevin, Michael; Pankow, Chris; Kalogera, Vasilliki; Rasio, Frederic A. [Center for Interdisciplinary Exploration and Research in Astrophysics (CIERA) and Department of Physics and Astronomy, Northwestern University, 2145 Sheridan Road, Evanston, IL 60208 (United States)

2016-11-20

The recent detections of the binary black hole mergers GW150914 and GW151226 have inaugurated the field of gravitational-wave astronomy. For the two main formation channels that have been proposed for these sources, isolated binary evolution in galactic fields and dynamical formation in dense star clusters, the predicted masses and merger rates overlap significantly, complicating any astrophysical claims that rely on measured masses alone. Here, we examine the distribution of spin–orbit misalignments expected for binaries from the field and from dense star clusters. Under standard assumptions for black hole natal kicks, we find that black hole binaries similar to GW150914 could be formed with significant spin–orbit misalignment only through dynamical processes. In particular, these heavy-black hole binaries can only form with a significant spin–orbit anti -alignment in the dynamical channel. Our results suggest that future detections of merging black hole binaries with measurable spins will allow us to identify the main formation channel for these systems.

Computerization of administration and operation management in Polish black coal mines

Energy Technology Data Exchange (ETDEWEB)

Mastej, R.; Syrkiewicz, J. (Centralny Osrodek Informatyki Gornictwa (Poland))

1990-08-01

Characterizes main solutions of the computerized management model adopted in Poland for the mining industry and the technical and oganizational structure of computer system application. Computer systems for black coal mines and the range of microprocessor application are shown in block diagrams. The COIG mining information center makes about 45 computer system modules with independent implementation available for black coal mines. The general concept foresees central data processing in the COIG center on the ODRA 1305 and ICL 297 computers with the G-3 operating system in the first stage and an ICL series 39 computer with the VME operating system in the second stage. For mines where no transmission lines are available local solutions based on smaller ICL computers, minicomputers or computer networks with the NOVELL network operating system or multi-access systems with the UNIX operating system are planned. 3 refs.

NASA Observatory Confirms Black Hole Limits

Science.gov (United States)

2005-02-01

The very largest black holes reach a certain point and then grow no more, according to the best survey to date of black holes made with NASA's Chandra X-ray Observatory. Scientists have also discovered many previously hidden black holes that are well below their weight limit. These new results corroborate recent theoretical work about how black holes and galaxies grow. The biggest black holes, those with at least 100 million times the mass of the Sun, ate voraciously during the early Universe. Nearly all of them ran out of 'food' billions of years ago and went onto a forced starvation diet. Focus on Black Holes in the Chandra Deep Field North Focus on Black Holes in the Chandra Deep Field North On the other hand, black holes between about 10 and 100 million solar masses followed a more controlled eating plan. Because they took smaller portions of their meals of gas and dust, they continue growing today. "Our data show that some supermassive black holes seem to binge, while others prefer to graze", said Amy Barger of the University of Wisconsin in Madison and the University of Hawaii, lead author of the paper describing the results in the latest issue of The Astronomical Journal (Feb 2005). "We now understand better than ever before how supermassive black holes grow." One revelation is that there is a strong connection between the growth of black holes and the birth of stars. Previously, astronomers had done careful studies of the birthrate of stars in galaxies, but didn't know as much about the black holes at their centers. DSS Optical Image of Lockman Hole DSS Optical Image of Lockman Hole "These galaxies lose material into their central black holes at the same time that they make their stars," said Barger. "So whatever mechanism governs star formation in galaxies also governs black hole growth." Astronomers have made an accurate census of both the biggest, active black holes in the distance, and the relatively smaller, calmer ones closer by. Now, for the first

Thermal Oxidation of Tail Gases from the Production of Oil-furnace Carbon Black

Directory of Open Access Journals (Sweden)

Bosak, Z.

2009-01-01

Full Text Available This paper describes the production technology of oil-furnace carbon black, as well as the selected solution for preventing the emissions of this process from contaminating the environment.The products of industrial oil-furnace carbon black production are different grades of carbon black and process tail gases. The qualitative composition of these tail gases during the production of oil-furnace carbon black are: carbon(IV oxide, carbon(II oxide, hydrogen, methane, hydrogen sulfide, nitrogen, oxygen, and water vapor.The quantitative composition and lower caloric value of process tail gases change depending on the type of feedstock used in the production, as well as the type of process. The lower caloric value of process tail gases is relatively small with values ranging between 1500 and 2300 kJ m–3.In the conventional production of oil-furnace carbon black, process tail gases purified from carbon black dust are freely released into the atmosphere untreated. In this manner, the process tail gases pollute the air in the town of Kutina, because their quantitative values are much higher than the prescribed emissions limits for hydrogen sulfide and carbon(II oxide. A logical solution for the prevention of such air pollution is combustion of the process tail gases, i. e. their thermal oxidation. For this purpose, a specially designed flare system has been developed. Consuming minimum amounts of natural gas needed for oxidation, the flare system is designed to combust low caloric process tail gases with 99 % efficiency. Thus, the toxic and flammable components of the tail gases (hydrogen sulfide, hydrogen, carbon(II oxide, methane and other trace hydrocarbons would be transformed into environmentally acceptable components (sulfur(IV oxide, water, carbon(IV oxide and nitrogen(IV oxide, which are in compliance with the emissions limit values prescribed by law.Proper operation of this flare system in the production of oil-furnace carbon black would solve

CONSTRAINTS ON BLACK HOLE GROWTH, QUASAR LIFETIMES, AND EDDINGTON RATIO DISTRIBUTIONS FROM THE SDSS BROAD-LINE QUASAR BLACK HOLE MASS FUNCTION

International Nuclear Information System (INIS)

Kelly, Brandon C.; Hernquist, Lars; Siemiginowska, Aneta; Vestergaard, Marianne; Fan Xiaohui; Hopkins, Philip

2010-01-01

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 1 it is highly incomplete at M BH ∼ 9 M sun and L/L Edd ∼ BL > 150 ± 15 Myr for black holes at z = 1 with a mass of M BH = 10 9 M sun , and we constrain the maximum mass of a black hole in a BLQSO to be ∼3 x 10 10 M sun . Our estimated distribution of BLQSO Eddington ratios peaks at L/L Edd ∼ 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 > 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.

Two-Phase Equilibrium Properties in Charged Topological Dilaton AdS Black Holes

Directory of Open Access Journals (Sweden)

Hui-Hua Zhao

2016-01-01

Full Text Available We discuss phase transition of the charged topological dilaton AdS black holes by Maxwell equal area law. The two phases involved in the phase transition could coexist and we depict the coexistence region in P-v diagrams. The two-phase equilibrium curves in P-T diagrams are plotted, the Clapeyron equation for the black hole is derived, and the latent heat of isothermal phase transition is investigated. We also analyze the parameters of the black hole that could have an effect on the two-phase coexistence. The results show that the black holes may go through a small-large phase transition similar to that of a usual nongravity thermodynamic system.

The Dynamical Evolution of Stellar-Mass Black Holes in Dense Star Clusters