Minimal Length Effects on Tunnelling from Spherically Symmetric Black Holes
Directory of Open Access Journals (Sweden)
Benrong Mu
2015-01-01
Full Text Available We investigate effects of the minimal length on quantum tunnelling from spherically symmetric black holes using the Hamilton-Jacobi method incorporating the minimal length. We first derive the deformed Hamilton-Jacobi equations for scalars and fermions, both of which have the same expressions. The minimal length correction to the Hawking temperature is found to depend on the black hole’s mass and the mass and angular momentum of emitted particles. Finally, we calculate a Schwarzschild black hole's luminosity and find the black hole evaporates to zero mass in infinite time.
Timelike geodesics around a charged spherically symmetric dilaton black hole
Directory of Open Access Journals (Sweden)
Blaga C.
2015-01-01
Full Text Available In this paper we study the timelike geodesics around a spherically symmetric charged dilaton black hole. The trajectories around the black hole are classified using the effective potential of a free test particle. This qualitative approach enables us to determine the type of orbit described by test particle without solving the equations of motion, if the parameters of the black hole and the particle are known. The connections between these parameters and the type of orbit described by the particle are obtained. To visualize the orbits we solve numerically the equation of motion for different values of parameters envolved in our analysis. The effective potential of a free test particle looks different for a non-extremal and an extremal black hole, therefore we have examined separately these two types of black holes.
No nonminimally coupled massless scalar hair for spherically symmetric neutral black holes
Directory of Open Access Journals (Sweden)
Shahar Hod
2017-08-01
Full Text Available We provide a remarkably compact proof that spherically symmetric neutral black holes cannot support static nonminimally coupled massless scalar fields. The theorem is based on causality restrictions imposed on the energy-momentum tensor of the fields near the regular black-hole horizon.
No hair for spherically symmetric neutral black holes: Nonminimally coupled massive scalar fields
Hod, Shahar
2017-12-01
It is proved that spherically symmetric asymptotically flat neutral black holes cannot support spatially regular static configurations made of massive scalar fields with nonminimal coupling to gravity. Interestingly, our compact no-hair theorem is valid for generic values of the dimensionless physical parameter ξ which quantifies the strength of coupling between the scalar field and the spacetime curvature.
Spherically symmetric charged black holes in f(R) gravitational theories
Nashed, G. G. L.
2018-01-01
In this study, we have derived electric and magnetic spherically symmetric black holes for the class f(R)=R+ζ R2 without assuming any restrictions on the Ricci scalar. These black holes asymptotically behave as the de Sitter spacetime under certain constrains. We have shown that the magnetic charge contributes in the metric spacetime similarly to the electric charge. The most interesting feature of some of these black holes is the fact that the Cauchy horizon is not identical to the event horizon. We have calculated the invariants of Ricci and Kretschmann scalars to investigate the nature of singularities of such black holes. Also, we have calculated the conserved quantities to match the constants of integration with the physical quantities. Finally, the thermodynamical quantities, like Hawking temperature, entropy, etc., have been evaluated and the validity of the first law of thermodynamics has been verified.
Entropy function and the attractor mechanism for spherically symmetric extremal black holes
International Nuclear Information System (INIS)
Cai Ronggen; Cao Liming
2007-01-01
In this paper we elaborate on the relation between the entropy formula of Wald and the 'entropy function' method proposed by Sen. For spherically symmetric extremal black holes, it is shown that the expression of extremal black hole entropy given by Sen can be derived from the general entropy definition of Wald, without the help of the treatment of rescaling the AdS 2 part of the near horizon geometry of extremal black holes. In our procedure, we only require that the surface gravity approaches to zero, and it is easy to understand the Legendre transformation of f, the integration of Lagrangian density on the horizon, with respect to the electric charges. Since the Noether charge form can be defined in an 'off-shell' form, we define a corresponding entropy function, with which one can discuss the attractor mechanism for extremal black holes with scalar fields
Greybody factors for a spherically symmetric Einstein-Gauss-Bonnet-de Sitter black hole
Zhang, Cheng-Yong; Li, Peng-Cheng; Chen, Bin
2018-02-01
We study the greybody factors of the scalar fields in spherically symmetric Einstein-Gauss-Bonnet-de Sitter black holes in higher dimensions. We derive the greybody factors analytically for both minimally and nonminimally coupled scalar fields. Moreover, we discuss the dependence of the greybody factor on various parameters including the angular momentum number, the nonminimally coupling constant, the spacetime dimension, the cosmological constant, and the Gauss-Bonnet coefficient in detail. We find that the nonminimal coupling may suppress the greybody factor and the Gauss-Bonnet coupling could enhance it, but they both suppress the energy emission rate of Hawking radiation.
Higher spins tunneling from a time dependent and spherically symmetric black hole
International Nuclear Information System (INIS)
Siahaan, Haryanto M.
2016-01-01
The discussions of Hawking radiation via tunneling method have been performed extensively in the case of scalar particles. Moreover, there are also several works in discussing the tunneling method for Hawking radiation by using higher spins, e.g. neutrino, photon, and gravitino, in the background of static black holes. Interestingly, it is found that the Hawking temperature for static black holes using the higher spins particles has no difference compared to the one computed using scalars. In this paper, we study the Hawking radiation for a spherically symmetric and time dependent black holes using the tunneling of Dirac particles, photon, and gravitino. We find that the obtained Hawking temperature is similar to the one derived in the tunneling method by using scalars. (orig.)
Cyclic and heteroclinic flows near general static spherically symmetric 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, Engineering Faculty, Ankara (Turkey); Faizal, Mir [University of Lethbridge, Department of Physics and Astronomy, Alberta (Canada); University of Waterloo, Department of Physics and Astronomy, Waterloo, ON (Canada)
2016-05-15
We investigate the Michel-type accretion onto a static spherically symmetric black hole. Using a Hamiltonian dynamical approach, we show that the standard method employed for tackling the accretion problem has masked some properties of the fluid flow. We determine new analytical solutions that are neither transonic nor supersonic as the fluid approaches the horizon(s); rather, they remain subsonic for all values of the radial coordinate. Moreover, the three-velocity vanishes and the pressure diverges on the horizon(s), resulting in a flow-out of the fluid under the effect of its own pressure. This is in favor of the earlier prediction that pressure-dominant regions form near the horizon. This result does not depend on the form of the metric and it applies to a neighborhood of any horizon where the time coordinate is timelike. For anti-de Sitter-like f(R) black holes we discuss the stability of the critical flow and determine separatrix heteroclinic orbits. For de Sitter-like f(R) black holes, we construct polytropic cyclic, non-homoclinic, physical flows connecting the two horizons. These flows become non-relativistic for Hamiltonian values higher than the critical value, allowing for a good estimate of the proper period of the flow. (orig.)
Liang, Jun; Zhang, Fang-Hui; Zhang, Wei; Zhang, Jing
2014-01-01
By utilizing the improved Damour-Ruffini method with a new tortoise transformation, we study the Hawking radiation of Dirac particles from a general dynamical spherically symmetric black hole. In the improved Damour-Ruffini method, the position of the event horizon of the black hole is an undetermined function, and the temperature parameter κ is an undetermined constant. By requiring the Dirac equation to be the standard wave equation near the event horizon of the black hole, κ can be determined automatically. Therefore, the Hawking temperature can be obtained. The result is consistent with that of the Hawking radiation of scalar particles.
Energy Technology Data Exchange (ETDEWEB)
Horvat, Dubravko; Ilijic, Sasa; Narancic, Zoran [Department of Physics, Faculty of Electrical Engineering and Computing, University of Zagreb, Unska 3, HR-10 000 Zagreb (Croatia)
2005-10-07
Static spherically symmetric distributions of electrically counterpoised dust (ECD) are used to construct solutions to Einstein-Maxwell equations in the Majumdar-Papapetrou formalism. Unexpected bifurcating behaviour of solutions with regard to source strength is found for localized, as well as for the delta-function ECD distributions. Unified treatment of general ECD distributions is accomplished and it is shown that for certain source strengths one class of regular solutions approaches Minkowski spacetime, while the other comes arbitrarily close to black hole solutions.
Directory of Open Access Journals (Sweden)
Sergio C. Ulhoa
2017-01-01
Full Text Available In this paper we investigate scalar perturbations of black holes embedded in a five-dimensional bulk space. The quasinormal frequencies of such black holes are calculated using the third order of Wentzel, Kramers, and Brillouin (WKB approximation for scalar perturbations. The high overtones of quasinormal modes indicate a resonant-like set of black holes suggesting a serious constraint of embedding models in five dimensions.
A charged spherically symmetric solution
Indian Academy of Sciences (India)
A charged spherically symmetric solution. K MOODLEY, S D MAHARAJ and K S GOVINDER. School of Mathematical and Statistical Sciences, University of Natal, Durban 4041, South Africa. Email: maharaj@nu.ac.za. MS received 8 April 2002; revised 7 April 2003; accepted 23 June 2003. Abstract. We find a solution of the ...
International Nuclear Information System (INIS)
Chen Songbai; Wang Bin; Su Rukeng
2008-01-01
We present a solution of Einstein equations with quintessential matter surrounding a d-dimensional black hole, whose asymptotic structures are determined by the state of the quintessential matter. We examine the thermodynamics of this black hole and find that the mass of the black hole depends on the equation of state of the quintessence, while the first law is universal. Investigating the Hawking radiation in this black hole background, we observe that the Hawking radiation dominates on the brane in the low-energy regime. For different asymptotic structures caused by the equation of state of the quintessential matter surrounding the black hole, we learn that the influences by the state parameter of the quintessence on Hawking radiation are different
Spherically symmetric elasticity in relativity
Energy Technology Data Exchange (ETDEWEB)
Carot, J [Departament de Fisica, Universitat de les Illes Balears, Cra Valldemossa pk 7.5, E-07122 Palma (Spain); Brito, I; Vaz, E G L R, E-mail: jcarot@uib.ca, E-mail: ireneb@mct.uminho.p, E-mail: evaz@mct.uminho.p
2010-05-01
The relativistic theory of elasticity is reviewed within the spherically symmetric context with a view towards the modelling of star interiors possessing elastic properties such as the ones expected in neutron stars. Emphasis is placed on generality in the main sections of the paper, and the results are then applied to specific examples. Along the way, a few general results for spacetimes admitting isometries are deduced, and their consequences are fully exploited in the case of spherical symmetry relating them next to the the case in which the material content of the spacetime is some elastic material. This paper extends and generalizes the pioneering work by Magli and Kijowski [1], Magli [2] and [3], and complements, in a sense, that by Karlovini and Samuelsson in their interesting series of papers [4], [5] and [6].
Spherically symmetric inhomogeneous dust collapse in higher ...
Indian Academy of Sciences (India)
We consider a collapsing spherically symmetric inhomogeneous dust cloud in higher dimensional space-time. ... The existence of strong curvature naked singularities in gravitational collapse of spherically symmetric space-times ... where an over dot denotes partial derivative with respect to t. The functions F(r) and f(r).
Accretion processes for general spherically symmetric compact objects
International Nuclear Information System (INIS)
Bahamonde, Sebastian; Jamil, Mubasher
2015-01-01
We investigate the accretion process for different spherically symmetric space-time geometries for a static fluid. We analyze this procedure using the most general black hole metric ansatz. After that, we examine the accretion process for specific spherically symmetric metrics obtaining the velocity of the sound during the process and the critical speed of the flow of the fluid around the black hole. In addition, we study the behavior of the rate of change of the mass for each chosen metric for a barotropic fluid. (orig.)
Spherically symmetric inhomogeneous dust collapse in higher ...
Indian Academy of Sciences (India)
We consider a collapsing spherically symmetric inhomogeneous dust cloud in higher dimensional space-time. We show that the central singularity of collapse can be a strong curvature or a weak curvature naked singularity depending on the initial density distribution.
Spherically symmetric scalar field collapse
Indian Academy of Sciences (India)
2013-03-01
Mar 1, 2013 ... nonlinearity of Einstien equations could lead to critical phenomena close to the threshold of black hole ... we refer the reader to [4]). Furthermore, the scalar field collapse could also lead to .... Anyway, the physical motivation is that in this case the collapsing model will eventually become an FRW one.
Exact solutions of the spherically symmetric multidimensional ...
African Journals Online (AJOL)
The complete orthonormalised energy eigenfunctions and the energy eigenvalues of the spherically symmetric isotropic harmonic oscillator in N dimensions, are obtained through the methods of separation of variables. Also, the degeneracy of the energy levels are examined. KEY WORDS: - Schrödinger Equation, Isotropic ...
Energy Technology Data Exchange (ETDEWEB)
Azreg-Ainou, Mustapha [Baskent University, Engineering Faculty, Ankara (Turkey)
2017-01-15
We present new accretion solutions of a polytropic perfect fluid onto an f(R)-gravity de Sitter-like black hole. We consider two f(R)-gravity models and obtain finite-period cyclic flows oscillating between the event and cosmological horizons as well as semi-cyclic critical flows executing a two-way motion from and back to the same horizon. Besides the generalizations and new solutions presented in this work, a corrigendum to Eur. Phys. J. C (2016) 76:280 is provided. (orig.)
Canonical quantization of spherically symmetric dust collapse
Vaz, Cenalo; Witten, Louis
2011-12-01
Quantum gravity effects are likely to play a crucial role in determining the outcome of gravitational collapse during its final stages. In this contribution we will outline a canonical quantization of the LeMaitre-Tolman-Bondi (LTB) models, which describe the collapse of spherical, inhomogeneous, non-rotating dust. Although there are many models of gravitational collapse, this particular class of models stands out for its simplicity and the fact that both black holes and naked singularity end states may be realized on the classical level, depending on the initial conditions. We will obtain the appropriate Wheeler-DeWitt equation and then solve it exactly, after regularization on a spatial lattice. The solutions describe Hawking radiation and provide an elegant microcanonical description of black hole entropy, but they raise other questions, most importantly concerning the nature of gravity's fundamental degrees of freedom.
Global structure of static spherically symmetric solutions surrounded by quintessence
Cruz, Miguel; Ganguly, Apratim; Gannouji, Radouane; Leon, Genly; Saridakis, Emmanuel N.
2017-06-01
We investigate all static spherically symmetric solutions in the context of general relativity surrounded by a minimally-coupled quintessence field, using dynamical system analysis. Applying the 1 + 1 + 2 formalism and introducing suitable normalized variables involving the Gaussian curvature, we were able to reformulate the field equations as first order differential equations. In the case of a massless canonical scalar field we recovered all known black hole results, such as the Fisher solution, and we found that apart from the Schwarzschild solution all other solutions are naked singularities. Additionally, we identified the symmetric phase space which corresponds to the white hole part of the solution and in the case of a phantom field, we were able to extract the conditions for the existence of wormholes and define all possible classes of solutions such as cold black holes, singular spacetimes and wormholes such as the Ellis wormhole, for example. For an exponential potential, we found that the black hole solution which is asymptotically flat is unique and it is the Schwarzschild spacetime, while all other solutions are naked singularities. Furthermore, we found solutions connecting to a white hole through a maximum radius, and not a minimum radius (throat) such as wormhole solutions, therefore violating the flare-out condition. Finally, we have found a necessary and sufficient condition on the form of the potential to have an asymptotically AdS spacetime along with a necessary condition for the existence of asymptotically flat black holes.
Stability of transparent spherically symmetric thin shells and wormholes
International Nuclear Information System (INIS)
Ishak, Mustapha; Lake, Kayll
2002-01-01
The stability of transparent spherically symmetric thin shells (and wormholes) to linearized spherically symmetric perturbations about static equilibrium is examined. This work generalizes and systematizes previous studies and explores the consequences of including the cosmological constant. The approach shows how the existence (or not) of a domain wall dominates the landscape of possible equilibrium configurations
Stability of Schwarzschild-AdS for the spherically symmetric Einstein-Klein-Gordon system
Holzegel, Gustav; Smulevici, Jacques
2011-01-01
In this paper, we study the global behavior of solutions to the spherically symmetric coupled Einstein-Klein-Gordon (EKG) system in the presence of a negative cosmological constant. We prove that the Schwarzschild-AdS spacetimes (the trivial black hole solutions of the EKG system for which $\\phi=0$ identically) are asymptotically stable: Small perturbations of Schwarzschild-AdS initial data again lead to regular black holes, with the metric on the black hole exterior approaching a Schwarzschi...
Initial value formulation for the spherically symmetric dust solution
International Nuclear Information System (INIS)
Liu, H.
1990-01-01
An initial value formulation for the dust solution with spherical symmetry is given explicitly in which the initial distributions of dust and its velocity on an initial surface are chosen to be the initial data. As special cases, the Friedmann universe, the Schwarzschild solution in comoving coordinates, and a spherically symmetric and radially inhomogeneous cosmological model are derived
Flat synchronizations in spherically symmetric space-times
International Nuclear Information System (INIS)
Herrero, Alicia; Morales-Lladosa, Juan Antonio
2010-01-01
It is well known that the Schwarzschild space-time admits a spacelike slicing by flat instants and that the metric is regular at the horizon in the associated adapted coordinates (Painleve-Gullstrand metric form). We consider this type of flat slicings in an arbitrary spherically symmetric space-time. The condition ensuring its existence is analyzed, and then, we prove that, for any spherically symmetric flat slicing, the densities of the Weinberg momenta vanish. Finally, we deduce the Schwarzschild solution in the extended Painleve-Gullstrand-LemaItre metric form by considering the coordinate decomposition of the vacuum Einstein equations with respect to a flat spacelike slicing.
Implications of the Cosmological Constant for Spherically Symmetric Mass Distributions
Zubairi, Omair; Weber, Fridolin
2013-04-01
In recent years, scientists have made the discovery that the expansion rate of the Universe is increasing rather than decreasing. This acceleration leads to an additional term in Albert Einstein's field equations which describe general relativity and is known as the cosmological constant. This work explores the aftermath of a non-vanishing cosmological constant for relativistic spherically symmetric mass distributions, which are susceptible to change against Einstein's field equations. We introduce a stellar structure equation known as the Tolman-Oppenhiemer-Volkoff (TOV) equation modified for a cosmological constant, which is derived from Einstein's modified field equations. We solve this modified TOV equation for these spherically symmetric mass distributions and obtain stellar properties such as mass and radius and investigate changes that may occur depending on the value of the cosmological constant.
Spherically symmetric self-dual Yang-Mills instantons on curved backgrounds in all even dimensions
Radu, Eugen; Tchrakian, D. H.; Yang, Yisong
2008-02-01
We present several different classes of self-dual Yang-Mills instantons in all even d-dimensional backgrounds with Euclidean signature. In d=4p+2 the only solutions we found are on constant curvature dS (de Sitter) and AdS (anti de Sitter) backgrounds and are evaluated in closed form. In d=4p an interesting class of instantons are given on black hole backgrounds. One class of solutions are (Euclidean) time-independent and spherically symmetric in d-1 dimensions, and the other class are spherically symmetric in all d dimensions. Some of the solutions in the former class are evaluated numerically, all the rest being given in closed form. Analytic proofs of existence covering all numerically evaluated solutions are given. All instantons studied have finite action and vanishing energy momentum tensor and do not disturb the geometry.
A Generalized Field Theory: Charged Spherical Symmetric Solution
Wanas, M. I.
1985-06-01
Three solutions with spherical symmetry are obtained for the field equations of the generalized field theory established recently by Mikhail and Wanas. The solutions found are in agreement with classical known results. The solution representing a generalized field, outside a spherical symmetric charged body, is found to have an extra term compared with the Reissner-Nordström metric. The space used for application is of type FIGI, so the solutions obtained correspond to a field in a matter-free space. A brief comparison between the solutions obtained and those given by other field theories is given. Two methods have been used to get physical results: the first is the type analysis, and the second is the comparison with classical known results by writing down the metric of the associated Riemannian space.
Spherically symmetric high-velocity plasma expansions into background gases
Tan, T.-H.; Borovsky, J. E.
1986-01-01
Spherically symmetric plasmas with high expansion velocities have been produced by irradiating targets with eight beams from the Helios CO2 laser in the presence of gases at various pressures. Attention was given to the properties of the target-emitted ions in order to obtain information about the ion-acceleration mechanisms in plasma expansions. Photoionization of the ambient gases by the soft X-ray emission from the laser-irradiated targets produced background plasmas, permitting plasma counterstreaming experiments to be performed in spherical geometry. Successful laser-target coupling in the presence of back-ground gases is obtained; modification of the ion acceleration in accordance with isothermal-expansion models is observed; and an absence of collective coupling between collisionless counterstreaming plasmas is found.
Dimensional-reduction anomaly in spherically symmetric spacetimes
Sutton, P.
2000-08-01
In D-dimensional spacetimes which can be foliated by n-dimensional homogeneous subspaces, a quantum field can be decomposed in terms of modes on the subspaces, reducing the system to a collection of (D-n)-dimensional fields. This allows one to write bare D-dimensional field quantities like the Green function and the effective action as sums of their (D-n)-dimensional counterparts in the dimensionally reduced theory. It has been shown, however, that renormalization breaks this relationship between the original and dimensionally reduced theories, an effect called the dimensional-reduction anomaly. We examine the dimensional-reduction anomaly for the important case of spherically symmetric spaces.
All spherically symmetric charged anisotropic solutions for compact stars
Energy Technology Data Exchange (ETDEWEB)
Maurya, S.K. [University of Nizwa, Department of Mathematical and Physical Sciences, College of Arts and Science, Nizwa (Oman); Gupta, Y.K. [Raj Kumar Goel Institute of Technology, Department of Mathematics, Ghaziabad, UP (India); Ray, Saibal [Government College of Engineering and Ceramic Technology, Department of Physics, Kolkata, West Bengal (India)
2017-06-15
In the present paper we develop an algorithm for all spherically symmetric anisotropic charged fluid distributions. Considering a new source function ν(r) we find a set of solutions which is physically well behaved and represents compact stellar models. A detailed study specifically shows that the models actually correspond to strange stars in terms of their mass and radius. In this connection we investigate several physical properties like energy conditions, stability, mass-radius ratio, electric charge content, anisotropic nature and surface redshift through graphical plots and mathematical calculations. All the features from these studies are in excellent agreement with the already available evidence in theory as well as observations. (orig.)
Integral solution for the spherically symmetric Fokker-Planck equation
International Nuclear Information System (INIS)
Donoso, J.M.; Soler, M.
1993-01-01
We propose an integral method to deal with the spherically symmetric non-linear Fokker-Planck equation appearing in plasma physics. A probability transition expression is obtained, which takes into account the proper domain for the radial velocity component. The analytical and computational results are new, and the time evolution is completely satisfactory. The main achievement of the method is conservation of both the initial norm and energy for unlimited times, which has not been attained in the differential approach to the problem. (orig.)
Hawking radiation from a spherical loop quantum gravity black hole
International Nuclear Information System (INIS)
Gambini, Rodolfo; Pullin, Jorge
2014-01-01
We introduce quantum field theory on quantum space-times techniques to characterize the quantum vacua as a first step toward studying black hole evaporation in spherical symmetry in loop quantum gravity and compute the Hawking radiation. We use as quantum space-time the recently introduced exact solution of the quantum Einstein equations in vacuum with spherical symmetry and consider a spherically symmetric test scalar field propagating on it. The use of loop quantum gravity techniques in the background space-time naturally regularizes the matter content, solving one of the main obstacles to back-reaction calculations in more traditional treatments. The discreteness of area leads to modifications of the quantum vacua, eliminating the trans-Planckian modes close to the horizon, which in turn eliminates all singularities from physical quantities, like the expectation value of the stress–energy tensor. Apart from this, the Boulware, Hartle–Hawking and Unruh vacua differ little from the treatment on a classical space-time. The asymptotic modes near scri are reproduced very well. We show that the Hawking radiation can be computed, leading to an expression similar to the conventional one but with a high frequency cutoff. Since many of the conclusions concern asymptotic behavior, where the spherical mode of the field behaves in a similar way as higher multipole modes do, the results can be readily generalized to non spherically symmetric fields. (paper)
Stability of Schwarzschild-AdS for the Spherically Symmetric Einstein-Klein-Gordon System
Holzegel, Gustav; Smulevici, Jacques
2013-01-01
In this paper, we study the global behavior of solutions to the spherically symmetric coupled Einstein-Klein-Gordon (EKG) system in the presence of a negative cosmological constant. For the Klein-Gordon mass-squared satisfying a ≥ -1 (the Breitenlohner-Freedman bound being a > -9/8), we prove that the Schwarzschild-AdS spacetimes are asymptotically stable: Small perturbations of Schwarzschild-AdS initial data again lead to regular black holes, with the metric on the black hole exterior approaching, at an exponential rate, a Schwarzschild-AdS spacetime. The main difficulties in the proof arise from the lack of monotonicity for the Hawking mass and the asymptotically AdS boundary conditions, which render even (part of) the orbital stability intricate. These issues are resolved in a bootstrap argument on the black hole exterior, with the redshift effect and weighted Hardy inequalities playing the fundamental role in the analysis. Both integrated decay and pointwise decay estimates are obtained. As a corollary of our estimates on the Klein-Gordon field, one obtains in particular exponential decay in time of spherically-symmetric solutions to the linear Klein-Gordon equation on Schwarzschild-AdS.
All the Four-Dimensional Static, Spherically Symmetric Solutions of Abelian Kaluza-Klein Theory
International Nuclear Information System (INIS)
Cvetic, M.; Youm, D.
1995-01-01
We present the explicit form for all the four-dimensional, static, spherically symmetric solutions in (4+n)-d Abelian Kaluza-Klein theory by performing a subset of SO(2,n) transformations corresponding to four SO(1,1) boosts on the Schwarzschild solution, supplemented by SO(n)/SO(n-2) transformations. The solutions are parametrized by the mass M, Taub-NUT charge a, and n electric rvec Q and n magnetic rvec P charges. Nonextreme black holes (with zero Taub-NUT charge) have either the Reissner-Nordstroem or Schwarzschild global space-time. Supersymmetric extreme black holes have a null or naked singularity, while nonsupersymmetric extreme ones have a global space-time of extreme Reissner-Nordstroem black holes. copyright 1995 The American Physical Society
Absorbed dose from traversing spherically symmetric, Gaussian radioactive clouds
International Nuclear Information System (INIS)
Thompson, J.M.; Poston, J.W.
1999-01-01
If a large radioactive cloud is produced, sampling may require that an airplane traverse the cloud. A method to predict the absorbed dose to the aircrew from penetrating the radioactive cloud is needed. Dose rates throughout spherically symmetric Gaussian clouds of various sizes, and the absorbed doses from traversing the clouds, were calculated. Cloud size is a dominant parameter causing dose to vary by orders of magnitude for a given dose rate measured at some distance. A method to determine cloud size, based on dose rate readings at two or more distances from the cloud center, was developed. This method, however, failed to resolve the smallest cloud sizes from measurements made at 1,000 m to 2,000 m from the cloud center
Static spherically symmetric wormholes in f(R, T) gravity
Energy Technology Data Exchange (ETDEWEB)
Zubair, M.; Ahmad, Yasir [Institute Of Information Technology, Department of Mathematics, COMSATS, Lahore (Pakistan); Waheed, Saira [Prince Mohammad Bin Fahd University, Al Khobar (Saudi Arabia)
2016-08-15
In this work, we explore wormhole solutions in f(R, T) theory of gravity, where R is the scalar curvature and T is the trace of stress-energy tensor of matter. To investigate this, we consider a static spherically symmetric geometry with matter contents as anisotropic, isotropic, and barotropic fluids in three separate cases. By taking into account the Starobinsky f(R) model, we analyze the behavior of energy conditions for these different kinds of fluids. It is shown that the wormhole solutions can be constructed without exotic matter in few regions of space-time. We also give the graphical illustration of the results obtained and discuss the equilibrium picture for the anisotropic case only. It is concluded that the wormhole solutions with anisotropic matter are realistic and stable in this theory of gravity. (orig.)
Notes on entropy force in general spherically symmetric spacetimes
International Nuclear Information System (INIS)
Cai Ronggen; Cao Liming; Ohta, Nobuyoshi
2010-01-01
In a recent paper [arXiv:1001.0785], Verlinde has shown that the Newton gravity appears as an entropy force. In this paper we show how gravity appears as entropy force in Einstein's equation of gravitational field in a general spherically symmetric spacetime. We mainly focus on the trapping horizon of the spacetime. We find that when matter fields are absent, the change of entropy associated with the trapping horizon indeed can be identified with an entropy force. When matter fields are present, we see that heat flux of matter fields also leads to the change of entropy. Applying arguments made by Verlinde and Smolin, respectively, to the trapping horizon, we find that the entropy force is given by the surface gravity of the horizon. The cases in the untrapped region of the spacetime are also discussed.
Static spherically symmetric wormholes in f( R, T) gravity
Zubair, M.; Waheed, Saira; Ahmad, Yasir
2016-08-01
In this work, we explore wormhole solutions in f( R, T) theory of gravity, where R is the scalar curvature and T is the trace of stress-energy tensor of matter. To investigate this, we consider a static spherically symmetric geometry with matter contents as anisotropic, isotropic, and barotropic fluids in three separate cases. By taking into account the Starobinsky f( R) model, we analyze the behavior of energy conditions for these different kinds of fluids. It is shown that the wormhole solutions can be constructed without exotic matter in few regions of space-time. We also give the graphical illustration of the results obtained and discuss the equilibrium picture for the anisotropic case only. It is concluded that the wormhole solutions with anisotropic matter are realistic and stable in this theory of gravity.
Relativistic electromagnetic mass models in spherically symmetric spacetime
Maurya, S. K.; Gupta, Y. K.; Ray, Saibal; Chatterjee, Vikram
2016-10-01
Under the static spherically symmetric Einstein-Maxwell spacetime of embedding class one we explore possibility of constructing electromagnetic mass model where mass and other physical parameters have purely electromagnetic origin (Lorentz in Proc. Acad. Sci. Amst. 6, 1904). This work is in continuation of our earlier investigation of Maurya et al. (Eur. Phys. J. C 75:389, 2015a) where we developed an algorithm and found out three new solutions of electromagnetic mass model. In the present work we consider different metric potentials ν and λ and have analyzed them in a systematic way. It is observed that some of the previous solutions related to electromagnetic mass model are nothing but special cases of the presently obtained generalized solution set. We further verify the solution set and especially show that these are extremely applicable in the case of compact stars.
Spherically symmetric solutions in abelian Kaluza-Klein theories
International Nuclear Information System (INIS)
Angus, I.G.
1986-01-01
We present the most general spherically symmetric solution to the field equations of the truncated five-dimensional Kaluza-Klein theory. We also detail some of the special forms of this solution. With the exception of the Gross-Perry-Sorkin monopole and the Schwarzschild solutions we find that most, and we conjecture all, of the solutions have naked curvature singularities. We then proceed to consider higher-dimensional theories with toroidal compactification and we exhibit a class of nonsingular monopole solutions which are the natural generalization of the Gross-Perry-Sorkin monopole to more than five dimensions. We also present some selected solutions including a solution pertaining to a model with a Ricci-flat, but not curvature-flat, internal manifold. All of these other solutions have naked curvature singularities. (orig.)
Geometric inequalities for axially symmetric black holes
International Nuclear Information System (INIS)
Dain, Sergio
2012-01-01
A geometric inequality in general relativity relates quantities that have both a physical interpretation and a geometrical definition. It is well known that the parameters that characterize the Kerr-Newman black hole satisfy several important geometric inequalities. Remarkably enough, some of these inequalities also hold for dynamical black holes. This kind of inequalities play an important role in the characterization of the gravitational collapse; they are closely related with the cosmic censorship conjecture. Axially symmetric black holes are the natural candidates to study these inequalities because the quasi-local angular momentum is well defined for them. We review recent results in this subject and we also describe the main ideas behind the proofs. Finally, a list of relevant open problems is presented. (topical review)
On d = 4 Yang-Mills instantons in a spherically symmetric background
Brihaye, Y.; Radu, E.
2006-09-01
We present arguments for the existence of self-dual Yang-Mills instantons for several spherically symmetric backgrounds with Euclidean signature. The time-independent Yang-Mills field has finite action and a vanishing energy momentum tensor and does not disturb the geometry. We conjecture the existence of similar solutions for any nonextremal SO(3)-spherically symmetric background.
On $d=4$ Yang-Mills instantons in a spherically symmetric background
Brihaye, Yves; Radu, Eugen
2006-01-01
We present arguments for the existence of self-dual Yang-Mills instantons for several spherically symmetric backgrounds with Euclidean signature. The time-independent Yang-Mills field has finite action and a vanishing energy momentum tensor and does not disturb the geometry. We conjecture the existence of similar solutions for any nonextremal SO(3)-spherically symmetric background.
Meissner effect for axially symmetric charged black holes
Gürlebeck, Norman; Scholtz, Martin
2018-04-01
In our previous work [N. Gürlebeck and M. Scholtz, Phys. Rev. D 95, 064010 (2017), 10.1103/PhysRevD.95.064010], we have shown that electric and magnetic fields are expelled from the horizons of extremal, stationary and axially symmetric uncharged black holes; this is called the Meissner effect for black holes. Here, we generalize this result in several directions. First, we allow that the black hole carries charge, which requires a generalization of the definition of the Meissner effect. Next, we introduce the notion of almost isolated horizons, which is weaker than the usual notion of isolated horizons, since the geometry of the former is not necessarily completely time independent. Moreover, we allow the horizon to be pierced by strings, thereby violating the usual assumption on the spherical topology made in the definition of the weakly isolated horizon. Finally, we spell out in detail all assumptions entering the proof and show that the Meissner effect is an inherent property of black holes even in full nonlinear theory.
Stationary spherically symmetric one-kink model in Saez-Ballester theory of gravitation
Kiran, M.; Reddy, D. R. K.; Rao, V. U. M.; Bhaskara Rao, M. P. V. V.
2015-03-01
In this paper we consider stationary Spherically symmetric kink space-time in the scalar-tensor theory of gravitation proposed by Saez and Ballester (Phys. Lett. A 113:467, 1986) in the presence of perfect fluid distribution. It is shown that spherically symmetric kink space-time does not accommodate perfect fluid distribution in this theory. Hence a vacuum model is obtained which is asymptotically flat. This model corresponds to a one kink metric in this theory. This can be considered as an analogue of usual spherically symmetric Schwarzschild case in this theory.
Critical phenomena in the general spherically symmetric Einstein-Yang-Mills system
Maliborski, Maciej; Rinne, Oliver
2018-02-01
We study critical behavior in gravitational collapse of a general spherically symmetric Yang-Mills field coupled to the Einstein equations. Unlike the magnetic ansatz used in previous numerical work, the general Yang-Mills connection has two degrees of freedom in spherical symmetry. This fact changes the phenomenology of critical collapse dramatically. The magnetic sector features both type I and type II critical collapse, with universal critical solutions. In contrast, in the general system type I disappears and the critical behavior at the threshold between dispersal and black hole formation is always type II. We obtain values of the mass scaling and echoing exponents close to those observed in the magnetic sector, however we find some indications that the critical solution differs from the purely magnetic discretely self-similar attractor and exact self-similarity and universality might be lost. The additional "type III" critical phenomenon in the magnetic sector, where black holes form on both sides of the threshold but the Yang-Mills potential is in different vacuum states and there is a mass gap, also disappears in the general system. We support our dynamical numerical simulations with calculations in linear perturbation theory; for instance, we compute quasi-normal modes of the unstable attractor (the Bartnik-McKinnon soliton) in type I collapse in the magnetic sector.
A Model of Dust-like Spherically Symmetric Gravitational Collapse without Event Horizon Formation
Directory of Open Access Journals (Sweden)
Piñol M.
2015-10-01
Full Text Available Some dynamical aspects of gravitational collapse are explored in this paper. A time- dependent spherically symmetric metric is proposed and the corresponding Einstein field equations are derived. An ultrarelativistic dust-like stress-momentum tensor is considered to obtain analytical solutions of these equations, with the perfect fluid con- sisting of two purely radial fluxes — the inwards flux of collapsing matter and the outwards flux of thermally emitted radiation. Thermal emission is calculated by means of a simplistic but illustrative model of uninteracting collapsing shells. Our results show an asymptotic approach to a maximal space-time deformation without the formation of event horizons. The size of the body is slightly larger than the Schwarzschild radius during most of its lifetime, so that there is no contradiction with either observations or previous theorems on black holes. The relation of the latter with our results is scruti- nized in detail.
Static, spherically symmetric solutions with a scalar field in Rastall gravity
Bronnikov, K. A.; Fabris, J. C.; Piattella, O. F.; Santos, E. C.
2016-12-01
Rastall's theory belongs to the class of non-conservative theories of gravity. In vacuum, the only non-trivial static, spherically symmetric solution is the Schwarzschild one, except for a very special case. When a canonical scalar field is coupled to the gravity sector in this theory, new exact solutions appear for some values of the Rastall parameter a. Some of these solutions describe the same space-time geometry as the recently found solutions in the k-essence theory with a power function for the kinetic term of the scalar field. There is a large class of solutions (in particular, those describing wormholes and regular black holes) whose geometry coincides with that of solutions of GR coupled to scalar fields with nontrivial self-interaction potentials; the form of these potentials, however, depends on the Rastall parameter a. We also note that all solutions of GR with a zero trace of the energy-momentum tensor, including black-hole and wormhole ones, may be re-interpreted as solutions of Rastall's theory.
Synchrotron radiation from spherically accreting black holes
International Nuclear Information System (INIS)
Ipser, J.R.; Price, R.H.
1982-01-01
Spherical accretion onto a Schwartzchild black hole, of gas with frozen-in magnetic field, is studied numerically and analytically for a range of hole masses and accretion rates in which synchrotron emission is the dominant radiative mechanism. At small radii the equipartition of magnetic, kinetic, and gravitational energy is assumed to apply, and the gas is heated by dissipation of infalling magnetic energy, turbulent energy, etc. The models can be classified into three types: (a) synchrotron cooling negligible, (b) synchrotron cooling important but synchrotron self-absorption negligible, (c) synchrotron cooling and self-absorption important. In the first case gas temperatures become very high near the horizon but luminosity efficiencies (luminosity/mass-energy accretion rate) are low. In cases (b) and (c) the gas flow near the horizon is essentially isothermal and luminosity efficiencies are fairly high. The analysis and results for the isothermal cases (b) and (c) are valid only for moderate dissipative heating and synchrotron self-absorption. If self-absorption is very strong or if dissipated energy is comparable to infall energy, Comptonization effects, not included in the analysis, become important
Spherically symmetric quark-gluon plasma field configurations
Nachbagauer, Herbert
1995-01-01
We study field configurations in a hot quark-gluon plasma with spherical symmetry. We show that the electric fields point into radial direction and solve the effective non-abelian equations of motions. The corresponding charge density has a localized contribution which has a gauge invariant interpretation as a pointlike color charge. We discuss configurations oscillating periodically in time. Furthermore, we calculate the electric field induced by a constant local charge that is removed from ...
Even parity junction conditions for perturbations on most general spherically symmetric space--time
International Nuclear Information System (INIS)
Gerlach, U.H.; Sengupta, U.K.
1979-01-01
A new highly efficient and versatile general relativistic perturbational formalism for general matter occupied spherically symmetric space--times is developed. The perturbations are geometrical objects on the two dimensional totally geodesic submanifold spanned by the radial and time coordinates. The geometrical objects are ''gauge invariant'' scalars, vectors, and tensors which are independent of infinitesimal coordinate transformations on the background space--time. This article gives the even parity gauge invariant perturbation objects for arbitrary background scalars, vectors, and symmetric tensors on a spherically symmetric space--time. In particular, metric, matter, first and second fundamental forms, as well as vacuum-matter interface gauge invariant perturbations for a collapsing star are given. In addition four even parity continuity conditions across discontinuous timelike hypersurfaces are given. Two are conditions on the metric gauge invariants, one is a condition on the perturbation away from the spherical contour of the interface, and the fourth couples that contour perturbation to the metric gauge invariants
Spherically symmetric potential in noncommutative spacetime with a compactified extra dimensions
Energy Technology Data Exchange (ETDEWEB)
Guedezounme, Secloka Lazare [University of Abomey-Calavi, International Chair in Mathematical Physics and Applications (ICMPA-UNESCO Chair), Cotonou (Benin); Kanfon, Antonin Danvide [University of Abomey-Calavi, International Chair in Mathematical Physics and Applications (ICMPA-UNESCO Chair), Cotonou (Benin); University of d' Abomey-Calavi, Faculte des Sciences et Techniques, Cotonou (Benin); Samary, Dine Ousmane [University of Abomey-Calavi, International Chair in Mathematical Physics and Applications (ICMPA-UNESCO Chair), Cotonou (Benin); University of d' Abomey-Calavi, Faculte des Sciences et Techniques, Cotonou (Benin); Albert Einstein Institute, Max Planck Institute for Gravitational Physics, Potsdam (Germany)
2016-09-15
The Schroedinger equation of the spherically symmetrical quantum models such as the hydrogen atom problem seems to be analytically non-solvable in higher dimensions. When we try compactifying one or several dimensions this question can maybe solved. This paper presents a study of the spherically symmetrical quantum models on noncommutative spacetime with compactified extra dimensions. We provide analytically the resulting spectrum of the hydrogen atom and Yukawa problem in 4 + 1 dimensional noncommutative spacetime in the first order approximation of the noncommutative parameter. The case of higher dimensions D ≥ 4 is also discussed. (orig.)
Comment on "Self-gravitating spherically symmetric solutions in scalar-torsion theories"
Yaqin, Ainol; Gunara, Bobby Eka
2017-07-01
We find a crucial miscalculation in [G. Kofinas, E. Papantonopoulos, and E. N. Saridakis, Self-gravitating spherically symmetric solutions in scalar-torsion theories, Phys. Rev. D 91, 104034 (2015), 10.1103/PhysRevD.91.104034] which leads to the wrong master equation. This follows that there is no wormhole-like solution for hyperbolic scalar potential and the solution at large distances differs from that of [G. Kofinas, E. Papantonopoulos, and E. N. Saridakis, Self-gravitating spherically symmetric solutions in scalar-torsion theories, Phys. Rev. D 91, 104034 (2015), 10.1103/PhysRevD.91.104034].
Self-Gravitating Spherically Symmetric Solutions in Scalar-Torsion Theories
Kofinas, Georgios; Saridakis, Emmanuel N
2015-01-01
We studied spherically symmetric solutions in scalar-torsion gravity theories in which a scalar field is coupled to torsion with a derivative coupling. We obtained the general field equations from which we extracted a decoupled master equation, the solution of which leads to the specification of all other unknown functions. We first obtained an exact solution which represents a new wormhole-like solution dressed with a regular scalar field. Then, we found large distance linearized spherically symmetric solutions in which the space asymptotically is AdS.
Li, Ping; Li, Xin-zhou; Xi, Ping
2016-06-01
We present a detailed study of the spherically symmetric solutions in Lorentz-breaking massive gravity. There is an undetermined function { F }(X,{w}1,{w}2,{w}3) in the action of Stückelberg fields {S}φ ={{{Λ }}}4\\int {{{d}}}4x\\sqrt{-g}{ F }, which should be resolved through physical means. In general relativity, the spherically symmetric solution to the Einstein equation is a benchmark and its massive deformation also plays a crucial role in Lorentz-breaking massive gravity. { F } will satisfy the constraint equation {T}01=0 from the spherically symmetric Einstein tensor {G}01=0, if we maintain that any reasonable physical theory should possess the spherically symmetric solutions. The Stückelberg field {φ }i is taken as a ‘hedgehog’ configuration {φ }i=φ (r){x}i/r, whose stability is guaranteed by the topological one. Under this ansätz, {T}01=0 is reduced to d{ F }=0. The functions { F } for d{ F }=0 form a commutative ring {R}{ F }. We obtain an expression of the solution to the functional differential equation with spherical symmetry if { F }\\in {R}{ F }. If { F }\\in {R}{ F } and \\partial { F }/\\partial X=0, the functions { F } form a subring {S}{ F }\\subset {R}{ F }. We show that the metric is Schwarzschild, Schwarzschild-AdS or Schwarzschild-dS if { F }\\in {S}{ F }. When { F }\\in {R}{ F } but { F }\
Electromagnetic multipole fields in a finite, spherically symmetric region
International Nuclear Information System (INIS)
Steiger, A.D.
1980-01-01
The electromagnetic eigenfields for the region bounded by two concentric spheres are discussed and compared with the corresponding eigenfields of a spherical cavity. These characteristic fields are the solenoidal and irrotational multiple solutions of the vector Helmholtz equation that satisfy the source-free boundary conditions. They constitute a complete set for the expansion of an arbitrary, square-integrable electromagnetic field, which may be generated by surface and volume sources. The frequencies of the solenoidal and irrotational eigenfields for the angular region are analyzed as functions of the radius ratio, α=r 1 /r 2 (r 1 2 =constant), of the two concentric spheres. The results are illustrated by graphs and tables. Two relations obtained by applying the implicit function theorem to the transcendental eigenfrequency equations are also derived by calculating the work performed against the radiation pressure as the electromagnetic field is compressed adiabatically. The multipoles. Two formulas for the reduction of vector products of multipole fields to sums of vector spherical harmonics are derived
The general class of the vacuum spherically symmetric equations of the general relativity theory
Energy Technology Data Exchange (ETDEWEB)
Karbanovski, V. V., E-mail: Karbanovski_V_V@mail.ru; Sorokin, O. M.; Nesterova, M. I.; Bolotnyaya, V. A.; Markov, V. N., E-mail: Markov_Victor@mail.ru; Kairov, T. V.; Lyash, A. A.; Tarasyuk, O. R. [Murmansk State Pedagogical University (Russian Federation)
2012-08-15
The system of the spherical-symmetric vacuum equations of the General Relativity Theory is considered. The general solution to a problem representing two classes of line elements with arbitrary functions g{sub 00} and g{sub 22} is obtained. The properties of the found solutions are analyzed.
Brito, Irene; Mena, Filipe C
2017-08-01
We prove that, for a given spherically symmetric fluid distribution with tangential pressure on an initial space-like hypersurface with a time-like boundary, there exists a unique, local in time solution to the Einstein equations in a neighbourhood of the boundary. As an application, we consider a particular elastic fluid interior matched to a vacuum exterior.
Spherical and planar three-dimensional anti-de Sitter black holes
International Nuclear Information System (INIS)
Zanchin, Vilson T; Miranda, Alex S
2004-01-01
The technique of dimensional reduction was used in a recent paper (Zanchin V T, Kleber A and Lemos J P S 2002 Phys. Rev. D 66 064022) where a three-dimensional (3D) Einstein-Maxwell-dilaton theory was built from the usual four-dimensional (4D) Einstein-Maxwell-Hilbert action for general relativity. Starting from a class of 4D toroidal black holes in asymptotically anti-de Sitter (AdS) spacetimes several 3D black holes were obtained and studied in such a context. In the present work we choose a particular case of the 3D action which presents Maxwell field, dilaton field and an extra scalar field, besides gravity field and a negative cosmological constant, and obtain new 3D static black hole solutions whose horizons may have spherical or planar topology. We show that there is a 3D static spherically symmetric solution analogous to the 4D Reissner-Nordstroem-AdS black hole, and obtain other new 3D black holes with planar topology. From the static spherical solutions, new rotating 3D black holes are also obtained and analysed in some detail
Spherical null geodesics of rotating Kerr black holes
International Nuclear Information System (INIS)
Hod, Shahar
2013-01-01
The non-equatorial spherical null geodesics of rotating Kerr black holes are studied analytically. Unlike the extensively studied equatorial circular orbits whose radii are known analytically, no closed-form formula exists in the literature for the radii of generic (non-equatorial) spherical geodesics. We provide here an approximate formula for the radii r ph (a/M;cosi) of these spherical null geodesics, where a/M is the dimensionless angular momentum of the black hole and cos i is an effective inclination angle (with respect to the black-hole equatorial plane) of the orbit. It is well-known that the equatorial circular geodesics of the Kerr spacetime (the prograde and the retrograde orbits with cosi=±1) are characterized by a monotonic dependence of their radii r ph (a/M;cosi=±1) on the dimensionless spin-parameter a/M of the black hole. We use here our novel analytical formula to reveal that this well-known property of the equatorial circular geodesics is actually not a generic property of the Kerr spacetime. In particular, we find that counter-rotating spherical null orbits in the range (3√(3)−√(59))/4≲cosi ph (a/M;cosi=const) on the dimensionless rotation-parameter a/M of the black hole. Furthermore, it is shown that spherical photon orbits of rapidly-rotating black holes are characterized by a critical inclination angle, cosi=√(4/7), above which the coordinate radii of the orbits approach the black-hole radius in the extremal limit. We prove that this critical inclination angle signals a transition in the physical properties of the spherical null geodesics: in particular, it separates orbits which are characterized by finite proper distances to the black-hole horizon from orbits which are characterized by infinite proper distances to the horizon.
Sheet-like assemblies of spherical particles with point-symmetrical patches.
Mani, Ethayaraja; Sanz, Eduardo; Roy, Soumyajit; Dijkstra, Marjolein; Groenewold, Jan; Kegel, Willem K
2012-04-14
We report a computational study on the spontaneous self-assembly of spherical particles into two-dimensional crystals. The experimental observation of such structures stabilized by spherical objects appeared paradoxical so far. We implement patchy interactions with the patches point-symmetrically (icosahedral and cubic) arranged on the surface of the particle. In these conditions, preference for self-assembly into sheet-like structures is observed. We explain our findings in terms of the inherent symmetry of the patches and the competition between binding energy and vibrational entropy. The simulation results explain why hollow spherical shells observed in some Keplerate-type polyoxometalates (POM) appear. Our results also provide an explanation for the experimentally observed layer-by-layer growth of apoferritin--a quasi-spherical protein.
All static spherically symmetric perfect-fluid solutions of Einstein's equations
International Nuclear Information System (INIS)
Lake, Kayll
2003-01-01
An algorithm based on the choice of a single monotone function (subject to boundary conditions) is presented which generates all regular static spherically symmetric perfect-fluid solutions of Einstein's equations. For physically relevant solutions the generating functions must be restricted by nontrivial integral-differential inequalities. Nonetheless, the algorithm is demonstrated here by the construction of an infinite number of previously unknown physically interesting exact solutions
Rao, V. U. M.; Jayasudha, L.
2015-07-01
Five dimensional spherically symmetric space-time is considered in the presence of perfect fluid source in the scalar-tensor theory of gravitation proposed by Saez and Ballester (Phys. Lett. A 113:467, 1986). An exact solution of the field equations is obtained using a relation between the metric potentials which represents a stiff fluid model in this theory. Some physical properties of the model are also discussed.
Static spherically symmetric solutions of the classical Yang-Mills equations
International Nuclear Information System (INIS)
Pirilae, P.; Presnajder, P.
1978-06-01
All spherically symmetric solutions with time independent fields are found for the classical Yang-Mills equations with an extended charge in the case of SU(2) gauge group. There is a physically different solution corresponding to each choice of an arbitrary function of radius. In all solutions the energy and the charge are reduced compared to the Coulomb solution. For certain solutions the reduced charge and all fields outside the source vanish. (author)
Energy Technology Data Exchange (ETDEWEB)
Nashed, Gamal G.L. [The British University in Egypt, Centre for Theoretical Physics, P.O. Box 43, Sherouk City (Egypt); Ain Shams University, Mathematics Department, Faculty of Science, Cairo (Egypt)
2013-04-15
In this paper a non-diagonal, spherically symmetric, tetrad field that contains an arbitrary function, S(r), which corresponds to a local Lorentz transformation, is applied to the field equations of f(T) gravity theories. Analytic vacuum solutions with integration constants are derived. These constants are studied by calculating the total conserved charge associated with each solution. The study shows that the obtained solutions represent the Schwarzschild-Ads spacetime. (orig.)
Functional derivative of the kinetic energy functional for spherically symmetric systems.
Nagy, Á
2011-07-28
Ensemble non-interacting kinetic energy functional is constructed for spherically symmetric systems. The differential virial theorem is derived for the ensemble. A first-order differential equation for the functional derivative of the ensemble non-interacting kinetic energy functional and the ensemble Pauli potential is presented. This equation can be solved and a special case of the solution provides the original non-interacting kinetic energy of the density functional theory. © 2011 American Institute of Physics
A new approach to spherically symmetric junction surfaces and the matching of FLRW regions
International Nuclear Information System (INIS)
Kirchner, U
2004-01-01
We investigate timelike junctions (with surface layer) between spherically symmetric solutions of the Einstein-field equation. In contrast to previous investigations, this is done in a coordinate system in which the junction surface motion is absorbed in the metric, while all coordinates are continuous at the junction surface. The evolution equations for all relevant quantities are derived. We discuss the no-surface layer case (boundary surface) and study the behaviour for small surface energies. It is shown that one should expect cases in which the speed of light is reached within a finite proper time. We carefully discuss necessary and sufficient conditions for a possible matching of spherically symmetric sections. For timelike junctions between spherically symmetric spacetime sections we show explicitly that the time component of the Lanczos equation always reduces to an identity (independent of the surface equation of state). The results are applied to the matching of Friedmann-LemaItre-Robertson-Walker (FLRW) models. We discuss 'vacuum bubbles' and closed-open junctions in detail. As illustrations several numerical integration results are presented, some of them indicate that (observers comoving with) the junction surface can reach the speed of light within a finite time
Tortoise Coordinates and Hawking Radiation in a Dynamical Spherically Symmetric Spacetime
Yang, Jian; Zhao, Zheng; Tian, Gui-Hua; Liu, Wen-Biao
2009-12-01
Hawking effect from dynamical spherical Vaidya black hole, Vaidya-Bonner black hole, and Vaidya-de Sitter black hole is investigated using the improved Damour-Ruffini method. After the new tortoise coordinate transformation in which the position r of event horizon is an undetermined function and the temperature parameter κ is an undetermined constant, the Klein-Gordon equation can be written as the standard form at the event horizon, and both r and κ can be determined automatically. Then extending the outgoing wave from outside to inside of the horizon analytically, the Hawking temperature can also be obtained automatically.
Spherical aberration correction with an in-lens N-fold symmetric line currents model.
Hoque, Shahedul; Ito, Hiroyuki; Nishi, Ryuji
2018-04-01
In our previous works, we have proposed N-SYLC (N-fold symmetric line currents) models for aberration correction. In this paper, we propose "in-lens N-SYLC" model, where N-SYLC overlaps rotationally symmetric lens. Such overlap is possible because N-SYLC is free of magnetic materials. We analytically prove that, if certain parameters of the model are optimized, an in-lens 3-SYLC (N = 3) doublet can correct 3rd order spherical aberration. By computer simulation, we show that the required excitation current for correction is less than 0.25 AT for beam energy 5 keV, and the beam size after correction is smaller than 1 nm at the corrector image plane for initial slope less than 4 mrad. Copyright © 2018 Elsevier B.V. All rights reserved.
Energy and momentum of general spherically symmetric frames on the regularizing teleparallelism
Gamal, G. L. Nashed
2012-01-01
In the context of the covariant teleparallel framework, we use the 2-form translational momentum to compute the total energy of two general spherically symmetric frames. The first one is characterized by an arbitrary function H(r), which preserves the spherical symmetry and reproduces all the previous solutions, while the other one is characterized by a parameter ξ which ensures the vanishing of the axial of trace of the torsion. We calculate the total energy by using two procedures, i.e., when the Weitzenböck connection Γαβ is trivial, and show how H(r) and ξ play the role of an inertia that leads the total energy to be unphysical. Therefore, we take into account Γαβ and show that although the spacetimes we use contain an arbitrary function and one parameter, they have no effect on the form of the total energy and momentum as it should be.
Spherically Symmetric Solutions of the Einstein-Bach Equations and a Consistent Spin-2 Field Theory
International Nuclear Information System (INIS)
Janda, A.
2006-01-01
We briefly present a relationship between General Relativity coupled to certain spin-0 and spin-2 field theories and higher derivatives metric theories of gravity. In a special case, described by the Einstein-Bach equations, the spin-0 field drops out from the theory and we obtain a consistent spin-two field theory interacting gravitationally, which overcomes a well known inconsistency of the theory for a linear spin-two field coupled to the Einstein's gravity. Then we discuss basic properties of static spherically symmetric solutions of the Einstein-Bach equations. (author)
On spherically symmetric motions of a viscous compressible barotropic and selfgravitating gas
Czech Academy of Sciences Publication Activity Database
Ducomet, B.; Nečasová, Šárka; Vasseur, A.
2011-01-01
Roč. 13, č. 2 (2011), s. 191-211 ISSN 1422-6928 R&D Projects: GA ČR GA201/08/0012; GA MŠk LC06052 Institutional research plan: CEZ:AV0Z10190503 Keywords : spherically symmetric motion * selfgravitating gas * non monotone pressure law * density-dependent viscosities Subject RIV: BA - General Mathematics Impact factor: 0.768, year: 2011 http://link.springer.com/article/10.1007%2Fs00021-009-0010-5
On a general spherically symmetrical line-element in relativity physics
International Nuclear Information System (INIS)
Wagh, R.V.
1974-01-01
The principles of relativistic mechanics are all implicitly contained in Einstein's field equations. In order to obtain actual solutions for the field equations, appropriate expressions are required for the Christoffel three index symbols and for the components of the energy momentum tensor in terms of the quantities used in expressing the proposed line elements. The usual three-index symbols, the contracted curvature tensor and the equations of geodesics for a general spherically symmetrical line-element required for the purpose have been worked out. (K.B.)
A new approach to mixing length theory of convection for spherically symmetric supernova simulations
Warren, Mackenzie; Couch, Sean
2016-09-01
We have developed a new approach to the mixing length theory of convection for use in spherically symmetric core-collapse supernova simulations. This approach is based on the results of multidimensional simulations with the goal of more accurately reproducing successful explosions, the composition and thermodynamic variables in regions where nucleosynthesis occurs, and observed quantities such as neutrino luminosities and energies. We compare this approach with standard mixing length theory and the results of multidimensional supernova simulations and discuss prospects for systematic studies of the nuclear equation of state and heavy element nucleosynthesis in core-collapse supernovae.
Hod, Shahar
2017-10-01
Recent no-hair theorems have revealed the intriguing fact that horizonless stars with compact reflecting surfaces cannot support non-linear matter configurations made of scalar, vector, and tensor fields. In the present paper we extend the regime of validity of these no-hair theorems by explicitly proving that spherically symmetric compact reflecting stars cannot support static configurations made of massive scalar fields with non-minimal coupling to gravity. Interestingly, our no-hair theorem is valid for generic values of the dimensionless field-curvature coupling parameter ξ.
Spherically symmetric solution in higher-dimensional teleparallel equivalent of general relativity
Gamal, G. L. Nashed
2013-02-01
A theory of (N+1)-dimensional gravity is developed on the basis of the teleparallel equivalent of general relativity (TEGR). The fundamental gravitational field variables are the (N+1)-dimensional vector fields, defined globally on a manifold M, and the gravitational field is attributed to the torsion. The form of Lagrangian density is quadratic in torsion tensor. We then give an exact five-dimensional spherically symmetric solution (Schwarzschild (4+1)-dimensions). Finally, we calculate energy and spatial momentum using gravitational energy—momentum tensor and superpotential 2-form.
Directory of Open Access Journals (Sweden)
Shahar Hod
2017-10-01
Full Text Available Recent no-hair theorems have revealed the intriguing fact that horizonless stars with compact reflecting surfaces cannot support non-linear matter configurations made of scalar, vector, and tensor fields. In the present paper we extend the regime of validity of these no-hair theorems by explicitly proving that spherically symmetric compact reflecting stars cannot support static configurations made of massive scalar fields with non-minimal coupling to gravity. Interestingly, our no-hair theorem is valid for generic values of the dimensionless field-curvature coupling parameter ξ.
de Hoop, Maarten V.; Ilmavirta, Joonas
2017-12-01
We study ray transforms on spherically symmetric manifolds with a piecewise C1, 1 metric. Assuming the Herglotz condition, the x-ray transform is injective on the space of L 2 functions on such manifolds. We also prove injectivity results for broken ray transforms (with and without periodicity) on such manifolds with a C1, 1 metric. To make these problems tractable in low regularity, we introduce and study a class of generalized Abel transforms and study their properties. This low regularity setting is relevant for geophysical applications.
Classic tests of General Relativity described by brane-based spherically symmetric solutions
Energy Technology Data Exchange (ETDEWEB)
Cuzinatto, R.R. [Universidade Federal de Alfenas, Instituto de Ciencia e Tecnologia, Pocos de Caldas, MG (Brazil); Pompeia, P.J. [Departamento de Ciencia e Tecnologia Aeroespacial, Instituto de Fomento e Coordenacao Industrial, Sao Jose dos Campos, SP (Brazil); Departamento de Ciencia e Tecnologia Aeroespacial, Instituto Tecnologico de Aeronautica, Sao Jose dos Campos, SP (Brazil); De Montigny, M. [University of Alberta, Theoretical Physics Institute, Edmonton, AB (Canada); University of Alberta, Campus Saint-Jean, Edmonton, AB (Canada); Khanna, F.C. [University of Alberta, Theoretical Physics Institute, Edmonton, AB (Canada); TRIUMF, Vancouver, BC (Canada); University of Victoria, Department of Physics and Astronomy, PO box 1700, Victoria, BC (Canada); Silva, J.M.H. da [Universidade Estadual Paulista, Departamento de Fisica e Quimica, Guaratingueta, SP (Brazil)
2014-08-15
We discuss a way to obtain information about higher dimensions from observations by studying a brane-based spherically symmetric solution. The three classic tests of General Relativity are analyzed in detail: the perihelion shift of the planet Mercury, the deflection of light by the Sun, and the gravitational redshift of atomic spectral lines. The braneworld version of these tests exhibits an additional parameter b related to the fifth-coordinate. This constant b can be constrained by comparison with observational data for massive and massless particles. (orig.)
Spherically Symmetric Geometries in f(T and f(R Gravitational Theories
Directory of Open Access Journals (Sweden)
Gamal G. L. Nashed
2015-01-01
Full Text Available Using the well know relation between Ricci scalar, R, and torsion scalar, T, that is, R=-T-2∇αTα, we show that, for any spherically symmetric spacetime whose (i scalar torsion vanishing, that is, T=TμναSαμν=0 or (ii total derivative term, that is, ∇αTα with Tα is the contraction of the torsion, vanishing, or (iii the combination of scalar torsion and total derivative term vanishing, could be solution for f(T and f(R gravitational theories.
International Nuclear Information System (INIS)
Clarisse, J.M.
2007-01-01
A numerical scheme for computing linear Lagrangian perturbations of spherically symmetric flows of gas dynamics is proposed. This explicit first-order scheme uses the Roe method in Lagrangian coordinates, for computing the radial spherically symmetric mean flow, and its linearized version, for treating the three-dimensional linear perturbations. Fulfillment of the geometric conservation law discrete formulations for both the mean flow and its perturbation is ensured. This scheme capabilities are illustrated by the computation of free-surface mode evolutions at the boundaries of a spherical hollow shell undergoing an homogeneous cumulative compression, showing excellent agreement with reference results. (author)
Energy Technology Data Exchange (ETDEWEB)
Hod, Shahar [The Ruppin Academic Center, Emeq Hefer (Israel); The Hadassah Academic College, Jerusalem (Israel)
2017-12-15
It has recently been demonstrated that asymptotically flat neutral reflecting stars are characterized by an intriguing no-hair property. In particular, it has been proved that these horizonless compact objects cannot support spatially regular static matter configurations made of scalar (spin-0) fields, vector (spin-1) fields and tensor (spin-2) fields. In the present paper we shall explicitly prove that spherically symmetric compact reflecting stars can support stationary (rather than static) bound-state massive scalar fields in their exterior spacetime regions. To this end, we solve analytically the Klein-Gordon wave equation for a linearized scalar field of mass μ and proper frequency ω in the curved background of a spherically symmetric compact reflecting star of mass M and radius R{sub s}. It is proved that the regime of existence of these stationary composed star-field configurations is characterized by the simple inequalities 1 - 2M/R{sub s} < (ω/μ){sup 2} < 1. Interestingly, in the regime M/R{sub s} << 1 of weakly self-gravitating stars we derive a remarkably compact analytical equation for the discrete spectrum {ω(M,R_s, μ)}{sup n=∞}{sub n=1} of resonant oscillation frequencies which characterize the stationary composed compact-reflecting-star-linearized-massive-scalar-field configurations. Finally, we verify the accuracy of the analytically derived resonance formula of the composed star-field configurations with direct numerical computations. (orig.)
Spherically-symmetric solutions in general relativity using a tetrad-based approach
Kim, Do Young; Lasenby, Anthony N.; Hobson, Michael P.
2018-03-01
We present a tetrad-based method for solving the Einstein field equations for spherically-symmetric systems and compare it with the widely-used Lemaître-Tolman-Bondi (LTB) model. In particular, we focus on the issues of gauge ambiguity and the use of comoving versus `physical' coordinate systems. We also clarify the correspondences between the two approaches, and illustrate their differences by applying them to the classic examples of the Schwarzschild and Friedmann-Lemaître-Robertson-Walker spacetimes. We demonstrate that the tetrad-based method does not suffer from the gauge freedoms inherent to the LTB model, naturally accommodates non-uniform pressure and has a more transparent physical interpretation. We further apply our tetrad-based method to a generalised form of `Swiss cheese' model, which consists of an interior spherical region surrounded by a spherical shell of vacuum that is embedded in an exterior background universe. In general, we allow the fluid in the interior and exterior regions to support pressure, and do not demand that the interior region be compensated. We pay particular attention to the form of the solution in the intervening vacuum region and illustrate the validity of Birkhoff's theorem at both the metric and tetrad level. We then reconsider critically the original theoretical arguments underlying the so-called Rh = ct cosmological model, which has recently received considerable attention. These considerations in turn illustrate the interesting behaviour of a number of `horizons' in general cosmological models.
Spherically symmetric ADM gravity with variable G and Λc
International Nuclear Information System (INIS)
Esposito, Giampiero; Rubano, Claudio; Scudellaro, Paolo
2007-01-01
This paper investigates the Arnowitt-Deser-Misner (hereafter ADM) form of spherically symmetric gravity with variable Newton parameter G and cosmological term Λ c . The Newton parameter is here treated as a dynamical variable, rather than being merely an external parameter as in previous work on closely related topics. The resulting Hamilton equations are obtained; interestingly, a static solution exists, which reduces to Schwarzschild geometry in the limit of constant G, describing a Newton parameter ruled by a nonlinear differential equation in the radial variable r. A remarkable limiting case is the one for which the Newton parameter obeys an almost linear growth law at large r. An exact solution for G as a function of r is also obtained in the case of vanishing cosmological constant. Some observational implications of these solutions are obtained and briefly discussed
Energy eigenvalues of spherical symmetric potentials with relativistic corrections: analytic results
Energy Technology Data Exchange (ETDEWEB)
Dineykhan, M; Zhaugasheva, S A [Bogoliubov Laboratory of Theoretical Physics, Joint Institute for Nuclear Research, Dubna (Russian Federation); Toinbaeva, N Sh [al-Farabi Kazak National University, Almaty (Kazakhstan)
2010-01-14
Based on the investigation of the asymptotic behaviour of the polarization loop function for charged n scalar particles in an external gauge field, we determine the interaction Hamiltonian including the relativistic corrections. The energy eigenvalues of spherical symmetric potentials for two-particle bound state systems with relativistic corrections are analytically derived. The energy spectra of linear and funnel potentials with orbital and radial excitations are determined. The energy spectrum of a superposition of Coulomb and Yukawa potentials is also determined. Our result shows that the energy spectrum with the relativistic corrections for the linear, harmonic oscillator and funnel potentials is smaller than the upper boundaries for the energy spectrum established in the framework of the spinless Salpeter equation for the orbital and radial excited states. The relativistic corrections to the energy spectrum of a superposition of the attractive Coulomb potential and the Yukawa (exponentially screened Coulomb) potentials are very small.
Mimoso, José Pedro; Mena, Filipe C
2010-01-01
We investigate spherically symmetric perfect fluid spacetimes and discuss the existence and stability of a dividing shell separating expanding and collapsing regions. We perform a 3+1 splitting and obtain gauge invariant conditions relating the intrinsic spatial curvature of the shells to the ADM mass and to a function of the pressure which we introduce and that generalises the Tolman-Oppenheimer-Volkoff equilibrium condition. We analyse the particular cases of the Lema\\^itre-Tolman-Bondi dust models with a cosmological constant as an example of a $\\Lambda$-CDM model and its generalization to contain a central perfect fluid core. These models provide simple, but physically interesting illustrations of our results.
On the Stability of Spherically Symmetric Self-Gravitating Classical and Quantum Systems
DEFF Research Database (Denmark)
Makedonski, Mathias
We study the energetic stability of spherically symmetric self-gravitating systems beginning with an extensive review of the literature on perfect fluid bodies in Newtonian gravity with a particular focus on existence and uniqueness results for solutions of the Chandrasekhar equation. Moving...... on to the description of the corresponding systems in the setting of general relativity, it is shown, that the Tolman-Oppenheimer-Volko equation can be obtained from a suitable variation of the total energy. We prove a previously unnoticed energetic instability of the model. Staying in the general relativistic setting......, we examine the self-gravitating massive free scalar eld. It is shown, by proving suitable dierentiability properties of the occurring functionals, that Einstein's equations in this setting can again be obtained by a constrained variation of the total mass as dened by Arnowitt, Deser and Misner...
A new model for spherically symmetric charged compact stars of embedding class 1
Energy Technology Data Exchange (ETDEWEB)
Maurya, S.K. [University of Nizwa, Department of Mathematical and Physical Sciences, College of Arts and Science, Nizwa (Oman); Gupta, Y.K. [Raj Kumar Goel Institute of Technology, Department of Mathematics, Ghaziabad, U.P. (India); Ray, Saibal [Government College of Engineering and Ceramic Technology, Department of Physics, Kolkata, West Bengal (India); Deb, Debabrata [Indian Institute of Engineering Science and Technology, Department of Physics, Howrah, West Bengal (India)
2017-01-15
In the present study we search for a new stellar model with spherically symmetric matter and a charged distribution in a general relativistic framework. The model represents a compact star of embedding class 1. The solutions obtained here are general in nature, having the following two features: first of all, the metric becomes flat and also the expressions for the pressure, energy density, and electric charge become zero in all the cases if we consider the constant A = 0, which shows that our solutions represent the so-called 'electromagnetic mass model' [17], and, secondly, the metric function ν(r), for the limit n tending to infinity, converts to ν(r) = Cr{sup 2}+ ln B, which is the same as considered by Maurya et al. [11]. We have investigated several physical aspects of the model and find that all the features are acceptable within the requirements of contemporary theoretical studies and observational evidence. (orig.)
Odd-parity pertubations of spherically symmetric star clusters in general relativity
International Nuclear Information System (INIS)
Semenzato, R.; Ipser, J.R.
1981-01-01
The theory of odd-parity nonspherical peturbations of collisionless, isotropic, spherically symmetric star clusters is developed within general relativity for l> or =2. A variational principle is derived for the associated normal modes of oscillation. The variational expression reveals that an unstable normal mode has a pure exponentially growing time dependence--the corresponding complex ''eigenfrequency'' is purely imaginary--and hence that a normal mode can become unstable in a smooth fashion only thorugh zero frequency. Further, it is shown that no instabilities can set in through zero-frequency modes along smooth sequences of models with fewer high-energy stars than low-energy stars. Unless unstable normal modes suddenly appear in a nonsmooth fashion, the implications is that these models possess no unstable normal modes
Merging black holes in non-spherical nuclear star clusters
Petrovich, Cristobal
2018-04-01
The Milky Way and a significant fraction of galaxies are observed to host a central Massive Black Hole (MBH) embedded in a non-spherical nuclear star cluster. I will discuss the orbital evolution of stellar binaries in these environments and argue that their merger rates are expected to be greatly enhanced when the effect from cluster potential is taken into account in the binary-MBH triple system. I will apply our results to compact-object binary mergers mediated by gravitational wave radiation and show that this merger channel can contribute significantly to the LIGO/Virgo detections.
Linear perturbations in spherically symmetric dust cosmologies including a cosmological constant
Meyer, Sven; Bartelmann, Matthias
2017-12-01
We study the dynamical behaviour of gauge-invariant linear perturbations in spherically symmetric dust cosmologies including a cosmological constant. In contrast to spatially homogeneous FLRW models, the reduced degree of spatial symmetry causes a non-trivial dynamical coupling of gauge-invariant quantities already at first order perturbation theory and the strength and influence of this coupling on the spacetime evolution is investigated here. We present results on the underlying dynamical equations augmented by a cosmological constant and integrate them numerically. We also present a method to derive cosmologically relevant initial variables for this setup. Estimates of angular power spectra for each metric variable are computed and evaluated on the central observer's past null cone. By comparing the full evolution to the freely evolved initial profiles, the coupling strength will be determined for a best fit radially inhomogeneous patch obtained in previous works (see [1]). We find that coupling effects are not noticeable within the cosmic variance limit and can therefore safely be neglected for a relevant cosmological scenario. On the contrary, we find very strong coupling effects in a best fit spherical void model matching the distance redshift relation of SNe which is in accordance with previous findings using parametric void models.
Tang, Xiaping; Churazov, Eugene
2018-04-01
We analyze the impact of thermal conduction on the appearance of a shock-heated gas shell which is produced when a spherically symmetric outburst of a supermassive black hole inflates bubbles of relativistic plasma at the center of a galaxy cluster. The presence of the hot and low-density shell can be used as an ancillary indicator for a high rate of energy release during the outburst, which is required to drive strong shocks into the gas. Here we show that conduction can effectively erase such shell, unless the diffusion of electrons is heavily suppressed. We conclude that a more robust proxy to the energy release rate is the ratio between the shock radius and bubble radius. We also revisited the issue of sound waves dissipation induced by thermal conduction in a scenario, where characteristic wavelength of the sound wave is set by the total energy of the outburst. For a fiducial short outburst model, the dissipation length does not exceed the cooling radius in a typical cluster, provided that the conduction is suppressed by a factor not larger than ˜100. For quasi-continuous energy injection neither the shock-heated shell nor the outgoing sound wave are important and the role of conduction is subdominant.
Ajello, J. M.; Witt, N.; Blum, P. W.
1979-01-01
Four Mariner 10 observations of interplanetary hydrogen 1216-A and helium 584-A emissions are analyzed by using radiation models that employ spherically symmetric solar radiation fields. It is shown that the measured 584-A intensities can be represented with a statistical accuracy of about 10% by a model that assumes spherical symmetry for the 584-A solar radiation and that the 1216-A intensities can be represented to within 15% by a model based on spherically symmetric solar corpuscular and EUV radiation. An interstellar wind velocity of 22 km/s, a helium number density of 0.008 per cu cm, and an interstellar neutral-gas temperature of 1500 K near the solar system are obtained from Copernicus satellite measurements.
Axially symmetric static scalar solitons and black holes with scalar hair
Energy Technology Data Exchange (ETDEWEB)
Kleihaus, Burkhard, E-mail: kleihaus@theorie.physik.uni-oldenburg.de; Kunz, Jutta; Radu, Eugen; Subagyo, Bintoro
2013-10-01
We construct static, asymptotically flat black hole solutions with scalar hair. They evade the no-hair theorems by having a scalar potential which is not strictly positive. By including an azimuthal winding number in the scalar field ansatz, we find hairy black hole solutions which are static but axially symmetric only. These solutions possess a globally regular limit, describing scalar solitons. A branch of axially symmetric black holes is found to possess a positive specific heat.
Herrera, L.
2018-02-01
We put forward a new definition of complexity, for static and spherically symmetric self-gravitating systems, based on a quantity, hereafter referred to as complexity factor, that appears in the orthogonal splitting of the Riemann tensor, in the context of general relativity. We start by assuming that the homogeneous (in the energy density) fluid, with isotropic pressure is endowed with minimal complexity. For this kind of fluid distribution, the value of complexity factor is zero. So, the rationale behind our proposal for the definition of complexity factor stems from the fact that it measures the departure, in the value of the active gravitational mass (Tolman mass), with respect to its value for a zero complexity system. Such departure is produced by a specific combination of energy density inhomogeneity and pressure anisotropy. Thus, zero complexity factor may also be found in self-gravitating systems with inhomogeneous energy density and anisotropic pressure, provided the effects of these two factors, on the complexity factor, cancel each other. Some exact interior solutions to the Einstein equations satisfying the zero complexity criterium are found, and prospective applications of this newly defined concept, to the study of the structure and evolution of compact objects, are discussed.
Existence and stability of circular orbits in general static and spherically symmetric spacetimes
Jia, Junji; Liu, Jiawei; Liu, Xionghui; Mo, Zhongyou; Pang, Xiankai; Wang, Yaoguang; Yang, Nan
2018-02-01
The existence and stability of circular orbits (CO) in static and spherically symmetric (SSS) spacetime are important because of their practical and potential usefulness. In this paper, using the fixed point method, we first prove a necessary and sufficient condition on the metric function for the existence of timelike COs in SSS spacetimes. After analyzing the asymptotic behavior of the metric, we then show that asymptotic flat SSS spacetime that corresponds to a negative Newtonian potential at large r will always allow the existence of CO. The stability of the CO in a general SSS spacetime is then studied using the Lyapunov exponent method. Two sufficient conditions on the (in)stability of the COs are obtained. For null geodesics, a sufficient condition on the metric function for the (in)stability of null CO is also obtained. We then illustrate one powerful application of these results by showing that three SSS spacetimes whose metric function is not completely known will allow the existence of timelike and/or null COs. We also used our results to assert the existence and (in)stabilities of a number of known SSS metrics.
Zhdanov, V.; Stashko, O.
2016-12-01
We study exact special solutions of the joint system of Einstein equations and scalar field equations with a non-zero self-interaction potential, which describe spherically symmetric static configurations. The space-time is asymptotically flat with a naked singularity at the center. The testbody motion is analyzed; we found conditions for existence of non-connected regions of stable circular orbits. We show the existence of static trajectories of particles that hang above the configuration.
Energy Technology Data Exchange (ETDEWEB)
Araújo, M.E. [Departamento de Física-Matemática, Instituto de Física, Universidade Federal do Rio de Janeiro, Av. Athos da Silveira Ramos 149, 21.945-970, Rio de Janeiro, R.J. (Brazil); Stoeger, W.R., E-mail: mearaujo@me.com, E-mail: wstoeger@as.arizona.edu [Vatican Observatory Research Group, Steward Observatory, University of Arizona, 933 N. Cherry Ave., Tucson, AZ 85721 (United States)
2011-07-01
One of the continuing challenges in cosmology has been to determine the large-scale space-time metric from observations with a minimum of assumptions — without, for instance, assuming that the universe is almost Friedmann-Lemaître-Robertson-Walker (FLRW). If we are lucky enough this would be a way of demonstrating that our universe is FLRW, instead of presupposing it or simply showing that the observations are consistent with FLRW. Showing how to do this within the more general spherically symmetric, inhomogeneous space-time framework takes us a long way towards fulfilling this goal. In recent work researchers have shown how this can be done both in the traditional Lemaître-Tolman-Bondi (LTB) 3 + 1 coordinate framework, and in the observational coordinate (OC) framework, in which the radial coordinate y is null (light-like) and measured down the past light cone of the observer. In this paper we investigate the stability of solutions, and the use of data in the OC field equations including their time evolution — i.e. our procedure is not restricted to our past light cone — and compare both approaches with respect to the singularity problem at the maximum of the angular-diameter distance, the stability of solutions, and the use of data in the field equations. We also compare the two approaches with regard to determining the cosmological constant Λ. This allows a more detailed account and assessment of the OC integration procedure, and enables a comparison of the relative advantages of the two equivalent solution frameworks. Both formulations and integration procedures should, in principle, lead to the same results. However, as we show in this paper, the OC procedure manifests certain advantages, particularly in the avoidance of coordinate singularities at the maximum of the angular-diameter distance, and in the stability of the solutions obtained. This particular feature is what allows us to do the best fitting of the data to smooth data functions and the
Boundary causality versus hyperbolicity for spherical black holes in Gauss–Bonnet gravity
International Nuclear Information System (INIS)
Andrade, Tomás; Cáceres, Elena; Keeler, Cynthia
2017-01-01
We explore the constraints boundary causality places on the allowable Gauss–Bonnet gravitational couplings in asymptotically AdS spaces, specifically considering spherical black hole solutions. We additionally consider the hyperbolicity properties of these solutions, positing that hyperbolicity-violating solutions are sick solutions whose causality properties provide no information about the theory they reside in. For both signs of the Gauss–Bonnet coupling, spherical black holes violate boundary causality at smaller absolute values of the coupling than planar black holes do. For negative coupling, as we tune the Gauss–Bonnet coupling away from zero, both spherical and planar black holes violate hyperbolicity before they violate boundary causality. For positive coupling, the only hyperbolicity-respecting spherical black holes which violate boundary causality do not do so appreciably far from the planar bound. Consequently, eliminating hyperbolicity-violating solutions means the bound on Gauss–Bonnet couplings from the boundary causality of spherical black holes is no tighter than that from planar black holes. (paper)
Boundary causality versus hyperbolicity for spherical black holes in Gauss-Bonnet gravity
Andrade, Tomás; Cáceres, Elena; Keeler, Cynthia
2017-07-01
We explore the constraints boundary causality places on the allowable Gauss-Bonnet gravitational couplings in asymptotically AdS spaces, specifically considering spherical black hole solutions. We additionally consider the hyperbolicity properties of these solutions, positing that hyperbolicity-violating solutions are sick solutions whose causality properties provide no information about the theory they reside in. For both signs of the Gauss-Bonnet coupling, spherical black holes violate boundary causality at smaller absolute values of the coupling than planar black holes do. For negative coupling, as we tune the Gauss-Bonnet coupling away from zero, both spherical and planar black holes violate hyperbolicity before they violate boundary causality. For positive coupling, the only hyperbolicity-respecting spherical black holes which violate boundary causality do not do so appreciably far from the planar bound. Consequently, eliminating hyperbolicity-violating solutions means the bound on Gauss-Bonnet couplings from the boundary causality of spherical black holes is no tighter than that from planar black holes.
Two-component Jaffe models with a central black hole - I. The spherical case
Ciotti, Luca; Ziaee Lorzad, Azadeh
2018-02-01
Dynamical properties of spherically symmetric galaxy models where both the stellar and total mass density distributions are described by the Jaffe (1983) profile (with different scalelengths and masses) are presented. The orbital structure of the stellar component is described by Osipkov-Merritt anisotropy, and a black hole (BH) is added at the centre of the galaxy; the dark matter halo is isotropic. First, the conditions required to have a nowhere negative and monotonically decreasing dark matter halo density profile are derived. We then show that the phase-space distribution function can be recovered by using the Lambert-Euler W function, while in absence of the central BH only elementary functions appears in the integrand of the inversion formula. The minimum value of the anisotropy radius for consistency is derived in terms of the galaxy parameters. The Jeans equations for the stellar component are solved analytically, and the projected velocity dispersion at the centre and at large radii are also obtained analytically for generic values of the anisotropy radius. Finally, the relevant global quantities entering the Virial Theorem are computed analytically, and the fiducial anisotropy limit required to prevent the onset of Radial Orbit Instability is determined as a function of the galaxy parameters. The presented models, even though highly idealized, represent a substantial generalization of the models presented in Ciotti, and can be useful as starting point for more advanced modelling, the dynamics and the mass distribution of elliptical galaxies.
International Nuclear Information System (INIS)
Alexandre, Jean; Pasipoularides, Pavlos
2011-01-01
In this note we examine whether spherically symmetric solutions in covariant Horava-Lifshitz gravity can reproduce Newton's Law in the IR limit λ→1. We adopt the position that the auxiliary field A is independent of the space-time metric [J. Alexandre and P. Pasipoularides, Phys. Rev. D 83, 084030 (2011).][J. Greenwald, V. H. Satheeshkumar, and A. Wang, J. Cosmol. Astropart. Phys. 12 (2010) 007.], and we assume, as in [A. M. da Silva, Classical Quantum Gravity 28, 055011 (2011).], that λ is a running coupling constant. We show that under these assumptions, spherically symmetric solutions fail to restore the standard Newtonian physics in the IR limit λ→1, unless λ does not run, and has the fixed value λ=1. Finally, we comment on the Horava and Melby-Thompson approach [P. Horava and C. M. Melby-Thompson, Phys. Rev. D 82, 064027 (2010).] in which A is assumed as a part of the space-time metric in the IR.
Investigation of the stability of collision-less spherically symmetric systems
Energy Technology Data Exchange (ETDEWEB)
Polyachenko, V.L.; Shukhman, I.G. (AN SSSR, Leningrad. Inst. Teoreticheskoj Astronomii)
The matrix equation star is suggested for investigating the large- scale stability of general spherical collisionless star systems. The equation derived is used for a stability analysis of Idlis one-parametric series of distribution functions. It is shown that the stability condition restricts strongly the permissible degree of anisotropy of the stellar velocity distribution.
Solution of the spherically symmetric linear thermoviscoelastic problem in the inertia-free limit
DEFF Research Database (Denmark)
Christensen, Tage Emil; Dyre, J. C.
2008-01-01
The coupling between mechanical and thermal properties due to thermal expansion complicates the problem of measuring frequency-dependent thermoviscoelastic properties, in particular for highly viscous liquids. A simplification arises if there is spherical symmetry where-as detailed in the present...
Inversion symmetric initial data for N charged black holes
International Nuclear Information System (INIS)
Bowen, J.M.
1985-01-01
The initial value equations for gravitational and electric fields on a multiply connected manifold are addressed. The manifold considered represents two physically identical asymptotically flat universes with N throats connecting them. Matching conditions for the fields are derived for the case of a conformally flat maximal (but not time-symmetric) initial slice. A formal solution incorporating these conditions is given in terms of a simple geometric algorithm, and the method is applied to give explicit expressions for the background electric field of two oppositely charged bodies. Unlike previous methods, this procedure is general enough to allow arbitrary a priori specification of charge, angular momentum, and linear momentum for any number of separate charged moving bodies
E(7) symmetric area of the black hole horizon
International Nuclear Information System (INIS)
Kallosh, R.; Kol, B.
1996-01-01
Extreme black holes with 1/8 of unbroken N=8 supersymmetry are characterized by the nonvanishing area of the horizon. The central charge matrix has four generic eigenvalues. The area is proportional to the square root of the invariant quartic form of E 7(7) . It vanishes in all cases when 1/4 or 1/2 of supersymmetry is unbroken. The supergravity nonrenormalization theorem for the area of the horizon in the N=8 case protects the unique U-duality invariant. copyright 1996 The American Physical Society
Winkler, Franz-Günter
2013-09-01
The geodesic equations for the general case of diagonal metrics of static, spherically symmetric fields are calculated. The elimination of the proper time variable gives the motion equations for test particles with respect to coordinate time and an account of "gravitational acceleration from the coordinate perspective". The results are applied to the Schwarzschild metric and to the so-called exponential metric. In an attempt to add an account of "gravitational force from the coordinate perspective", the special relativistic mass-energy relation is generalized to diagonal metrics involving location dependent and possibly anisotropic light speeds. This move requires a distinction between two aspects of the mass of a test particle (parallel and perpendicular to the field). The obtained force expressions do not reveal "gravitational repulsion" for the Schwarzschild metric and for the exponential metric.
International Nuclear Information System (INIS)
Araujo, M. E.; Stoeger, W. R.
2009-01-01
A rigorous demonstration that given appropriate data on our past light cone leads to the determination of the metric functions and all their time derivatives on our past light cone is presented, thus showing how to evolve the solution we obtain from data on the light cone off it in a well-defined and straightforward way. It also automatically gives a procedure for constructing the solution for all spherically symmetric, inhomogeneous cosmological Lemaitre-Tolman-Bondi models in observational coordinates as a Taylor series in time of however many terms we need. Our procedure takes into account the essential data giving the maximum of the observer area (angular-diameter) distance, and the redshift z max at which that occurs. This enables the determination of the vacuum-energy density μ Λ , which would otherwise remain undetermined.
Spherical accretion of matter by charged black holes on f(T) Gravity
Rodrigues, M. E.; Junior, E. L. B.
2018-03-01
We studied the spherical accretion of matter by charged black holes on f(T) Gravity. Considering the accretion model of a isentropic perfect fluid we obtain the general form of the Hamiltonian and the dynamic system for the fluid. We have analysed the movements of an isothermal fluid model with p=ω e and where p is the pressure and e the total energy density. The analysis of the cases shows the possibility of spherical accretion of fluid by black holes, revealing new phenomena as cyclical movement inside the event horizon.
IMPETUS: Consistent SPH calculations of 3D spherical Bondi accretion onto a black hole
Ramírez-Velasquez, J. M.; Sigalotti, L. Di G.; Gabbasov, R.; Cruz, F.; Klapp, J.
2018-04-01
We present three-dimensional calculations of spherically symmetric Bondi accretion onto a stationary supermassive black hole (SMBH) of mass 108M⊙ within a radial range of 0.02 - 10 pc, using a modified version of the smoothed particle hydrodynamics (SPH) GADGET-2 code, which ensures approximate first-order consistency (i.e., second-order accuracy) for the particle approximation. First-order consistency is restored by allowing the number of neighbours, nneigh, and the smoothing length, h, to vary with the total number of particles, N, such that the asymptotic limits nneigh → ∞ and h → 0 hold as N → ∞. The ability of the method to reproduce the isothermal (γ = 1) and adiabatic (γ = 5/3) Bondi accretion is investigated with increased spatial resolution. In particular, for the isothermal models the numerical radial profiles closely match the Bondi solution, except near the accretor, where the density and radial velocity are slightly underestimated. However, as nneigh is increased and h is decreased, the calculations approach first-order consistency and the deviations from the Bondi solution decrease. The density and radial velocity profiles for the adiabatic models are qualitatively similar to those for the isothermal Bondi accretion. Steady-state Bondi accretion is reproduced by the highly resolved consistent models with a percent relative error of ≲ 1% for γ = 1 and ˜9% for γ = 5/3, with the adiabatic accretion taking longer than the isothermal case to reach steady flow. The performance of the method is assessed by comparing the results with those obtained using the standard GADGET-2 and the GIZMO codes.
Directory of Open Access Journals (Sweden)
Khalaf A. M.
2015-04-01
Full Text Available The interacting boson model (sd-IBM1 with intrinsic coherent state is used to study the shape phase transitions from spherical U(5 to prolate deformed SU(3 shapes in Nd- Sm isotopic chains. The Hamiltonian is written in the creation and annihilation form with one and two body terms.For each nucleus a fitting procedure is adopted to get the best model parameters by fitting selected experimental energy levels, B(E2 transi- tion rates and two-neutron separation energies with the calculated ones.The U(5-SU(3 IBM potential energy surfaces (PES’s are analyzed and the critical phase transition points are identified in the space of model parameters.In Nd-Sm isotopic chains nuclei evolve from spherical to deformed shapes by increasing the boson number. The nuclei 150 Nd and 152 Sm have been found to be close to critical points.We have also studied the energy ratios and the B(E2 values for yrast band at the critical points.
Diakogiannis, Foivos I.; Lewis, Geraint F.; Ibata, Rodrigo A.
2014-09-01
The spherical Jeans equation is widely used to estimate the mass content of stellar systems with apparent spherical symmetry. However, this method suffers from a degeneracy between the assumed mass density and the kinematic anisotropy profile, β(r). In a previous work, we laid the theoretical foundations for an algorithm that combines smoothing B splines with equations from dynamics to remove this degeneracy. Specifically, our method reconstructs a unique kinematic profile of σ _{rr}^2 and σ _{tt}^2 for an assumed free functional form of the potential and mass density (Φ, ρ) and given a set of observed line-of-sight velocity dispersion measurements, σ _los^2. In Paper I, we demonstrated the efficiency of our algorithm with a very simple example and we commented on the need for optimum smoothing of the B-spline representation; this is in order to avoid unphysical variational behaviour when we have large uncertainty in our data. In the current contribution, we present a process of finding the optimum smoothing for a given data set by using information of the behaviour from known ideal theoretical models. Markov Chain Monte Carlo methods are used to explore the degeneracy in the dynamical modelling process. We validate our model through applications to synthetic data for systems with constant or variable mass-to-light ratio Υ. In all cases, we recover excellent fits of theoretical functions to observables and unique solutions. Our algorithm is a robust method for the removal of the mass-anisotropy degeneracy of the spherically symmetric Jeans equation for an assumed functional form of the mass density.
From black holes to white holes: a quantum gravitational, symmetric bounce
International Nuclear Information System (INIS)
Olmedo, Javier; Saini, Sahil; Singh, Parampreet
2017-01-01
Recently, a consistent non-perturbative quantization of the Schwarzschild interior resulting in a bounce from black hole to white hole geometry has been obtained by loop quantizing the Kantowski–Sachs vacuum spacetime. As in other spacetimes where the singularity is dominated by the Weyl part of the spacetime curvature, the structure of the singularity is highly anisotropic in the Kantowski–Sachs vacuum spacetime. As a result, the bounce turns out to be in general asymmetric, creating a large mass difference between the parent black hole and the child white hole. In this manuscript, we investigate under what circumstances a symmetric bounce scenario can be constructed in the above quantization. Using the setting of Dirac observables and geometric clocks, we obtain a symmetric bounce condition which can be satisfied by a slight modification in the construction of loops over which holonomies are considered in the quantization procedure. These modifications can be viewed as quantization ambiguities, and are demonstrated in three different flavors, all of which lead to a non-singular black to white hole transition with identical masses. Our results show that quantization ambiguities can mitigate or even qualitatively change some key features of the physics of singularity resolution. Further, these results are potentially helpful in motivating and constructing symmetric black to white hole transition scenarios. (paper)
International Nuclear Information System (INIS)
Hosokawa, Takashi; Omukai, Kazuyuki
2009-01-01
The final mass of a newborn star is set at the epoch when the mass accretion onto the star is terminated. We study the evolution of accreting protostars and the limits of accretion in low-metallicity environments under spherical symmetry. Accretion rates onto protostars are estimated via the temperature evolution of prestellar cores with different metallicities. The derived rates increase with decreasing metallicity, from M-dot≅10 -6 M odot yr -1 at Z = Z sun to 10 -3 M sun yr -1 at Z = 0. With the derived accretion rates, the protostellar evolution is numerically calculated. We find that, at lower metallicity, the protostar has a larger radius and reaches the zero-age main sequence (ZAMS) at higher stellar mass. Using this protostellar evolution, we evaluate the upper stellar mass limit where the mass accretion is hindered by radiative feedback. We consider the effects of radiation pressure exerted on the accreting envelope, and expansion of an H II region. The mass accretion is finally terminated by radiation pressure on dust grains in the envelope for Z ∼> 10 -3 Z sun and by the expanding H II region for lower metallicity. The mass limit from these effects increases with decreasing metallicity from M * ≅ 10 M sun at Z = Z sun to ≅300 M sun at Z = 10 -6 Z sun . The termination of accretion occurs after the central star arrives at the ZAMS at all metallicities, which allows us to neglect protostellar evolution effects in discussing the upper mass limit by stellar feedback. The fragmentation induced by line cooling in low-metallicity clouds yields prestellar cores with masses large enough that the final stellar mass is set by the feedback effects. Although relaxing the assumption of spherical symmetry will alter feedback effects, our results will be a benchmark for more realistic evolution to be explored in future studies.
Raju, P.; Sobhanbabu, K.; Reddy, D. R. K.
2016-02-01
Five-dimensional spherically symmetric space-time filled with two minimally interacting fields, matter and holographic dark energy components, is investigated in a scalar tensor theory of gravitation proposed by Saez and Ballester (Phys. Lett. A 113:467, 1986). An explicit solution of the field equations is obtained. Some physical and kinematic properties of the model are also studied.
Sound wave generation by a spherically symmetric outburst and AGN feedback in galaxy clusters
Tang, Xiaping; Churazov, Eugene
2017-07-01
We consider the evolution of an outburst in a uniform medium under spherical symmetry, having in mind active galactic nucleus feedback in the intracluster medium. For a given density and pressure of the medium, the spatial structure and energy partition at a given time tage (since the onset of the outburst) are fully determined by the total injected energy Einj and the duration tb of the outburst. We are particularly interested in the late phase evolution when the strong shock transforms into a sound wave. We studied the energy partition during such transition with different combinations of Einj and tb. For an instantaneous outburst with tb → 0, which corresponds to the extension of classic Sedov-Taylor solution with counter-pressure, the fraction of energy that can be carried away by sound waves is ≲12 per cent of Einj. As tb increases, the solution approaches the 'slow piston' limit, with the fraction of energy in sound waves approaching zero. We then repeat the simulations using radial density and temperature profiles measured in Perseus and M87/Virgo clusters. We find that the results with a uniform medium broadly reproduce an outburst in more realistic conditions once proper scaling is applied. We also develop techniques to map intrinsic properties of an outburst (Einj, tb and tage) to the observables like the Mach number of the shock and radii of the shock and ejecta. For the Perseus cluster and M87, the estimated (Einj, tb and tage) agree with numerical simulations tailored for these objects with 20-30 per cent accuracy.
Energy Technology Data Exchange (ETDEWEB)
Zhuk, Alexander [The International Center of Future Science of the Jilin University, Changchun City (China); Odessa National University, Astronomical Observatory, Odessa (Ukraine); Chopovsky, Alexey; Fakhr, Seyed Hossein [Odessa National University, Astronomical Observatory, Odessa (Ukraine); Shulga, Valerii [The International Center of Future Science of the Jilin University, Changchun City (China); Institut of Radio Astronomy of National Academy of Sciences of Ukraine, Kharkov (Ukraine); Wei, Han [The International Center of Future Science of the Jilin University, Changchun City (China)
2017-11-15
In a multidimensional Kaluza-Klein model with Ricci-flat internal space, we study the gravitational field in the weak-field limit. This field is created by two coupled sources. First, this is a point-like massive body which has a dust-like equation of state in the external space and an arbitrary parameter Ω of equation of state in the internal space. The second source is a static spherically symmetric massive scalar field centered at the origin where the point-like massive body is. The found perturbed metric coefficients are used to calculate the parameterized post-Newtonian (PPN) parameter γ. We define under which conditions γ can be very close to unity in accordance with the relativistic gravitational tests in the solar system. This can take place for both massive or massless scalar fields. For example, to have γ ∼ 1 in the solar system, the mass of scalar field should be μ >or similar 5.05 x 10{sup -49} g ∝ 2.83 x 10{sup -16} eV. In all cases, we arrive at the same conclusion that to be in agreement with the relativistic gravitational tests, the gravitating mass should have tension: Ω = -1/2. (orig.)
Spherical photon orbits around a 5D Myers-Perry black hole
Bugden, Mark
2018-03-01
We study the motion of bound null geodesics with fixed coordinate radius around a five-dimensional rotating black hole. These spherical photon orbits are not confined to a plane, and can exhibit interesting quasiperiodic behaviour. We provide necessary conditions for the existence of these orbits, and explicitly compute the radii of circular orbits in the equatorial and polar planes. Finally, we plot representative examples of some of the types of possible orbits, commenting on their qualitative features.
Three-dimensional stationary cyclic symmetric Einstein-Maxwell solutions; black holes
International Nuclear Information System (INIS)
Garcia, Alberto A.
2009-01-01
From a general metric for stationary cyclic symmetric gravitational fields coupled to Maxwell electromagnetic fields within the (2 + 1)-dimensional gravity the uniqueness of wide families of exact solutions is established. Among them, all uniform electromagnetic solutions possessing electromagnetic fields with vanishing covariant derivatives, all fields having constant electromagnetic invariants F μν F μν and T μν T μν , the whole classes of hybrid electromagnetic solutions, and also wide classes of stationary solutions are derived for a third-order nonlinear key equation. Certain of these families can be thought of as black hole solutions. For the most general set of Einstein-Maxwell equations, reducible to three nonlinear equations for the three unknown functions, two new classes of solutions - having anti-de Sitter spinning metric limit - are derived. The relationship of various families with those reported by different authors' solutions has been established. Among the classes of solutions with cosmological constant a relevant place is occupied by the electrostatic and magnetostatic Peldan solutions, the stationary uniform and spinning Clement classes, the constant electromagnetic invariant branches with the particular Kamata-Koikawa solution, the hybrid cyclic symmetric stationary black hole fields, and the non-less important solutions generated via SL(2,R)-transformations where the Clement spinning charged solution, the Martinez-Teitelboim-Zanelli black hole solution, and Dias-Lemos metric merit mention.
Energy Technology Data Exchange (ETDEWEB)
Burikham, Piyabut [Chulalongkorn University, High Energy Physics Theory Group, Department of Physics, Faculty of Science, Bangkok (Thailand); Cheamsawat, Krai [Chulalongkorn University, High Energy Physics Theory Group, Department of Physics, Faculty of Science, Bangkok (Thailand); Imperial College, Theoretical Physics Group, Blackett Laboratory, London (United Kingdom); Harko, Tiberiu [Babes-Bolyai University, Department of Physics, Cluj-Napoca (Romania); University College London, Department of Mathematics, London (United Kingdom); Lake, Matthew J. [Naresuan University, The Institute for Fundamental Study, ' ' The Tah Poe Academia Institute' ' , Phitsanulok (Thailand); Ministry of Education, Thailand Center of Excellence in Physics, Bangkok (Thailand)
2016-03-15
We obtain bounds for the minimum and maximum mass/radius ratio of a stable, charged, spherically symmetric compact object in a D-dimensional space-time in the framework of general relativity, and in the presence of dark energy. The total energy, including the gravitational component, and the stability of objects with minimum mass/radius ratio is also investigated. The minimum energy condition leads to a representation of the mass and radius of the charged objects with minimum mass/radius ratio in terms of the charge and vacuum energy only. As applied to the electron in the four-dimensional case, this procedure allows one to re-obtain the classical electron radius from purely general relativistic considerations. By combining the lower mass bound, in four space-time dimensions, with minimum length uncertainty relations (MLUR) motivated by quantum gravity, we obtain an alternative bound for the maximum charge/mass ratio of a stable, gravitating, charged quantum mechanical object, expressed in terms of fundamental constants. Evaluating this limit numerically, we obtain again the correct order of magnitude value for the charge/mass ratio of the electron, as required by the stability conditions. This suggests that, if the electron were either less massive (with the same charge) or if its charge were any higher (for fixed mass), a combination of electrostatic and dark energy repulsion would destabilize the Compton radius. In other words, the electron would blow itself apart. Our results suggest the existence of a deep connection between gravity, the presence of the cosmological constant, and the stability of fundamental particles. (orig.)
Izquierdo, Germán; Blanquet-Jaramillo, Roberto C.; Sussman, Roberto A.
2018-01-01
The quasi-local scalar variables approach is applied to a spherically symmetric inhomogeneous Lemaître-Tolman-Bondi metric containing a mixture of non-relativistic cold dark matter and coupled dark energy with constant equation of state. The quasi-local coupling term considered is proportional to the quasi-local cold dark matter energy density and a quasi-local Hubble factor-like scalar via a coupling constant α . The autonomous numerical system obtained from the evolution equations is classified for different choices of the free parameters: the adiabatic constant of the dark energy w and α . The presence of a past attractor in a non-physical region of the energy densities phase-space of the system makes the coupling term non physical when the energy flows from the matter to the dark energy in order to avoid negative values of the dark energy density in the past. On the other hand, if the energy flux goes from dark energy to dark matter, the past attractor lies in a physical region. The system is also numerically solved for some interesting initial profiles leading to different configurations: an ever expanding mixture, a scenario where the dark energy is completely consumed by the non-relativistic matter by means of the coupling term, a scenario where the dark energy disappears in the inner layers while the outer layers expand as a mixture of both sources, and, finally, a structure formation toy model scenario, where the inner shells containing the mixture collapse while the outer shells expand.
Hysteresis in η /s for QFTs dual to spherical black holes
Cadoni, Mariano; Franzin, Edgardo; Tuveri, Matteo
2017-12-01
We define and compute the (analog) shear viscosity to entropy density ratio \\tilde{η }/s for the QFTs dual to spherical AdS black holes both in Einstein and Gauss-Bonnet gravity in five spacetime dimensions. Although in this case, owing to the lack of translational symmetry of the background, \\tilde{η } does not have the usual hydrodynamic meaning, it can be still interpreted as the rate of entropy production due to a strain. At large and small temperatures it is found that \\tilde{η }/s is a monotonic increasing function of the temperature. In particular, at large temperatures it approaches a constant value, whereas at small temperatures, when the black hole has a regular, stable extremal limit, \\tilde{η }/s goes to zero with scaling law behavior. Whenever the phase diagram of the black hole has a Van der Waals-like behavior, i.e. it is characterized by the presence of two stable states (small and large black holes), connected by a meta-stable region (intermediate black holes), the system evolution must occur through the meta-stable region- and temperature-dependent hysteresis of \\tilde{η }/s is generated by non-equilibrium thermodynamics.
Hysteresis in η/s for QFTs dual to spherical black holes
Energy Technology Data Exchange (ETDEWEB)
Cadoni, Mariano; Franzin, Edgardo; Tuveri, Matteo [Cagliari Univ., Monserrato (Italy). Dipt. di Fisica; INFN, Sezione di Cagliari, Monserrato (Italy)
2017-12-15
We define and compute the (analog) shear viscosity to entropy density ratio η/s for the QFTs dual to spherical AdS black holes both in Einstein and Gauss-Bonnet gravity in five spacetime dimensions. Although in this case, owing to the lack of translational symmetry of the background, η does not have the usual hydrodynamic meaning, it can be still interpreted as the rate of entropy production due to a strain. At large and small temperatures it is found that η/s is a monotonic increasing function of the temperature. In particular, at large temperatures it approaches a constant value, whereas at small temperatures, when the black hole has a regular, stable extremal limit, η/s goes to zero with scaling law behavior. Whenever the phase diagram of the black hole has a Van der Waals-like behavior, i.e. it is characterized by the presence of two stable states (small and large black holes), connected by a meta-stable region (intermediate black holes), the system evolution must occur through the meta-stable region- and temperature-dependent hysteresis of η/s is generated by non-equilibrium thermodynamics. (orig.)
Quasinormal modes of plane-symmetric black holes according to the AdS/CFT correspondence
Miranda, Alex S.; Morgan, Jaqueline; Zanchin, Vilson T.
2008-11-01
The electromagnetic and gravitational quasinormal spectra of (3+1)-dimensional plane-symmetric anti-de Sitter black holes are analyzed in the context of the AdS/CFT correspondence. According to such a correspondence, the electromagnetic and gravitational quasinormal frequencies of these black holes are associated respectively to the poles of retarded correlation functions of R-symmetry currents and stress-energy tensor in the holographically dual conformal field theory: the (2+1)-dimensional Script N = 8 super-Yang-Mills theory. The connection between AdS black holes and the corresponding field theory is used to unambiguously fix the boundary conditions that enter the proper definition of quasinormal modes. Such a procedure also helps one to decide, among the various different possibilities, what are the appropriate gauge-invariant quantities one should use in order to correctly describe the electromagnetic and gravitational blackhole perturbations. These choices imply in different dispersion relations for the quasinormal modes when compared to some of the results in the literature. In particular, the long-distance, low-frequency limit of dispersion relations presents the characteristic hydrodynamic behavior of a conformal field theory with the presence of diffusion, shear, and sound wave modes. There is also a family of purely damped electromagnetic modes which tend to the bosonic Matsubara frequencies in the long-wavelength regime.
Quasinormal modes of plane-symmetric black holes according to the AdS/CFT correspondence
International Nuclear Information System (INIS)
Miranda, Alex S.; Morgan, Jaqueline; Zanchin, Vilson T.
2008-01-01
The electromagnetic and gravitational quasinormal spectra of (3+1)-dimensional plane-symmetric anti-de Sitter black holes are analyzed in the context of the AdS/CFT correspondence. According to such a correspondence, the electromagnetic and gravitational quasinormal frequencies of these black holes are associated respectively to the poles of retarded correlation functions of R-symmetry currents and stress-energy tensor in the holographically dual conformal field theory: the (2+1)-dimensional N = 8 super-Yang-Mills theory. The connection between AdS black holes and the corresponding field theory is used to unambiguously fix the boundary conditions that enter the proper definition of quasinormal modes. Such a procedure also helps one to decide, among the various different possibilities, what are the appropriate gauge-invariant quantities one should use in order to correctly describe the electromagnetic and gravitational blackhole perturbations. These choices imply in different dispersion relations for the quasinormal modes when compared to some of the results in the literature. In particular, the long-distance, low-frequency limit of dispersion relations presents the characteristic hydrodynamic behavior of a conformal field theory with the presence of diffusion, shear, and sound wave modes. There is also a family of purely damped electromagnetic modes which tend to the bosonic Matsubara frequencies in the long-wavelength regime.
Hoseinzadeh, S.; Rezaei-Aghdam, A.
2017-10-01
We introduce a four-dimensional extension of the Poincaré algebra (N) in (1 + 1)-dimensional space-time and obtain a (1 + 1)-dimensional gauge symmetric gravity model using the algebra N. We show that the obtained gravity model is dual (canonically transformed) to the (1 + 1)-dimensional anti de Sitter (AdS) gravity. We also obtain some black hole and Friedmann-Robertson-Walker (FRW) solutions by solving its classical equations of motion. Then, we study A4,8A1/⊗A1 gauged Wess-Zumino-Witten (WZW) model and obtain some exact black hole and cosmological solutions in string theory. We show that some obtained black hole and cosmological metrics in string theory are same as the metrics obtained in solutions of our gauge symmetric gravity model.
International Nuclear Information System (INIS)
Nagatani, Yukinori
2004-01-01
We investigate the Hawking radiation in the gauge Higgs-Yukawa theory. The ballistic model is proposed as an effective description of the system. We find that a spherical domain wall around the black hole is formed by field dynamics rather than thermal phase transition. The formation is a general property of the black hole whose Hawking temperature is equal to or greater than the energy scale of the theory. The formation of the electroweak wall and that of the GUT wall are shown. We also find a phenomenon of the spontaneous charging-up of the black hole by the wall. The Hawking radiation drives a mechanism of the charge transportation into the black hole when C- and CP-violation are assumed. The mechanism can strongly transport the hyper-charge into a black hole of the electroweak scale
International Nuclear Information System (INIS)
El Ghazi, Haddou; Jorio, Anouar
2014-01-01
Within the framework of effective-mass approximation and finite parabolic potential barrier, single particle and ground-state interband recombination energies in Core|well|shell based on GaN|(In,Ga)N|GaN spherical QDQW are investigated as a function of the inner and the outer radii. The temperature dependency of effective-mass, band-gap energy and potential barrier is taken into account. Particle eigenvalue and band-gap energy competing effects are speculated to explain our numerical results which show that the interband recombination energy increases when the temperature increases. The results we obtained are in quite good agreement with the findings
Black hole evaporation in conformal gravity
Energy Technology Data Exchange (ETDEWEB)
Bambi, Cosimo; Rachwał, Lesław [Center for Field Theory and Particle Physics and Department of Physics, Fudan University, 220 Handan Road, 200433 Shanghai (China); Modesto, Leonardo [Department of Physics, Southern University of Science and Technology, 1088 Xueyuan Road, Shenzhen 518055 (China); Porey, Shiladitya, E-mail: bambi@fudan.edu.cn, E-mail: lmodesto@sustc.edu.cn, E-mail: shilp@iitk.ac.in, E-mail: rachwal@fudan.edu.cn [Department of Physics, Indian Institute of Technology, 208016 Kanpur (India)
2017-09-01
We study the formation and the evaporation of a spherically symmetric black hole in conformal gravity. From the collapse of a spherically symmetric thin shell of radiation, we find a singularity-free non-rotating black hole. This black hole has the same Hawking temperature as a Schwarzschild black hole with the same mass, and it completely evaporates either in a finite or in an infinite time, depending on the ensemble. We consider the analysis both in the canonical and in the micro-canonical statistical ensembles. Last, we discuss the corresponding Penrose diagram of this physical process.
Energy Technology Data Exchange (ETDEWEB)
Burikham, Piyabut; Cheamsawat, Krai [Chulalongkorn University, High Energy Physics Theory Group, Department of Physics, Faculty of Science, Bangkok (Thailand); Harko, Tiberiu [University College London, Department of Mathematics, London (United Kingdom); Lake, Matthew J. [Naresuan University, The Institute for Fundamental Study, ' ' The Tah Poe Academia Institute' ' , Phitsanulok (Thailand); Ministry of Education, Thailand Center of Excellence in Physics, Bangkok (Thailand)
2015-09-15
The existence of both a minimum mass and a minimum density in nature, in the presence of a positive cosmological constant, is one of the most intriguing results in classical general relativity. These results follow rigorously from the Buchdahl inequalities in four-dimensional de Sitter space. In this work, we obtain the generalized Buchdahl inequalities in arbitrary space-time dimensions with Λ ≠ 0 and consider both the de Sitter and the anti-de Sitter cases. The dependence on D, the number of space-time dimensions, of the minimum and maximum masses for stable spherical objects is explicitly obtained. The analysis is then extended to the case of dark energy satisfying an arbitrary linear barotropic equation of state. The Jeans instability of barotropic dark energy is also investigated, for arbitrary D, in the framework of a simple Newtonian model with and without viscous dissipation, and we determine the dispersion relation describing the dark energy-matter condensation process, along with estimates of the corresponding Jeans mass (and radius). Finally, the quantum mechanical implications of the mass limits are investigated, and we show that the existence of a minimum mass scale naturally leads to a model in which dark energy is composed of a 'sea' of quantum particles, each with an effective mass proportional to Λ{sup 1/4}. (orig.)
International Nuclear Information System (INIS)
Sussman, R.A.
1988-01-01
Geometrical and physical properties of the solutions derived and classified in Part I [J. Math. Phys. 28, 1118 (1987)] are examined in detail. It is shown how the imposition of zero shear restricts the possible choices of equations of state. Two types of singular boundaries arising in these solutions are examined by verifying the local behavior of causal curves approaching these boundaries. For this purpose, a criterion due to C. J. S. Clarke (private communication) is given, allowing one to test the completeness of arbitrary accelerated timelike curves in terms of their acceleration and proper time. One of these boundaries is a spacelike singularity at which causal curves terminate as pressure diverges but matter-energy and charge densities remain finite. At the other boundary, which is timelike if the expansion Θ is finite, proper volume of local fluid elements vanishes as all state variables diverge but causal curves are complete. If Θ diverges at this boundary, a null singularity arises as the end product of the collapse of a two-sphere generated by a given class of timelike curves. The gravitational collapse of bounded spheres matched to a Schwarzschild or Reissner--Nordstroem exterior is also examined in detail. It is shown that the spacelike singularity mentioned above could be naked under certain parameter choices. Solutions presenting the other boundary produce very peculiar black holes in which the ''surface'' of the sphere collapses into the above mentioned null singularity, while the ''interior'' fluid layers avoid this singularity and evolve towards their infinite future
Rotating black holes can have short bristles
Directory of Open Access Journals (Sweden)
Shahar Hod
2014-12-01
Full Text Available The elegant ‘no short hair’ theorem states that, if a spherically-symmetric static black hole has hair, then this hair must extend beyond 3/2 the horizon radius. In the present paper we provide evidence for the failure of this theorem beyond the regime of spherically-symmetric static black holes. In particular, we show that rotating black holes can support extremely short-range stationary scalar configurations (linearized scalar ‘clouds’ in their exterior regions. To that end, we solve analytically the Klein–Gordon–Kerr–Newman wave equation for a linearized massive scalar field in the regime of large scalar masses.
A black hole with torsion in 5D Lovelock gravity
Cvetković, B.; Simić, D.
2018-03-01
We analyze static spherically symmetric solutions of five dimensional (5D) Lovelock gravity in the first order formulation. In the Riemannian sector, when torsion vanishes, the Boulware–Deser black hole represents a unique static spherically symmetric black hole solution for the generic choice of the Lagrangian parameters. We show that a special choice of the Lagrangian parameters, different from the Lovelock Chern–Simons gravity, leads to the existence of a static black hole solution with torsion, the metric of which is asymptotically anti-de Sitter (AdS). We calculate the conserved charges and thermodynamical quantities of this black hole solution.
A charged spherically symmetric solution
Indian Academy of Sciences (India)
By setting the charge contribution to zero we regain an (uncharged) perfect ﬂuid solution found previously with the equation of state =+ constant, which is a generalisation of a stiff equation of state. Our class of ... Govinder1. School of Mathematical and Statistical Sciences, University of Natal, Durban 4041, South Africa ...
Spherically symmetric scalar field collapse
Indian Academy of Sciences (India)
2013-03-01
Mar 1, 2013 ... Abstract. It is shown that a scalar field, minimally coupled to gravity, may have collapsing modes even when the energy condition is violated, that is, for (ρ + 3p) < 0. This result may be useful in the investigation of the possible clustering of dark energy. All the examples dealt with have apparent horizons ...
Spherically symmetric scalar field collapse
Indian Academy of Sciences (India)
It is shown that a scalar field, minimally coupled to gravity, may have collapsing modes even when the energy condition is violated, that is, for ( + 3) < 0. This result may be useful in the investigation of the possible clustering of dark energy. All the examples dealt with have apparent horizons formed before the formation of ...
Black holes and traversible wormholes: a synthesis
Hayward, Sean A.
2002-01-01
A unified framework for black holes and traversible wormholes is described, where both are locally defined by outer trapping horizons, two-way traversible for wormholes and one-way traversible for black or white holes. In a two-dimensional dilaton gravity model, examples are given of: construction of wormholes from black holes; operation of wormholes for transport, including back-reaction; maintenance of an operating wormhole; and collapse of wormholes to black holes. In spherically symmetric...
Effect of scalar field mass on gravitating charged scalar solitons and black holes in a cavity
Energy Technology Data Exchange (ETDEWEB)
Ponglertsakul, Supakchai, E-mail: supakchai.p@gmail.com; Winstanley, Elizabeth, E-mail: E.Winstanley@sheffield.ac.uk
2017-01-10
We study soliton and black hole solutions of Einstein charged scalar field theory in cavity. We examine the effect of introducing a scalar field mass on static, spherically symmetric solutions of the field equations. We focus particularly on the spaces of soliton and black hole solutions, as well as studying their stability under linear, spherically symmetric perturbations of the metric, electromagnetic field, and scalar field.
Sufficient condition for black-hole formation in spherical gravitational collapse
International Nuclear Information System (INIS)
Giambo, Roberto; Giannoni, Fabio; Magli, Giulio
2002-01-01
A sufficient condition for the validity of cosmic censorship in spherical gravitational collapse is formulated and proved. The condition relies on an attractive mathematical property of the apparent horizon, which holds if 'minimal' requirements of physical reasonableness are satisfied by the matter model. (letter to the editor)
Black Hole Space-time In Dark Matter Halo
Xu, Zhaoyi; Hou, Xian; Gong, Xiaobo; Wang, Jiancheng
2018-01-01
For the first time, we obtain the analytical form of black hole space-time metric in dark matter halo for the stationary situation. Using the relation between the rotation velocity (in the equatorial plane) and the spherical symmetric space-time metric coefficient, we obtain the space-time metric for pure dark matter. By considering the dark matter halo in spherical symmetric space-time as part of the energy-momentum tensors in the Einstein field equation, we then obtain the spherical symmetr...
Rotating black hole and quintessence
International Nuclear Information System (INIS)
Ghosh, Sushant G.
2016-01-01
We discuss spherically symmetric exact solutions of the Einstein equations for quintessential matter surrounding a black hole, which has an additional parameter (ω) due to the quintessential matter, apart from the mass (M). In turn, we employ the Newman-Janis complex transformation to this spherical quintessence black hole solution and present a rotating counterpart that is identified, for α = -e 2 ≠ 0 and ω = 1/3, exactly as the Kerr-Newman black hole, and as the Kerr black hole when α = 0. Interestingly, for a given value of parameter ω, there exists a critical rotation parameter (a = a E ), which corresponds to an extremal black hole with degenerate horizons, while for a < a E , it describes a nonextremal black hole with Cauchy and event horizons, and no black hole for a > a E . We find that the extremal value a E is also influenced by the parameter ω and so is the ergoregion. (orig.)
Matter ouside a Static Higher-dimensional Black Hole
Rogatko, Marek
2012-01-01
We considered matter fields composed of a perfect fluid in the static higher-dimensional spherically symmetric asymptotically flat black hole spacetime. The proof of the nonexistence of perfect fluid matter in such a background was provided under the auxiliary condition, which can be interpreted as a relation connecting the stellar mass and the black hole mass in question.
Energy Technology Data Exchange (ETDEWEB)
Clarisse, J.M
2007-07-01
A numerical scheme for computing linear Lagrangian perturbations of spherically symmetric flows of gas dynamics is proposed. This explicit first-order scheme uses the Roe method in Lagrangian coordinates, for computing the radial spherically symmetric mean flow, and its linearized version, for treating the three-dimensional linear perturbations. Fulfillment of the geometric conservation law discrete formulations for both the mean flow and its perturbation is ensured. This scheme capabilities are illustrated by the computation of free-surface mode evolutions at the boundaries of a spherical hollow shell undergoing an homogeneous cumulative compression, showing excellent agreement with reference results. (author)
Black-hole creation in quantum cosmology
Energy Technology Data Exchange (ETDEWEB)
Zhong Chao, Wu [Rome, Univ. `La Sapienza` (Italy). International Center for Relativistic Astrophysics]|[Specola Vaticana, Vatican City State (Vatican City State, Holy See)
1997-11-01
It is proven that the probability of a black hole created from the de Sitter space-time background, at the Wkb level, is the exponential of one quarter of the sum of the black hole and cosmological horizon areas, or the total entropy of the universe. This is true not only for the spherically symmetric cases of the Schwarzschild or Reissner-Nordstroem black holes, but also for the rotating cases of the Kerr black hole and the rotating charged case of the Newman black hole. The de Sitter metric is the most probable evolution at the Planckian era of the universe.
March, N. H.; Nagy, Á.
2008-10-01
The differential virial theorem relates the force -∂V/∂r associated with the one-body potential V(r) of density-functional theory to the Laplacian ∇2n of the ground-state density n(r) and to a quantity zs(r) involving the kinetic energy density tensor tαβ(r) . Having the concept of the Pauli potential VP(r) , zs is derived for spherically symmetric ground-state densities n(r) in terms of the von Weizsäcker kinetic energy density and the first derivative of VP(r) . zs is related solely to the gradient kinetic energy density tG(r) for Be-like atomic ions.
Asymptotically flat, stable black hole solutions in Einstein-Yang-Mills-Chern-Simons theory.
Brihaye, Yves; Radu, Eugen; Tchrakian, D H
2011-02-18
We construct finite mass, asymptotically flat black hole solutions in d=5 Einstein-Yang-Mills-Chern-Simons theory. Our results indicate the existence of a second order phase transition between Reissner-Nordström solutions and the non-Abelian black holes which generically are thermodynamically preferred. Some of the non-Abelian configurations are also stable under linear, spherically symmetric perturbations.
Accretion onto some well-known regular black holes
International Nuclear Information System (INIS)
Jawad, Abdul; Shahzad, M.U.
2016-01-01
In this work, we discuss the accretion onto static spherically symmetric regular black holes for specific choices of the equation of state parameter. The underlying regular black holes are charged regular black holes using the Fermi-Dirac distribution, logistic distribution, nonlinear electrodynamics, respectively, and Kehagias-Sftesos asymptotically flat regular black holes. We obtain the critical radius, critical speed, and squared sound speed during the accretion process near the regular black holes. We also study the behavior of radial velocity, energy density, and the rate of change of the mass for each of the regular black holes. (orig.)
Black holes and relativitic gravity theories
Fennelly, A. J.; Pavelle, R.
1977-01-01
All presently known relativistic gravitation theories were considered which have a Riemannian background geometry and possess exact static, spherically symmetric solutions which are asymptotically flat. Each theory predicts the existence of trapped surfaces (black holes). For a general static isotropic metric, MACSYMA was used to compute the Newman-Penrose equations, the black hole radius, the impact parameter, and capture radius for photon accretion. These results were then applied to several of the better known gravitation theories.
International Nuclear Information System (INIS)
Martel, Karl; Poisson, Eric
2002-01-01
A one-parameter family of time-symmetric initial data for the radial infall of a particle into a Schwarzschild black hole is constructed within the framework of black-hole perturbation theory. The parameter measures the amount of gravitational radiation present on the initial spacelike surface. These initial data sets are then evolved by integrating the Zerilli-Moncrief wave equation in the presence of the particle. Numerical results for the gravitational waveforms and their power spectra are presented; we show that the choice of initial data strongly influences the waveforms, both in their shapes and their frequency content. We also calculate the total energy radiated by the particle-black-hole system, as a function of the initial separation between the particle and the black hole, and as a function of the choice of initial data. Our results confirm that for large initial separations, a conformally flat initial three-geometry minimizes the initial gravitational-wave content, so that the total energy radiated is also minimized. For small initial separations, however, we show that the conformally flat solution no longer minimizes the energy radiated
Moduli and (un)attractor black hole thermodynamics
Astefanesei, D.; Goldstein, K.D.; Mahapatra, S.
2008-01-01
We investigate four-dimensional spherically symmetric black hole solutions in gravity theories with massless, neutral scalars non-minimally coupled to gauge fields. In the non-extremal case, we explicitly show that, under the variation of the moduli, the scalar charges appear in the first law of
A Brief Observational History of the Black-Hole Spacetimes
Directory of Open Access Journals (Sweden)
Wolfgang Kundt
2015-01-01
Full Text Available In this year (2015, black holes (BHs celebrate their 100th birthday, if their birth is taken to be triggered by a handwritten letter from Martin Schwarzschild to Albert Einstein, in connection with his newly found spherically symmetric vacuum solution.
Charged black holes in Hořava gravity
International Nuclear Information System (INIS)
Janiszewski, Stefan; Karch, Andreas; Robinson, Brandon; Sommer, David
2014-01-01
We explore static spherically symmetric black hole solutions allowing a bulk U(1) vector field in the khronometric formulation of Hořava gravity by way of Einstein-Æther. We examine analytic solutions and study numerical results in the limit that the khronon does not backreact on the metric
Monten, Ruben; Toldo, Chiara
2018-02-01
We present new AdS4 black hole solutions in N =2 gauged supergravity coupled to vector and hypermultiplets. We focus on a particular consistent truncation of M-theory on the homogeneous Sasaki–Einstein seven-manifold M 111, characterized by the presence of one Betti vector multiplet. We numerically construct static and spherically symmetric black holes with electric and magnetic charges, corresponding to M2 and M5 branes wrapping non-contractible cycles of the internal manifold. The novel feature characterizing these nonzero temperature configurations is the presence of a massive vector field halo. Moreover, we verify the first law of black hole mechanics and we study the thermodynamics in the canonical ensemble. We analyze the behavior of the massive vector field condensate across the small-large black hole phase transition and we interpret the process in the dual field theory.
International Nuclear Information System (INIS)
Dias, Goncalo A. S.; Lemos, Jose P. S.
2009-01-01
The Hamiltonian thermodynamics formalism is applied to the general d-dimensional Reissner-Nordstroem-anti-de Sitter black hole with spherical, planar, and hyperbolic horizon topology. After writing its action and performing a Legendre transformation, surface terms are added in order to guarantee a well-defined variational principle with which to obtain sensible equations of motion, and also to allow later on the thermodynamical analysis. Then a Kuchar canonical transformation is done, which changes from the metric canonical coordinates to the physical parameters coordinates. Again, a well-defined variational principle is guaranteed through boundary terms. These terms influence the falloff conditions of the variables and at the same time the form of the new Lagrange multipliers. Reduction to the true degrees of freedom is performed, which are the conserved mass and charge of the black hole. Upon quantization a Lorentzian partition function Z is written for the grand canonical ensemble, where the temperature T and the electric potential φ are fixed at infinity. After imposing Euclidean boundary conditions on the partition function, the respective effective action I * , and thus the thermodynamical partition function, is determined for any dimension d and topology k. This is a quite general action. Several previous results can be then condensed in our single general formula for the effective action I * . Phase transitions are studied for the spherical case, and it is shown that all the other topologies have no phase transitions. A parallel with the Bose-Einstein condensation can be established. Finally, the expected values of energy, charge, and entropy are determined for the black hole solution.
Soft black hole absorption rates as conservation laws
Energy Technology Data Exchange (ETDEWEB)
Avery, Steven G. [Brown University, Department of Physics,182 Hope St, Providence, RI, 02912 (United States); Michigan State University, Department of Physics and Astronomy,East Lansing, MI, 48824 (United States); Schwab, Burkhard UniversityW. [Harvard University, Center for Mathematical Science and Applications,1 Oxford St, Cambridge, MA, 02138 (United States)
2017-04-10
The absorption rate of low-energy, or soft, electromagnetic radiation by spherically symmetric black holes in arbitrary dimensions is shown to be fixed by conservation of energy and large gauge transformations. We interpret this result as the explicit realization of the Hawking-Perry-Strominger Ward identity for large gauge transformations in the background of a non-evaporating black hole. Along the way we rederive and extend previous analytic results regarding the absorption rate for the minimal scalar and the photon.
Black Holes in Supergravity: the non-BPS Branch
Gimon, Eric G; Simon, Joan; PH-TH
2008-01-01
We construct extremal, spherically symmetric black hole solutions to 4D supergravity with charge assignments that preclude BPS-saturation. In particular, we determine the ground state energy as a function of charges and moduli. We find that the mass of the non-BPS black hole remains that of a marginal bound state of four basic constituents throughout the entire moduli space and that there is always a non-zero gap above the BPS bound.
Black holes in supergravity: the non-BPS branch
Energy Technology Data Exchange (ETDEWEB)
Gimon, Eric; Gimon, Eric G.; Larsen, Finn; Simon, Joan
2007-10-25
We construct extremal, spherically symmetric black hole solutions to 4D supergravity with charge assignments that preclude BPS-saturation. In particular, we determine the ground state energy as a function of charges and moduli. We find that the mass of the non-BPS black hole remains that of a marginal bound state of four basic constituents throughout the entire moduli space and that there is always a non-zero gap above the BPS bound.
Fundamentals of spherical array processing
Rafaely, Boaz
2015-01-01
This book provides a comprehensive introduction to the theory and practice of spherical microphone arrays. It is written for graduate students, researchers and engineers who work with spherical microphone arrays in a wide range of applications. The first two chapters provide the reader with the necessary mathematical and physical background, including an introduction to the spherical Fourier transform and the formulation of plane-wave sound fields in the spherical harmonic domain. The third chapter covers the theory of spatial sampling, employed when selecting the positions of microphones to sample sound pressure functions in space. Subsequent chapters present various spherical array configurations, including the popular rigid-sphere-based configuration. Beamforming (spatial filtering) in the spherical harmonics domain, including axis-symmetric beamforming, and the performance measures of directivity index and white noise gain are introduced, and a range of optimal beamformers for spherical arrays, includi...
An investigation of embeddings for spherically symmetric ...
Indian Academy of Sciences (India)
Abstract. Embeddings into higher dimensions are very important in the study of higher- dimensional theories of our Universe and in high-energy physics. Theorems which have been developed recently guarantee the existence of embeddings of pseudo-Riemannian manifolds into. Einstein spaces and more general ...
An investigation of embeddings for spherically symmetric ...
Indian Academy of Sciences (India)
These results provide a technique that can be used to determine solutions for such embeddings. Here we consider local isometric ... Jothi Moodley1 Gareth Amery1. Astrophysics and Cosmology Research Unit, School of Mathematical Sciences, University of KwaZulu-Natal, Private Bag X54001, Durban 4000, South Africa ...
Gao, Changjun; Lu, Youjun; Shen, You-Gen; Faraoni, Valerio
2018-01-01
The Hawking-Penrose singularity theorem states that a singularity forms inside a black hole in general relativity. To remove this singularity one must resort to a more fundamental theory. Using a corrected dynamical equation arising in loop quantum cosmology and braneworld models, we study the gravitational collapse of a perfect fluid sphere with a rather general equation of state. In the frame of an observer comoving with this fluid, the sphere pulsates between a maximum and a minimum size, avoiding the singularity. The exterior geometry is also constructed. There are usually an outer and an inner apparent horizon, resembling the Reissner-Nordström situation. For a distant observer the horizon crossing occurs in an infinite time and the pulsations of the black hole quantum "beating heart" are completely unobservable. However, it may be observable if the black hole is not spherical symmetric and radiates gravitational wave due to the quadrupole moment, if any.
Information Retention by Stringy Black Holes
Ellis, John
2015-01-01
Building upon our previous work on two-dimensional stringy black holes and its extension to spherically-symmetric four-dimensional stringy black holes, we show how the latter retain information. A key r\\^ole is played by an infinite-dimensional $W_\\infty$ symmetry that preserves the area of an isolated black-hole horizon and hence its entropy. The exactly-marginal conformal world-sheet operator representing a massless stringy particle interacting with the black hole necessarily includes a contribution from $W_\\infty$ generators in its vertex function. This admixture manifests the transfer of information between the string black hole and external particles. We discuss different manifestations of $W_\\infty$ symmetry in black-hole physics and the connections between them.
International Nuclear Information System (INIS)
Ramond, P.
1993-01-01
The Wolfenstein parametrization is extended to the quark masses in the deep ultraviolet, and an algorithm to derive symmetric textures which are compatible with existing data is developed. It is found that there are only five such textures
Higher order WKB corrections to black hole entropy in brick wall formalism
Energy Technology Data Exchange (ETDEWEB)
Kim, Wontae [Sogang University, Center for Quantum Spacetime (CQUeST), Seoul (Korea, Republic of); Sogang University, Department of Physics, Seoul (Korea, Republic of); Kulkarni, Shailesh [Sogang University, Center for Quantum Spacetime (CQUeST), Seoul (Korea, Republic of)
2013-04-15
We calculate the statistical entropy of a quantum field with an arbitrary spin propagating on the spherical symmetric black hole background by using the brick wall formalism at higher orders in the WKB approximation. For general spins, we find that the correction to the standard Bekenstein-Hawking entropy depends logarithmically on the area of the horizon. Furthermore, we apply this analysis to the Schwarzschild and Schwarzschild-AdS(dS) black holes and discuss our results. (orig.)
Greybody factors for d-dimensional black holes
DEFF Research Database (Denmark)
Harmark, Troels; Natário, José; Schiappa, Ricardo
2010-01-01
Gravitational greybody factors are analytically computed for static, spherically symmetric black holes in d-dimensions, including black holes with charge and in the presence of a cosmological constant (where a proper definition of greybody factors for both asymptotically de Sitter and anti...... of the details of the black hole. For asymptotically de Sitter black holes the greybody factor is different for even or odd spacetime dimension, and proportional to the ratio of the areas of the event and cosmological horizons. For asymptotically Ads black holes the greybody factor has a rich structure in which...... universality is hidden in the transmission and reflection coefficients. For either charged or asymptotically de Sitter black holes the greybody factors are given by non-trivial functions, while for asymptotically Ads black holes the greybody factor precisely equals one (corresponding to pure blackbody emission)....
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.)
Quantum corrections to Schwarzschild black hole
Energy Technology Data Exchange (ETDEWEB)
Calmet, Xavier; El-Menoufi, Basem Kamal [University of Sussex, Department of Physics and Astronomy, Brighton (United Kingdom)
2017-04-15
Using effective field theory techniques, we compute quantum corrections to spherically symmetric solutions of Einstein's gravity and focus in particular on the Schwarzschild black hole. Quantum modifications are covariantly encoded in a non-local effective action. We work to quadratic order in curvatures simultaneously taking local and non-local corrections into account. Looking for solutions perturbatively close to that of classical general relativity, we find that an eternal Schwarzschild black hole remains a solution and receives no quantum corrections up to this order in the curvature expansion. In contrast, the field of a massive star receives corrections which are fully determined by the effective field theory. (orig.)
Thermodynamic properties of massive dilaton black holes II
Tamaki, Takashi
2002-01-01
We numerically reanalyze static and spherically symmetric black hole solutions in an Einstein-Maxwell-dilaton system with a dilaton potential $m_{d}^{2}\\phi^{2}$. We investigate thermodynamic properties for various dilaton coupling constants and find that thermodynamic properties change at a critical dilaton mass $m_{d,crit}$. For $m_{d}\\geq m_{d,crit}$, the black hole becomes an extreme solution for a nonzero horizon radius $r_{h,ex}$ as the Reissner-Nordstr\\"om black hole. However, if $m_{d...
Measuring the $W$-hair of String Black Holes
Ellis, Jonathan Richard; Nanopoulos, Dimitri V; Ellis, John
1992-01-01
We have argued previously that the infinitely many gauge symmetries of string theory provide an infinite set of conserved (gauge) quantum numbers ($W$-hair) which characterise black hole states and maintain quantum coherence. Here we study ways of measuring the $W$-hair of spherically-symmetric four-dimensional objects with event horizons, treated as effectively two-dimensional string black holes. Measurements can be done either through the s-wave scattering of light particles off the string black-hole background, or through interference experiments of Aharonov-Bohm type. In the first type of measurement, selection rules
Overcharging higher-dimensional black holes with point particles
Revelar, Karl Simon; Vega, Ian
2017-09-01
We investigate the possibility of overcharging spherically symmetric black holes in spacetime dimensions D >4 by the capture of a charged particle. We generalize Wald's classic result that extremal black holes cannot be overcharged. For nearly extremal black holes, we also generalize Hubeny's scenario by showing that overcharging is possible in a small region of parameter space. We check how D affects the overcharging parameter space and find that this appears to shrink in the large-D limit, which suggests that overcharging becomes increasingly difficult in higher dimensions.
How Spherical Is a Cube (Gravitationally)?
Sanny, Jeff; Smith, David
2015-01-01
An important concept that is presented in the discussion of Newton's law of universal gravitation is that the gravitational effect external to a spherically symmetric mass distribution is the same as if all of the mass of the distribution were concentrated at the center. By integrating over ring elements of a spherical shell, we show that the…
Generalizations of the Smarr formula for black holes with nonlinear electromagnetic fields
Gulin, Luka; Smolić, Ivica
2018-01-01
We present a direct, geometric derivation of the generalized Smarr formula for the stationary axially symmetric black holes with nonlinear electromagnetic fields. The additional term is proven to be proportional to the integral of the trace of the electromagnetic energy-momentum tensor and can be written as a product of two conjugate variables. From the novel relation we can deduce all previously proposed forms of the generalized Smarr formula, which were derived only for the spherically symmetric black holes, and provide the lowest order quantum correction to the classical relation from the Euler–Heisenberg Lagrangian.
Classical resolution of black hole singularities via wormholes
Energy Technology Data Exchange (ETDEWEB)
Olmo, Gonzalo J. [Universidad de Valencia, Departamento de Fisica Teorica and IFIC, Centro Mixto Universidad de Valencia-CSIC, Valencia (Spain); Universidade Federal da Paraiba, Departamento de Fisica, Joao Pessoa, Paraiba (Brazil); Rubiera-Garcia, D. [Universidade de Lisboa, Faculdade de Ciencias, Instituto de Astrofisica e Ciencias do Espaco, Lisbon (Portugal); Fudan University, Department of Physics, Center for Field Theory and Particle Physics, Shanghai (China); Sanchez-Puente, A. [Universidad de Valencia, Departamento de Fisica Teorica and IFIC, Centro Mixto Universidad de Valencia-CSIC, Valencia (Spain)
2016-03-15
In certain extensions of General Relativity, wormholes generated by spherically symmetric electric fields can resolve black hole singularities without necessarily removing curvature divergences. This is shown by studying geodesic completeness, the behavior of time-like congruences going through the divergent region, and by means of scattering of waves off the wormhole. This provides an example of the logical independence between curvature divergences and space-time singularities, concepts very often identified with each other in the literature. (orig.)
Wenninger, Magnus J
2012-01-01
Well-illustrated, practical approach to creating star-faced spherical forms that can serve as basic structures for geodesic domes. Complete instructions for making models from circular bands of paper with just a ruler and compass. Discusses tessellation, or tiling, and how to make spherical models of the semiregular solids and concludes with a discussion of the relationship of polyhedra to geodesic domes and directions for building models of domes. "". . . very pleasant reading."" - Science. 1979 edition.
Cohen, Taco S.; Geiger, Mario; Koehler, Jonas; Welling, Max
2018-01-01
Convolutional Neural Networks (CNNs) have become the method of choice for learning problems involving 2D planar images. However, a number of problems of recent interest have created a demand for models that can analyze spherical images. Examples include omnidirectional vision for drones, robots, and autonomous cars, molecular regression problems, and global weather and climate modelling. A naive application of convolutional networks to a planar projection of the spherical signal is destined t...
Dirac equation of spin particles and tunneling radiation from a Kinnersly black hole
Energy Technology Data Exchange (ETDEWEB)
Li, Guo-Ping; Zu, Xiao-Tao [University of Electronic Science and Technology of China, School of Physical Electronics, Chengdu (China); Feng, Zhong-Wen [University of Electronic Science and Technology of China, School of Physical Electronics, Chengdu (China); China West Normal University, College of Physics and Space Science, Nanchong (China); Li, Hui-Ling [University of Electronic Science and Technology of China, School of Physical Electronics, Chengdu (China); Shenyang Normal University, College of Physics Science and Technology, Shenyang (China)
2017-04-15
In curved space-time, the Hamilton-Jacobi equation is a semi-classical particle equation of motion, which plays an important role in the research of black hole physics. In this paper, starting from the Dirac equation of spin 1/2 fermions and the Rarita-Schwinger equation of spin 3/2 fermions, respectively, we derive a Hamilton-Jacobi equation for the non-stationary spherically symmetric gravitational field background. Furthermore, the quantum tunneling of a charged spherically symmetric Kinnersly black hole is investigated by using the Hamilton-Jacobi equation. The result shows that the Hamilton-Jacobi equation is helpful to understand the thermodynamic properties and the radiation characteristics of a black hole. (orig.)
Bopp-Podolsky black holes and the no-hair theorem
Cuzinatto, R. R.; de Melo, C. A. M.; Medeiros, L. G.; Pimentel, B. M.; Pompeia, P. J.
2018-01-01
Bopp-Podolsky electrodynamics is generalized to curved space-times. The equations of motion are written for the case of static spherically symmetric black holes and their exterior solutions are analyzed using Bekenstein's method. It is shown that the solutions split up into two parts, namely a non-homogeneous (asymptotically massless) regime and a homogeneous (asymptotically massive) sector which is null outside the event horizon. In addition, in the simplest approach to Bopp-Podolsky black holes, the non-homogeneous solutions are found to be Maxwell's solutions leading to a Reissner-Nordström black hole. It is also demonstrated that the only exterior solution consistent with the weak and null energy conditions is the Maxwell one. Thus, in the light of the energy conditions, it is concluded that only Maxwell modes propagate outside the horizon and, therefore, the no-hair theorem is satisfied in the case of Bopp-Podolsky fields in spherically symmetric space-times.
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
Quantum horizon fluctuations of an evaporating black hole
International Nuclear Information System (INIS)
Roura, Albert
2007-01-01
The quantum fluctuations of a black hole spacetime are studied within a low-energy effective field theory approach to quantum gravity. Our approach accounts for both intrinsic metric fluctuations and those induced by matter fields interacting with the gravitational field. Here we will concentrate on spherically symmetric fluctuations of the black hole horizon. Our results suggest that for a sufficiently massive evaporating black hole, fluctuations can accumulate over time and become significant well before reaching Planckian scales. In addition, we provide the sketch of a proof that the symmetrized two-point function of the stress-tensor operator smeared over a null hypersurface is actually divergent and discuss the implications for the analysis of horizon fluctuations. Finally, a natural way to probe quantum metric fluctuations near the horizon is briefly described
First Order Description of Black Holes in Moduli Space
Andrianopoli, Laura; Orazi, Emanuele; Trigiante, Mario
2007-01-01
We show that the second order field equations characterizing extremal solutions for spherically symmetric, stationary black holes are in fact implied by a system of first order equations given in terms of a prepotential W. This confirms and generalizes the results in hep-th/0702088. When the black holes are solutions of extended supergravities we are able to find an explicit expression for the prepotentials which reproduce all the attractors of the four dimensional N>2 theories. We discuss a possible extension of our considerations to the non extremal case.
Geometrothermodynamics of phantom AdS black holes
Energy Technology Data Exchange (ETDEWEB)
Quevedo, Hernando [Universidad Nacional Autonoma de Mexico, Instituto de Ciencias Nucleares, Mexico (Mexico); Universita di Roma ' ' La Sapienza' ' , Dipartimento di Fisica ed ICRANet, Rome (Italy); Quevedo, Maria N. [Facultad de Ciencias Basicas, Universidad Militar Nueva Granada, Departamento de Matematicas, Bogota (Colombia); Sanchez, Alberto [CIIDET, Departamento de Posgrado, Queretaro (Mexico)
2016-03-15
We show that to investigate the thermodynamic properties of charged phantom spherically symmetric anti-de Sitter black holes, it is necessary to consider the cosmological constant as a thermodynamic variable so that the corresponding fundamental equation is a homogeneous function defined on an extended equilibrium space. We explore all the thermodynamic properties of this class of black holes by using the classical physical approach, based upon the analysis of the fundamental equation, and the alternative mathematical approach as proposed in geometrothermodynamics. We show that both approaches are compatible and lead to equivalent results. (orig.)
On the motion of hairy black holes in Einstein-Maxwell-dilaton theories
Julié, Félix-Louis
2018-01-01
Starting from the static, spherically symmetric black hole solutions in massless Einstein-Maxwell-dilaton (EMD) theories, we build a "skeleton" action, that is, we phenomenologically replace black holes by an appropriate effective point particle action, which is well suited to the formal treatment of the many-body problem in EMD theories. We find that, depending crucially on the value of their scalar cosmological environment, black holes can undergo steep "scalarization" transitions, inducing large deviations to the general relativistic two-body dynamics, as shown, for example, when computing the first post-Keplerian Lagrangian of EMD theories.
Abundant stable gauge field hair for black holes in anti-de Sitter space.
Baxter, J E; Helbling, Marc; Winstanley, Elizabeth
2008-01-11
We present new hairy black hole solutions of SU(N) Einstein-Yang-Mills (EYM) theory in asymptotically anti-de Sitter (AdS) space. These black holes are described by N+1 independent parameters and have N-1 independent gauge field degrees of freedom. Solutions in which all gauge field functions have no zeros exist for all N, and for a sufficiently large (and negative) cosmological constant. At least some of these solutions are shown to be stable under classical, linear, spherically symmetric perturbations. Therefore there is no upper bound on the amount of stable gauge field hair with which a black hole in AdS can be endowed.
Spherical symmetry as a test case for unconstrained hyperboloidal evolution
International Nuclear Information System (INIS)
Vañó-Viñuales, Alex; Husa, Sascha; Hilditch, David
2015-01-01
We consider the hyperboloidal initial value problem for the Einstein equations in numerical relativity, motivated by the goal to evolve radiating compact objects such as black hole binaries with a numerical grid that includes null infinity. Unconstrained evolution schemes promise optimal efficiency, but are difficult to regularize at null infinity, where the compactified Einstein equations are formally singular. In this work we treat the spherically symmetric case, which already poses nontrivial problems and constitutes an important first step. We have carried out stable numerical evolutions with the generalized BSSN and Z4 equations coupled to a scalar field. The crucial ingredients have been to find an appropriate evolution equation for the lapse function and to adapt constraint damping terms to handle null infinity. (paper)
Wormholes and black universes without phantom fields in Einstein-Cartan theory
Bronnikov, K. A.; Galiakhmetov, A. M.
2016-12-01
We obtain a family of regular static, spherically symmetric solutions in Einstein-Cartan theory with an electromagnetic field and a nonminimally coupled scalar field with the correct sign of kinetic energy density. At different values of its parameters, the solution, being asymptotically flat at large values of the radial coordinate, describes (i) twice asymptotically flat symmetric wormholes, (ii) asymmetric wormholes with an AdS asymptotic at the "far end," (iii) regular black holes with an extremal horizon or two simple horizons, and (iv) black universes with a de Sitter asymptotic at the far end. As in other black universe models, it is a black hole as seen by a distant observer, but beyond its horizon there is a nonsingular expanding universe. In all these cases, both the metric and the torsion are regular in the whole space.
Bronnikov, K A; Fabris, J C
2006-06-30
We study self-gravitating, static, spherically symmetric phantom scalar fields with arbitrary potentials (favored by cosmological observations) and single out 16 classes of possible regular configurations with flat, de Sitter, and anti-de Sitter asymptotics. Among them are traversable wormholes, bouncing Kantowski-Sachs (KS) cosmologies, and asymptotically flat black holes (BHs). A regular BH has a Schwarzschild-like causal structure, but the singularity is replaced by a de Sitter infinity, giving a hypothetic BH explorer a chance to survive. It also looks possible that our Universe has originated in a phantom-dominated collapse in another universe, with KS expansion and isotropization after crossing the horizon. Explicit examples of regular solutions are built and discussed. Possible generalizations include k-essence type scalar fields (with a potential) and scalar-tensor gravity.
Cuspidal discrete series for semisimple symmetric spaces
DEFF Research Database (Denmark)
Andersen, Nils Byrial; Flensted-Jensen, Mogens; Schlichtkrull, Henrik
2012-01-01
We propose a notion of cusp forms on semisimple symmetric spaces. We then study the real hyperbolic spaces in detail, and show that there exists both cuspidal and non-cuspidal discrete series. In particular, we show that all the spherical discrete series are non-cuspidal. (C) 2012 Elsevier Inc. All...
Quantum and thermodynamical aspects of black holes
International Nuclear Information System (INIS)
Sande e Lemos, J.P. de.
1982-08-01
The collapse of a spherically symmetric matter distribution resulting in Schwarzschild's black holes (BH) is discussed. Using Kerr metric, some dynamical results envolving test particles orbiting around BH with rotation are obtained. Quantum field theory is used to discuss the results obtained by Hawking in which one BH can emit a stationary flux of particles working a BH in a given temperature. Then, thermodynamics is introduced, some properties are verified and some phenomena of BH-radiation and BH-BH interaction are studied. (L.C.) [pt
Exact black hole formation in three dimensions
Directory of Open Access Journals (Sweden)
Wei Xu
2014-11-01
Full Text Available We consider three dimensional Einstein gravity non-minimally coupled to a real scalar field with a self-interacting scalar potential and present the exact black hole formation in three dimensions. Firstly we obtain an exact time-dependent spherically symmetric solution describing the gravitational collapse to a scalar black hole at the infinite time, i.e. in the static limit. The solution can only be asymptotically AdS because of the No–Go theorem in three dimensions which is resulting from the existence of a smooth black hole horizon. Then we analyze their geometric properties and properties of the time evolution. We also get the exact time-dependent solution in the minimal coupling model after taking a conformal transformation.
Accretion of Ghost Condensate by Black Holes
Energy Technology Data Exchange (ETDEWEB)
Frolov, A
2004-06-02
The intent of this letter is to point out that the accretion of a ghost condensate by black holes could be extremely efficient. We analyze steady-state spherically symmetric flows of the ghost fluid in the gravitational field of a Schwarzschild black hole and calculate the accretion rate. Unlike minimally coupled scalar field or quintessence, the accretion rate is set not by the cosmological energy density of the field, but by the energy scale of the ghost condensate theory. If hydrodynamical flow is established, it could be as high as tenth of a solar mass per second for 10MeV-scale ghost condensate accreting onto a stellar-sized black hole, which puts serious constraints on the parameters of the ghost condensate model.
Hairy black hole solutions in U(1) gauge-invariant scalar-vector-tensor theories
Heisenberg, Lavinia; Tsujikawa, Shinji
2018-05-01
In U (1) gauge-invariant scalar-vector-tensor theories with second-order equations of motion, we study the properties of black holes (BH) on a static and spherically symmetric background. In shift-symmetric theories invariant under the shift of scalar ϕ → ϕ + c, we show the existence of new hairy BH solutions where a cubic-order scalar-vector interaction gives rise to a scalar hair manifesting itself around the event horizon. In the presence of a quartic-order interaction besides the cubic coupling, there are also regular BH solutions endowed with scalar and vector hairs.
Optical properties of black holes in the presence of a plasma: The shadow
Abdujabbarov, Ahmadjon
2016-07-01
We have studied photon motion around axially symmetric rotating Kerr black holes in the presence of a plasma with radial power-law density. It is shown that in the presence of a plasma, the observed shape and size of the shadow changes depending on the (i) plasma parameters, (ii) black hole spin, and (iii) inclination angle between the observer plane and the axis of rotation of the black hole. In order to extract the pure effect of the plasma influence on the black hole image, the particular case of the Schwarzschild black hole has also been investigated and it has been shown that the photon sphere around the spherically symmetric black hole is left unchanged under the plasma influence; however, the Schwarzschild black hole shadow size in the plasma is reduced due to the refraction of the electromagnetic radiation in the plasma environment of the black hole. The study of the energy emission from the black hole in plasma environment shows that in the presence of the plasma the maximal energy emission rate from the black hole decreases.
Gravitational Field of Spherical Branes
Gogberashvili, Merab
The warped solution of Einstein's equations corresponding to the spherical brane in five-dimensional AdS is considered. This metric represents interiors of black holes on both sides of the brane and can provide gravitational trapping of physical fields on the shell. It is found that the analytic form of the coordinate transformations from the Schwarzschild to co-moving frame that exists only in five dimensions. It is shown that in the static coordinates active gravitational mass of the spherical brane, in agreement with Tolman's formula, is negative, i.e. such objects are gravitationally repulsive.
Nonlinear evolution of stellar spherical systems
Energy Technology Data Exchange (ETDEWEB)
Polyachenko, V.L. (AN SSSR, Irkutsk. Sibirskij Inst. Zemnogo Magnetizma Ionosfery i Rasprostraneniya Radiovoln)
1981-03-01
A universal method for computer realization of collisionless models according to a given distribution function is suggested. By employing this method it is shown that the development of instabilities in spherically-symmetric systems with nearly radial trajectories of the system constituents leads to a distinct elliptical deformation of the system.
Collapsing spherical null shells in general relativity
Directory of Open Access Journals (Sweden)
S Khakshournia
2011-03-01
Full Text Available In this work, the gravitational collapse of a spherically symmetric null shell with the flat interior and a charged Vaidya exterior spacetimes is studied. There is no gravitational impulsive wave present on the null hypersurface which is shear-free and contracting. It follows that there is a critical radius at which the shell bounces and starts expanding.
Hawking radiation from dilatonic black holes via anomalies
International Nuclear Information System (INIS)
Jiang Qingquan; Cai Xu; Wu Shuangqing
2007-01-01
Recently, Hawking radiation from a Schwarzschild-type black hole via a gravitational anomaly at the horizon has been derived by Robinson and Wilczek. Their result shows that, in order to demand general coordinate covariance at the quantum level to hold in the effective theory, the flux of the energy-momentum tensor required to cancel the gravitational anomaly at the horizon of the black hole is exactly equal to that of (1+1)-dimensional blackbody radiation at the Hawking temperature. In this paper, we attempt to apply the analysis to derive Hawking radiation from the event horizons of static, spherically symmetric dilatonic black holes with arbitrary coupling constant α, and that from the rotating Kaluza-Klein (α=√(3)) as well as the Kerr-Sen (α=1) black holes via an anomalous point of view. Our results support Robinson and Wilczek's opinion. In addition, the properties of the obtained physical quantities near the extreme limit are qualitatively discussed
Bose-Einstein condensates in charged black-hole spacetimes
Castellanos, Elías; Degollado, Juan Carlos; Lämmerzahl, Claus; Macías, Alfredo; Perlick, Volker
2018-01-01
We analyze Bose-Einstein condensates on three types of spherically symmetric and static charged black-hole spacetimes: the Reissner-Nordström spacetime, Hoffmann's Born-Infeld black-hole spacetime, and the regular Ayón-Beato-García spacetime. The Bose-Einstein condensate is modeled in terms of a massive scalar field that satisfies a Klein-Gordon equation with a self-interaction term. The scalar field is assumed to be uncharged and not self-gravitating. If the mass parameter of the scalar field is chosen sufficiently small, there are quasi-bound states of the scalar field that may be interpreted as dark matter clouds. We estimate the size and the total energy of such clouds around charged supermassive black holes and we investigate if their observable features can be used for discriminating between the different types of charged black holes.
Accretion onto a noncommutative geometry inspired black hole
Energy Technology Data Exchange (ETDEWEB)
Kumar, Rahul [Jamia Millia Islamia, Centre for Theoretical Physics, New Delhi (India); Ghosh, Sushant G. [Jamia Millia Islamia, Centre for Theoretical Physics, New Delhi (India); Jamia Millia Islamia, Multidisciplinary Centre for Advanced Research and Studies (MCARS), New Delhi (India); University of KwaZulu-Natal, Astrophysics and Cosmology Research Unit, School of Mathematics, Statistics and Computer Science, Durban (South Africa)
2017-09-15
The spherically symmetric accretion onto a noncommutative (NC) inspired Schwarzschild black hole is treated for a polytropic fluid. The critical accretion rate M, sonic speed a{sub s} and other flow parameters are generalized for the NC inspired static black hole and compared with the results obtained for the standard Schwarzschild black holes. Also explicit expressions for gas compression ratios and temperature profiles below the accretion radius and at the event horizon are derived. This analysis is a generalization of Michel's solution to the NC geometry. Owing to the NC corrected black hole, the accretion flow parameters also have been modified. It turns out that M ∼ M{sup 2} is still achievable but r{sub s} seems to be substantially decreased due to the NC effects. They in turn do affect the accretion process. (orig.)
First-order flow equations for extremal and non-extremal black holes
International Nuclear Information System (INIS)
Perz, Jan; Vercnocke, Bert; Smyth, Paul; Van Riet, Thomas
2009-01-01
We derive a general form of first-order flow equations for extremal and non-extremal, static, spherically symmetric black holes in theories with massless scalars and vectors coupled to gravity. By rewriting the action as a sum of squares a la Bogomol'nyi, we identify the function governing the first-order gradient flow, the 'generalised superpotential', which reduces to the 'fake superpotential' for non-supersymmetric extremal black holes and to the central charge for supersymmetric black holes. For theories whose scalar manifold is a symmetric space after a timelike dimensional reduction, we present the condition for the existence of a generalised superpotential. We provide examples to illustrate the formalism in four and five spacetime dimensions.
Collisions in spherical stellar systems
Energy Technology Data Exchange (ETDEWEB)
Polyachenko, V.L.; Shukhman, I.G. (AN SSSR, Irkutsk. Sibirskij Inst. Zemnogo Magnetizma Ionosfery i Rasprostraneniya Radiovoln)
From the set of the equations for the stellar distribution function and for the two-particle correlation in the action- angle variables, by averaging over fast finite motions the general expression for the collisional term of a finite stellar system with ''rare'' Coulomb collisions is obtained. In the case of a spherically symmetrical system with the distribution function f/sub 0/=f/sub 0/(E, L) (E, L being the energy and the angular momentum of a star), the kinetic equation is reduced to the standard form of the two-dimensional Fokker-Planck equations.
Thermodynamics and geometrothermodynamics of Born-Infeld black holes with cosmological constant
Quevedo, Hernando; Quevedo, María N.; Sánchez, Alberto
2015-08-01
In this paper, we investigate a class of spherically symmetric Born-Infeld black holes which contains the mass, electric charge, Born-Infeld parameter and the cosmological constant as physical parameters. We show that for the mass to be an extensive thermodynamic variable, it is necessary to consider the cosmological constant and the Born-Infeld parameter as thermodynamic variables as well. We analyze the properties of such a thermodynamic system, explore the range of values where the system is thermodynamically well-defined, and the phase transition structure. In addition, we show that the equilibrium manifold in the context of geometrothermodynamics reproduces correctly the thermodynamic properties of this black hole class.
Symmetrization of Facade Layouts
Jiang, Haiyong
2016-02-26
We present an automatic approach for symmetrizing urban facade layouts. Our method can generate a symmetric layout through minimally modifying the original input layout. Based on the principles of symmetry in urban design, we formulate facade layout symmetrization as an optimization problem. Our method further enhances the regularity of the final layout by redistributing and aligning elements in the layout. We demonstrate that the proposed solution can effectively generate symmetric facade layouts.
Jiang, Haiyong
2016-04-11
We present an automatic algorithm for symmetrizing facade layouts. Our method symmetrizes a given facade layout while minimally modifying the original layout. Based on the principles of symmetry in urban design, we formulate the problem of facade layout symmetrization as an optimization problem. Our system further enhances the regularity of the final layout by redistributing and aligning boxes in the layout. We demonstrate that the proposed solution can generate symmetric facade layouts efficiently. © 2015 IEEE.
Black holes as quantum gravity condensates
Oriti, Daniele; Pranzetti, Daniele; Sindoni, Lorenzo
2018-03-01
We model spherically symmetric black holes within the group field theory formalism for quantum gravity via generalized condensate states, involving sums over arbitrarily refined graphs (dual to three-dimensional triangulations). The construction relies heavily on both the combinatorial tools of random tensor models and the quantum geometric data of loop quantum gravity, both part of the group field theory formalism. Armed with the detailed microscopic structure, we compute the entropy associated with the black hole horizon, which turns out to be equivalently the Boltzmann entropy of its microscopic degrees of freedom and the entanglement entropy between the inside and outside regions. We recover the area law under very general conditions, as well as the Bekenstein-Hawking formula. The result is also shown to be generically independent of any specific value of the Immirzi parameter.
Semiclassical geons as solitonic black hole remnants
Energy Technology Data Exchange (ETDEWEB)
Lobo, Francisco S.N. [Centro de Astronomia e Astrofísica da Universidade de Lisboa, Campo Grande, Ed. C8 1749-016 Lisboa (Portugal); Olmo, Gonzalo J.; Rubiera-Garcia, D., E-mail: flobo@cii.fc.ul.pt, E-mail: gonzalo.olmo@csic.es, E-mail: drubiera@fisica.ufpb.br2 [Departamento de Física Teórica and IFIC, Centro Mixto Universidad de Valencia - CSIC. Universidad de Valencia, Burjassot-46100, Valencia (Spain)
2013-07-01
We find that the end state of black hole evaporation could be represented by non-singular and without event horizon stable solitonic remnants with masses of the order the Planck scale and up to ∼ 16 units of charge. Though these objects are locally indistinguishable from spherically symmetric, massive electric (or magnetic) charges, they turn out to be sourceless geons containing a wormhole generated by the electromagnetic field. Our results are obtained by interpreting semiclassical corrections to Einstein's theory in the first-order (Palatini) formalism, which yields second-order equations and avoids the instabilities of the usual (metric) formulation of quadratic gravity. We also discuss the potential relevance of these solutions for primordial black holes and the dark matter problem.
Astrophysical black holes in screened modified gravity
International Nuclear Information System (INIS)
Davis, Anne-Christine; Jha, Rahul; Muir, Jessica; Gregory, Ruth
2014-01-01
Chameleon, environmentally dependent dilaton, and symmetron gravity are three models of modified gravity in which the effects of the additional scalar degree of freedom are screened in dense environments. They have been extensively studied in laboratory, cosmological, and astrophysical contexts. In this paper, we present a preliminary investigation into whether additional constraints can be provided by studying these scalar fields around black holes. By looking at the properties of a static, spherically symmetric black hole, we find that the presence of a non-uniform matter distribution induces a non-constant scalar profile in chameleon and dilaton, but not necessarily symmetron gravity. An order of magnitude estimate shows that the effects of these profiles on in-falling test particles will be sub-leading compared to gravitational waves and hence observationally challenging to detect
Astrophysical black holes in screened modified gravity
Energy Technology Data Exchange (ETDEWEB)
Davis, Anne-Christine; Jha, Rahul; Muir, Jessica [Department of Applied Mathematics and Theoretical Physics, Centre for Mathematical Sciences, University of Cambridge, Wilberforce Road, Cambridge, CB3 0WA (United Kingdom); Gregory, Ruth, E-mail: acd@damtp.cam.ac.uk, E-mail: r.a.w.gregory@durham.ac.uk, E-mail: r.jha@damtp.cam.ac.uk, E-mail: jlmuir@umich.edu [Centre for Particle Theory, South Road, Durham, DH1 3LE (United Kingdom)
2014-08-01
Chameleon, environmentally dependent dilaton, and symmetron gravity are three models of modified gravity in which the effects of the additional scalar degree of freedom are screened in dense environments. They have been extensively studied in laboratory, cosmological, and astrophysical contexts. In this paper, we present a preliminary investigation into whether additional constraints can be provided by studying these scalar fields around black holes. By looking at the properties of a static, spherically symmetric black hole, we find that the presence of a non-uniform matter distribution induces a non-constant scalar profile in chameleon and dilaton, but not necessarily symmetron gravity. An order of magnitude estimate shows that the effects of these profiles on in-falling test particles will be sub-leading compared to gravitational waves and hence observationally challenging to detect.
Stable gravastars - an alternative to black holes?
International Nuclear Information System (INIS)
Visser, Matt; Wiltshire, David L
2004-01-01
The 'gravastar' picture developed by Mazur and Mottola is one of a very small number of serious challenges to our usual conception of a 'black hole'. In the gravastar picture there is effectively a phase transition at/near where the event horizon would have been expected to form, and the interior of what would have been the black hole is replaced by a segment of de Sitter space. While Mazur and Mottola were able to argue for the thermodynamic stability of their configuration, the question of dynamic stability against spherically symmetric perturbations of the matter or gravity fields remains somewhat obscure. In this paper we construct a model that shares the key features of the Mazur-Mottola scenario, and which is sufficiently simple for a full dynamical analysis. We find that there are some physically reasonable equations of state for the transition layer that lead to stability
Black holes in modified gravity (MOG)
Energy Technology Data Exchange (ETDEWEB)
Moffat, J.W. [Perimeter Institute for Theoretical Physics, Waterloo, ON (Canada); University of Waterloo, Department of Physics and Astronomy, Waterloo, ON (Canada)
2015-04-15
The field equations for scalar-tensor-vector gravity (STVG) or modified gravity (MOG) have a static, spherically symmetric black hole solution determined by the mass M with two horizons. The strength of the gravitational constant is G = G{sub N} (1 + α) where α is a parameter. A regular singularity-free MOG solution is derived using a nonlinear field dynamics for the repulsive gravitational field component and a reasonable physical energy-momentum tensor. The Kruskal-Szekeres completion of the MOG black hole solution is obtained. The Kerr-MOG black hole solution is determined by the mass M, the parameter α and the spin angular momentum J = Ma. The equations of motion and the stability condition of a test particle orbiting the MOG black hole are derived, and the radius of the black hole photosphere and the shadows cast by the Schwarzschild-MOG and Kerr-MOG black holes are calculated. A traversable wormhole solution is constructed with a throat stabilized by the repulsive component of the gravitational field. (orig.)
Ineffective higher derivative black hole hair
Goldstein, Kevin; Mashiyane, James Junior
2018-01-01
Inspired by the possibility that the Schwarzschild black hole may not be the unique spherically symmetric vacuum solution to generalizations of general relativity, we consider black holes in pure fourth order higher derivative gravity treated as an effective theory. Such solutions may be of interest in addressing the issue of higher derivative hair or during the later stages of black hole evaporation. Non-Schwarzschild solutions have been studied but we have put earlier results on a firmer footing by finding a systematic asymptotic expansion for the black holes and matching them with known numerical solutions obtained by integrating out from the near-horizon region. These asymptotic expansions can be cast in the form of trans-series expansions which we conjecture will be a generic feature of non-Schwarzschild higher derivative black holes. Excitingly we find a new branch of solutions with lower free energy than the Schwarzschild solution, but as found in earlier work, solutions only seem to exist for black holes with large curvatures, meaning that one should not generically neglect even higher derivative corrections. This suggests that one effectively recovers the nonhair theorems in this context.
Turduckening black holes: An analytical and computational study
International Nuclear Information System (INIS)
Brown, David; Diener, Peter; Schnetter, Erik; Sarbach, Olivier; Tiglio, Manuel
2009-01-01
We provide a detailed analysis of several aspects of the turduckening technique for evolving black holes. At the analytical level we study the constraint propagation for a family of formulations of Einstein's field equations and identify under what conditions the turducken procedure is rigorously justified and under what conditions constraint violations will propagate to the outside of the black holes. We present high resolution spherically symmetric studies which verify our analytical predictions. Then we present three-dimensional simulations of single distorted black holes using different variations of the turduckening method and also the puncture method. We study the effect that these different methods have on the coordinate conditions, constraint violations, and extracted gravitational waves. We find that the waves agree up to small but nonvanishing differences, caused by escaping superluminal gauge modes. These differences become smaller with increasing detector location.
Effective photon mass from black-hole formation
Directory of Open Access Journals (Sweden)
Slava Emelyanov
2017-06-01
Full Text Available We compute the value of effective photon mass mγ at one-loop level in QED in the background of small (1010 g≲M≪1016 g spherically symmetric black hole in asymptotically flat spacetime. This effect is associated with the modification of electron/positron propagator in presence of event horizon. Physical manifestations of black-hole environment are compared with those of hot neutral plasma. We estimate the distance to the nearest black hole from the upper bound on mγ obtained in the Coulomb-law test. We also find that corrections to electron mass me and fine structure constant α at one-loop level in QED are negligible in the weak gravity regime.
Spherically symmetric random walks. II. Dimensionally dependent critical behavior
International Nuclear Information System (INIS)
Bender, C.M.; Boettcher, S.; Meisinger, P.N.
1996-01-01
A recently developed model of random walks on a D-dimensional hyperspherical lattice, where D is not restricted to integer values, is extended to include the possibility of creating and annihilating random walkers. Steady-state distributions of random walkers are obtained for all dimensions D approx-gt 0 by solving a discrete eigenvalue problem. These distributions exhibit dimensionally dependent critical behavior as a function of the birth rate. This remarkably simple model exhibits a second-order phase transition with a universal, nontrivial critical exponent for all dimensions D approx-gt 0. copyright 1996 The American Physical Society
Spherically symmetric static solutions of the Einstein-Maxwell equations
International Nuclear Information System (INIS)
Krishna Rao, J.; Trivedi, M.M.
1998-01-01
We report a new formalism to obtain solutions of Einstein-Maxwell's equations for static spheres assuming the matter content to be a charged perfect fluid of null-conductivity. Defining three new variables u = 4 4πΕr 2 , v= 4πpr 2 and w= (4π/3)(ρ+ε)r 2 where Ε, ρ and ε denote respectively energy densities of the electric, matter and free gravitational fields whereas p is the fluid pressure, Einstein's field equations are rewritten in an elegant form. The solutions given are all shown to possess simple relations between u, v and w. Another solution for which all the three functions, u, v and w are constants is a trivial case of the present formalism. We have presented six new solutions with ε= 2ρ. For the first three solutions w and u are constants with v as a variable whereas the remaining three solutions satisfy the equation of state for isothermal gas; v=kw=-ku where: i) k is an arbitrary constant but not equal to 1 or 1/3, ii) k= 1 and iii) k= 1/3. We also obtained a generalization of Cooperstock and De la Cruz's solution which is regular for 2ρ > ε but singular for 2ρ ≤ ε. (author)
Spherically Symmetric Waves of a Reaction-Diffusion Equation.
1980-02-01
travelling pulses of the Fitzhugh- Nagumo and Hodgkin - Huxley equations, travelling fronts in some scalar equations such as the Fisher equation and...appropriate function space. A semiflow on a space Y is a func- + + tion S : Y x R - Y (whose domain may not be all of Y x IR , but must be an open subset...which satisfies (1) S(S( y ,t),s) = S( y ,t+s) and (2) S is continuous on its domain. S is said to be a local semiflow if for each y E Y , a set of the form ( y
Spherically symmetric inhomogeneous bianisotropic media: Wave propagation and light scattering
DEFF Research Database (Denmark)
Novitsky, Andrey; Shalin, Alexander S.; Lavrinenko, Andrei
2017-01-01
We develop a technique for finding closed-form expressions for electromagnetic fields in radially inhomogeneous bianisotropic media, both the solutions of the Maxwell equations and material tensors being defined by the set of auxiliary two-dimensional matrices. The approach is applied to determine...
International Nuclear Information System (INIS)
Rockstroh, J.M.
1977-01-01
Cosmic-ray electrons generate the observed radio-frequency background. Previous attempts in the literature to reconcile quantitatively the measured radio-frequency intensity with the intensity deduced from the electron spectrum measured at earth have culminated in the problem that to get the respective emissivities to agree, an unacceptably high interstellar B field must be chosen. In the light of new experimental data on the emissivity as deduced from H II region studies and on the functional dependence of the diffusion coefficient with solar radius and particle rigidity, the assumptions under which the electron emissivity comparison has been made have been reexamined closely. The paradox between predicted and measured emissivity was resolved by ascribing to the magnetic fields of the galaxy a distribution of magnetic field strengths. From modified synchrotron formulas, the interstellar electron spectrum has been constructed from the radio frequency emission data with greatly improved precision. The interstellar electron spectrum has been determined independently of the solar modulation and provides, therefore, an estimate of the absolute depth of the electron modulation. Then the measured electron, proton, and helium-nuclei fluxes were systematically compared to the predictions of the spherically symmetric Fokker-Planck equation using the electron modulation as a base. A previously unnoticed non-tracking of the modulation parameters was observed during the recent recovery that did not occur during the 1965 to 1969 period. Although the argument could be presented just as well by attributing the anomaly to the nuclei, the discussion here arbitrarily tailored it to the electrons, and this new phenomenon was named, the modulation reluctance of the cosmic-ray electrons
International Nuclear Information System (INIS)
Sahni, D.C.; Sharma, A.
2000-01-01
The integral form of one-speed, spherically symmetric neutron transport equation with isotropic scattering is considered. Two standard problems are solved using normal mode expansion technique. The expansion coefficients are obtained by solving their singular integral equations. It is shown that these expansion coefficients provide a representation of all spherical harmonics moments of the angular flux as a superposition of Bessel functions. It is seen that large errors occur in the computation of higher moments unless we take certain precautions. The reasons for this phenomenon are explained. They throw some light on the failure of spherical harmonics method in treating spherical geometry problems as observed by Aronsson
Golden, Ryan; Cho, Ilwoo
2015-01-01
In this paper, we study structure theorems of algebras of symmetric functions. Based on a certain relation on elementary symmetric polynomials generating such algebras, we consider perturbation in the algebras. In particular, we understand generators of the algebras as perturbations. From such perturbations, define injective maps on generators, which induce algebra-monomorphisms (or embeddings) on the algebras. They provide inductive structure theorems on algebras of symmetric polynomials. As...
New mathematical framework for spherical gravitational collapse
International Nuclear Information System (INIS)
Giambo, Roberto; Giannoni, Fabio; Magli, Giulio; Piccione, Paolo
2003-01-01
A theorem, giving necessary and sufficient condition for naked singularity formation in spherically symmetric non-static spacetimes under hypotheses of physical acceptability, is formulated and proved. The theorem relates the existence of singular null geodesics to the existence of regular curves which are supersolutions of the radial null geodesic equation, and allows us to treat all the known examples of naked singularities from a unified viewpoint. New examples are also found using this approach, and perspectives are discussed. (letter to the editor)
Mass inflation inside black holes revisited
International Nuclear Information System (INIS)
Dokuchaev, Vyacheslav I
2014-01-01
The mass inflation phenomenon implies that black hole interiors are unstable due to a back-reaction divergence of the perturbed black hole mass function at the Cauchy horizon. The mass inflation was initially derived by using the generalized Dray–’t Hooft–Redmount (DTR) relation in the linear approximation of the Einstein equations near the perturbed Cauchy horizon of the Reissner–Nordström black hole. However, this linear approximation for the DTR relation is improper for the highly nonlinear behavior of back-reaction perturbations at the black hole horizons. An additional weak point in the standard mass inflation calculations is in a fallacious using of the global Cauchy horizon as a place for the maximal growth of the back-reaction perturbations instead of the local inner apparent horizon. It is derived the new spherically symmetric back-reaction solution for two counter-streaming light-like fluxes near the inner apparent horizon of the charged black hole by taking into account its separation from the Cauchy horizon. In this solution the back-reaction perturbations of the background metric are truly the largest at the inner apparent horizon, but, nevertheless, remain small. The back reaction, additionally, removes the infinite blue-shift singularity at the inner apparent horizon and at the Cauchy horizon. (paper)
Black hole scattering via pseudospectral methods
Energy Technology Data Exchange (ETDEWEB)
Clemente, Paula C.M.; Oliveira, Henrique P. de; Rodrigues, Eduardo L. [Universidade do Estado do Rio de Janeiro (UERJ), RJ (Brazil)
2012-07-01
Full text: We have considered the problem which refers to scattering and absorption of perturbations from a black hole. These perturbations can be scalar, electromagnetic or gravitational waves and satisfy a Schrodinger-type equation, where the potential is specified by the black hole under consideration. Unfortunately, this problem can not be solved by a standard pseudospectral method, the reason is that does not exist a infinite interval basis set, capable of modelling the ingoing and outgoing waves. By using the rational Chebyshev functions and, adding to it, special functions called 'radiation functions' we are able to compute with high precision the transmission and reflection coefficients. These difficulties emerge, because the rational Chebyshev functions can not correctly represent the asymptotic sine waves present in the work. In order to introduce the various concepts involved in the study of wave scattering by black holes, we have assumed in this work, the easiest relativistic case, where scalar waves are scattered by a potential generated by a static and spherically symmetric Schwarzschild black hole. We have adapted and modified the pseudospectral method devised by Boyd, (Computer in Physics, 83 (1990)) which consists in a potential barrier problem in one dimension, the concept of numerical implementation remains the same. The extension of the code for the wave scattering by other black holes is, also, discussed. (author)
Extremal Kerr–Newman black holes with extremely short charged scalar hair
Directory of Open Access Journals (Sweden)
Shahar Hod
2015-12-01
Full Text Available The recently proved ‘no short hair’ theorem asserts that, if a spherically-symmetric static black hole has hair, then this hair (the external fields must extend beyond the null circular geodesic (the “photonsphere” of the corresponding black-hole spacetime: rfield>rnull. In this paper we provide compelling evidence that the bound can be violated by non-spherically symmetric hairy black-hole configurations. To that end, we analytically explore the physical properties of cloudy Kerr–Newman black-hole spacetimes – charged rotating black holes which support linearized stationary charged scalar configurations in their exterior regions. In particular, for given parameters {M,Q,J} of the central black hole, we find the dimensionless ratio q/μ of the field parameters which minimizes the effective lengths (radii of the exterior stationary charged scalar configurations (here {M,Q,J} are respectively the mass, charge, and angular momentum of the black hole, and {μ,q} are respectively the mass and charge coupling constant of the linearized scalar field. This allows us to prove explicitly that (non-spherically symmetric non-static composed Kerr–Newman-charged-scalar-field configurations can violate the no-short-hair lower bound. In particular, it is shown that extremely compact stationary charged scalar ‘clouds’, made of linearized charged massive scalar fields with the property rfield→rH, can be supported in the exterior spacetime regions of extremal Kerr–Newman black holes (here rfield is the peak location of the stationary scalar configuration and rH is the black-hole horizon radius. Furthermore, we prove that these remarkably compact stationary field configurations exist in the entire range s≡J/M2∈(0,1 of the dimensionless black-hole angular momentum. In particular, in the large-mass limit they are characterized by the simple dimensionless ratio q/μ=(1−2s2/(1−s2.
On the W-hair of string black holes and the singularity problem
Ellis, John R.; Nanopoulos, Dimitri V.
1992-01-01
We argue that the infinitely many gauge symmetries of string theory provide an infinite set of conserved (gauge) quantum numbers (W-hair) which characterise black hole states and maintain quantum coherence, even during exotic processes like black hole evaporation/decay. We study ways of measuring the W-hair of spherically-symmetric four-dimensional objects with event horizons, treated as effectively two-dimensional string black holes. Measurements can be done either through the s-wave scattering of light particles off the string black-hole background, or through interference experiments of Aharonov-Bohm type. We also speculate on the role of the extended W-symmetries possessed by the topological field theories that describe the region of space-time around a singularity.
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
Visible, invisible and trapped ghosts as sources of wormholes and black universes
International Nuclear Information System (INIS)
Bolokhov, S V; Bronnikov, K A; Korolyov, P A; Skvortsova, M V
2016-01-01
We construct explicit examples of globally regular static, spherically symmetric solutions in general relativity with scalar and electromagnetic fields, describing traversable wormholes with flat and AdS asymptotics and regular black holes, in particular, black universes. (A black universe is a regular black hole with an expanding, asymptotically isotropic space-time beyond the horizon.) Such objects exist in the presence of scalar fields with negative kinetic energy (“phantoms”, or “ghosts”), which are not observed under usual physical conditions. To account for that, we consider what we call “trapped ghosts” (scalars whose kinetic energy is only negative in a strong-field region of space-time) and “invisible ghosts”, i.e., phantom scalar fields sufficiently rapidly decaying in the weak-field region. The resulting configurations contain different numbers of Killing horizons, from zero to four. (paper)
What happens at the horizon(s) of an extreme black hole?
International Nuclear Information System (INIS)
Murata, Keiju; Reall, Harvey S; Tanahashi, Norihiro
2013-01-01
A massless scalar field exhibits an instability at the event horizon of an extreme black hole. We study numerically the nonlinear evolution of this instability for spherically symmetric perturbations of an extreme Reissner–Nordstrom (RN) black hole. We find that generically the endpoint of the instability is a non-extreme RN solution. However, there exist fine-tuned initial perturbations for which the instability never decays. In this case, the perturbed spacetime describes a time-dependent extreme black hole. Such solutions settle down to extreme RN outside, but not on, the event horizon. The event horizon remains smooth but certain observers who cross it at late time experience large gradients there. Our results indicate that these dynamical extreme black holes admit a C 1 extension across an inner (Cauchy) horizon. (paper)
Quantum Bounded Symmetric Domains
Vaksman, L. L.
2008-01-01
This is Leonid Vaksman's monograph "Quantum bounded symmetric domains" (in Russian), preceded with an English translation of the table of contents and (a part) of the introduction. Quantum bounded symmetric domains are interesting from several points of view. In particular, they provide interesting examples for noncommutative complex analysis (i.e., the theory of subalgebras of C^*-algebars) initiated by W. Arveson.
Symmetric cryptographic protocols
Ramkumar, Mahalingam
2014-01-01
This book focuses on protocols and constructions that make good use of symmetric pseudo random functions (PRF) like block ciphers and hash functions - the building blocks for symmetric cryptography. Readers will benefit from detailed discussion of several strategies for utilizing symmetric PRFs. Coverage includes various key distribution strategies for unicast, broadcast and multicast security, and strategies for constructing efficient digests of dynamic databases using binary hash trees. • Provides detailed coverage of symmetric key protocols • Describes various applications of symmetric building blocks • Includes strategies for constructing compact and efficient digests of dynamic databases
Exponential fading to white of black holes in quantum gravity
International Nuclear Information System (INIS)
Barceló, Carlos; Carballo-Rubio, Raúl; Garay, Luis J
2017-01-01
Quantization of the gravitational field may allow the existence of a decay channel of black holes into white holes with an explicit time-reversal symmetry. The definition of a meaningful decay probability for this channel is studied in spherically symmetric situations. As a first nontrivial calculation, we present the functional integration over a set of geometries using a single-variable function to interpolate between black-hole and white-hole geometries in a bounded region of spacetime. This computation gives a finite result which depends only on the Schwarzschild mass and a parameter measuring the width of the interpolating region. The associated probability distribution displays an exponential decay law on the latter parameter, with a mean lifetime inversely proportional to the Schwarzschild mass. In physical terms this would imply that matter collapsing to a black hole from a finite radius bounces back elastically and instantaneously, with negligible time delay as measured by external observers. These results invite to reconsider the ultimate nature of astrophysical black holes, providing a possible mechanism for the formation of black stars instead of proper general relativistic black holes. The existence of both this decay channel and black stars can be tested in future observations of gravitational waves. (paper)
Black holes in Lorentz-violating gravity theories
International Nuclear Information System (INIS)
Barausse, Enrico; Sotiriou, Thomas P
2013-01-01
Lorentz symmetry and the notion of light cones play a central role in the definition of horizons and the existence of black holes. Current observations provide strong indications that astrophysical black holes do exist in Nature. Here we explore what happens to the notion of a black hole in gravity theories where local Lorentz symmetry is violated, and discuss the relevant astrophysical implications. Einstein-aether theory and Hořava gravity are used as the theoretical background for addressing this question. We review earlier results about static, spherically symmetric black holes, which demonstrate that in Lorentz-violating theories there can be a new type of horizon and, hence, a new notion of black hole. We also present both known and new results on slowly rotating black holes in these theories, which provide insights on how generic these new horizons are. Finally, we discuss the differences between black holes in Lorentz-violating theories and in General Relativity, and assess to what extent they can be probed with present and future observations. (paper)
Black Hole Solutions in $R^2$ Gravity
Kehagias, Alex; Lust, Dieter; Riotto, Antonio
2015-01-01
We find static spherically symmetric solutions of scale invariant $R^2$ gravity. The latter has been shown to be equivalent to General Relativity with a positive cosmological constant and a scalar mode. Therefore, one expects that solutions of the $R^2$ theory will be identical to that of Einstein theory. Indeed, we find that the solutions of $R^2$ gravity are in one-to-one correspondence with solutions of General Relativity in the case of non-vanishing Ricci scalar. However, scalar-flat $R=0$ solutions are global minima of the $R^2$ action and they cannot in general be mapped to solutions of the Einstein theory. As we will discuss, the $R=0$ solutions arise in Einstein gravity as solutions in the tensionless, strong coupling limit $M_P\\rightarrow 0$. As a further result, there is no corresponding Birkhoff theorem and the Schwarzschild black hole is by no means unique in this framework. In fact, $R^2$ gravity has a rich structure of vacuum static spherically symmetric solutions partially uncovered here. We al...
Rodrigue, Kamiko Kouemeni Jean; Saleh, Mahamat; Thomas, Bouetou Bouetou; Kofane, Timoleon Crepin
2018-05-01
In this paper, we investigate the thermodynamics and Hawking radiation of Schwarzschild black hole with quintessence-like matter and deficit solid angle. From the metric of the black hole, we derive the expressions of temperature and specific heat using the laws of black hole thermodynamics. Using the null geodesics method and Parikh-Wilczeck tunneling method, we derive the expressions of Boltzmann factor and the change of Bekenstein-Hawking entropy for the black hole. The behaviors of the temperature, specific heat, Boltzmann factor and the change of Bekenstein entropy versus the deficit solid angle (ɛ 2) and the density of static spherically symmetric quintessence-like matter (ρ 0) were explicitly plotted. The results show that, when the deficit solid angle (ɛ 2) and the density of static spherically symmetric quintessence-like matter at r=1 (ρ 0) vanish (ρ 0=ɛ =0), these four thermodynamics quantities are reduced to those obtained for the simple case of Schwarzschild black hole. For low entropies, the presence of quintessence-like matter induces a first order phase transition of the black hole and for the higher values of the entropies, we observe the second order phase transition. When increasing ρ 0, the transition points are shifted to lower entropies. The same thing is observed when increasing ɛ 2. In the absence of quintessence-like matter (ρ 0=0), these transition phenomena disappear. Moreover the rate of radiation decreases when increasing ρ 0 or (ɛ ^2).
A symmetrical rail accelerator
International Nuclear Information System (INIS)
Igenbergs, E.
1991-01-01
This paper reports on the symmetrical rail accelerator that has four rails, which are arranged symmetrically around the bore. The opposite rails have the same polarity and the adjacent rails the opposite polarity. In this configuration the radial force acting upon the individual rails is significantly smaller than in a conventional 2-rail configuration and a plasma armature is focussed towards the axis of the barrel. Experimental results indicate a higher efficiency compared to a conventional rail accelerator
International Nuclear Information System (INIS)
Matsuki, Takayuki
1976-01-01
Symmetric eikonal expansion for the scattering amplitude is formulated for nonrelativistic and relativistic potential scatterings and also for the quantum field theory. The first approximations coincide with those of Levy and Sucher. The obtained scattering amplitudes are time reversal invariant for all cases and are crossing symmetric for the quantum field theory in each order of approximation. The improved eikonal phase introduced by Levy and Sucher is also derived from the different approximation scheme from the above. (auth.)
Higher spin black holes with soft hair
Energy Technology Data Exchange (ETDEWEB)
Grumiller, Daniel [Institute for Theoretical Physics, TU Wien,Wiedner Hauptstrasse 8-10/136, Vienna, A-1040 (Austria); Pérez, Alfredo [Centro de Estudios Científicos (CECs),Av. Arturo Prat 514, Valdivia (Chile); Prohazka, Stefan [Institute for Theoretical Physics, TU Wien,Wiedner Hauptstrasse 8-10/136, Vienna, A-1040 (Austria); Tempo, David; Troncoso, Ricardo [Centro de Estudios Científicos (CECs),Av. Arturo Prat 514, Valdivia (Chile)
2016-10-21
We construct a new set of boundary conditions for higher spin gravity, inspired by a recent “soft Heisenberg hair”-proposal for General Relativity on three-dimensional Anti-de Sitter space. The asymptotic symmetry algebra consists of a set of affine û(1) current algebras. Its associated canonical charges generate higher spin soft hair. We focus first on the spin-3 case and then extend some of our main results to spin-N, many of which resemble the spin-2 results: the generators of the asymptotic W{sub 3} algebra naturally emerge from composite operators of the û(1) charges through a twisted Sugawara construction; our boundary conditions ensure regularity of the Euclidean solutions space independently of the values of the charges; solutions, which we call “higher spin black flowers”, are stationary but not necessarily spherically symmetric. Finally, we derive the entropy of higher spin black flowers, and find that for the branch that is continuously connected to the BTZ black hole, it depends only on the affine purely gravitational zero modes. Using our map to W-algebra currents we recover well-known expressions for higher spin entropy. We also address higher spin black flowers in the metric formalism and achieve full consistency with previous results.
Structural aspects of asymptotically safe black holes
Koch, Benjamin; Saueressig, Frank
2014-01-01
We study the quantum modifications of classical, spherically symmetric Schwarzschild (anti-) de Sitter black holes within quantum Einstein gravity. The quantum effects are incorporated through the running coupling constants Gk and Λk, computed within the exact renormalization group approach, and a common scale-setting procedure. We find that, in contrast to common intuition, it is actually the cosmological constant that determines the short-distance structure of the RG-improved black hole: in the asymptotic UV the structure of the quantum solutions is universal and given by the classical Schwarzschild-de Sitter solution, entailing a self-similarity between the classical and quantum regime. As a consequence asymptotically safe black holes evaporate completely and no Planck-size remnants are formed. Moreover, the thermodynamic entropy of the critical Nariai black hole is shown to agree with the microstate count based on the effective average action, suggesting that the entropy originates from quantum fluctuations around the mean-field geometry.
Spherical Accretion in a Uniformly Expanding Universe
Colpi, Monica; Shapiro, Stuart L.; Wasserman, Ira
1996-10-01
We consider spherically symmetric accretion of material from an initially homogeneous, uniformly expanding medium onto a Newtonian point mass M. The gas is assumed to evolve adiabatically with a constant adiabatic index F, which we vary over the range Γ ɛ [1, 5/3]. We use a one-dimensional Lagrangian code to follow the spherical infall of material as a function of time. Outflowing shells gravitationally bound to the point mass fall back, giving rise to a inflow rate that, after a rapid rise, declines as a power law in time. If there were no outflow initially, Bondi accretion would result, with a characteristic accretion time-scale ta,0. For gas initially expanding at a uniform rate, with a radial velocity U = R/t0 at radius R, the behavior of the flow at all subsequent times is determined by ta,0/t0. If ta,0/t0 ≫ 1, the gas has no time to respond to pressure forces, so the fluid motion is nearly collisionless. In this case, only loosely bound shells are influenced by pressure gradients and are pushed outward. The late-time evolution of the mass accretion rate Mdot is close to the result for pure dust, and we develop a semianalytic model that accurately accounts for the small effect of pressure gradients in this limit. In the opposite regime, ta,0/t0 ≪ 1, pressure forces significantly affect the motion of the gas. At sufficiently early times, t ≤ ttr, the flow evolved along a sequence of quasi-stationary, Bondi-like states, with a time-dependent Mdot determined by the slowly varying gas density at large distances. However, at later times, t ≥ ttr, the fluid flow enters a dustllke regime; ttr is the time when the instantaneous Bondi accretion radius reaches the marginally bound radius. The transition time ttr depends sensitively on ta,0/t0 for a given Γ and can greatly exceed t0. We show that there exists a critical value Γ = 11/9, below which the transition from fluid to ballistic motion disappears. As one application of our calculations, we consider the
Hawking radiation from AdS black holes
Hemming, Samuli; Keski-Vakkuri, Esko
2001-08-01
We investigate Hawking radiation from black holes in (d+1)-dimensional anti-de Sitter space. We focus on s waves, make use of the geometrical optics approximation, and follow three approaches to analyze the radiation. First, we compute a Bogoliubov transformation between Kruskal and asymptotic coordinates and compare the different vacua. Second, following a method due to Kraus, Parikh, and Wilczek, we view Hawking radiation as a tunneling process across the horizon and compute the tunneling probability. This approach uses an anti-de Sitter version of a metric originally introduced by Painlevé for Schwarzschild black holes. From the tunneling probability one also finds a leading correction to the semiclassical emission rate arising from back reaction to the background geometry. Finally, we consider a spherically symmetric collapse geometry and the Bogoliubov transformation between the initial vacuum state and the vacuum of an asymptotic observer.
Thermodynamics of Einstein-Proca AdS black holes
Energy Technology Data Exchange (ETDEWEB)
Liu, Hai-Shan [Institute for Advanced Physics & Mathematics, Zhejiang University of Technology, Hangzhou 310023 (China); Lü, H. [Department of Physics, Beijing Normal University, Beijing 100875 (China); Pope, C.N. [George P. & Cynthia Woods Mitchell Institute for Fundamental Physics and Astronomy, Texas A& M University, College Station, TX 77843 (United States); DAMTP, Centre for Mathematical Sciences, Cambridge University, Wilberforce Road, Cambridge CB3 OWA (United Kingdom)
2014-06-18
We study static spherically-symmetric solutions of the Einstein-Proca equations in the presence of a negative cosmological constant. We show that the theory admits solutions describing both black holes and also solitons in an asymptotically AdS background. Interesting subtleties can arise in the computation of the mass of the solutions and also in the derivation of the first law of thermodynamics. We make use of holographic renormalisation in order to calculate the mass, even in cases where the solutions have a rather slow approach to the asymptotic AdS geometry. By using the procedure developed by Wald, we derive the first law of thermodynamics for the black hole and soliton solutions. This includes a non-trivial contribution associated with the Proca “charge”. The solutions cannot be found analytically, and so we make use of numerical integration techniques to demonstrate their existence.
Black holes and first order flows in supergravity
Andrianopoli, L; Trigiante, M; Ferrara, S
2011-01-01
We review the description of static, spherically symmetric, asymptotically- flat black holes in four dimensional supergravity in terms of an autonomous Hamiltonian system. A special role in this analysis is played by the so called fake superpotenti alW, which is identified with a particular solution to the Hamilton-Jacobi equation. This function defines a first order, gradient-flow, description of the radial flow of the scalar fields, coupled to the solution, and of the red-shift factor. Identifying W with the Liapunovs function, we can make the general statement that critical points of W are asymptotically stable equilibrium points of the corresponding first order dynamical system (in the sense of Liapunov). Such equilibrium points way only exist f or extremal regular solutions and define their near horizon behavior. Thus the fake superpotential provides an alternative characterization of the attractor phenomenon. We focus on extremal black holes and deduce very general properties of the fake superp otential...
d-dimensional black hole entropy spectrum from quasinormal modes.
Kunstatter, G
2003-04-25
Starting from recent observations about quasinormal modes, we use semiclassical arguments to derive the Bekenstein-Hawking entropy spectrum for d-dimensional spherically symmetric black holes. We find that, as first suggested by Bekenstein, the entropy spectrum is equally spaced: S(BH)=kln((m(0))n, where m(0) is a fixed integer that must be derived from the microscopic theory. As shown in O. Dreyer, gr-qc/0211076, 4D loop quantum gravity yields precisely such a spectrum with m(0)=3 providing the Immirzi parameter is chosen appropriately. For d-dimensional black holes of radius R(H)(M), our analysis predicts the existence of a unique quasinormal mode frequency in the large damping limit omega((d))(M)=alpha((d))c/R(H)(M) with coefficient [formula: see text], where m(0) is an integer.
Horizons in Matter:. Black Hole Hair Versus Null Big Bang
Bronnikov, K. A.; Zaslavskii, Oleg B.
It is shown that only particular kinds of matter (in terms of the "radial" pressure-to-density ratio w) can coexist with Killing horizons in black hole or cosmological space-times. Thus, for arbitrary (not necessarily spherically symmetric) static black holes, admissible are vacuum matter (w = -1, i.e. the cosmological constant or its generalization with the same value of w) and matter with certain values of w between 0 and -1, in particular a gas of disordered cosmic strings (w = -1/3). If the cosmological evolution starts from a horizon (the so-called null big bang scenarios), this horizon can coexist with vacuum matter and certain kinds of phantom matter with w ≤ -3. It is concluded that normal matter in such scenarios is entirely created from vacuum.
Geometro-thermodynamics of tidal charged black holes
International Nuclear Information System (INIS)
Gergely, Laszlo Arpad; Pidokrajt, Narit; Winitzki, Sergei
2011-01-01
Tidal charged spherically symmetric vacuum brane black holes are characterized by their mass m and tidal charge q, an imprint of the five-dimensional Weyl curvature. For q>0 they are formally identical to the Reissner-Nordstroem black hole of general relativity. We study the thermodynamics and thermodynamic geometries of tidal charged black holes and discuss similarities and differences as compared to the Reissner-Nordstroe m black hole. As a similarity, we show that (for q>0) the heat capacity of the tidal charged black hole diverges on a set of measure zero of the parameter space, nevertheless both the regularity of the Ruppeiner metric and a Poincare stability analysis show no phase transition at those points. The thermodynamic state spaces being different indicates that the underlying statistical models could be different. We find that the q<0 parameter range, which enhances the localization of gravity on the brane, is thermodynamically preferred. Finally we constrain for the first time the possible range of the tidal charge from the thermodynamic limit on gravitational radiation efficiency at black hole mergers. (orig.)
Hawking radiation from black holes in de Sitter spaces
International Nuclear Information System (INIS)
Jiang Qingquan
2007-01-01
Recently, Hawking radiation has been treated, by Robinson and Wilczek (2005 Phys. Rev. Lett. 95 011303), as a compensating flux of the energy-momentum tensor required to cancel a gravitational anomaly at the event horizon (EH) of a Schwarzschild-type black hole. In this paper, motivated by this work, Hawking radiation from the event horizon (EH) and the de Sitter cosmological horizon (CH) of black holes in de Sitter spaces, specifically including the purely de Sitter black hole and the static, spherically symmetric Schwarzschild-de Sitter black hole as well as the rotating Kerr-de Sitter black hole, have been studied by anomalies. The results show that the gauge-current and energy-momentum tensor fluxes, required to restore gauge invariance and general coordinate covariance at the EH and the CH, are precisely equal to those of Hawking radiation from the EH and the CH, respectively. It should be noted that gauge and gravitational anomalies taking place at the CH arise from the fact that the effective field theory is formulated inside the CH to integrate out the classically irrelevant outgoing modes at the CH, which are different from those at the black hole horizon
Absorption of scalars by extremal black holes in string theory
Moura, Filipe
2017-09-01
We show that the low frequency absorption cross section of minimally coupled test massless scalar fields by extremal spherically symmetric black holes in d dimensions is equal to the horizon area, even in the presence of string-theoretical α ' corrections. Classically one has the relation σ = 4 GS between that absorption cross section and the black hole entropy. By comparing in each case the values of the horizon area and Wald's entropy, we discuss the validity of such relation in the presence of higher derivative corrections for extremal black holes in many different contexts: in the presence of electric and magnetic charges; for nonsupersymmetric and supersymmetric black holes; in d=4 and d=5 dimensions. The examples we consider seem to indicate that this relation is not verified in the presence of α ' corrections in general, although being valid in some specific cases (electrically charged maximally supersymmetric black holes in d=5). We argue that the relation σ = 4 GS should in general be valid for the absorption cross section of scalar fields which, although being independent from the black hole solution, have their origin from string theory, and therefore are not minimally coupled.
Hydrodynamics of primordial black hole formation
Nadezhin, D. K.; Novikov, I. D.; Polnarev, A. G.
1979-01-01
The hydrodynamic picture of the formation of primordial black holes (PBH) at the early stages of expansion of the Universe is considered. It is assumed that close to singularity, expansion occurs in a quasi-isotropic way. Using an EVM, a spherically symmetrical nonlinear problem of the evolution of primary strong deviation from the Fridman solution was solved. What these deviations must be, so that the formation of PBH occurred was clarified. Attention was devoted to the role of pressure gradients. It is pointed out that at the moment of formation of PBH, only a small part of matter enters into it, primarily the component of perturbation. It is also pointed out that at this moment, the mass of PBH essentially is smaller than the mass considered within the cosmic horizon. The possibility of changing the mass of the PBH as a result of accretion is analyzed.
Loop quantization of the Schwarzschild black hole.
Gambini, Rodolfo; Pullin, Jorge
2013-05-24
We quantize spherically symmetric vacuum gravity without gauge fixing the diffeomorphism constraint. Through a rescaling, we make the algebra of Hamiltonian constraints Abelian, and therefore the constraint algebra is a true Lie algebra. This allows the completion of the Dirac quantization procedure using loop quantum gravity techniques. We can construct explicitly the exact solutions of the physical Hilbert space annihilated by all constraints. New observables living in the bulk appear at the quantum level (analogous to spin in quantum mechanics) that are not present at the classical level and are associated with the discrete nature of the spin network states of loop quantum gravity. The resulting quantum space-times resolve the singularity present in the classical theory inside black holes.
Regular and black hole solutions of Einstein-Yang-Mills dilaton theory
Lavrelashvili, George; Maison, Dieter
1993-12-01
We present numerical and analytical results on static spherically symmetric solutions of an SU(2) Yang-Mills field coupled to the gravitational field and to a dilaton. For any value of the dilaton coupling constant we find a discrete family of globally regular solutions of finite mass. In addition our analysis indicates the existence of a similar discrete family of black hole solutions for any given radius rh of their horizon. All these solutions turn out to be unstable in linearized perturbation theory.
Leung, Ka-Ngo
2006-11-21
A spherical neutron generator is formed with a small spherical target and a spherical shell RF-driven plasma ion source surrounding the target. A deuterium (or deuterium and tritium) ion plasma is produced by RF excitation in the plasma ion source using an RF antenna. The plasma generation region is a spherical shell between an outer chamber and an inner extraction electrode. A spherical neutron generating target is at the center of the chamber and is biased negatively with respect to the extraction electrode which contains many holes. Ions passing through the holes in the extraction electrode are focused onto the target which produces neutrons by D-D or D-T reactions.
Symmetric Tensor Decomposition
DEFF Research Database (Denmark)
Brachat, Jerome; Comon, Pierre; Mourrain, Bernard
2010-01-01
We present an algorithm for decomposing a symmetric tensor, of dimension n and order d, as a sum of rank-1 symmetric tensors, extending the algorithm of Sylvester devised in 1886 for binary forms. We recall the correspondence between the decomposition of a homogeneous polynomial in n variables...... of polynomial equations of small degree in non-generic cases. We propose a new algorithm for symmetric tensor decomposition, based on this characterization and on linear algebra computations with Hankel matrices. The impact of this contribution is two-fold. First it permits an efficient computation...... of the decomposition of any tensor of sub-generic rank, as opposed to widely used iterative algorithms with unproved global convergence (e.g. Alternate Least Squares or gradient descents). Second, it gives tools for understanding uniqueness conditions and for detecting the rank....
Multiparty symmetric sum types
DEFF Research Database (Denmark)
Nielsen, Lasse; Yoshida, Nobuko; Honda, Kohei
2010-01-01
This paper introduces a new theory of multiparty session types based on symmetric sum types, by which we can type non-deterministic orchestration choice behaviours. While the original branching type in session types can represent a choice made by a single participant and accepted by others...... determining how the session proceeds, the symmetric sum type represents a choice made by agreement among all the participants of a session. Such behaviour can be found in many practical systems, including collaborative workflow in healthcare systems for clinical practice guidelines (CPGs). Processes...... with the symmetric sums can be embedded into the original branching types using conductor processes. We show that this type-driven embedding preserves typability, satisfies semantic soundness and completeness, and meets the encodability criteria adapted to the typed setting. The theory leads to an efficient...
Reissner–Nordström black holes with non-Abelian hair
Directory of Open Access Journals (Sweden)
Carlos Herdeiro
2017-09-01
Full Text Available We consider d⩾4 Einstein–(extended-Yang–Mills theory, where the gauge sector is augmented by higher order terms. Linearising the (extended Yang–Mills equations on the background of the electric Reissner–Nordström (RN black hole, we show the existence of normalisable zero modes, dubbed non-Abelian magnetic stationary clouds. The non-linear realisation of these clouds bifurcates the RN family into a branch of static, spherically symmetric, electrically charged and asymptotically flat black holes with non-Abelian hair. Generically, the hairy black holes are thermodynamically preferred over the RN solution, which, in this model, becomes unstable against the formation of non-Abelian hair, for sufficiently large values of the electric charge.
Reissner-Nordström black holes with non-Abelian hair
Herdeiro, Carlos; Paturyan, Vanush; Radu, Eugen; Tchrakian, D. H.
2017-09-01
We consider d ⩾ 4 Einstein-(extended-)Yang-Mills theory, where the gauge sector is augmented by higher order terms. Linearising the (extended) Yang-Mills equations on the background of the electric Reissner-Nordström (RN) black hole, we show the existence of normalisable zero modes, dubbed non-Abelian magnetic stationary clouds. The non-linear realisation of these clouds bifurcates the RN family into a branch of static, spherically symmetric, electrically charged and asymptotically flat black holes with non-Abelian hair. Generically, the hairy black holes are thermodynamically preferred over the RN solution, which, in this model, becomes unstable against the formation of non-Abelian hair, for sufficiently large values of the electric charge.
Regular nonminimal magnetic black holes in spacetimes with a cosmological constant
Balakin, Alexander B.; Lemos, José P. S.; Zayats, Alexei E.
2016-01-01
We consider new regular exact spherically symmetric solutions of a nonminimal Einstein-Yang-Mills theory with a cosmological constant and a gauge field of magnetic Wu-Yang type. The most interesting solutions found are black holes with metric and curvature invariants that are regular everywhere, i.e., regular black holes. We set up a classification of the solutions according to the number and type of horizons. The structure of these regular black holes is characterized by four specific features: a small cavity in the neighborhood of the center, a repulsion barrier off the small cavity, a distant equilibrium point, in which the metric function has a minimum, and a region of Newtonian attraction. Depending on the sign and value of the cosmological constant, the solutions are asymptotically de Sitter (dS), asymptotically flat, or asymptotically anti-de Sitter (AdS).
Static configurations and evolution of higher dimensional brane-dilaton black hole system
Energy Technology Data Exchange (ETDEWEB)
Nakonieczna, Anna [Institute of Physics, Maria Curie-Skłodowska University,Plac Marii Curie-Skłodowskiej 1, 20-031 Lublin (Poland); Institute of Theoretical Physics, Faculty of Physics, University of Warsaw,ul. Pasteura 5, 02-093 Warsaw (Poland); Nakonieczny, Łukasz [Institute of Theoretical Physics, Faculty of Physics, University of Warsaw,ul. Pasteura 5, 02-093 Warsaw (Poland); Moderski, Rafał [Nicolaus Copernicus Astronomical Center, Polish Academy of Sciences,ul. Bartycka 18, 00-716 Warsaw (Poland); Rogatko, Marek [Institute of Physics, Maria Curie-Skłodowska University,Plac Marii Curie-Skłodowskiej 1, 20-031 Lublin (Poland)
2016-12-15
Static configurations and a dynamical evolution of the system composed of a higher-dimensional spherically symmetric dilaton black hole and the Dirac-Goto-Nambu brane were investigated. The studies were conducted for three values of the dilaton coupling constant, describing the uncoupled case, the low-energy limit of the string theory and dimensionally reduced Klein-Kaluza theories. When the black hole is nonextremal, two types of static configurations are observed, a brane which intersects the black hole horizon and a brane not having any common points with the accompanying black hole. As the number of spacetime dimensions increases, the brane bend in the vicinity of the black hole disappears closer to its horizon. Dynamical evolution of the system results in an expulsion of the black hole from the brane. It proceeds faster for bigger values of the bulk spacetime dimension and thicker branes. The value of the dilatonic coupling constant does not influence neither the static configurations nor the dynamical behavior of the examined nonextremal system. In the extremal dilaton black hole case one obtains expulsion of the brane which is independent on the spacetime dimensionality and the value of the coupling constant. Dynamical studies of the configurations in the extremal case reveal that the course of evolution of the system is similar to the nonextremal one, except for a slightly earlier expulsion of the black hole from the brane.
Merger transitions in brane-black-hole systems: Criticality, scaling, and self-similarity
International Nuclear Information System (INIS)
Frolov, Valeri P.
2006-01-01
We propose a toy model for studying merger transitions in a curved spacetime with an arbitrary number of dimensions. This model includes a bulk N-dimensional static spherically symmetric black hole and a test D-dimensional brane (D≤N-1) interacting with the black hole. The brane is asymptotically flat and allows a O(D-1) group of symmetry. Such a brane-black-hole (BBH) system has two different phases. The first one is formed by solutions describing a brane crossing the horizon of the bulk black hole. In this case the internal induced geometry of the brane describes a D-dimensional black hole. The other phase consists of solutions for branes which do not intersect the horizon, and the induced geometry does not have a horizon. We study a critical solution at the threshold of the brane-black-hole formation, and the solutions which are close to it. In particular, we demonstrate that there exists a striking similarity of the merger transition, during which the phase of the BBH system is changed, both with the Choptuik critical collapse and with the merger transitions in the higher dimensional caged black-hole-black-string system
Chiral pion dynamics for spherical nucleon bags
International Nuclear Information System (INIS)
Vento, V.; Rho, M.; Nyman, E.M.; Jun, J.H.; Brown, G.E.; CEA Centre d'Etudes Nucleaires de Saclay, 91 - Gif-sur-Yvette
1980-01-01
A chirally symmetric quark-bag model for the nucleon is obtained by introducing an explicit, classical, pion field exterior to the bag. The coupling at the bag surface is determined by the requirement of a conserved axial-vector current. The pion field satisfies equations of motion corresponding to the non-linear sigma-model. We study on this paper the simplified case where the bag and the pion field are spherically symmetric. Corrections due to gluon exchange between the quarks are ignored along with other interactions which split the N- and Δ-masses. The equations of motion for the pion field are solved and we find a substantial pion pressure at the bag surface, along with an attractive contribution to the nucleon self-energy. The total energy of the system, bag plus meson cloud, turns out to be approximately Msub(n)c 2 for a wide range of bag radii, from 1.5 fm down to about 0.5 fm. Introduction of a form factor for the pion would extend the range of possible radii to even smaller values. We propose that the bag with the smallest allowed radius be identified with the 'little bag' discussed before. One surprising result of the paper is that as long as one restricts to spherically symmetric bags, restoring chiral symmetry to the bag model makes the axial-vector current coupling constant gsub(A) to be always too large compared with the experimental value for any bag radius, suggesting a deviation from spherical symmetry for the intrinsic bag wave functions of the 'ground-state' hadrons. (orig.)
Spontaneous spherical symmetry breaking in atomic confinement
Sveshnikov, Konstantin; Tolokonnikov, Andrey
2017-07-01
The effect of spontaneous breaking of initial SO(3) symmetry is shown to be possible for an H-like atom in the ground state, when it is confined in a spherical box under general boundary conditions of "not going out" through the box surface (i.e. third kind or Robin's ones), for a wide range of physically reasonable values of system parameters. The most novel and nontrivial result, which has not been reported previously, is that such an effect takes place not only for attractive, but also for repulsive interactions of atomic electrons with the cavity environment. Moreover, in the limit of a large box size R ≫ aB the regime of an atom, soaring over a plane with boundary condition of "not going out", is reproduced, rather than a spherically symmetric configuration, which would be expected on the basis of the initial SO(3) symmetry of the problem.
International Nuclear Information System (INIS)
Amore, Paolo; Fernández, Francisco M.; Garcia, Javier; Gutierrez, German
2014-01-01
We study both analytically and numerically the spectrum of inhomogeneous strings with PT-symmetric density. We discuss an exactly solvable model of PT-symmetric string which is isospectral to the uniform string; for more general strings, we calculate exactly the sum rules Z(p)≡∑ n=1 ∞ 1/E n p , with p=1,2,… and find explicit expressions which can be used to obtain bounds on the lowest eigenvalue. A detailed numerical calculation is carried out for two non-solvable models depending on a parameter, obtaining precise estimates of the critical values where pair of real eigenvalues become complex. -- Highlights: •PT-symmetric Hamiltonians exhibit real eigenvalues when PT symmetry is unbroken. •We study PT-symmetric strings with complex density. •They exhibit regions of unbroken PT symmetry. •We calculate the critical parameters at the boundaries of those regions. •There are exact real sum rules for some particular complex densities
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
Black holes and neutron stars in vector Galileons
Chagoya, Javier; Niz, Gustavo; Tasinato, Gianmassimo
2017-08-01
The direct detection of gravitational waves opens new perspectives for measuring properties of gravitationally bound compact objects. It is then important to investigate black holes and neutron stars in alternative theories of gravity, since they can have features that make them observationally distinguishable from their general relativity (GR) counterparts. In this work, we examine a special case of vector Galileons, a vector-tensor theory of gravity with interesting cosmological properties, which consists of a one parameter modification of the Einstein-Maxwell action. Within this theory, we study configurations describing asymptotically flat, spherically symmetric black holes and neutron stars. The set of black hole solutions in this theory is surprisingly rich, generalising results found in GR or in related scalar-tensor theories. We investigate the properties and conserved charges of black holes, using both analytical and numerical techniques, highlighting configurations that are more compact than in GR. We then study properties of neutron stars, showing how the vector profile can influence the star internal structure. Depending on properties of matter and fields inside the star, neutron stars can be more massive than in GR, and they can be even more compact than Schwarzschild black holes, making these objects observationally interesting. We also comment on possible extensions of our configurations to magnetically charged or rotating configurations.
Dirac fermions in nontrivial topology black hole backgrounds
International Nuclear Information System (INIS)
Gozdz, Marek; Nakonieczny, Lukasz; Rogatko, Marek
2010-01-01
We discuss the behavior of the Dirac fermions in a general spherically symmetric black hole background with a nontrivial topology of the event horizon. Both massive and massless cases are taken into account. We will conduct an analytical study of intermediate and late-time behavior of massive Dirac hair in the background of a black hole with a global monopole and dilaton black hole pierced by a cosmic string. In the case of a global monopole swallowed by a static black hole, the intermediate late-time behavior depends on the mass of the Dirac field, the multiple number of the wave mode, and the global monopole parameter. The late-time behavior is quite independent of these factors and has a decay rate proportional to t -5/6 . As far as the black hole pierced by a cosmic string is concerned, the intermediate late-time behavior depends only on the hair mass and the multipole number of the wave mode, while the late-time behavior dependence is the same as in the previous case. The main modification stems from the topology of the S 2 sphere pierced by a cosmic string. This factor modifies the eigenvalues of the Dirac operator acting on the transverse manifold.
Homogenous finitary symmetric groups
Directory of Open Access Journals (Sweden)
Otto. H. Kegel
2015-03-01
Full Text Available We characterize strictly diagonal type of embeddings of finitary symmetric groups in terms of cardinality and the characteristic. Namely, we prove the following. Let kappa be an infinite cardinal. If G=underseti=1stackrelinftybigcupG i , where G i =FSym(kappan i , (H=underseti=1stackrelinftybigcupH i , where H i =Alt(kappan i , is a group of strictly diagonal type and xi=(p 1 ,p 2 ,ldots is an infinite sequence of primes, then G is isomorphic to the homogenous finitary symmetric group FSym(kappa(xi (H is isomorphic to the homogenous alternating group Alt(kappa(xi , where n 0 =1,n i =p 1 p 2 ldotsp i .
Chen, Yan; Feng, Huijuan; Ma, Jiayao; Peng, Rui; You, Zhong
2016-06-01
The traditional waterbomb origami, produced from a pattern consisting of a series of vertices where six creases meet, is one of the most widely used origami patterns. From a rigid origami viewpoint, it generally has multiple degrees of freedom, but when the pattern is folded symmetrically, the mobility reduces to one. This paper presents a thorough kinematic investigation on symmetric folding of the waterbomb pattern. It has been found that the pattern can have two folding paths under certain circumstance. Moreover, the pattern can be used to fold thick panels. Not only do the additional constraints imposed to fold the thick panels lead to single degree of freedom folding, but the folding process is also kinematically equivalent to the origami of zero-thickness sheets. The findings pave the way for the pattern being readily used to fold deployable structures ranging from flat roofs to large solar panels.
Symmetric vectors and algebraic classification
International Nuclear Information System (INIS)
Leibowitz, E.
1980-01-01
The concept of symmetric vector field in Riemannian manifolds, which arises in the study of relativistic cosmological models, is analyzed. Symmetric vectors are tied up with the algebraic properties of the manifold curvature. A procedure for generating a congruence of symmetric fields out of a given pair is outlined. The case of a three-dimensional manifold of constant curvature (''isotropic universe'') is studied in detail, with all its symmetric vector fields being explicitly constructed
Representations of locally symmetric spaces
International Nuclear Information System (INIS)
Rahman, M.S.
1995-09-01
Locally symmetric spaces in reference to globally and Hermitian symmetric Riemannian spaces are studied. Some relations between locally and globally symmetric spaces are exhibited. A lucid account of results on relevant spaces, motivated by fundamental problems, are formulated as theorems and propositions. (author). 10 refs
Minamitsuji, Masato
2014-01-01
We investigate the quasinormal modes of a test massless, minimally coupled scalar field on a static and spherically symmetric black hole in the scalar-tensor theory with field derivative coupling to the Einstein tensor, which is a part of the Horndeski theory with the shift symmetry. In our solution, the spacetime is asymptotically AdS (anti-de Sitter), where the effective AdS curvature scale is determined solely by the derivative coupling constant. The metric approaches the AdS spacetime in ...
BOOK REVIEW: Black Holes, Cosmology and Extra Dimensions Black Holes, Cosmology and Extra Dimensions
Frolov, Valeri P.
2013-10-01
The book Black holes, Cosmology and Extra Dimensions written by Kirill A Bronnikov and Sergey G Rubin has been published recently by World Scientific Publishing Company. The authors are well known experts in gravity and cosmology. The book is a monograph, a considerable part of which is based on the original work of the authors. Their original point of view on some of the problems makes the book quite interesting, covering a variety of important topics of the modern theory of gravity, astrophysics and cosmology. It consists of 11 chapters which are organized in three parts. The book starts with an introduction, where the authors briefly discuss the main ideas of General Relativity, giving some historical remarks on its development and application to cosmology, and mentioning some more recent subjects such as brane worlds, f(R)-theories and gravity in higher dimensions. Part I of the book is called 'Gravity'. Chapters two and three are devoted to the Einstein equations and their spherical symmetric black hole solutions. This material is quite standard and can be found in practically any book on General Relativity. A brief summary of the Kerr metric and black hole thermodynamics are given in chapter four. The main part of this chapter is devoted to spherically symmetric black holes in non-Einstein gravity (with scalar and phantom fields), black holes with regular interior, and black holes in brane worlds. Chapters five and six are mainly dedicated to wormholes and the problem of their stability. Part II (Cosmology) starts with discussion of the Friedmann-Robertson-Walker and de Sitter solutions of the Einstein equations and their properties. It follows by describing a `big picture' of the modern cosmology (inflation, post-inflationary reheating, the radiation-dominated and matter-dominated states, and modern stage of the (secondary) inflation). The authors explain how the inflation models allow one to solve many of the long-standing problems of cosmology, such as
Peeples, Steven
2015-01-01
A three degree of freedom (DOF) spherical actuator is proposed that will replace functions requiring three single DOF actuators in robotic manipulators providing space and weight savings while reducing the overall failure rate. Exploration satellites, Space Station payload manipulators, and rovers requiring pan, tilt, and rotate movements need an actuator for each function. Not only does each actuator introduce additional failure modes and require bulky mechanical gimbals, each contains many moving parts, decreasing mean time to failure. A conventional robotic manipulator is shown in figure 1. Spherical motors perform all three actuation functions, i.e., three DOF, with only one moving part. Given a standard three actuator system whose actuators have a given failure rate compared to a spherical motor with an equal failure rate, the three actuator system is three times as likely to fail over the latter. The Jet Propulsion Laboratory reliability studies of NASA robotic spacecraft have shown that mechanical hardware/mechanism failures are more frequent and more likely to significantly affect mission success than are electronic failures. Unfortunately, previously designed spherical motors have been unable to provide the performance needed by space missions. This inadequacy is also why they are unavailable commercially. An improved patentable spherically actuated motor (SAM) is proposed to provide the performance and versatility required by NASA missions.
Notes on nonsingular models of black holes
Frolov, Valeri P.
2016-11-01
We discuss static spherically symmetric metrics which represent nonsingular black holes in four- and higher-dimensional spacetime. We impose a set of restrictions, such as a regularity of the metric at the center r =0 and Schwarzschild asymptotic behavior at large r . We assume that the metric besides mass M contains an additional parameter ℓ, which determines the scale where modification of the solution of the Einstein equations becomes significant. We require that the modified metric obeys the limiting curvature condition; that is, its curvature is uniformly restricted by the value ˜ℓ-2. We also make a "more technical" assumption that the metric coefficients are rational functions of r . In particular, the invariant (∇r )2 has the form Pn(r )/P˜n(r ), where Pn and P˜n are polynomials of the order of n . We discuss first the case of four dimensions. We show that when n ≤2 such a metric cannot describe a nonsingular black hole. For n =3 we find a suitable metric, which besides M and ℓ contains a dimensionless numerical parameter. When this parameter vanishes, the obtained metric coincides with Hayward's one. The characteristic property of such spacetimes is -ξ2=(∇r )2, where ξ2 is a timelike at infinity Killing vector. We describe a possible generalization of a nonsingular black-hole metric to the case when this equality is violated. We also obtain a metric for a charged nonsingular black hole obeying similar restrictions as the neutral one and construct higher dimensional models of neutral and charged black holes.
Spherical geodesic mesh generation
Energy Technology Data Exchange (ETDEWEB)
Fung, Jimmy [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Kenamond, Mark Andrew [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Burton, Donald E. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Shashkov, Mikhail Jurievich [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
2015-02-27
In ALE simulations with moving meshes, mesh topology has a direct influence on feature representation and code robustness. In three-dimensional simulations, modeling spherical volumes and features is particularly challenging for a hydrodynamics code. Calculations on traditional spherical meshes (such as spin meshes) often lead to errors and symmetry breaking. Although the underlying differencing scheme may be modified to rectify this, the differencing scheme may not be accessible. This work documents the use of spherical geodesic meshes to mitigate solution-mesh coupling. These meshes are generated notionally by connecting geodesic surface meshes to produce triangular-prismatic volume meshes. This mesh topology is fundamentally different from traditional mesh topologies and displays superior qualities such as topological symmetry. This work describes the geodesic mesh topology as well as motivating demonstrations with the FLAG hydrocode.
Black hole critical phenomena without black holes
Indian Academy of Sciences (India)
denotes the partial derivatives of . The construction of a numerical method with which ... which configurations form black holes and which disperse (the only two options in this model). The problem in picturing such a space is that it is infinite ..... 4.1 The future: Less symmetry. The work described above all assumes spherical ...
Non-extremal black hole solutions from the c-map
International Nuclear Information System (INIS)
Errington, D.; Mohaupt, T.; Vaughan, O.
2015-01-01
We construct new static, spherically symmetric non-extremal black hole solutions of four-dimensional N=2 supergravity, using a systematic technique based on dimensional reduction over time (the c-map) and the real formulation of special geometry. For a certain class of models we actually obtain the general solution to the full second order equations of motion, whilst for other classes of models, such as those obtainable by dimensional reduction from five dimensions, heterotic tree-level models, and type-II Calabi-Yau compactifications in the large volume limit a partial set of solutions are found. When considering specifically non-extremal black hole solutions we find that regularity conditions reduce the number of integration constants by one half. Such solutions satisfy a unique set of first order equations, which we identify. Several models are investigated in detail, including examples of non-homogeneous spaces such as the quantum deformed STU model. Though we focus on static, spherically symmetric solutions of ungauged supergravity, the method is adaptable to other types of solutions and to gauged supergravity.
Non-Abelian black holes in D=5 maximal gauged supergravity
International Nuclear Information System (INIS)
Cvetic, M.; Lue, H.; Pope, C. N.
2010-01-01
We investigate static non-Abelian black hole solutions of anti-de Sitter (AdS) Einstein-Yang-Mills-dilaton gravity, which is obtained as a consistent truncation of five-dimensional maximal gauged supergravity. If the dilaton is (consistently) set to zero, the remaining equations of motion, with a spherically-symmetric ansatz, may be derived from a superpotential. The associated first-order equations admit an explicit solution supported by a non-Abelian SU(2) gauge potential, which has a logarithmically growing mass term. In an extremal limit the horizon geometry becomes AdS 2 xS 3 . If the dilaton is also excited, the equations of motion cannot easily be solved explicitly, but we obtain the asymptotic form of the more general non-Abelian black holes in this case. An alternative consistent truncation, in which the Yang-Mills fields are set to zero, also admits a description in terms of a superpotential. This allows us to construct explicit wormhole solutions (neutral spherically-symmetric domain walls). These solutions may be generalized to dimensions other than five.
Black hole perturbation under a 2 +2 decomposition in the action
Ripley, Justin L.; Yagi, Kent
2018-01-01
Black hole perturbation theory is useful for studying the stability of black holes and calculating ringdown gravitational waves after the collision of two black holes. Most previous calculations were carried out at the level of the field equations instead of the action. In this work, we compute the Einstein-Hilbert action to quadratic order in linear metric perturbations about a spherically symmetric vacuum background in Regge-Wheeler gauge. Using a 2 +2 splitting of spacetime, we expand the metric perturbations into a sum over scalar, vector, and tensor spherical harmonics, and dimensionally reduce the action to two dimensions by integrating over the two sphere. We find that the axial perturbation degree of freedom is described by a two-dimensional massive vector action, and that the polar perturbation degree of freedom is described by a two-dimensional dilaton massive gravity action. Varying the dimensionally reduced actions, we rederive covariant and gauge-invariant master equations for the axial and polar degrees of freedom. Thus, the two-dimensional massive vector and massive gravity actions we derive by dimensionally reducing the perturbed Einstein-Hilbert action describe the dynamics of a well-studied physical system: the metric perturbations of a static black hole. The 2 +2 formalism we present can be generalized to m +n -dimensional spacetime splittings, which may be useful in more generic situations, such as expanding metric perturbations in higher dimensional gravity. We provide a self-contained presentation of m +n formalism for vacuum spacetime splittings.
Indian Academy of Sciences (India)
D. Bhattacharyya
2018-02-09
Feb 9, 2018 ... metric linear regression method for their analysis and in this process both the variables M• and σ had an unique error in measurements as well as intrinsic scatter, while the later used non-symmetrical least square regression, where it was assumed that σ had no uncertainty in measurement and M• had the ...
Indian Academy of Sciences (India)
D. Bhattacharyya
2018-02-09
Feb 9, 2018 ... (2000) reported p = 3.75 ± 0.3. The former used sym- metric linear regression method for their analysis and in this process both the variables M• and σ had an unique error in measurements as well as intrinsic scatter, while the later used non-symmetrical least square regression, where it was assumed that σ ...
Symmetric spaces and the Kashiwara-Vergne method
Rouvière, François
2014-01-01
Gathering and updating results scattered in journal articles over thirty years, this self-contained monograph gives a comprehensive introduction to the subject. Its goal is to: - motivate and explain the method for general Lie groups, reducing the proof of deep results in invariant analysis to the verification of two formal Lie bracket identities related to the Campbell-Hausdorff formula (the "Kashiwara-Vergne conjecture"); - give a detailed proof of the conjecture for quadratic and solvable Lie algebras, which is relatively elementary; - extend the method to symmetric spaces; here an obstruction appears, embodied in a single remarkable object called an "e-function"; - explain the role of this function in invariant analysis on symmetric spaces, its relation to invariant differential operators, mean value operators and spherical functions; - give an explicit e-function for rank one spaces (the hyperbolic spaces); - construct an e-function for general symmetric spaces, in the spirit of Kashiwara and Vergne's or...
Strong gravitational lensing by a charged Kiselev black hole
Energy Technology Data Exchange (ETDEWEB)
Azreg-Ainou, Mustapha [Baskent University, Engineering Faculty, Ankara (Turkey); Bahamonde, Sebastian [University College London, Department of Mathematics, London (United Kingdom); Jamil, Mubasher [National University of Sciences and Technology (NUST), Department of Mathematics, School of Natural Sciences (SNS), Islamabad (Pakistan)
2017-06-15
We study the gravitational lensing scenario where the lens is a spherically symmetric charged black hole (BH) surrounded by quintessence matter. The null geodesic equations in the curved background of the black hole are derived. The resulting trajectory equation is solved analytically via perturbation and series methods for a special choice of parameters, and the distance of the closest approach to black hole is calculated. We also derive the lens equation giving the bending angle of light in the curved background. In the strong field approximation, the solution of the lens equation is also obtained for all values of the quintessence parameter w{sub q}. For all w{sub q}, we show that there are no stable closed null orbits and that corrections to the deflection angle for the Reissner-Nordstroem black hole when the observer and the source are at large, but finite, distances from the lens do not depend on the charge up to the inverse of the distances squared. A part of the present work, analyzed, however, with a different approach, is the extension of Younas et al. (Phys Rev D 92:084042, 2015) where the uncharged case has been treated. (orig.)
Noncommutative geometry inspired Einstein–Gauss–Bonnet black holes
Ghosh, Sushant G.
2018-04-01
Low energy limits of a string theory suggests that the gravity action should include quadratic and higher-order curvature terms, in the form of dimensionally continued Gauss–Bonnet densities. Einstein–Gauss–Bonnet is a natural extension of the general relativity to higher dimensions in which the first and second-order terms correspond, respectively, to general relativity and Einstein–Gauss–Bonnet gravity. We obtain five-dimensional (5D) black hole solutions, inspired by a noncommutative geometry, with a static spherically symmetric, Gaussian mass distribution as a source both in the general relativity and Einstein–Gauss–Bonnet gravity cases, and we also analyzes their thermodynamical properties. Owing the noncommutative corrected black hole, the thermodynamic quantities have also been modified, and phase transition is shown to be achievable. The phase transitions for the thermodynamic stability, in both the theories, are characterized by a discontinuity in the specific heat at r_+=rC , with the stable (unstable) branch for r ) rC . The metric of the noncommutative inspired black holes smoothly goes over to the Boulware–Deser solution at large distance. The paper has been appended with a calculation of black hole mass using holographic renormalization.
General theories of linear gravitational perturbations to a Schwarzschild black hole
Tattersall, Oliver J.; Ferreira, Pedro G.; Lagos, Macarena
2018-02-01
We use the covariant formulation proposed by Tattersall, Lagos, and Ferreira [Phys. Rev. D 96, 064011 (2017), 10.1103/PhysRevD.96.064011] to analyze the structure of linear perturbations about a spherically symmetric background in different families of gravity theories, and hence study how quasinormal modes of perturbed black holes may be affected by modifications to general relativity. We restrict ourselves to single-tensor, scalar-tensor and vector-tensor diffeomorphism-invariant gravity models in a Schwarzschild black hole background. We show explicitly the full covariant form of the quadratic actions in such cases, which allow us to then analyze odd parity (axial) and even parity (polar) perturbations simultaneously in a straightforward manner.
A no-hair theorem for black holes in f(R) gravity
Cañate, Pedro
2018-01-01
In this work we present a no-hair theorem which discards the existence of four-dimensional asymptotically flat, static and spherically symmetric or stationary axisymmetric, non-trivial black holes in the frame of f(R) gravity under metric formalism. Here we show that our no-hair theorem also can discard asymptotic de Sitter stationary and axisymmetric non-trivial black holes. The novelty is that this no-hair theorem is built without resorting to known mapping between f(R) gravity and scalar–tensor theory. Thus, an advantage will be that our no-hair theorem applies as well to metric f(R) models that cannot be mapped to scalar–tensor theory.
Symmetric instability of monsoon flows
Krishnakumar, V.; Lau, K.-M.
2011-01-01
Using a zonally symmetric multi-level moist linear model, we have examined the possibility of symmetric instability in the monsoon region. Stability analyses with a zonally symmetric model using monthly ECMWF (Jan – Dec) zonal basic flows revealed both unstable as well as neutral modes. In the absence of cumulus heating, the linear stability of the monsoon flow changes dramatically with the emergence of many unstable modes in the month of May and lasting through August; whereas with the inclu...
Black hole solutions in mimetic Born-Infeld gravity.
Chen, Che-Yu; Bouhmadi-López, Mariam; Chen, Pisin
2018-01-01
The vacuum, static, and spherically symmetric solutions in the mimetic Born-Infeld gravity are studied. The mimetic Born-Infeld gravity is a reformulation of the Eddington-inspired-Born-Infeld (EiBI) model under the mimetic approach. Due to the mimetic field, the theory contains non-trivial vacuum solutions different from those in Einstein gravity. We find that with the existence of the mimetic field, the spacelike singularity inside a Schwarzschild black hole could be altered to a lightlike singularity, even though the curvature invariants still diverge at the singularity. Furthermore, in this case, the maximal proper time for a timelike radially-infalling observer to reach the singularity is found to be infinite.
Black Hole Entropy for Two Higher Derivative Theories of Gravity
Directory of Open Access Journals (Sweden)
Lorenzo Sebastiani
2010-10-01
Full Text Available The dark energy issue is attracting the attention of an increasing number of physicists all over the world. Among the possible alternatives to explain what as been named the “Mystery of the Millennium” are the so-called Modified Theories of Gravity. A crucial test for such models is represented by the existence and (if this is the case the properties of their black hole solutions. Nowadays, to our knowledge, only two non-trivial, static, spherically symmetric, solutions with vanishing cosmological constant are known by Barrow & Clifton (2005 and Deser, Sarioglu & Tekin (2008. The aim of the paper is to discuss some features of such solutions, with emphasis on their thermodynamic properties such as entropy and temperature.
Directory of Open Access Journals (Sweden)
Giuseppe Dattoli
1996-05-01
Full Text Available q analog of bessel functions, symmetric under the interchange of q and q^ −1 are introduced. The definition is based on the generating function realized as product of symmetric q-exponential functions with appropriate arguments. Symmetric q-Bessel function are shown to satisfy various identities as well as second-order q-differential equations, which in the limit q → 1 reproduce those obeyed by the usual cylindrical Bessel functions. A brief discussion on the possible algebraic setting for symmetric q-Bessel functions is also provided.
International Nuclear Information System (INIS)
Berg, S.; Semmes, P.B.; Nazarewicz, W.
1997-01-01
Various theoretical approaches to proton emission from spherical nuclei are investigated, and it is found that all the methods employed give very similar results. The calculated decay widths are found to be qualitatively insensitive to the parameters of the proton-nucleus potential, i.e., changing the potential parameters over a fairly large range typically changes the decay width by no more than a factor of ∼3. Proton half-lives of observed heavy proton emitters are, in general, well reproduced by spherical calculations with the spectroscopic factors calculated in the independent quasiparticle approximation. The quantitative agreement with experimental data obtained in our study requires that the parameters of the proton-nucleus potential be chosen carefully. It also suggests that deformed proton emitters will provide invaluable spectroscopic information on the angular momentum decomposition of single-proton orbitals in deformed nuclei. copyright 1997 The American Physical Society
Spherical rhenium metal powder
International Nuclear Information System (INIS)
Leonhardt, T.; Moore, N.; Hamister, M.
2001-01-01
The development of a high-density, spherical rhenium powder (SReP) possessing excellent flow characteristics has enabled the use of advanced processing techniques for the manufacture of rhenium components. The techniques that were investigated were vacuum plasma spraying (VPS), direct-hot isostatic pressing (D-HIP), and various other traditional powder metallurgy processing methods of forming rhenium powder into near-net shaped components. The principal disadvantages of standard rhenium metal powder (RMP) for advanced consolidation applications include: poor flow characteristics; high oxygen content; and low and varying packing densities. SReP will lower costs, reduce processing times, and improve yields when manufacturing powder metallurgy rhenium components. The results of the powder characterization of spherical rhenium powder and the consolidation of the SReP are further discussed. (author)
Black Holes, Cosmology and Extra Dimensions
International Nuclear Information System (INIS)
Frolov, Valeri P
2013-01-01
Book review: The book Black holes, Cosmology and Extra Dimensions written by Kirill A Bronnikov and Sergey G Rubin has been published recently by World Scientific Publishing Company. The authors are well known experts in gravity and cosmology. The book is a monograph, a considerable part of which is based on the original work of the authors. Their original point of view on some of the problems makes the book quite interesting, covering a variety of important topics of the modern theory of gravity, astrophysics and cosmology. It consists of 11 chapters which are organized in three parts. The book starts with an introduction, where the authors briefly discuss the main ideas of General Relativity, giving some historical remarks on its development and application to cosmology, and mentioning some more recent subjects such as brane worlds, f (R)−theories and gravity in higher dimensions. Part I of the book is called ‘Gravity’. Chapters two and three are devoted to the Einstein equations and their spherical symmetric black hole solutions. Part II (Cosmology) starts with discussion of the Friedmann–Robertson–Walker and de Sitter solutions of the Einstein equations and their properties. Part III covers the material on extra dimensions. It describes how Einstein gravity is modified in the presence of one or more additional spatial dimensions and how these extra dimensions are compactified in the Kaluza–Klein scheme
The Spherical Deformation Model
DEFF Research Database (Denmark)
Hobolth, Asgar
2003-01-01
Miller et al. (1994) describe a model for representing spatial objects with no obvious landmarks. Each object is represented by a global translation and a normal deformation of a sphere. The normal deformation is defined via the orthonormal spherical-harmonic basis. In this paper we analyse the s...... a single central section of the object. We use maximum-likelihood-based inference for this purpose and demonstrate the suggested methods on real data....
Design and Transmission Analysis of an Asymmetrical Spherical Parallel Manipulator
DEFF Research Database (Denmark)
Wu, Guanglei; Caro, Stéphane; Wang, Jiawei
2015-01-01
This paper presents an asymmetrical spherical parallel manipulator and its transmissibility analysis. This manipulator contains a center shaft to both generate a decoupled unlimited-torsion motion and support the mobile platform for high positioning accuracy. This work addresses the transmission...... analysis and optimal design of the proposed manipulator based on its kinematic analysis. The input and output transmission indices of the manipulator are defined for its optimum design based on the virtual coefficient between the transmission wrenches and twist screws. The sets of optimal parameters...... are identified and the distribution of the transmission index is visualized. Moreover, a comparative study regarding to the performances with the symmetrical spherical parallel manipulators is conducted and the comparison shows the advantages of the proposed manipulator with respect to its spherical parallel...
The space-time outside a source of gravitational radiation: the axially symmetric null fluid
Energy Technology Data Exchange (ETDEWEB)
Herrera, L. [Universidad Central de Venezuela, Escuela de Fisica, Facultad de Ciencias, Caracas (Venezuela, Bolivarian Republic of); Universidad de Salamanca, Instituto Universitario de Fisica Fundamental y Matematicas, Salamanca (Spain); Di Prisco, A. [Universidad Central de Venezuela, Escuela de Fisica, Facultad de Ciencias, Caracas (Venezuela, Bolivarian Republic of); Ospino, J. [Universidad de Salamanca, Departamento de Matematica Aplicada and Instituto Universitario de Fisica Fundamental y Matematicas, Salamanca (Spain)
2016-11-15
We carry out a study of the exterior of an axially and reflection symmetric source of gravitational radiation. The exterior of such a source is filled with a null fluid produced by the dissipative processes inherent to the emission of gravitational radiation, thereby representing a generalization of the Vaidya metric for axially and reflection symmetric space-times. The role of the vorticity, and its relationship with the presence of gravitational radiation is put in evidence. The spherically symmetric case (Vaidya) is, asymptotically, recovered within the context of the 1 + 3 formalism. (orig.)
CSIR Research Space (South Africa)
Khawula, TNY
2016-03-01
Full Text Available Molybdenum disulfide-modified carbon nanospheres (MoS(sub2)/CNS) with two different morphologies (spherical and flower-like) have been synthesized using hydrothermal techniques and investigated as symmetric pseudocapacitors in an aqueous electrolyte...
Thermodynamic properties of static and rotating unparticle black holes
Alencar, G.; Muniz, C. R.
2018-03-01
In this paper we find analytical expressions for thermodynamic quantities of scalar (tensor) and vector unparticle static black holes. We also find rotating solutions to these systems and analyse their thermodynamics. First we consider the static case with a spherically symmetric source for both the vector and scalar (tensor) unparticles. We obtain thus analytical expressions to the principal thermodynamic quantities: Hawking temperature, entropy, heat capacity and free energy. For the scalar (tensor) case we find that the black hole presents a residual value for the entropy when its radius goes to zero but the other thermodynamic quantities give, for any horizon radius, a thermodynamically unstable behavior similar to the standard black hole. For the vector case we find a richer structure in the region in which the horizon radius is less than the characteristic length of the unparticle theory. We identify a phase transition and a region where the black hole can be thermodynamically stable. Following, we show that the mentioned modifications in the standard gravity are formally similar to those ones present in the black holes with quintessence. With this we also show, notwithstanding, that the unparticles cannot be a source of quintessence. By using this similarity we find two different rotating solutions to the unparticle black holes based on works by Ghosh and Toshmatov et al.. For both cases we compute the Hawking temperature and in the ungravity dominated regime we find, as in the static cases, a fractalization of the event horizon. For the Gosh-like solution the fractal dimension depends on the polar angle and on the rotation of the source. For the Toshmatov-like one it is equal to the static case and therefore the fractalization is not dependent on the rotation of the source.
Symmetric Decomposition of Asymmetric Games.
Tuyls, Karl; Pérolat, Julien; Lanctot, Marc; Ostrovski, Georg; Savani, Rahul; Leibo, Joel Z; Ord, Toby; Graepel, Thore; Legg, Shane
2018-01-17
We introduce new theoretical insights into two-population asymmetric games allowing for an elegant symmetric decomposition into two single population symmetric games. Specifically, we show how an asymmetric bimatrix game (A,B) can be decomposed into its symmetric counterparts by envisioning and investigating the payoff tables (A and B) that constitute the asymmetric game, as two independent, single population, symmetric games. We reveal several surprising formal relationships between an asymmetric two-population game and its symmetric single population counterparts, which facilitate a convenient analysis of the original asymmetric game due to the dimensionality reduction of the decomposition. The main finding reveals that if (x,y) is a Nash equilibrium of an asymmetric game (A,B), this implies that y is a Nash equilibrium of the symmetric counterpart game determined by payoff table A, and x is a Nash equilibrium of the symmetric counterpart game determined by payoff table B. Also the reverse holds and combinations of Nash equilibria of the counterpart games form Nash equilibria of the asymmetric game. We illustrate how these formal relationships aid in identifying and analysing the Nash structure of asymmetric games, by examining the evolutionary dynamics of the simpler counterpart games in several canonical examples.
Lagrangian formulation of symmetric space sine-Gordon models
Bakas, Ioannis; Shin, H J; Park, Q Han
1996-01-01
The symmetric space sine-Gordon models arise by conformal reduction of ordinary 2-dim \\sigma-models, and they are integrable exhibiting a black-hole type metric in target space. We provide a Lagrangian formulation of these systems by considering a triplet of Lie groups F \\supset G \\supset H. We show that for every symmetric space F/G, the generalized sine-Gordon models can be derived from the G/H WZW action, plus a potential term that is algebraically specified. Thus, the symmetric space sine-Gordon models describe certain integrable perturbations of coset conformal field theories at the classical level. We also briefly discuss their vacuum structure, Backlund transformations, and soliton solutions.
Entropy of an extremal electrically charged thin shell and the extremal black hole
Directory of Open Access Journals (Sweden)
José P.S. Lemos
2015-11-01
Full Text Available There is a debate as to what is the value of the entropy S of extremal black holes. There are approaches that yield zero entropy S=0, while there are others that yield the Bekenstein–Hawking entropy S=A+/4, in Planck units. There are still other approaches that give that S is proportional to r+ or even that S is a generic well-behaved function of r+. Here r+ is the black hole horizon radius and A+=4πr+2 is its horizon area. Using a spherically symmetric thin matter shell with extremal electric charge, we find the entropy expression for the extremal thin shell spacetime. When the shell's radius approaches its own gravitational radius, and thus turns into an extremal black hole, we encounter that the entropy is S=S(r+, i.e., the entropy of an extremal black hole is a function of r+ alone. We speculate that the range of values for an extremal black hole is 0≤S(r+≤A+/4.
Black hole perturbations in vector-tensor theories: the odd-mode analysis
Kase, Ryotaro; Minamitsuji, Masato; Tsujikawa, Shinji; Zhang, Ying-li
2018-02-01
In generalized Proca theories with vector-field derivative couplings, a bunch of hairy black hole solutions have been derived on a static and spherically symmetric background. In this paper, we formulate the odd-parity black hole perturbations in generalized Proca theories by expanding the corresponding action up to second order and investigate whether or not black holes with vector hair suffer ghost or Laplacian instabilities. We show that the models with cubic couplings G3(X), where X=‑AμAμ/2 with a vector field Aμ, do not provide any additional stability condition as in General Relativity. On the other hand, the exact charged stealth Schwarzschild solution with a nonvanishing longitudinal vector component A1, which originates from the coupling to the Einstein tensor GμνAμ Aν equivalent to the quartic coupling G4(X) containing a linear function of X, is unstable in the vicinity of the event horizon. The same instability problem also persists for hairy black holes arising from general quartic power-law couplings G4(X) ⊃ β4 Xn with the nonvanishing A1, while the other branch with A1=0 can be consistent with conditions for the absence of ghost and Laplacian instabilities. We also discuss the case of other exact and numerical black hole solutions associated with intrinsic vector-field derivative couplings and show that there exists a wide range of parameter spaces in which the solutions suffer neither ghost nor Laplacian instabilities against odd-parity perturbations.
Horizon of quantum black holes in various dimensions
Directory of Open Access Journals (Sweden)
Roberto Casadio
2016-09-01
Full Text Available We adapt the horizon wave-function formalism to describe massive static spherically symmetric sources in a general (1+D-dimensional space-time, for D>3 and including the D=1 case. We find that the probability PBH that such objects are (quantum black holes behaves similarly to the probability in the (3+1 framework for D>3. In fact, for D≥3, the probability increases towards unity as the mass grows above the relevant D-dimensional Planck scale mD. At fixed mass, however, PBH decreases with increasing D, so that a particle with mass m≃mD has just about 10% probability to be a black hole in D=5, and smaller for larger D. This result has a potentially strong impact on estimates of black hole production in colliders. In contrast, for D=1, we find the probability is comparably larger for smaller masses, but PBH3. For D=1 we instead find the uncertainty due to the horizon fluctuations has the same form as the usual Heisenberg contribution, and therefore no fundamental scale exists.
Black holes, dark wormholes, and solitons in f (T ) gravities
Mai, Zhan-Feng; Lü, H.
2017-06-01
By choosing an appropriate vielbein basis, we obtain a class of spherically-symmetric solutions in f (T ) gravities. The solutions are asymptotic to Minkowski spacetimes with leading falloffs the same as those of the Schwarzschild black hole. In general, these solutions have branch-cut singularities in the middle. For appropriately chosen f (T ) functions, extremal black holes can also emerge. Furthermore, we obtain wormhole configurations whose spatial section is analogous to an Ellis wormhole, but -gt t runs from 0 to 1 as the proper radial coordinate runs from -∞ to +∞ . Thus a signal sent from -∞ to +∞ through the wormhole will be infinitely red-shifted. We call such a spacetime configuration a dark wormhole. By introducing a bare cosmological constant Λ0, we construct smooth solitons that are asymptotic to local AdS with an effective Λeff. In the middle of bulk, the soliton metric behaves like the AdS of bare Λ0 in global coordinates. We also embed AdS planar and Lifshitz black holes in f (T ) gravities. Finally we couple the Maxwell field to the f (T ) theories and construct electrically-charged solutions.
Thin-shell wormholes from the regular Hayward black hole
Energy Technology Data Exchange (ETDEWEB)
Halilsoy, M.; Ovgun, A.; Mazharimousavi, S.H. [Eastern Mediterranean University, Department of Physics, Mersin 10 (Turkey)
2014-03-15
We revisit the regular black hole found by Hayward in 4-dimensional static, spherically symmetric spacetime. To find a possible source for such a spacetime we resort to the nonlinear electrodynamics in general relativity. It is found that a magnetic field within this context gives rise to the regular Hayward black hole. By employing such a regular black hole we construct a thin-shell wormhole for the case of various equations of state on the shell. We abbreviate a general equation of state by p = ψ(σ) where p is the surface pressure which is a function of the mass density (σ). In particular, linear, logarithmic, Chaplygin, etc. forms of equations of state are considered. In each case we study the stability of the thin shell against linear perturbations.We plot the stability regions by tuning the parameters of the theory. It is observed that the role of the Hayward parameter is to make the TSW more stable. Perturbations of the throat with small velocity condition are also studied. The matter of our TSWs, however, remains exotic. (orig.)
Symmetric $q$-deformed KP hierarch
Tian, Kelei; He, Jingsong; Su, Yucai
2014-01-01
Based on the analytic property of the symmetric $q$-exponent $e_q(x)$, a new symmetric $q$-deformed Kadomtsev-Petviashvili ($q$-KP) hierarchy associated with the symmetric $q$-derivative operator $\\partial_q$ is constructed. Furthermore, the symmetric $q$-CKP hierarchy and symmetric $q$-BKP hierarchy are defined. Here we also investigate the additional symmetries of the symmetric $q$-KP hierarchy.
Non-supersymmetric Attractors in Symmetric Coset Spaces
Li, Wei
We develop a method of constructing generic black hole attractor solutions, both BPS and non-BPS, single-centered as well as multi-centered, in a large class of 4D N = 2 supergravities coupled to vector-multiplets with cubic prepotentials. The method is applicable to models for which the 3D moduli spaces obtained via c ∗-map are symmetric coset spaces. All attractor solutions in such a 3D moduli space can be constructed algebraically in a unified way. Then the 3D attractor solutions are mapped back into four dimensions to give 4D extremal black holes.
The Role of Orthogonal Polynomials in Tailoring Spherical Distributions to Kurtosis Requirements
Directory of Open Access Journals (Sweden)
Luca Bagnato
2016-08-01
Full Text Available This paper carries out an investigation of the orthogonal-polynomial approach to reshaping symmetric distributions to fit in with data requirements so as to cover the multivariate case. With this objective in mind, reference is made to the class of spherical distributions, given that they provide a natural multivariate generalization of univariate even densities. After showing how to tailor a spherical distribution via orthogonal polynomials to better comply with kurtosis requirements, we provide operational conditions for the positiveness of the resulting multivariate Gram–Charlier-like expansion, together with its kurtosis range. Finally, the approach proposed here is applied to some selected spherical distributions.
Mostert, W.
2017-01-27
We present numerical simulations of ideal magnetohydrodynamics showing suppression of the Richtmyer-Meshkov instability in spherical implosions in the presence of an octahedrally symmetric magnetic field. This field configuration is of interest owing to its high degree of spherical symmetry in comparison with previously considered dihedrally symmetric fields. The simulations indicate that the octahedral field suppresses the instability comparably to the other previously considered candidate fields for light-heavy interface accelerations while retaining a highly symmetric underlying flow even at high field strengths. With this field, there is a reduction in the root-mean-square perturbation amplitude of up to approximately 50% at representative time under the strongest field tested while maintaining a homogeneous suppression pattern compared to the other candidate fields.
Spherical tokamak development in Brazil
International Nuclear Information System (INIS)
Ludwig, Gerson Otto; Bosco, Edson Del; Ferreira, Julio Guimaraes
2003-01-01
The general characteristics of spherical tokamaks, or spherical tori, with a brief view of work in this area already performed or in progress at several institutions worldwide are described. The paper presents also the steps in the development of the ETE (Experiment Tokamak spheric) project, its research program, technical characteristics and operating conditions as of December, 2002 a the Associated Plasma Laboratory (LAP) of the National Space Research Institute (INPE) in Brazil. (author)
Spherical tokamak development in Brazil
Energy Technology Data Exchange (ETDEWEB)
Ludwig, Gerson Otto; Bosco, Edson Del; Ferreira, Julio Guimaraes [Instituto Nacional de Pesquisas Espaciais (INPE), Sao Jose dos Campos, SP (Brazil). Lab. Associado de Plasma] (and others)
2003-07-01
The general characteristics of spherical tokamaks, or spherical tori, with a brief view of work in this area already performed or in progress at several institutions worldwide are described. The paper presents also the steps in the development of the ETE (Experiment Tokamak spheric) project, its research program, technical characteristics and operating conditions as of December, 2002 a the Associated Plasma Laboratory (LAP) of the National Space Research Institute (INPE) in Brazil. (author)
The ETE spherical Tokamak project
International Nuclear Information System (INIS)
Ludwig, Gerson Otto; Andrade, Maria Celia Ramos de; Barbosa, Luis Filipe Wiltgen
1999-01-01
This paper describes the general characteristics of spherical tokamaks, with a brief overview of work in the area of spherical torus already performed or in progress at several institutions. The paper presents also the historical development of the ETE (Spherical Tokamak Experiment) project, its research program, technical characteristics and status of construction in September, 1998 at the Associated plasma Laboratory (LAP) of the National Institute for Space Research (INPE) in Brazil. (author)
The ETE spherical Tokamak project
Energy Technology Data Exchange (ETDEWEB)
Ludwig, Gerson Otto; Andrade, Maria Celia Ramos de; Barbosa, Luis Filipe Wiltgen [Instituto Nacional de Pesquisas Espaciais (INPE), Sao Jose dos Campos, SP (Brazil). Lab. Associado de Plasma] [and others]. E-mail: ludwig@plasma.inpe.br
1999-07-01
This paper describes the general characteristics of spherical tokamaks, with a brief overview of work in the area of spherical torus already performed or in progress at several institutions. The paper presents also the historical development of the ETE (Spherical Tokamak Experiment) project, its research program, technical characteristics and status of construction in September, 1998 at the Associated plasma Laboratory (LAP) of the National Institute for Space Research (INPE) in Brazil. (author)
Generalized reorientation cross section for cylindrically symmetric velocity distributions
International Nuclear Information System (INIS)
Generalized reorientation cross sections are derived for the case of atom--molecule collisions where the molecules initially have a velocity distribution cylindrically symmetric about an axis in the laboratory reference frame. This spatial ordering of the velocity can come about, for instance, by exciting molecular electronic states with a light source whose linewidth is much narrower than the Doppler-broadened absorption line. A simple kinetic theory can be set up in terms of state multipoles that are not completely irreducible; the resulting reorientation cross sections are only slightly more complex than the cross sections occurring in a spherically symmetric velocity field. Two approximations are investigated: a McGuire--Kouri m/sub j/-conserving model and a semiclassical model where the orientation of the rotation plane is conserved. The import of the generalized cross sections for several types of experiment and the applicability of the approximate models are discussed
Spherical grating spectrometers
O'Donoghue, Darragh; Clemens, J. Christopher
2014-07-01
We describe designs for spectrometers employing convex dispersers. The Offner spectrometer was the first such instrument; it has almost exclusively been employed on satellite platforms, and has had little impact on ground-based instruments. We have learned how to fabricate curved Volume Phase Holographic (VPH) gratings and, in contrast to the planar gratings of traditional spectrometers, describe how such devices can be used in optical/infrared spectrometers designed specifically for curved diffraction gratings. Volume Phase Holographic gratings are highly efficient compared to conventional surface relief gratings; they have become the disperser of choice in optical / NIR spectrometers. The advantage of spectrometers with curved VPH dispersers is the very small number of optical elements used (the simplest comprising a grating and a spherical mirror), as well as illumination of mirrors off axis, resulting in greater efficiency and reduction in size. We describe a "Half Offner" spectrometer, an even simpler version of the Offner spectrometer. We present an entirely novel design, the Spherical Transmission Grating Spectrometer (STGS), and discuss exemplary applications, including a design for a double-beam spectrometer without any requirement for a dichroic. This paradigm change in spectrometer design offers an alternative to all-refractive astronomical spectrometer designs, using expensive, fragile lens elements fabricated from CaF2 or even more exotic materials. The unobscured mirror layout avoids a major drawback of the previous generation of catadioptric spectrometer designs. We describe laboratory measurements of the efficiency and image quality of a curved VPH grating in a STGS design, demonstrating, simultaneously, efficiency comparable to planar VPH gratings along with good image quality. The stage is now set for construction of a prototype instrument with impressive performance.
Subleading contributions to the black hole entropy in the brick wall approach
International Nuclear Information System (INIS)
Sarkar, Sudipta; Shankaranarayanan, S.; Sriramkumar, L.
2008-01-01
The brick wall model is a semiclassical approach to understand the microscopic origin of black hole entropy. In this approach, the black hole geometry is assumed to be a fixed classical background on which matter fields propagate, and the entropy of black holes supposedly arises due to the canonical entropy of matter fields outside the black hole event horizon, evaluated at the Hawking temperature. Apart from certain lower dimensional cases, the density of states of the matter fields around black holes cannot be evaluated exactly. As a result, often, in the brick wall model, the density of states and the resulting canonical entropy of the matter fields are evaluated at the leading order (in terms of (ℎ/2π)) in the WKB approximation. The success of the approach is reflected by the fact that the Bekenstein-Hawking area law - viz. that the entropy of black holes is equal to one-quarter the area of their event horizon, say, A H - has been recovered using this model in a variety of black hole spacetimes. In this work, we compute the canonical entropy of a quantum scalar field around static and spherically symmetric black holes through the brick wall approach at the higher orders (in fact, up to the sixth order in (ℎ/2π)) in the WKB approximation. We explicitly show that the brick wall model generally predicts corrections to the Bekenstein-Hawking entropy in all spacetime dimensions. In four dimensions, we find that the corrections to the Bekenstein-Hawking entropy are of the form [A H n logA H ], while, in six dimensions, the corrections behave as [A H m +A H n logA H ], where (m,n)<1. We compare our results with the corrections to the Bekenstein-Hawking entropy that have been obtained through the other approaches in the literature, and discuss the implications.
Thermodynamic analysis of black hole solutions in gravitating nonlinear electrodynamics
Diaz-Alonso, J.; Rubiera-Garcia, D.
2013-10-01
We perform a general study of the thermodynamic properties of static electrically charged black hole solutions of nonlinear electrodynamics minimally coupled to gravitation in three space dimensions. The Lagrangian densities governing the dynamics of these models in flat space are defined as arbitrary functions of the gauge field invariants, constrained by some requirements for physical admissibility. The exhaustive classification of these theories in flat space, in terms of the behaviour of the Lagrangian densities in vacuum and on the boundary of their domain of definition, defines twelve families of admissible models. When these models are coupled to gravity, the flat space classification leads to a complete characterization of the associated sets of gravitating electrostatic spherically symmetric solutions by their central and asymptotic behaviours. We focus on nine of these families, which support asymptotically Schwarzschild-like black hole configurations, for which the thermodynamic analysis is possible and pertinent. In this way, the thermodynamic laws are extended to the sets of black hole solutions of these families, for which the generic behaviours of the relevant state variables are classified and thoroughly analyzed in terms of the aforementioned boundary properties of the Lagrangians. Moreover, we find universal scaling laws (which hold and are the same for all the black hole solutions of models belonging to any of the nine families) running the thermodynamic variables with the electric charge and the horizon radius. These scale transformations form a one-parameter multiplicative group, leading to universal "renormalization group"-like first-order differential equations. The beams of characteristics of these equations generate the full set of black hole states associated to any of these gravitating nonlinear electrodynamics. Moreover the application of the scaling laws allows to find a universal finite relation between the thermodynamic variables
Miniaturization of Spherical Magnetodielectric Antennas
DEFF Research Database (Denmark)
Hansen, Troels Vejle
; Arbitrary order of the spherical wave, arbitrary radius of the spherical antenna, as well as arbitrarily large core permeability and/or permittivity, given an inversely proportional frequency variation of the imaginary part(s) and an arbitrary dispersion of the real part(s) - thus describing both lossless...
Black Strings, Black Rings and State-space Manifold
Bellucci, Stefano
2011-01-01
State-space geometry is considered, for diverse three and four parameter non-spherical horizon rotating black brane configurations, in string theory and $M$-theory. We have explicitly examined the case of unit Kaluza-Klein momentum $D_1D_5P$ black strings, circular strings, small black rings and black supertubes. An investigation of the state-space pair correlation functions shows that there exist two classes of brane statistical configurations, {\\it viz.}, the first category divulges a degenerate intrinsic equilibrium basis, while the second yields a non-degenerate, curved, intrinsic Riemannian geometry. Specifically, the solutions with finitely many branes expose that the two charged rotating $D_1D_5$ black strings and three charged rotating small black rings consort real degenerate state-space manifolds. Interestingly, arbitrary valued $M_5$-dipole charged rotating circular strings and Maldacena Strominger Witten black rings exhibit non-degenerate, positively curved, comprehensively regular state-space con...
Directory of Open Access Journals (Sweden)
Igor Salom
2017-07-01
Full Text Available We construct the three-body permutation symmetric hyperspherical harmonics to be used in the non-relativistic three-body Schrödinger equation in three spatial dimensions (3D. We label the state vectors according to the S3⊗SO(3rot⊂O(2⊗SO(3rot⊂U(3⋊S2⊂O(6 subgroup chain, where S3 is the three-body permutation group and S2 is its two element subgroup containing transposition of first two particles, O(2 is the “democracy transformation”, or “kinematic rotation” group for three particles; SO(3rot is the 3D rotation group, and U(3,O(6 are the usual Lie groups. We discuss the good quantum numbers implied by the above chain of algebras, as well as their relation to the S3 permutation properties of the harmonics, particularly in view of the SO(3rot⊂SU(3 degeneracy. We provide a definite, practically implementable algorithm for the calculation of harmonics with arbitrary finite integer values of the hyper angular momentum K, and show an explicit example of this construction in a specific case with degeneracy, as well as tables of K≤6 harmonics. All harmonics are expressed as homogeneous polynomials in the Jacobi vectors (λ,ρ with coefficients given as algebraic numbers unless the “operator method” is chosen for the lifting of the SO(3rot⊂SU(3 multiplicity and the dimension of the degenerate subspace is greater than four – in which case one must resort to numerical diagonalization; the latter condition is not met by any K≤15 harmonic, or by any L≤7 harmonic with arbitrary K. We also calculate a certain type of matrix elements (the Gaunt integrals of products of three harmonics in two ways: 1 by explicit evaluation of integrals and 2 by reduction to known SU(3 Clebsch–Gordan coefficients. In this way we complete the calculation of the ingredients sufficient for the solution to the quantum-mechanical three-body bound state problem.
Differential geometry and symmetric spaces
Helgason, Sigurdur
2001-01-01
Sigurdur Helgason's Differential Geometry and Symmetric Spaces was quickly recognized as a remarkable and important book. For many years, it was the standard text both for Riemannian geometry and for the analysis and geometry of symmetric spaces. Several generations of mathematicians relied on it for its clarity and careful attention to detail. Although much has happened in the field since the publication of this book, as demonstrated by Helgason's own three-volume expansion of the original work, this single volume is still an excellent overview of the subjects. For instance, even though there
Looking for symmetric Bell inequalities
International Nuclear Information System (INIS)
Bancal, Jean-Daniel; Gisin, Nicolas; Pironio, Stefano
2010-01-01
Finding all Bell inequalities for a given number of parties, measurement settings and measurement outcomes is in general a computationally hard task. We show that all Bell inequalities which are symmetric under the exchange of parties can be found by examining a symmetrized polytope which is simpler than the full Bell polytope. As an illustration of our method, we generate 238 885 new Bell inequalities and 1085 new Svetlichny inequalities. We find, in particular, facet inequalities for Bell experiments involving two parties and two measurement settings that are not of the Collins-Gisin-Linden-Massar-Popescu type.
Symmetric autocompensating quantum key distribution
Walton, Zachary D.; Sergienko, Alexander V.; Levitin, Lev B.; Saleh, Bahaa E. A.; Teich, Malvin C.
2004-08-01
We present quantum key distribution schemes which are autocompensating (require no alignment) and symmetric (Alice and Bob receive photons from a central source) for both polarization and time-bin qubits. The primary benefit of the symmetric configuration is that both Alice and Bob may have passive setups (neither Alice nor Bob is required to make active changes for each run of the protocol). We show that both the polarization and the time-bin schemes may be implemented with existing technology. The new schemes are related to previously described schemes by the concept of advanced waves.
Static black holes with axial symmetry in asymptotically AdS4 spacetime
Kichakova, Olga; Kunz, Jutta; Radu, Eugen; Shnir, Yasha
2016-02-01
The known static electrovacuum black holes in a globally AdS4 background have an event horizon which is geometrically a round sphere. In this work we argue that the situation is different in models with matter fields possessing an explicit dependence on the azimuthal angle φ , which, however, does not manifest at the level of the energy-momentum tensor. As a result, the full solutions are axially symmetric only, possessing a single (timelike) Killing vector field. Explicit examples of such static black holes are constructed in Einstein-(complex) scalar field and Einstein-Yang-Mills theories. The basic properties of these solutions are discussed, looking for generic features. For example, we notice that the horizon has an oblate spheroidal shape for solutions with a scalar field and a prolate one for black holes with Yang-Mills fields. The deviation from sphericity of the horizon geometry manifests itself in the holographic stress tensor. Finally, based on the results obtained in the probe limit, we conjecture the existence in Einstein-Maxwell theory of static black holes with axial symmetry only.
Static black hole and vacuum energy: thin shell and incompressible fluid
Ho, Pei-Ming; Matsuo, Yoshinori
2018-03-01
With the back reaction of the vacuum energy-momentum tensor consistently taken into account, we study static spherically symmetric black-hole-like solutions to the semi-classical Einstein equation. The vacuum energy is assumed to be given by that of 2-dimensional massless scalar fields, as a widely used model in the literature for black holes. The solutions have no horizon. Instead, there is a local minimum in the radius. We consider thin shells as well as incompressible fluid as the matter content of the black-hole-like geometry. The geometry has several interesting features due to the back reaction of vacuum energy. In particular, Buchdahl's inequality can be violated without divergence in pressure, even if the surface is below the Schwarzschild radius. At the same time, the surface of the star can not be far below the Schwarzschild radius for a density not much higher than the Planck scale, and the proper distance from its surface to the origin can be very short even for very large Schwarzschild radius. The results also imply that, contrary to the folklore, in principle the Boulware vacuum can be physical for black holes.
Tensor spherical harmonics and tensor multipoles. II. Minkowski space
International Nuclear Information System (INIS)
Daumens, M.; Minnaert, P.
1976-01-01
The bases of tensor spherical harmonics and of tensor multipoles discussed in the preceding paper are generalized in the Hilbert space of Minkowski tensor fields. The transformation properties of the tensor multipoles under Lorentz transformation lead to the notion of irreducible tensor multipoles. We show that the usual 4-vector multipoles are themselves irreducible, and we build the irreducible tensor multipoles of the second order. We also give their relations with the symmetric tensor multipoles defined by Zerilli for application to the gravitational radiation
Near spherical illumination of ion-beam and laser targets
International Nuclear Information System (INIS)
Mark, J.W.K.
1985-01-01
A procedure is developed for reducing energy-deposition asymmetry in spherical targets driven directly by ion or laser beams. This work is part of a strategy for achieving illumination symmetry in such targets, which is proposed as an alternative to those in the literature. This strategy allows an axially symmetric placement of beamlets, which would be convenient for some driven or reactor scenarios. It also allows the use of beam currents or energy fluxes and beam transverse profiles to help reduce deposition asymmetry with fewer beamlets. In the ideal limit of thin deposition layers and controlled beam profiles, at most six beamlets are needed for target symmetry
Optimization of spherical facets for parabolic solar concentrators
White, J. E.; Erikson, R. J.; Sturgis, J. D.; Elfe, T. B.
1986-01-01
Solar concentrator designs which employ deployable hexagonal panels are being developed for space power systems. An offset optical configuration has been developed which offers significant system level advantages over previously proposed collector designs for space applications. Optical analyses have been performed which show offset reflector intercept factors to be only slightly lower than those for symmetric reflectors with the same slope error. Fluxes on the receiver walls are asymmetric but manageable by varying the tilt angle of the receiver. Greater producibility is achieved by subdividing the hexagonal panels into triangular mirror facets of spherical contour. Optical analysis has been performed upon these to yield near-optimum sizes and radii.
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...... suggested that appreciation of the highly personal motives of both Siouxsie Sioux and Janelle Monáe in wearing black may be achieved via analogies with the minimalist sublime of American artists Frank Stella’s and Ad Reinhardt’s black canvasses.......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 hinted by Rudyard Kipling’s illustration of ‘The [Black] Cat That Walked by Himself’ in his classic children’s tale). It was well understood by uniformed Anarchists, Fascists and the SS that there is an assertive presence connected with the black-clad figure. The paradox of black’s abstract elegance...
Controlled drug release on amine functionalized spherical MCM-41
Energy Technology Data Exchange (ETDEWEB)
Szegedi, Agnes, E-mail: szegedi@chemres.hu [Institute of Materials and Environmental Chemistry, Research Centre for Natural Sciences, Hungarian Academy of Sciences, 1025 Budapest, Pusztaszeri ut 59-67 (Hungary); Popova, Margarita; Goshev, Ivan [Institute of Organic Chemistry with Centre of Phytochemistry, Bulgarian Academy of Sciences, Sofia (Bulgaria); Klebert, Szilvia [Institute of Materials and Environmental Chemistry, Research Centre for Natural Sciences, Hungarian Academy of Sciences, 1025 Budapest, Pusztaszeri ut 59-67 (Hungary); Mihaly, Judit [Institute of Molecular Pharmacology, Research Centre for Natural Sciences, Hungarian Academy of Sciences, 1025 Budapest, Pusztaszeri ut 59-67 (Hungary)
2012-10-15
MCM-41 silica with spherical morphology and small particle sizes (100 nm) was synthesized and modified by post-synthesis method with different amounts of 3-aminopropyltriethoxysilane (APTES). A comparative study of the adsorption and release of a model drug, ibuprofen, was carried out. The modified and drug loaded mesoporous materials were characterized by XRD, TEM, N{sub 2} physisorption, elemental analysis, thermal analysis and FT-IR spectroscopy. A new method was developed for the quantitative determination of amino groups in surface modified mesoporous materials by the ninhydrin reaction. Good correlation was found between the amino content of the MCM-41 materials determined by the ninhydrin method and their ibuprofen adsorption capacity. Amino modification resulted in high degree of ibuprofen loading and slow release rate in comparison to the parent non-modified MCM-41. - Graphical abstract: Determination of surface amino groups by ninhidrin method. Highlights: Black-Right-Pointing-Pointer Spherical MCM-41 modified by different amounts of APTES was studied. Black-Right-Pointing-Pointer Ibuprofen (IBU) adsorption and release characteristics was tested. Black-Right-Pointing-Pointer The ninhydrin reaction was used for the quantitative determination of amino groups. Black-Right-Pointing-Pointer Stoichiometric amount of APTES is enough for totally covering the surface with amino groups. Black-Right-Pointing-Pointer Good correlation was found between the amino content and IBU adsorption capacity.
International Nuclear Information System (INIS)
Miao, Yan-Gang; Xu, Zhen-Ming
2017-01-01
We investigate the P - V criticality and the Maxwell equal area law for a five-dimensional spherically symmetric AdS black hole with a scalar hair in the absence of and in the presence of a Maxwell field, respectively. Especially in the charged case, we give the exact P - V critical values. More importantly, we analyze the validity and invalidity of the Maxwell equal area law for the AdS hairy black hole in the scenarios without and with charges, respectively. Within the scope of validity of the Maxwell equal area law, we point out that there exists a representative van der Waals-type oscillation in the P - V diagram. This oscillating part, which indicates the phase transition from a small black hole to a large one, can be replaced by an isobar. The small and large black holes have the same Gibbs free energy. We also give the distribution of the critical points in the parameter space both without and with charges, and we obtain for the uncharged case the fitting formula of the co-existence curve. Meanwhile, the latent heat is calculated, which gives the energy released or absorbed between the small and large black hole phases in the isothermal-isobaric procedure. (orig.)
Black holes in vector-tensor theories
Energy Technology Data Exchange (ETDEWEB)
Heisenberg, Lavinia [Institute for Theoretical Studies, ETH Zurich, Clausiusstrasse 47, 8092 Zurich (Switzerland); Kase, Ryotaro; Tsujikawa, Shinji [Department of Physics, Faculty of Science, Tokyo University of Science, 1-3, Kagurazaka, Shinjuku-ku, Tokyo 162-8601 (Japan); Minamitsuji, Masato, E-mail: lavinia.heisenberg@eth-its.ethz.ch, E-mail: r.kase@rs.tus.ac.jp, E-mail: masato.minamitsuji@tecnico.ulisboa.pt, E-mail: shinji@rs.kagu.tus.ac.jp [Centro Multidisciplinar de Astrofisica—CENTRA, Departamento de Fisica, Instituto Superior Tecnico—IST, Universidade de Lisboa—UL, Avenida Rovisco Pais 1, 1049-001 Lisboa (Portugal)
2017-08-01
We study static and spherically symmetric black hole (BH) solutions in second-order generalized Proca theories with nonminimal vector field derivative couplings to the Ricci scalar, the Einstein tensor, and the double dual Riemann tensor. We find concrete Lagrangians which give rise to exact BH solutions by imposing two conditions of the two identical metric components and the constant norm of the vector field. These exact solutions are described by either Reissner-Nordström (RN), stealth Schwarzschild, or extremal RN solutions with a non-trivial longitudinal mode of the vector field. We then numerically construct BH solutions without imposing these conditions. For cubic and quartic Lagrangians with power-law couplings which encompass vector Galileons as the specific cases, we show the existence of BH solutions with the difference between two non-trivial metric components. The quintic-order power-law couplings do not give rise to non-trivial BH solutions regular throughout the horizon exterior. The sixth-order and intrinsic vector-mode couplings can lead to BH solutions with a secondary hair. For all the solutions, the vector field is regular at least at the future or past horizon. The deviation from General Relativity induced by the Proca hair can be potentially tested by future measurements of gravitational waves in the nonlinear regime of gravity.
Sirius-T, a symmetrically illuminated ICF tritium production facility
International Nuclear Information System (INIS)
Sviatoslavsky, I.N.; Sawan, M.E.; Moses, G.A.; Kulcinski, G.L.; Engelstad, R.L.; Larsen, E.; Lovell, E.; MacFarlane, J.; Peterson, R.R.; Wittenberg, L.J.
1989-01-01
A scoping study of a symmetrically illuminated ICF tritium production facility utilizing a KrF laser is presented. A single shell ICF target is illuminated by 92 beams symmetrically distributed around a spherical cavity filled with xenon gas at 1.0 torr. The driver energy and target gain are taken to be 2 MJ and 50 for the optimistic case and 1 MJ and 100 for the conservative case. Based on a graphite dry wall evaporation rate of 0.1 cm/y for a 100 MJ yield, the authors estimate a cavity radius of 3.5 m for a rep-rate of 10 Hz and 3.0 m for 5 Hz. A spherical structural frame has been scoped out capable of supporting 92 blanket modules, each with a beam port in the center. They have selected liquid lithium in vanadium structure as the primary breeding concept utilizing beryllium as a neutron multiplier. A tritium breeding ratio of 1.83 can be achieved in the 3 m radius cavity which at 10 Hz and an availability of 75% provides an annual tritium surplus of 32.6 kg. Assuming 100% debt financing over a 30 year reactor lifetime, the production cost of T 2 for the 2 MJ driver case is $7,325/g for a 5% interest rate and $12,370/g for a 10% interest rate. 8 refs., 3 figs., 4 tabs
Linearized vector radiative transfer model MCC++ for a spherical atmosphere
International Nuclear Information System (INIS)
Postylyakov, O.V.
2004-01-01
Application of radiative transfer models has shown that optical remote sensing requires extra characteristics of radiance field in addition to the radiance intensity itself. Simulation of spectral measurements, analysis of retrieval errors and development of retrieval algorithms are in need of derivatives of radiance with respect to atmospheric constituents under investigation. The presented vector spherical radiative transfer model MCC++ was linearized, which allows the calculation of derivatives of all elements of the Stokes vector with respect to the volume absorption coefficient simultaneously with radiance calculation. The model MCC++ employs Monte Carlo algorithm for radiative transfer simulation and takes into account aerosol and molecular scattering, gas and aerosol absorption, and Lambertian surface albedo. The model treats a spherically symmetrical atmosphere. Relation of the estimated derivatives with other forms of radiance derivatives: the weighting functions used in gas retrieval and the air mass factors used in the DOAS retrieval algorithms, is obtained. Validation of the model against other radiative models is overviewed. The computing time of the intensity for the MCC++ model is about that for radiative models treating sphericity of the atmosphere approximately and is significantly shorter than that for the full spherical models used in the comparisons. The simultaneous calculation of all derivatives (i.e. with respect to absorption in all model atmosphere layers) and the intensity is only 1.2-2 times longer than the calculation of the intensity only
Symmetric Key Authentication Services Revisited
Crispo, B.; Popescu, B.C.; Tanenbaum, A.S.
2004-01-01
Most of the symmetric key authentication schemes deployed today are based on principles introduced by Needham and Schroeder [15] more than twenty years ago. However, since then, the computing environment has evolved from a LAN-based client-server world to include new paradigms, including wide area
The symmetric longest queue system
van Houtum, Geert-Jan; Adan, Ivo; van der Wal, Jan
1997-01-01
We derive the performance of the exponential symmetric longest queue system from two variants: a longest queue system with Threshold Rejection of jobs and one with Threshold Addition of jobs. It is shown that these two systems provide lower and upper bounds for the performance of the longest queue
Symmetric group representations and Z
Adve, Anshul; Yong, Alexander
2017-01-01
We discuss implications of the following statement about the representation theory of symmetric groups: every integer appears infinitely often as an irreducible character evaluation, and every nonnegative integer appears infinitely often as a Littlewood-Richardson coefficient and as a Kronecker coefficient.
A characterization of symmetric domains
Czech Academy of Sciences Publication Activity Database
Engliš, Miroslav
2006-01-01
Roč. 46, č. 1 (2006), s. 123-146 ISSN 0023-608X R&D Projects: GA AV ČR(CZ) IAA1019304 Institutional research plan: CEZ:AV0Z10190503 Keywords : Kaehler manifold * symmetric space * Berezin transform Subject RIV: BA - General Mathematics Impact factor: 0.270, year: 2006
Vassiliev Invariants from Symmetric Spaces
DEFF Research Database (Denmark)
Biswas, Indranil; Gammelgaard, Niels Leth
We construct a natural framed weight system on chord diagrams from the curvature tensor of any pseudo-Riemannian symmetric space. These weight systems are of Lie algebra type and realized by the action of the holonomy Lie algebra on a tangent space. Among the Lie algebra weight systems, they are ...
Symmetric imaging findings in neuroradiology
International Nuclear Information System (INIS)
Zlatareva, D.
2015-01-01
Full text: Learning objectives: to make a list of diseases and syndromes which manifest as bilateral symmetric findings on computed tomography and magnetic resonance imaging; to discuss the clinical and radiological differential diagnosis for these diseases; to explain which of these conditions necessitates urgent therapy and when additional studies and laboratory can precise diagnosis. There is symmetry in human body and quite often we compare the affected side to the normal one but in neuroradiology we might have bilateral findings which affected pair structures or corresponding anatomic areas. It is very rare when clinical data prompt diagnosis. Usually clinicians suspect such an involvement but Ct and MRI can reveal symmetric changes and are one of the leading diagnostic tool. The most common location of bilateral findings is basal ganglia and thalamus. There are a number of diseases affecting these structures symmetrically: metabolic and systemic diseases, intoxication, neurodegeneration and vascular conditions, toxoplasmosis, tumors and some infections. Malformations of cortical development and especially bilateral perisylvian polymicrogyria requires not only exact report on the most affected parts but in some cases genetic tests or combination with other clinical symptoms. In the case of herpes simplex encephalitis bilateral temporal involvement is common and this finding very often prompt therapy even before laboratory results. Posterior reversible encephalopathy syndrome (PReS) and some forms of hypoxic ischemic encephalopathy can lead to symmetric changes. In these acute conditions MR plays a crucial role not only in diagnosis but also in monitoring of the therapeutic effect. Patients with neurofibromatosis type 1 or type 2 can demonstrate bilateral optic glioma combined with spinal neurofibroma and bilateral acoustic schwanoma respectively. Mirror-image aneurysm affecting both internal carotid or middle cerebral arteries is an example of symmetry in
D3-brane shells to black branes on the Coulomb branch
International Nuclear Information System (INIS)
Giddings, Steven B.; Ross, Simon F.
2000-01-01
We use the AdS-CFT duality to study the special point on the Coulomb branch of N=4 SU(N) gauge theory which corresponds to a spherically symmetric shell of D3-branes. This point is of interest both because the spacetime region inside the shell is flat, and because this configuration gives a very simple example of the transition between D-branes in the perturbative string regime and the nonperturbative regime of black holes. We discuss how this geometry is described in the dual gauge theory, through its effect on the two-point functions and Wilson loops. In the calculation of the two-point function, we stress the importance of absorption by the branes. (c) 1999 The American Physical Society
Axisymmetric accretion flows very near black holes and Rosen-collapsed objects
International Nuclear Information System (INIS)
Stoeger, W.R.
1979-01-01
Motivated by the need for stronger observational leverage on the black hole hypothesis and for a more detailed characterization of axisymmetric accretion flows across the marginally stable circular orbit rsub(ms), a general approach for describing the non-Keplerian accretion in the region rsub(H) 0 , where rsub(H) = radius of the event horizon and r 0 > = rsub(ms) is developed. The procedure possesses many advantages, including easily imposed consistency with the Keplerian for r > rsub(o), the avoidance of ad hoc boundary conditions at rsub(ms) and/or at rsub(H) and its application also to accretion in Rosen's bimetric theory, whose spherically symmetric solution has the same qualitative orbital topography as that of general relativity. It becomes apparent, furthermore, that the particular viscosity law chosen in this procedure will have a crucial bearing on the flow in the region rsub(ms) 0 . (author)
Nonsingular black holes, wormholes, and de Sitter cores from anisotropic fluids
Menchon, Cintia C.; Olmo, Gonzalo J.; Rubiera-Garcia, Diego
2017-11-01
We study Born-Infeld gravity coupled to an anisotropic fluid in a static, spherically symmetric background. The free function characterizing the fluid is selected on the following grounds: i) recovery of the Reissner-Nordström solution of General Relativity at large distances, ii) fulfillment of classical energy conditions, and iii) inclusion of models of nonlinear electrodynamics as particular examples. Four branches of solutions are obtained, depending on the signs of two parameters on the gravity and matter sectors. On each branch, we discuss in detail the modifications on the innermost region of the corresponding solutions, which provides a plethora of configurations, including nonsingular black holes and naked objects, wormholes, and de Sitter cores. The regular character of these configurations is discussed according to the completeness of geodesics and the behavior of curvature scalars.
JUST: Joint Upgraded Spherical Tokamak
International Nuclear Information System (INIS)
Azizov, E.A.; Dvorkin, N.Ya.; Filatov, O.G.
1997-01-01
The main goals, ideas and the programme of JUST, spherical tokamak (ST) for the plasma burn investigation, are presented. The place and prospects of JUST in thermonuclear investigations are discussed. (author)
Spherical Primary Optical Telescope Testbed
National Aeronautics and Space Administration — This IRAD proposes to continue operation of the Spherical Primary Optical Telescope (SPOT) testbed as an image-based wavefront sensing demonstrator. In addition to...
Understanding symmetrical components for power system modeling
Das, J C
2017-01-01
This book utilizes symmetrical components for analyzing unbalanced three-phase electrical systems, by applying single-phase analysis tools. The author covers two approaches for studying symmetrical components; the physical approach, avoiding many mathematical matrix algebra equations, and a mathematical approach, using matrix theory. Divided into seven sections, topics include: symmetrical components using matrix methods, fundamental concepts of symmetrical components, symmetrical components –transmission lines and cables, sequence components of rotating equipment and static load, three-phase models of transformers and conductors, unsymmetrical fault calculations, and some limitations of symmetrical components.
Spherical tokamak development in Brazil
Energy Technology Data Exchange (ETDEWEB)
Ludwig, G.O.; Del Bosco, E.; Ferreira, J.G.; Berni, L.A.; Oliveira, R.M.; Andrade, M.C.R.; Shibata, C.S.; Ueda, M.; Barroso, J.J.; Castro, P.J. [Instituto Nacional de Pesquisas Espaciais (INPE), Sao Jose dos Campos, SP (Brazil). Lab. Associado de Plasma; Barbosa, L.F.W. [Universidade do Vale do Paraiba (UNIVAP), Sao Jose dos Campos, SP (Brazil). Faculdade de Engenharia, Arquitetura e Urbanismo; Patire Junior, H. [Instituto Nacional de Pesquisas Espaciais (INPE), Sao Jose dos Campos, SP (Brazil). Div. de Mecanica Espacial e Controle; The high-power microwave sources group
2003-12-01
This paper describes the general characteristics of spherical tokamaks, or spherical tori, with a brief overview of work in this area already performed or in progress at several institutions worldwide. The paper presents also the steps in the development of the ETE (Experimento Tokamak Esferico) project, its research program, technical characteristics and operating conditions as of December, 2002 at the Associated Plasma Laboratory (LAP) of the National Space Research Institute (INPE) in Brazil. (author)
Spherical tokamak development in Brazil
International Nuclear Information System (INIS)
Ludwig, G.O.; Del Bosco, E.; Ferreira, J.G.; Berni, L.A.; Oliveira, R.M.; Andrade, M.C.R.; Shibata, C.S.; Ueda, M.; Barroso, J.J.; Castro, P.J.; Barbosa, L.F.W.; Patire Junior, H.; The high-power microwave sources group
2003-01-01
This paper describes the general characteristics of spherical tokamaks, or spherical tori, with a brief overview of work in this area already performed or in progress at several institutions worldwide. The paper presents also the steps in the development of the ETE (Experimento Tokamak Esferico) project, its research program, technical characteristics and operating conditions as of December, 2002 at the Associated Plasma Laboratory (LAP) of the National Space Research Institute (INPE) in Brazil. (author)
Black hole in closed spacetime with an anisotropic fluid
Kim, Hyeong-Chan
2017-09-01
We study spherically symmetric geometries made of anisotropic perfect fluid based on general relativity. The purpose of this work is to find and classify black hole solutions in closed spacetime. In a general setting, we find that a static and closed space exists only when the radial pressure is negative but its size is smaller than the density. The Einstein equation is eventually cast into a first-order autonomous equation on a two-dimensional plane of scale-invariant variables, which are equivalent to the Tolman-Oppenheimer-Volkoff equation in general relativity. Then, we display various solution curves numerically. An exact solution describing a black hole solution in a closed spacetime was known in [I. Cho and H. C. Kim, Phys. Rev. D 95, 084052 (2017), 10.1103/PhysRevD.95.084052], which bears a naked singularity and negative-energy era. We find that these two deficits can be remedied when ρ +3 p1>0 and ρ +p1+2 p2<0 , where the second violates the strong energy condition.
Normal range of facial asymmetry in spherical coordinates: a CBCT study
Energy Technology Data Exchange (ETDEWEB)
Yoon, Suk Ja [Dept. of Oral and Maxillofacial Radiology, School of Dentistry, Dental Science Research Institute, Chonnam National University, Gwangju (Korea, Republic of); Wang, Rui Feng [Research Laboratory Specialist Intermediate, Department of Biologic and Material Sciences, School of Dentistry, University of Michigan, Ann Arbor, MI (United States); Na, Hee Ja [Dept. ofDental Hygiene, Honam University, Gwangju (Korea, Republic of); Palomo, Juan Matin [Dept. of Orthodontics, School of Dental Medicine, Case Western Reserve University, Cleveland (United States)
2013-03-15
This study aimed to measure the bilateral differences of facial lines in spherical coordinates from faces within a normal range of asymmetry utilizing cone-beam computed tomography (CBCT). CBCT scans from 22 females with normal symmetric-looking faces (mean age 24 years and 8 months) were selected for the study. The average menton deviation was 1.01{+-}0.66 mm. The spherical coordinates, length, and midsagittal and coronal inclination angles of the ramal and mandibular lines were calculated from CBCT. The bilateral differences in the facial lines were determined. All of the study subjects had minimal bilateral differences of facial lines. The normal range of facial asymmetry of the ramal and mandibular lines was obtained in spherical coordinates. The normal range of facial asymmetry in the spherical coordinate system in this study should be useful as a reference for diagnosing facial asymmetry.
Homotheties of cylindrically symmetric static spacetimes
International Nuclear Information System (INIS)
Qadir, A.; Ziad, M.; Sharif, M.
1998-08-01
In this note we consider the homotheties of cylindrically symmetric static spacetimes. We find that we can provide a complete list of all metrics that admit non-trivial homothetic motions and are cylindrically symmetric static. (author)
On convergence completeness in symmetric spaces | Moshokoa ...
African Journals Online (AJOL)
convergence complete symmetric space. As applications of convergence completeness, we present some fixed point results for self-maps defined on a symmetric space. Keywords: completeness; convergence completeness; fixed points; metric ...
[Symmetrical lividity of the fingers].
Kocsard, E; Kossard, S
1988-07-01
Symmetric lividity of the soles of the feet was first reported in two children in 1925 by Pernet. The characteristic manifestation of this dermatosis consisted in hyperkeratosis and hyperhidrosis with livid discoloration of the pressure areas of the soles. Later the same name was applied to a similar dermatosis in which the hyperkeratotic and hyperhidrotic patches of skin on the soles had a whitish grey discoloration and the livid color, if present at all, was seen only over the marginal areas not affected by the keratosis. Similar livid keratoses affecting the palmar sides of the fingers have been seen only occasionally. The 17-year-old girl presented in this paper had a 11-year history of emotional hyperhidrosis and is a rare illustration of symmetrical lividity in its original form, localized to the fingers only.
Parity-Time Symmetric Photonics
Zhao, Han
2018-01-17
The establishment of non-Hermitian quantum mechanics (such as parity-time (PT) symmetry) stimulates a paradigmatic shift for studying symmetries of complex potentials. Owing to the convenient manipulation of optical gain and loss in analogy to the complex quantum potentials, photonics provides an ideal platform for visualization of many conceptually striking predictions from the non-Hermitian quantum theory. A rapidly developing field has emerged, namely, PT symmetric photonics, demonstrating intriguing optical phenomena including eigenstate coalescence and spontaneous PT symmetry breaking. The advance of quantum physics, as the feedback, provides photonics with brand-new paradigms to explore the entire complex permittivity plane for novel optical functionalities. Here, we review recent exciting breakthroughs in PT symmetric photonics while systematically presenting their underlying principles guided by non-Hermitian symmetries. The potential device applications for optical communication and computing, bio-chemical sensing, and healthcare are also discussed.
Bilateral Symmetrical Parietal Extradural Hematoma
Agrawal, Amit
2011-01-01
The occurrence of bilateral extradural hematomas (EDH) is an uncommon consequence of craniocerebral trauma, and acute symmetrical bilateral epidural hematomas are extremely rare. We discuss the technique adopted by us for the management of this rare entity. A 55-year-old patient presented with history of fall of branch of tree on her head. She had loss of consciousness since then and had multiple episodes of vomiting. Examination of the scalp was suggestive of diffuse subgaleal hematoma. Her ...
Symmetric two-coordinate photodiode
Directory of Open Access Journals (Sweden)
Dobrovolskiy Yu. G.
2008-12-01
Full Text Available The two-coordinate photodiode is developed and explored on the longitudinal photoeffect, which allows to get the coordinate descriptions symmetric on the steepness and longitudinal resistance great exactness. It was shown, that the best type of the coordinate description is observed in the case of scanning by the optical probe on the central part of the photosensitive element. The ways of improvement of steepness and linear of its coordinate description were analyzed.
Maximally Symmetric Composite Higgs Models.
Csáki, Csaba; Ma, Teng; Shu, Jing
2017-09-29
Maximal symmetry is a novel tool for composite pseudo Goldstone boson Higgs models: it is a remnant of an enhanced global symmetry of the composite fermion sector involving a twisting with the Higgs field. Maximal symmetry has far-reaching consequences: it ensures that the Higgs potential is finite and fully calculable, and also minimizes the tuning. We present a detailed analysis of the maximally symmetric SO(5)/SO(4) model and comment on its observational consequences.
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 2k+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.
A symmetric integral identity for Bessel functions with applications to integral geometry
Salman, Yehonatan
2017-12-01
In the article of Kunyansky (Inverse Probl 23(1):373-383, 2007) a symmetric integral identity for Bessel functions of the first and second kind was proved in order to obtain an explicit inversion formula for the spherical mean transform where our data is given on the unit sphere in Rn . The aim of this paper is to prove an analogous symmetric integral identity in case where our data for the spherical mean transform is given on an ellipse E in R2 . For this, we will use the recent results obtained by Cohl and Volkmer (J Phys A Math Theor 45:355204, 2012) for the expansions into eigenfunctions of Bessel functions of the first and second kind in elliptical coordinates.
A Lovelock black hole bestiary
International Nuclear Information System (INIS)
Camanho, Xián O; Edelstein, José D
2013-01-01
We revisit the study of (A)dS black holes in Lovelock theories. We present a new tool that allows to attack this problem in full generality. In analyzing maximally symmetric Lovelock black holes with non-planar horizon topologies, many distinctive and interesting features are observed. Among them, the existence of maximally symmetric vacua does not support black holes in vast regions of the space of gravitational couplings, multi-horizon black holes and branches of solutions that suggest the existence of a rich diagram of phase transitions. The appearance of naked singularities seems unavoidable in some cases, raising the question about the fate of the cosmic censorship conjecture in these theories. There is a preferred branch of solutions for planar black holes, as well as for non-planar black holes with high enough mass or temperature. Our study clarifies the role of all branches of solutions, including asymptotically dS black holes, and whether they should be considered when studying these theories in the context of AdS/CFT. (paper)
Spherical Demons: Fast Surface Registration
Yeo, B.T. Thomas; Sabuncu, Mert; Vercauteren, Tom; Ayache, Nicholas; Fischl, Bruce; Golland, Polina
2009-01-01
We present the fast Spherical Demons algorithm for registering two spherical images. By exploiting spherical vector spline interpolation theory, we show that a large class of regularizers for the modified demons objective function can be efficiently implemented on the sphere using convolution. Based on the one parameter subgroups of diffeomorphisms, the resulting registration is diffeomorphic and fast – registration of two cortical mesh models with more than 100k nodes takes less than 5 minutes, comparable to the fastest surface registration algorithms. Moreover, the accuracy of our method compares favorably to the popular FreeSurfer registration algorithm. We validate the technique in two different settings: (1) parcellation in a set of in-vivo cortical surfaces and (2) Brodmann area localization in ex-vivo cortical surfaces. PMID:18979813
Conditions for Effective Application of Analysis of Symmetrically-Predicted Endogenous Subgroups
Peck, Laura R.
2015-01-01
Several analytic strategies exist for opening up the "black box" to reveal more about what drives policy and program impacts. This article focuses on one of these strategies: the Analysis of Symmetrically-Predicted Endogenous Subgroups (ASPES). ASPES uses exogenous baseline data to identify endogenously-defined subgroups, keeping the…
Spherical agglomeration of acetylsalicylic acid
Directory of Open Access Journals (Sweden)
Polowczyk Izabela
2016-01-01
Full Text Available In this paper spherical agglomeration of acetylsalicylic acid was described. In the first step, the system of good and poor solvents as well as bridging liquid was selected. As a result of a preliminary study, ethyl alcohol, water and carbon tetrachloride were used as the good solvent, poor one, and bridging liquid, respectively. Then, the amount of acetylsalicylic acid and the ratio of the solvents as well as the volume of the bridging liquid were examined. In the last step, the agglomeration conditions, such as mixing intensity and time, were investigated. The spherical agglomerates obtained under optimum conditions could be subjected to a tableting process afterwards.
Directory of Open Access Journals (Sweden)
M.R. Setare
2017-01-01
Full Text Available In this paper we study the near horizon symmetry algebra of the non-extremal black hole solutions of the Chern–Simons-like theories of gravity, which are stationary but are not necessarily spherically symmetric. We define the extended off-shell ADT current which is an extension of the generalized ADT current. We use the extended off-shell ADT current to define quasi-local conserved charges such that they are conserved for Killing vectors and asymptotically Killing vectors which depend on dynamical fields of the considered theory. We apply this formalism to the Generalized Minimal Massive Gravity (GMMG and obtain conserved charges of a spacetime which describes near horizon geometry of non-extremal black holes. Eventually, we find the algebra of conserved charges in Fourier modes. It is interesting that, similar to the Einstein gravity in the presence of negative cosmological constant, for the GMMG model also we obtain the Heisenberg algebra as the near horizon symmetry algebra of the black flower solutions. Also the vacuum state and all descendants of the vacuum have the same energy. Thus these zero energy excitations on the horizon appear as soft hairs on the black hole.
Energy Technology Data Exchange (ETDEWEB)
Miao, Yan-Gang; Xu, Zhen-Ming [Nankai University, School of Physics, Tianjin (China)
2017-06-15
We investigate the P - V criticality and the Maxwell equal area law for a five-dimensional spherically symmetric AdS black hole with a scalar hair in the absence of and in the presence of a Maxwell field, respectively. Especially in the charged case, we give the exact P - V critical values. More importantly, we analyze the validity and invalidity of the Maxwell equal area law for the AdS hairy black hole in the scenarios without and with charges, respectively. Within the scope of validity of the Maxwell equal area law, we point out that there exists a representative van der Waals-type oscillation in the P - V diagram. This oscillating part, which indicates the phase transition from a small black hole to a large one, can be replaced by an isobar. The small and large black holes have the same Gibbs free energy. We also give the distribution of the critical points in the parameter space both without and with charges, and we obtain for the uncharged case the fitting formula of the co-existence curve. Meanwhile, the latent heat is calculated, which gives the energy released or absorbed between the small and large black hole phases in the isothermal-isobaric procedure. (orig.)
Gravitational amplitudes in black hole evaporation: the effect of non-commutative geometry
International Nuclear Information System (INIS)
Grezia, Elisabetta Di; Esposito, Giampiero; Miele, Gennaro
2006-01-01
Recent work in the literature has studied the quantum-mechanical decay of a Schwarzschild-like black hole, formed by gravitational collapse, into almost-flat spacetime and weak radiation at a very late time. The relevant quantum amplitudes have been evaluated for bosonic and fermionic fields, showing that no information is lost in collapse to a black hole. On the other hand, recent developments in non-commutative geometry have shown that, in general relativity, the effects of non-commutativity can be taken into account by keeping the standard form of the Einstein tensor on the left-hand side of the field equations and introducing a modified energy-momentum tensor as a source on the right-hand side. The present paper, relying on the recently obtained non-commutativity effect on a static, spherically symmetric metric, considers from a new perspective the quantum amplitudes in black hole evaporation. The general relativity analysis of spin-2 amplitudes is shown to be modified by a multiplicative factor F depending on a constant non-commutativity parameter and on the upper limit R of the radial coordinate. Limiting forms of F are derived which are compatible with the adiabatic approximation here exploited. Approximate formulae for the particle emission rate are also obtained within this framework
Black hole radiation with modified dispersion relation in tunneling paradigm: Static frame
Directory of Open Access Journals (Sweden)
Jun Tao
2017-09-01
Full Text Available To study possible deviations from the Hawking's prediction, we assume that the dispersion relations of matter fields are modified at high energies and use the Hamilton–Jacobi method to investigate the corresponding effects on the Hawking radiation in this paper. The preferred frame is the static frame of the black hole. The dispersion relation adopted agrees with the relativistic one at low energies but is modified near the Planck mass mp. We calculate the corrections to the Hawking temperature for massive and charged particles to O(mp−2 and massless and neutral particles to all orders. Our results suggest that the thermal spectrum of radiations near horizon is robust, e.g. corrections to the Hawking temperature are suppressed by mp. After the spectrum of radiations near the horizon is obtained, we use the brick wall model to compute the thermal entropy of a massless scalar field near the horizon of a 4D spherically symmetric black hole. We find that the subleading logarithmic term of the entropy does not depend on how the dispersion relations of matter fields are modified. Finally, the luminosities of black holes are computed by using the geometric optics approximation.
Exact black hole formation in asymptotically (AdS and flat spacetimes
Directory of Open Access Journals (Sweden)
Xuefeng Zhang
2014-09-01
Full Text Available We consider four-dimensional Einstein gravity minimally coupled to a dilaton scalar field with a supergravity-inspired scalar potential. We obtain an exact time-dependent spherically symmetric solution describing gravitational collapse to a static scalar-hairy black hole. The solution can be asymptotically AdS, flat or dS depending on the value of the cosmological constant parameter Λ in the potential. As the advanced time u increases, the metric approaches the static limit in an exponential fashion, i.e., e−u/u0 with u0∼1/(α4M01/3, where M0 is the mass of the final black hole and α is the second parameter in the potential. Similarly to the Vaidya solution, at u=0, the spacetime can be matched to an (AdS or flat vacuum except that at the origin a naked singularity may occur. Moreover, a limiting case of our solution with α=0 gives rise to an (AdS generalization of the Roberts solution. Our results provide a new model for investigating formation of real life black holes with Λ≥0. For Λ<0, it can be instead used to study non-equilibrium thermalization of certain strongly-coupled field theory.
Radiating black holes in Einstein-Maxwell-dilaton theory and cosmic censorship violation
Energy Technology Data Exchange (ETDEWEB)
Aniceto, Pedro [CENTRA, Departamento de Física, Instituto Superior Técnico, Universidade de Lisboa,Avenida Rovisco Pais 1, 1049 Lisboa (Portugal); Pani, Paolo [Dipartimento di Fisica, “Sapienza” Università di Roma & Sezione INFN Roma 1,Piazzale Aldo Moro 5, 00185 Roma (Italy); CENTRA, Departamento de Física, Instituto Superior Técnico, Universidade de Lisboa,Avenida Rovisco Pais 1, 1049 Lisboa (Portugal); Rocha, Jorge V. [Departament de Física Fonamental, Institut de Ciències del Cosmos (ICCUB),Universitat de Barcelona,Martí i Franquès 1, E-08028 Barcelona (Spain)
2016-05-19
We construct exact, time-dependent, black hole solutions of Einstein-Maxwell-dilaton theory with arbitrary dilaton coupling, a. For a=1 this theory arises as the four-dimensional low-energy effective description of heterotic string theory. These solutions represent electrically charged, spherically symmetric black holes emitting or absorbing charged null fluids and generalize the Vaidya and Bonnor-Vaidya solutions of general relativity and of Einstein-Maxwell theory, respectively. The a=1 case stands out as special, in the sense that it is the only choice of the coupling that allows for a time-dependent dilaton field in this class of solutions. As a by-product, when a=1 we show that an electrically charged black hole in this theory can be overcharged by bombarding it with a stream of electrically charged null fluid, resulting in the formation of a naked singularity. This provides an example of cosmic censorship violation in an exact dynamical solution to low-energy effective string theory and in a case in which the total stress-energy tensor satisfies all energy conditions. When a≠1, our solutions necessarily have a time-independent scalar field and consequently cannot be overcharged.
Energy Distribution of a Regular Black Hole Solution in Einstein-Nonlinear Electrodynamics
Directory of Open Access Journals (Sweden)
I. Radinschi
2015-01-01
Full Text Available A study about the energy momentum of a new four-dimensional spherically symmetric, static and charged, regular black hole solution developed in the context of general relativity coupled to nonlinear electrodynamics is presented. Asymptotically, this new black hole solution behaves as the Reissner-Nordström solution only for the particular value μ=4, where μ is a positive integer parameter appearing in the mass function of the solution. The calculations are performed by use of the Einstein, Landau-Lifshitz, Weinberg, and Møller energy momentum complexes. In all the aforementioned prescriptions, the expressions for the energy of the gravitating system considered depend on the mass M of the black hole, its charge q, a positive integer α, and the radial coordinate r. In all these pseudotensorial prescriptions, the momenta are found to vanish, while the Landau-Lifshitz and Weinberg prescriptions give the same result for the energy distribution. In addition, the limiting behavior of the energy for the cases r→∞, r→0, and q=0 is studied. The special case μ=4 and α=3 is also examined. We conclude that the Einstein and Møller energy momentum complexes can be considered as the most reliable tools for the study of the energy momentum localization of a gravitating system.
Radiating black holes in Einstein-Maxwell-dilaton theory and cosmic censorship violation
Aniceto, Pedro; Pani, Paolo; Rocha, Jorge V.
2016-05-01
We construct exact, time-dependent, black hole solutions of Einstein-Maxwell-dilaton theory with arbitrary dilaton coupling, a. For a = 1 this theory arises as the four-dimensional low-energy effective description of heterotic string theory. These solutions represent electrically charged, spherically symmetric black holes emitting or absorbing charged null fluids and generalize the Vaidya and Bonnor-Vaidya solutions of general relativity and of Einstein-Maxwell theory, respectively. The a = 1 case stands out as special, in the sense that it is the only choice of the coupling that allows for a time-dependent dilaton field in this class of solutions. As a by-product, when a = 1 we show that an electrically charged black hole in this theory can be overcharged by bombarding it with a stream of electrically charged null fluid, resulting in the formation of a naked singularity. This provides an example of cosmic censorship violation in an exact dynamical solution to low-energy effective string theory and in a case in which the total stress-energy tensor satisfies all energy conditions. When a ≠ 1, our solutions necessarily have a time-independent scalar field and consequently cannot be overcharged.
Immanant Conversion on Symmetric Matrices
Directory of Open Access Journals (Sweden)
Purificação Coelho M.
2014-01-01
Full Text Available Letr Σn(C denote the space of all n χ n symmetric matrices over the complex field C. The main objective of this paper is to prove that the maps Φ : Σn(C -> Σn (C satisfying for any fixed irre- ducible characters X, X' -SC the condition dx(A +aB = dχ·(Φ(Α + αΦ(Β for all matrices A,В ε Σ„(С and all scalars a ε C are automatically linear and bijective. As a corollary of the above result we characterize all such maps Φ acting on ΣИ(С.
Baryon symmetric big bang cosmology
International Nuclear Information System (INIS)
Stecker, F.W.
1978-01-01
It is stated that the framework of baryon symmetric big bang (BSBB) cosmology offers our greatest potential for deducting the evolution of the Universe because its physical laws and processes have the minimum number of arbitrary assumptions about initial conditions in the big-bang. In addition, it offers the possibility of explaining the photon-baryon ratio in the Universe and how galaxies and galaxy clusters are formed. BSBB cosmology also provides the only acceptable explanation at present for the origin of the cosmic γ-ray background radiation. (author)
Solutions of the linearized Bach-Einstein equation in the static spherically symmetric case
International Nuclear Information System (INIS)
Schmidt, H.J.
1985-01-01
The Bach-Einstein equation linearized around Minkowski space-time is completely solved. The set of solutions depends on three parameters; a two-parameter subset of it becomes asymptotically flat. In that region the gravitational potential is of the type phi = -m/r + epsilon exp (-r/l). Because of the different asymptotic behaviour of both terms, it became necessary to linearize also around the Schwarzschild solution phi = -m/r. The linearized equation resulting in this case is discussed using qualitative methods. The result is that for m = 2l phi = -m/r + epsilon r -2 exp (-r/l) u, where u is some bounded function; m is arbitrary and epsilon again small. Further, the relation between the solution of the linearized and the full equation is discussed. (author)
Czech Academy of Sciences Publication Activity Database
Kubát, Jiří
2001-01-01
Roč. 366, č. 1 (2001), s. 210-214 ISSN 0004-6361 R&D Projects: GA AV ČR KSK1003601; GA ČR GA205/96/1198; GA AV ČR IAA3003805; GA AV ČR KSK1043601 Institutional research plan: CEZ:AV0Z1003909 Keywords : stars atmospheres * numerical methods * radiative transfer Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics Impact factor: 2.790, year: 2000
Spherically Symmetric NLTE Model Atmospheres of Hot Hydrogen-Helium First Stars
Czech Academy of Sciences Publication Activity Database
Kubát, Jiří
2012-01-01
Roč. 203, č. 2 (2012), 20/1-20/10 ISSN 0067-0049 R&D Projects: GA ČR GA205/08/0003 Institutional support: RVO:67985815 Keywords : radiative transfer * stars * atmospheres Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics Impact factor: 16.238, year: 2012
(n+1)-dimensional spherically symmetric expanding structures in R2-gravity
Ebrahimi, Esmaeil
2015-05-01
In this work, we consider higher-dimensional structures in R2-gravity in an expanding background. We assume a Ricci scalar constant background and use this assumption as the basic constraint to find solutions. Two classes of solutions are presented in which every one includes naked singularity and wormhole geometries. Both classes of solutions show inflationary phase of expansion favored by recent acceleration of the universe. Traversability of the wormhole solutions is discussed. The possibility of satisfying or violating the weak energy condition (WEC) for wormholes is explored. For one class of solutions, particular choices of constants result in wormholes which satisfy the WEC all over the spacetime.
Spherically Symmetric Solutions on a Non-Trivial Frame in f(T) Theories of Gravity
Gamal, G. L. Nashed
2012-05-01
A new solution with constant torsion is derived using the field equations of f(T). Asymptotic forms of energy density, radial and transversal pressures are shown to meet the standard energy conditions, i.e., weak and null energy conditions according to some restrictions on T0, f(T0) and fT(T0). Other solutions are obtained for vanishing radial pressure and for specific choices of f(T). The physics relevant to the resulting models is discussed.
On the Stability of Spherically Symmetric Self-Gravitating Classical and Quantum Systems
DEFF Research Database (Denmark)
Makedonski, Mathias
on to the description of the corresponding systems in the setting of general relativity, it is shown, that the Tolman-Oppenheimer-Volko equation can be obtained from a suitable variation of the total energy. We prove a previously unnoticed energetic instability of the model. Staying in the general relativistic setting......, we examine the self-gravitating massive free scalar eld. It is shown, by proving suitable dierentiability properties of the occurring functionals, that Einstein's equations in this setting can again be obtained by a constrained variation of the total mass as dened by Arnowitt, Deser and Misner...
Spherical Pendulum, Actions, and Spin
Richter, Peter H.; Dullin, Holger R.; Waalkens, Holger; Wiersig, Jan
1996-01-01
The classical and quantum mechanics of a spherical pendulum are worked out, including the dynamics of a suspending frame with moment of inertia θ. The presence of two separatrices in the bifurcation diagram of the energy-momentum mapping has its mathematical expression in the hyperelliptic nature of
Testing for Bivariate Spherical Symmetry
Einmahl, J.H.J.; Gantner, M.
2010-01-01
An omnibus test for spherical symmetry in R2 is proposed, employing localized empirical likelihood. The thus obtained test statistic is distri- bution-free under the null hypothesis. The asymptotic null distribution is established and critical values for typical sample sizes, as well as the
Cooperative effects in spherical spasers
DEFF Research Database (Denmark)
Bordo, Vladimir
2017-01-01
A fully analytical semiclassical theory of cooperative optical processes which occur in an ensemble of molecules embedded in a spherical core-shell nanoparticle is developed from first principles. Both the plasmonic Dicke effect and spaser generation are investigated for the designs in which...
Testing for bivariate spherical symmetry
Einmahl, J.H.J.; Gantner, M.
2012-01-01
An omnibus test for spherical symmetry in R2 is proposed, employing localized empirical likelihood. The thus obtained test statistic is distribution free under the null hypothesis. The asymptotic null distribution is established and critical values for typical sample sizes, as well as the asymptotic
Laplacian eigenmodes for spherical spaces
International Nuclear Information System (INIS)
Lachieze-Rey, M; Caillerie, S
2005-01-01
The possibility that our space is multi-rather than singly-connected has gained renewed interest after the discovery of the low power for the first multipoles of the CMB by WMAP. To test the possibility that our space is a multi-connected spherical space, it is necessary to know the eigenmodes of such spaces. Except for lens and prism space, and to some extent for dodecahedral space, this remains an open problem. Here we derive the eigenmodes of all spherical spaces. For dodecahedral space, the demonstration is much shorter, and the calculation method much simpler than before. We also apply our method to tetrahedric, octahedric and icosahedric spaces. This completes the knowledge of eigenmodes for spherical spaces, and opens the door to new observational tests of the cosmic topology. The vector space V k of the eigenfunctions of the Laplacian on the 3-sphere S 3 , corresponding to the same eigenvalue λ k = -k(k + 2), has dimension (k + 1) 2 . We show that the Wigner functions provide a basis for such a space. Using the properties of the latter, we express the behaviour of a general function of V k under an arbitrary rotation G of SO(4). This offers the possibility of selecting those functions of V k which remain invariant under G. Specifying G to be a generator of the holonomy group of a spherical space X, we give the expression of the vector space V x k of the eigenfunctions of X. We provide a method to calculate the eigenmodes up to an arbitrary order. As an illustration, we give the first modes for the spherical spaces mentioned
The spinor heat kernel in maximally symmetric spaces
International Nuclear Information System (INIS)
Camporesi, R.
1992-01-01
The heat kernel K(x, x', t) of the iterated Dirac operator on an N-dimensional simply connected maximally symmetric Riemannian manifold is calculated. On the odd-dimensional hyperbolic spaces K is a Minakshisundaram-DeWitt expansion which terminates to the coefficient a (N-1)/2 and is exact. On the odd spheres the heat kernel may be written as an image sum of WKB kernels, each term corresponding to a classical path (geodesic). In the even dimensional case the WKB approximation is not exact, but a closed form of K is derived both in terms of (spherical) eigenfunctions and of a 'sum over classical paths'. The spinor Plancherel measure μ(λ) and ζ function in the hyperbolic case are also calculated. A simple relation between the analytic structure of μ on H N and the degeneracies of the Dirac operator on S N is found. (orig.)
Rayleigh-Taylor instability of a self-similar spherical expansion
International Nuclear Information System (INIS)
Bernstein, I.B.; Book, D.L.
1978-01-01
The self-similar motion of a spherically symmetric isentropic cloud of ideal gas driven outward by an expanding low-density medium (e.g., radiation pressure from a pulsar) is shown to be unstable to Rayleigh-Taylor modes which develop in the neighborhood of the interface. A complete solution of the linearized equations of motion is obtained. The implications for astrophysical phenomena are discussed
Angular shift in scattering the spherical analogous of the Goos-Hanchen effect
International Nuclear Information System (INIS)
Ferrari Junior, N.F.; Nussenzveig, H.M.
1983-01-01
A generalization of the time and spatial delay concept is obtained, for the scattering of transversaly incident beam restricted by a spherically symmetric scatterer using the methods of the complex angular momentum, valid for the angular momentum and angle conjufated variable pair. The result obtained is known validity domain, within the semiclassical approximation. Applied to the scttering problem in the high frequency limit by a transparent sphere with refractive index N [pt
On the Field of a Stationary Charged Spherical Source
Directory of Open Access Journals (Sweden)
Stavroulakis N.
2009-04-01
Full Text Available The equations of gravitation related to the field of a spherical charged source imply the existence of an interdependence between gravitation and electricity [5]. The present paper deals with the joint action of gravitation and electricity in the case of a stationary charged spherical source. Let m and " be respectively the mass and the charge of the source, and let k be the gravitational constant. Then the equations of gravitation need specific discussion according as j " j m p k (source strongly charged. In any case the curvature radius of the sphere bounding the matter possesses a strictly positive greatest lower hound, so that the source is necessarily an extended object. Pointwise sources do not exist. In particular, charged black holes do not exist.
Quantum radiation from an evaporating nonsingular black hole
Frolov, Valeri P.; Zelnikov, Andrei
2017-06-01
In this paper we study quantum radiation from an evaporating spherically symmetric nonsingular black hole. We used a modified Hayward metric for a description of a nonsingular black hole interior. We assume that the mass parameter of this metric depends on the advanced time, and choose this dependence so that it properly reproduces both black hole formation and its subsequent evaporation. We consider a quantum massless scalar field propagating in this geometry and use two-dimensional approximation for the calculation of the quantum average of the stress-energy tensor in the initial vacuum state. For the calculation of this quantity it is sufficient to find a map between the Killing times u+ and u- at the future and past null infinities, established by the propagation of the radial null rays. In this formalism the quantum energy flux at the future null infinity can be expressed in terms of the function u+(u-) and its derivatives up to the third order. We developed a special formalism, which allows one to reduce the problem of the calculation of the quantum energy flux and other observables to a solution of a simple set of ordinary differential equations. We used this approach to study quantum effects in two cases: (i) with the trivial, α =1 , and (ii) the nontrivial, α ≠1 , redshift function. We demonstrated that in both cases there exists an outburst of the quantum energy radiation from the inner domain of the black hole, close to the inner part of its apparent horizon. For α =1 this outburst is exponentially large. Its appearance is a direct consequence of the so-called mass inflation effect. We also demonstrated that this severe problem can be solved by a proper choice of the redshift function. However, even in this case the emitted energy can be much larger than the initial mass of the evaporating black hole. This means that for a construction of a self-consistent model of a nonsingular evaporating black hole the backreaction effects are highly important.
Probabilistic cloning of three symmetric states
International Nuclear Information System (INIS)
Jimenez, O.; Bergou, J.; Delgado, A.
2010-01-01
We study the probabilistic cloning of three symmetric states. These states are defined by a single complex quantity, the inner product among them. We show that three different probabilistic cloning machines are necessary to optimally clone all possible families of three symmetric states. We also show that the optimal cloning probability of generating M copies out of one original can be cast as the quotient between the success probability of unambiguously discriminating one and M copies of symmetric states.
Black holes and the multiverse
Energy Technology Data Exchange (ETDEWEB)
Garriga, Jaume [Departament de Fisica Fonamental i Institut de Ciencies del Cosmos, Universitat de Barcelona, Marti i Franques, 1, Barcelona, 08028 Spain (Spain); Vilenkin, Alexander; Zhang, Jun, E-mail: jaume.garriga@ub.edu, E-mail: vilenkin@cosmos.phy.tufts.edu, E-mail: jun.zhang@tufts.edu [Institute of Cosmology, Tufts University, 574 Boston Ave, Medford, MA, 02155 (United States)
2016-02-01
Vacuum bubbles may nucleate and expand during the inflationary epoch in the early universe. After inflation ends, the bubbles quickly dissipate their kinetic energy; they come to rest with respect to the Hubble flow and eventually form black holes. The fate of the bubble itself depends on the resulting black hole mass. If the mass is smaller than a certain critical value, the bubble collapses to a singularity. Otherwise, the bubble interior inflates, forming a baby universe, which is connected to the exterior FRW region by a wormhole. A similar black hole formation mechanism operates for spherical domain walls nucleating during inflation. As an illustrative example, we studied the black hole mass spectrum in the domain wall scenario, assuming that domain walls interact with matter only gravitationally. Our results indicate that, depending on the model parameters, black holes produced in this scenario can have significant astrophysical effects and can even serve as dark matter or as seeds for supermassive black holes. The mechanism of black hole formation described in this paper is very generic and has important implications for the global structure of the universe. Baby universes inside super-critical black holes inflate eternally and nucleate bubbles of all vacua allowed by the underlying particle physics. The resulting multiverse has a very non-trivial spacetime structure, with a multitude of eternally inflating regions connected by wormholes. If a black hole population with the predicted mass spectrum is discovered, it could be regarded as evidence for inflation and for the existence of a multiverse.
Critical phenomena of regular black holes in anti-de Sitter space-time
Energy Technology Data Exchange (ETDEWEB)
Fan, Zhong-Ying [Peking University, Center for High Energy Physics, Beijing (China)
2017-04-15
In General Relativity, addressing coupling to a non-linear electromagnetic field, together with a negative cosmological constant, we obtain the general static spherical symmetric black hole solution with magnetic charges, which is asymptotic to anti-de Sitter (AdS) space-times. In particular, for a degenerate case the solution becomes a Hayward-AdS black hole, which is regular everywhere in the full space-time. The existence of such a regular black hole solution preserves the weak energy condition, while the strong energy condition is violated. We then derive the first law and the Smarr formula of the black hole solution. We further discuss its thermodynamic properties and study the critical phenomena in the extended phase space where the cosmological constant is treated as a thermodynamic variable as well as the parameter associated with the non-linear electrodynamics. We obtain many interesting results such as: the Maxwell equal area law in the P-V (or S-T) diagram is violated and consequently the critical point (T{sub *},P{sub *}) of the first order small-large black hole transition does not coincide with the inflection point (T{sub c},P{sub c}) of the isotherms; the Clapeyron equation describing the coexistence curve of the Van der Waals (vdW) fluid is no longer valid; the heat capacity at constant pressure is finite at the critical point; the various exponents near the critical point are also different from those of the vdW fluid. (orig.)
Nonlinear PT-symmetric plaquettes
International Nuclear Information System (INIS)
Li Kai; Kevrekidis, P G; Malomed, Boris A; Günther, Uwe
2012-01-01
We introduce four basic two-dimensional (2D) plaquette configurations with onsite cubic nonlinearities, which may be used as building blocks for 2D PT-symmetric lattices. For each configuration, we develop a dynamical model and examine its PTsymmetry. The corresponding nonlinear modes are analyzed starting from the Hamiltonian limit, with zero value of the gain–loss coefficient, γ. Once the relevant waveforms have been identified (chiefly, in an analytical form), their stability is examined by means of linearization in the vicinity of stationary points. This reveals diverse and, occasionally, fairly complex bifurcations. The evolution of unstable modes is explored by means of direct simulations. In particular, stable localized modes are found in these systems, although the majority of identified solutions are unstable. This article is part of a special issue of Journal of Physics A: Mathematical and Theoretical devoted to ‘Quantum physics with non-Hermitian operators’. (paper)
Classification of symmetric toroidal orbifolds
Energy Technology Data Exchange (ETDEWEB)
Fischer, Maximilian; Ratz, Michael; Torrado, Jesus [Technische Univ. Muenchen, Garching (Germany). Physik-Department; Vaudrevange, Patrick K.S. [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany)
2012-09-15
We provide a complete classification of six-dimensional symmetric toroidal orbifolds which yield N{>=}1 supersymmetry in 4D for the heterotic string. Our strategy is based on a classification of crystallographic space groups in six dimensions. We find in total 520 inequivalent toroidal orbifolds, 162 of them with Abelian point groups such as Z{sub 3}, Z{sub 4}, Z{sub 6}-I etc. and 358 with non-Abelian point groups such as S{sub 3}, D{sub 4}, A{sub 4} etc. We also briefly explore the properties of some orbifolds with Abelian point groups and N=1, i.e. specify the Hodge numbers and comment on the possible mechanisms (local or non-local) of gauge symmetry breaking.
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
Testing for bivariate spherical symmetry
Einmahl, J.H.J.; Gantner, M.
2012-01-01
An omnibus test for spherical symmetry in R2 is proposed, employing localized empirical likelihood. The thus obtained test statistic is distri- bution-free under the null hypothesis. The asymptotic null distribution is established and critical values for typical sample sizes, as well as the asymptotic ones, are presented. In a simulation study, the good perfor- mance of the test is demonstrated. Furthermore, a real data example is presented.
Solutocapillary convection in spherical shells
Subramanian, Pravin; Zebib, Abdelfattah; McQuillan, Barry
2005-01-01
A linear stability study of solutocapillary driven Marangoni instabilities in small spherical shells is presented. The shells contain a binary fluid with an evaporating solvent. The viscosity is a strong function of the solvent concentration, the inner surface of the shell is assumed impermeable and stress free, while nonlinear boundary conditions are modeled and prescribed at the receding outer boundary. A time-dependent diffusive state is possible and may lose stability through the Marangoni mechanism due to surface tension dependence on solvent concentration (buoyant forces are negligible in this microscale problem). A frozen-time or quasisteady state linear stability analysis is performed to compute the critical Reynolds number and degree of surface harmonics, as well as the maximum growth rate of perturbations at specified parameters. The development of maximum growth rates in time was also computed by solving the initial value problem with random initial conditions. Results from both approaches are in good agreement except at short times where there is dependence on initial conditions. The physical problem models the manufacturing of spherical shells used as targets in inertial confinement fusion experiments where perfect sphericity is demanded for efficient fusion ignition. It is proposed that the Marangoni instability might be the source of observed surface roughness. Comparisons with the available experiments are made with reasonable qualitative and quantitative agreement.
Spherical space Bessel-Legendre-Fourier mode solver for Maxwell's wave equations
Alzahrani, Mohammed A.; Gauthier, Robert C.
2015-02-01
For spherically symmetric dielectric structures, a basis set composed of Bessel, Legendre and Fourier functions, BLF, are used to cast Maxwell's wave equations into an eigenvalue problem from which the localized modes can be determined. The steps leading to the eigenmatrix are reviewed and techniques used to reduce the order of matrix and tune the computations for particular mode types are detailed. The BLF basis functions are used to expand the electric and magnetic fields as well as the inverse relative dielectric profile. Similar to the common plane wave expansion technique, the BLF matrix returns the eigen-frequencies and eigenvectors, but in BLF only steady states, non-propagated, are obtained. The technique is first applied to a air filled spherical structure with perfectly conducting outer surface and then to a spherical microsphere located in air. Results are compared published values were possible.
Bilò, Vittorio; Mavronicolas, Marios
2017-01-01
We study the complexity of decision problems about symmetric Nash equilibria for symmetric multi-player games. These decision problems concern the existence of a symmetric Nash equilibrium with certain natural properties. We show that a handful of such decision problems are Existential-R-complete; that is, they are exactly as hard as deciding the Existential Theory of the Reals.
Measurement of Poloidal Velocity on the National Spherical Torus Experiment
Energy Technology Data Exchange (ETDEWEB)
Ronald E. Bell and Russell Feder
2010-06-04
A diagnostic suite has been developed to measure impurity poloidal flow using charge exchange recombination spectroscopy on the National Spherical Torus Experiment. Toroidal and poloidal viewing systems measure all quantities required to determine the radial electric field. Two sets of up/down symmetric poloidal views are used to measure both active emission in the plane of the neutral heating beams and background emission in a radial plane away from the neutral beams. Differential velocity measurements isolate the line-integrated poloidal velocity from apparent flows due to the energy-dependent chargeexchange cross section. Six f/1.8 spectrometers measure 276 spectra to obtain 75 active and 63 background channels every 10 ms. Local measurements from a similar midplane toroidal viewing system are mapped into two dimensions to allow the inversion of poloidal line-integrated measurements to obtain local poloidal velocity profiles. Radial resolution after inversion is 0.6-1.8 cm from the plasma edge to the center.
Static spherical wormhole models in f (R, T) gravity
Yousaf, Z.; Ilyas, M.; Zaeem-ul-Haq Bhatti, M.
2017-06-01
This paper explores the possibility of the existence of wormhole geometries coupled with relativistic matter configurations by taking a particular model of f(R,T) gravity (where T is the trace of energy-momentum tensor). For this purpose, we take the static form of spherically symmetric spacetime and after assuming a specific form of matter and combinations of shape function, the validity of energy conditions is checked. We have discussed our results through graphical representation and studied the equilibrium background of wormhole models by taking an anisotropic fluid. The extra curvature quantities coming from f(R,T) gravity could be interpreted as a gravitational entity supporting these non-standard astrophysical wormhole models. We have shown that in the context of anisotropic fluid and R+α R^2+λ T gravity, wormhole models could possibly exist in few zones in the space of parameters without the need for exotic matter.
Self-similar spherical metrics with tangential pressure
Gair, J R
2002-01-01
A family of spherically symmetric spacetimes is discussed, which have anisotropic pressure and possess a homothetic Killing vector. The spacetimes are composed of dust with a tangential pressure provided by angular momentum of the dust particles. The solution is given implicitly by an elliptic integral and depends on four arbitrary functions. These represent the initial configurations of angular momentum, mass, energy and position of the shells. The solution is derived by imposing self-similarity in the coordinates R, the shell label, and tau, the proper time experienced by the dust. Conditions for evolution without shell crossing and a description of singularity formation are given and types of solution discussed. General properties of the solutions are illustrated by reference to a particular case, which represents a universe that exists for an infinite time, but in which every shell expands and recollapses in a finite time.
CANONICAL EXTENSIONS OF SYMMETRIC LINEAR RELATIONS
Sandovici, Adrian; Davidson, KR; Gaspar, D; Stratila, S; Timotin, D; Vasilescu, FH
2006-01-01
The concept of canonical extension of Hermitian operators has been recently introduced by A. Kuzhel. This paper deals with a generalization of this notion to the case of symmetric linear relations. Namely, canonical regular extensions of symmetric linear relations in Hilbert spaces are studied. The
On completeness in symmetric spaces | Moshokoa | Quaestiones ...
African Journals Online (AJOL)
In the literature completeness for symmetric spaces is done through the classical Cauchy criterion for metric spaces. However, unlike the situation in metric spaces a convergent sequence in a symmetric space is not necessarily a Cauchy sequence. In the paper we introduce a notion of convergence completeness for ...
Generalized geometry and non-symmetric gravity
Jurco, Branislav; Khoo, Fech Scen; Schupp, Peter; Vysoky, Jan
2015-01-01
Generalized geometry provides the framework for a systematic approach to non-symmetric metric gravity theory and naturally leads to an Einstein-Kalb-Ramond gravity theory with totally anti-symmetric contortion. The approach is related to the study of the low-energy effective closed string gravity actions.
Nonlocal Fordy - Kulish Equations on Symmetric Spaces
Gurses, Metin
2017-01-01
We present nonlocal integrable reductions of the Fordy-Kulish system of nonlinear Schrodinger equations and the Fordy system of derivative nonlinear Schrodinger equations on Hermitian symmetric spaces. Examples are given on the symmetric space $\\frac{SU(4)}{SU(2) \\times SU(2)}$.
Growth of black holes in the interior of rotating neutron stars
DEFF Research Database (Denmark)
Kouvaris, C.; Tinyakov, P.
2014-01-01
Mini-black holes made of dark matter that can potentially form in the interior of neutron stars always have been thought to grow by accreting the matter of the core of the star via a spherical Bondi accretion. However, neutron stars have sometimes significant angular velocities that can...... in principle stall the spherical accretion and potentially change the conclusions derived about the time it takes for black holes to destroy a star. We study the effect of the star rotation on the growth of such black holes and the evolution of the black hole spin. Assuming no mechanisms of angular momentum...... evacuation, we find that even moderate rotation rates can in fact destroy spherical accretion at the early stages of the black hole growth. However, we demonstrate that the viscosity of nuclear matter can alleviate the effect of rotation, making it possible for the black hole to maintain spherical accretion...
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)
Brown, Angela Khristin
2013-01-01
The migration of blacks in North America through slavery became united. The population of blacks passed down 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…
A Spherical Aerial Terrestrial Robot
Dudley, Christopher J.
This thesis focuses on the design of a novel, ultra-lightweight spherical aerial terrestrial robot (ATR). The ATR has the ability to fly through the air or roll on the ground, for applications that include search and rescue, mapping, surveillance, environmental sensing, and entertainment. The design centers around a micro-quadcopter encased in a lightweight spherical exoskeleton that can rotate about the quadcopter. The spherical exoskeleton offers agile ground locomotion while maintaining characteristics of a basic aerial robot in flying mode. A model of the system dynamics for both modes of locomotion is presented and utilized in simulations to generate potential trajectories for aerial and terrestrial locomotion. Details of the quadcopter and exoskeleton design and fabrication are discussed, including the robot's turning characteristic over ground and the spring-steel exoskeleton with carbon fiber axle. The capabilities of the ATR are experimentally tested and are in good agreement with model-simulated performance. An energy analysis is presented to validate the overall efficiency of the robot in both modes of locomotion. Experimentally-supported estimates show that the ATR can roll along the ground for over 12 minutes and cover the distance of 1.7 km, or it can fly for 4.82 minutes and travel 469 m, on a single 350 mAh battery. Compared to a traditional flying-only robot, the ATR traveling over the same distance in rolling mode is 2.63-times more efficient, and in flying mode the system is only 39 percent less efficient. Experimental results also demonstrate the ATR's transition from rolling to flying mode.
Black holes in six-dimensional conformal gravity
Lü, H.; Pang, Yi; Pope, C. N.
2013-05-01
We study conformally invariant theories of gravity in six dimensions. In four dimensions, there is a unique such theory that is polynomial in the curvature and its derivatives, namely, Weyl-squared, and furthermore all solutions of Einstein gravity are also solutions of the conformal theory. By contrast, in six dimensions there are three independent conformally invariant polynomial terms one could consider. There is a unique linear combination (up to overall scale) for which Einstein metrics are also solutions, and this specific theory forms the focus of our attention in this paper. We reduce the equations of motion for the most general spherically symmetric black hole to a single fifth-order differential equation. We obtain the general solution in the form of an infinite series, characterized by five independent parameters, and we show how a finite three-parameter truncation reduces to the already known Schwarzschild-AdS metric and its conformal scaling. We derive general results for the thermodynamics and the first law for the full five-parameter solutions. We also investigate solutions in extended theories coupled to conformally invariant matter, and in addition we derive some general results for conserved charges in cubic-curvature theories in arbitrary dimensions.
Substring-Searchable Symmetric Encryption
Directory of Open Access Journals (Sweden)
Chase Melissa
2015-06-01
Full Text Available In this paper, we consider a setting where a client wants to outsource storage of a large amount of private data and then perform substring search queries on the data – given a data string s and a search string p, find all occurrences of p as a substring of s. First, we formalize an encryption paradigm that we call queryable encryption, which generalizes searchable symmetric encryption (SSE and structured encryption. Then, we construct a queryable encryption scheme for substring queries. Our construction uses suffix trees and achieves asymptotic efficiency comparable to that of unencrypted suffix trees. Encryption of a string of length n takes O(λn time and produces a ciphertext of size O(λn, and querying for a substring of length m that occurs k times takes O(λm+k time and three rounds of communication. Our security definition guarantees correctness of query results and privacy of data and queries against a malicious adversary. Following the line of work started by Curtmola et al. (ACM CCS 2006, in order to construct more efficient schemes we allow the query protocol to leak some limited information that is captured precisely in the definition. We prove security of our substring-searchable encryption scheme against malicious adversaries, where the query protocol leaks limited information about memory access patterns through the suffix tree of the encrypted string.
Baryon symmetric big bang cosmology
Stecker, F. W.
1978-01-01
Both the quantum theory and Einsteins theory of special relativity lead to the supposition that matter and antimatter were produced in equal quantities during the big bang. It is noted that local matter/antimatter asymmetries may be reconciled with universal symmetry by assuming (1) a slight imbalance of matter over antimatter in the early universe, annihilation, and a subsequent remainder of matter; (2) localized regions of excess for one or the other type of matter as an initial condition; and (3) an extremely dense, high temperature state with zero net baryon number; i.e., matter/antimatter symmetry. Attention is given to the third assumption, which is the simplest and the most in keeping with current knowledge of the cosmos, especially as pertains the universality of 3 K background radiation. Mechanisms of galaxy formation are discussed, whereby matter and antimatter might have collided and annihilated each other, or have coexisted (and continue to coexist) at vast distances. It is pointed out that baryon symmetric big bang cosmology could probably be proved if an antinucleus could be detected in cosmic radiation.
Charting the Replica Symmetric Phase
Coja-Oghlan, Amin; Efthymiou, Charilaos; Jaafari, Nor; Kang, Mihyun; Kapetanopoulos, Tobias
2018-02-01
Diluted mean-field models are spin systems whose geometry of interactions is induced by a sparse random graph or hypergraph. Such models play an eminent role in the statistical mechanics of disordered systems as well as in combinatorics and computer science. In a path-breaking paper based on the non-rigorous `cavity method', physicists predicted not only the existence of a replica symmetry breaking phase transition in such models but also sketched a detailed picture of the evolution of the Gibbs measure within the replica symmetric phase and its impact on important problems in combinatorics, computer science and physics (Krzakala et al. in Proc Natl Acad Sci 104:10318-10323, 2007). In this paper we rigorise this picture completely for a broad class of models, encompassing the Potts antiferromagnet on the random graph, the k-XORSAT model and the diluted k-spin model for even k. We also prove a conjecture about the detection problem in the stochastic block model that has received considerable attention (Decelle et al. in Phys Rev E 84:066106, 2011).
A method of spherical harmonic analysis in the geosciences via hierarchical Bayesian inference
Muir, J. B.; Tkalčić, H.
2015-11-01
The problem of decomposing irregular data on the sphere into a set of spherical harmonics is common in many fields of geosciences where it is necessary to build a quantitative understanding of a globally varying field. For example, in global seismology, a compressional or shear wave speed that emerges from tomographic images is used to interpret current state and composition of the mantle, and in geomagnetism, secular variation of magnetic field intensity measured at the surface is studied to better understand the changes in the Earth's core. Optimization methods are widely used for spherical harmonic analysis of irregular data, but they typically do not treat the dependence of the uncertainty estimates on the imposed regularization. This can cause significant difficulties in interpretation, especially when the best-fit model requires more variables as a result of underestimating data noise. Here, with the above limitations in mind, the problem of spherical harmonic expansion of irregular data is treated within the hierarchical Bayesian framework. The hierarchical approach significantly simplifies the problem by removing the need for regularization terms and user-supplied noise estimates. The use of the corrected Akaike Information Criterion for picking the optimal maximum degree of spherical harmonic expansion and the resulting spherical harmonic analyses are first illustrated on a noisy synthetic data set. Subsequently, the method is applied to two global data sets sensitive to the Earth's inner core and lowermost mantle, consisting of PKPab-df and PcP-P differential traveltime residuals relative to a spherically symmetric Earth model. The posterior probability distributions for each spherical harmonic coefficient are calculated via Markov Chain Monte Carlo sampling; the uncertainty obtained for the coefficients thus reflects the noise present in the real data and the imperfections in the spherical harmonic expansion.
Spherical Orbifolds for Cosmic Topology
International Nuclear Information System (INIS)
Kramer, Peter
2012-01-01
Harmonic analysis is a tool to infer cosmic topology from the measured astrophysical cosmic microwave background CMB radiation. For overall positive curvature, Platonic spherical manifolds are candidates for this analysis. We combine the specific point symmetry of the Platonic manifolds with their deck transformations. This analysis in topology leads from manifolds to orbifolds. We discuss the deck transformations of the orbifolds and give eigenmodes for the harmonic analysis as linear combinations of Wigner polynomials on the 3-sphere. These provide new tools for detecting cosmic topology from the CMB radiation.
PERIODIC-ORBITS IN K-SYMMETRICAL DYNAMICAL-SYSTEMS
BRANDS, H; LAMB, JSW; HOVEIJN, [No Value
1995-01-01
A map L is called k-symmetric if its kth iterate L(k) possesses more symmetry than L, for some value of k. In k-symmetric systems, there exists a notion of k-symmetric orbits. This paper deals with k-symmetric periodic orbits. We derive a relation between orbits that are k-symmetric with respect to
Approximate ballistics formulas for spherical pellets in free flight
Directory of Open Access Journals (Sweden)
E.J. Allen
2018-02-01
Full Text Available The ballistics equations for spherical pellets in free flight are simplified through appropriate scaling of the pellet velocity and pellet distance. Two different drag coefficient curves are averaged to yield a single curve applicable to shot pellets and round balls. The resulting S-shaped drag coefficient curve is approximated by three straight-line segments. The scaled ballistics equations are then solved exactly and simple formulas are found for the velocity and flight time with respect to trajectory distance. The formulas are applicable to spherical shot pellets and round balls of any composition under any atmospheric conditions. The formulas are amenable to quick and easy computation and may also serve as an aid in understanding and comparing black-box ballistics calculators. For shotshell ballistics, an important assumption in the present investigation is that the pellets are moving as single, free spheres and not as a dense cloud or in a shot column, in particular, the pellets are not interacting during flight. Therefore, the formulas are most appropriate for single round balls, for large shot sizes, and for pellets of small shot size fired from open chokes. The formulas are clear and accessible, and can be implemented by military or law enforcement personnel as well as hunters and shooters. This work differs from previous investigations in that accurate ballistics formulas are derived for spherical projectiles of shotguns and muzzleloaders using realistic drag coefficients.
Stoeger, W. R.
1978-01-01
Since Rosen's bimetric theory of gravity provides at present a worthy devil's advocate for the black hole hypothesis, it is important for eventual observational work to elaborate the astrophysical consequences and possibilities peculiar to it. This work is begun by deriving the orbital topography of the spherically symmetric solution to Rosen's field equations - which is relevant to the behavior of relativistic axisymmetric accretion flows - and calculating predicted accretion disk efficiencies, which can be as much as 2.5 times higher than for a disk in Schwarzschild. Thereafter, a brief treatment of the shortest kinematic time scale and the time dilations for in-falling material is given. Finally it is shown that Birkhoff's theorem does not hold in Rosen's theory, and, therefore, that genuine gravitational monopole radiation is possible. The energy it carries, however, is not positive definite.
Casimir effect in spherical shells
International Nuclear Information System (INIS)
Ruggiero, J.R.
1985-01-01
The analytic regularization method is applied to study the Casimir effect for spherical cavities. Although many works have been presented in the past few years, problems related to the elimination of the regulator parameter still remain. A way to calculate the zero point energy of a perfectly conducting spherical shell which is a miscellaneous of those presented early is here proposed, How a cancelation of divergent terms occurs and how a finite parte is obtained after the elimination of the regulator parameter is shown. As a by-product the zero point energy of the interior vibration modes is obtained and this has some relevance to the quarks bag model. This relev ance is also discussed. The calculation of the energy fom the density view is also discussed. Some works in this field are criticized. The logarithmic divergent terms in the zero point energy are studied when the interior and exterior of the sphere are considered as a medium not dispersive and characterized by a dielectric constants ε 1 and ε 2 and peermeability constants μ 1 and μ 2 respectivelly. The logarithmic divergent terms are not present in the case of ε i μ i =K, with K some constant and i=1,2. (author) [pt
National Spherical Torus Experiment (NSTX)
International Nuclear Information System (INIS)
Masayuki Ono
2000-01-01
The main aim of National Spherical Torus Experiment (NSTX) is to establish the fusion physics principles of the innovative spherical torus (ST) concept. Physics outcome of the NSTX research program is relevant to near-term applications such as the Volume Neutron Source (VNS) and burning plasmas, and future applications such as the pilot and power plants. The NSTX device began plasma operations in February 1999 and the plasma current was successfully ramped up to the design value of 1 million amperes (MA) on December 14, 1999. The CHI (Coaxial Helicity Injection) and HHFW (High Harmonic Fast Wave) experiments have also started. Stable CHI discharges of up to 133 kA and 130-msec duration have been produced using 20 kA of injected current. Using eight antennas connected to two transmitters, up to 2 MW of HHFW power was successfully coupled to the plasma. The Neutral-beam Injection (NBI) heating system and associated NBI-based diagnostics such as the Charge-exchange Recombination Spectrometer (CHERS) will be operational in October 2000
Radiatively-suppressed spherical accretion under relativistic radiative transfer
Fukue, Jun
2018-03-01
We numerically examine radiatively-suppressed relativistic spherical accretion flows on to a central object with mass M under Newtonian gravity and special relativity. We simultaneously solve both the relativistic radiative transfer equation and the relativistic hydrodynamical equations for spherically symmetric flows under the double iteration process in the case of the intermediate optical depth. We find that the accretion flow is suppressed, compared with the freefall case in the nonrelativistic regime. For example, in the case of accretion on to a luminous core with accretion luminosity L*, the freefall velocity v normalized by the speed of light c under the radiative force in the nonrelativistic regime is β (\\hat{r}) = v/c = -√{(1-Γ _*)/(\\hat{r}+1-Γ _*)}, where Γ* (≡ L*/LE, LE being the Eddington luminosity) is the Eddington parameter and \\hat{r} (= r/rS, rS being the Schwarzschild radius) the normalized radius, whereas the infall speed at the central core is ˜0.7β(1), irrespective of the mass-accretion rate. This is due to the relativistic effect; the comoving flux is enhanced by the advective flux. We briefly examine and discuss an isothermal case, where the emission takes place in the entire space.
The symmetric extendibility of quantum states
International Nuclear Information System (INIS)
Nowakowski, Marcin L
2016-01-01
Studies on the symmetric extendibility of quantum states have become particularly important in the context of the analysis of one-way quantum measures of entanglement, and the distillability and security of quantum protocols. In this paper we analyze composite systems containing a symmetric extendible part, with particular attention devoted to the one-way security of such systems. Further, we introduce a new one-way entanglement monotone based on the best symmetric approximation of a quantum state and the extendible number of a quantum state. We underpin these results with geometric observations about the structures of multi-party settings which posses substantial symmetric extendible components in their subspaces. The impossibility of reducing the maximal symmetric extendibility by means of the one-way local operations and classical communication method is pointed out on multiple copies. Finally, we state a conjecture linking symmetric extendibility with the one-way distillability and security of all quantum states, analyzing the behavior of a private key in the neighborhood of symmetric extendible states. (paper)
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
Progress in octahedral spherical hohlraum study
Directory of Open Access Journals (Sweden)
Ke Lan
2016-01-01
Full Text Available In this paper, we give a review of our theoretical and experimental progress in octahedral spherical hohlraum study. From our theoretical study, the octahedral spherical hohlraums with 6 Laser Entrance Holes (LEHs of octahedral symmetry have robust high symmetry during the capsule implosion at hohlraum-to-capsule radius ratio larger than 3.7. In addition, the octahedral spherical hohlraums also have potential superiority on low backscattering without supplementary technology. We studied the laser arrangement and constraints of the octahedral spherical hohlraums, and gave a design on the laser arrangement for ignition octahedral hohlraums. As a result, the injection angle of laser beams of 50°–60° was proposed as the optimum candidate range for the octahedral spherical hohlraums. We proposed a novel octahedral spherical hohlraum with cylindrical LEHs and LEH shields, in order to increase the laser coupling efficiency and improve the capsule symmetry and to mitigate the influence of the wall blowoff on laser transport. We studied on the sensitivity of the octahedral spherical hohlraums to random errors and compared the sensitivity among the octahedral spherical hohlraums, the rugby hohlraums and the cylindrical hohlraums, and the results show that the octahedral spherical hohlraums are robust to these random errors while the cylindrical hohlraums are the most sensitive. Up till to now, we have carried out three experiments on the spherical hohlraum with 2 LEHs on Shenguang(SG laser facilities, including demonstration of improving laser transport by using the cylindrical LEHs in the spherical hohlraums, spherical hohlraum energetics on the SGIII prototype laser facility, and comparisons of laser plasma instabilities between the spherical hohlraums and the cylindrical hohlraums on the SGIII laser facility.
Linac design algorithm with symmetric segments
International Nuclear Information System (INIS)
Takeda, Harunori; Young, L.M.; Nath, S.; Billen, J.H.; Stovall, J.E.
1996-01-01
The cell lengths in linacs of traditional design are typically graded as a function of particle velocity. By making groups of cells and individual cells symmetric in both the CCDTL AND CCL, the cavity design as well as mechanical design and fabrication is simplified without compromising the performance. We have implemented a design algorithm in the PARMILA code in which cells and multi-cavity segments are made symmetric, significantly reducing the number of unique components. Using the symmetric algorithm, a sample linac design was generated and its performance compared with a similar one of conventional design
Quantum Mechanics and Black Holes in Four-Dimensional String Theory
Ellis, Jonathan Richard; Nanopoulos, Dimitri V
1992-01-01
In previous papers we have shown how strings in a two-dimensional target space reconcile quantum mechanics with general relativity, thanks to an infinite set of conserved quantum numbers, ``W-hair'', associated with topological soliton-like states. In this paper we extend these arguments to four dimensions, by considering explicitly the case of string black holes with radial symmetry. The key infinite-dimensional W-symmetry is associated with the $\\frac{SU(1,1)}{U(1)}$ coset structure of the dilaton-graviton sector that is a model-independent feature of spherically symmetric four-dimensional strings. Arguments are also given that the enormous number of string {\\it discrete (topological)} states account for the maintenance of quantum coherence during the (non-thermal) stringy evaporation process, as well as quenching the large Hawking-Bekenstein entropy associated with the black hole. Defining the latter as the measure of the loss of information for an observer at infinity, who - ignoring the higher string qua...
Scalar-field amplitudes in black-hole evaporation
International Nuclear Information System (INIS)
Farley, A.N.St.J.; D'Eath, P.D.
2004-01-01
We consider the quantum-mechanical decay of a Schwarzschild-like black hole into almost-flat space and weak radiation at a very late time. That is, we are concerned with evaluating quantum amplitudes (not just probabilities) for transitions from initial to final states. In this quantum description, no information is lost because of the black hole. The Lagrangian is taken, in the first instance, to consist of the simplest locally supersymmetric generalization of Einstein gravity and a massless scalar field. The quantum amplitude to go from given initial to final bosonic data in a slightly complexified time-interval T=τexp(-iθ) at infinity may be approximated by the form constxexp(-I), where I is the (complex) Euclidean action of the classical solution filling in between the boundary data. Additionally, in a pure supergravity theory, the amplitude constxexp(-I) is exact. Suppose that Dirichlet boundary data for gravity and the scalar field are posed on an initial spacelike hypersurface extending to spatial infinity, just prior to collapse, and on a corresponding final spacelike surface, sufficiently far to the future of the initial surface to catch all the Hawking radiation. Only in an averaged sense will this radiation have an approximately spherically-symmetric distribution. If the time-interval T had been taken to be exactly real, then the resulting 'hyperbolic Dirichlet boundary-value problem' would, as is well known, not be well posed. Provided instead ('Euclidean strategy') that one takes T complex, as above (0<θ=<π/2), one expects that the field equations become strongly elliptic, and that there exists a unique solution to the classical boundary-value problem. Within this context, by expanding the bosonic part of the action to quadratic order in perturbations about the classical solution, one obtains the quantum amplitude for weak-field final configurations, up to normalization. Such amplitudes are here calculated for weak final scalar fields
The ETE spherical Tokamak project. IAEA report
Energy Technology Data Exchange (ETDEWEB)
Ludwig, Gerson Otto; Del Bosco, E.; Berni, L.A.; Ferreira, J.G.; Oliveira, R.M.; Andrade, M.C.R.; Shibata, C.S.; Barroso, J.J.; Castro, P.J.; Patire Junior, H. [Instituto Nacional de Pesquisas Espaciais (INPE), Sao Jose dos Campos, SP (Brazil). Lab. Associado de Plasma]. E-mail: ludwig@plasma.inpe.br
2002-07-01
This paper describes the general characteristics of spherical tokamaks, or spherical tori, with a brief overview of work in this area already performed or in progress at several institutions worldwide. The paper presents also the historical development of the ETE (Spherical Tokamak Experiment) project, its research program, technical characteristics and operating conditions as of October, 2002 at the Associated Plasma Laboratory (LAP) of the National Space Research Institute (INPE) in Brazil. (author)
Relationships between solid spherical and toroidal harmonics
Majic, Matt; Ru, Eric C. Le
2018-01-01
We derive new relationships expressing solid spherical harmonics as series of toroidal harmonics and vice versa. The expansions include regular and irregular spherical harmonics, ring and axial toroidal harmonics of even and odd parity about the plane of the torus. The expansion coefficients are given in terms of a recurrence relation. As an example application we apply one of the expansions to express the potential of a charged conducting torus on a basis of spherical harmonics.
Topological derivation of black hole entropy by analogy with a chain polymer
International Nuclear Information System (INIS)
Siino, Masaru
2002-01-01
The generic crease set of an event horizon possesses anisotropic structure although most black holes are dynamically stable. This fact suggests that a generic almost spherical black hole has a very crumpled crease set on a microscopic scale although the crease set is similar to a pointwise crease set on a macroscopic scale. In the present article, we count the number of such microstates of an almost spherical black hole by analogy with an elastic chain polymer. This estimation of black hole entropy reproduces the well-known Bekenstein-Hawking entropy of a Schwarzschild black hole
symmetric sextic potential in two dimensions
Indian Academy of Sciences (India)
symmetric sextic potential in two dimensions. FAKIR CHAND1,∗, S C MISHRA1 and RAM MEHAR SINGH2 ... resonance scattering in atomic, molecular, and nuclear physics and to some chemical reactions ...... D R Nelson and N M Snerb, Phys.
Introduction to left-right symmetric models
International Nuclear Information System (INIS)
Grimus, W.
1993-01-01
We motivate left-right symmetric models by the possibility of spontaneous parity breaking. Then we describe the multiplets and the Lagrangian of such models. Finally we discuss lower bounds on the right-handed scale. (author)
Symmetrical parahiliar infiltrated, cough and dyspnoea
International Nuclear Information System (INIS)
Giraldo Estrada, Horacio; Escalante, Hector
2004-01-01
It is the case a patient to who is diagnosed symmetrical parahiliar infiltrated; initially she is diagnosed lymphoma Hodgkin, treaty with radiotherapy and chemotherapy, but the X rays of the thorax demonstrated parahiliars and paramediastinals infiltrated
Symmetric nuclear matter with Skyrme interaction
International Nuclear Information System (INIS)
Manisa, K.; Bicer, A.; Atav, U.
2010-01-01
The equation of state (EOS) and some properties of symmetric nuclear matter, such as the saturation density, saturation energy and incompressibility, are obtained by using Skyrme's density-dependent effective nucleon-nucleon interaction.
Martingale Rosenthal inequalities in symmetric spaces
Astashkin, S. V.
2014-12-01
We establish inequalities similar to the classical Rosenthal inequalities for sequences of martingale differences in general symmetric spaces; a central role is played here by the predictable quadratic characteristic of a martingale. Bibliography: 26 titles.
Martingale Rosenthal inequalities in symmetric spaces
Energy Technology Data Exchange (ETDEWEB)
Astashkin, S V [Samara State University, Samara (Russian Federation)
2014-12-31
We establish inequalities similar to the classical Rosenthal inequalities for sequences of martingale differences in general symmetric spaces; a central role is played here by the predictable quadratic characteristic of a martingale. Bibliography: 26 titles.
Functional Contractive Maps in Triangular Symmetric Spaces
Directory of Open Access Journals (Sweden)
Mihai Turinici
2013-01-01
Full Text Available Some fixed point results are given for a class of functional contractions acting on (reflexive triangular symmetric spaces. Technical connections with the corresponding theories over (standard metric and partial metric spaces are also being established.
Spherical Collapse in Chameleon Models
Brax, Ph; Steer, D A
2010-01-01
We study the gravitational collapse of an overdensity of nonrelativistic matter under the action of gravity and a chameleon scalar field. We show that the spherical collapse model is modified by the presence of a chameleon field. In particular, we find that even though the chameleon effects can be potentially large at small scales, for a large enough initial size of the inhomogeneity the collapsing region possesses a thin shell that shields the modification of gravity induced by the chameleon field, recovering the standard gravity results. We analyse the behaviour of a collapsing shell in a cosmological setting in the presence of a thin shell and find that, in contrast to the usual case, the critical density for collapse depends on the initial comoving size of the inhomogeneity.
Spherical collapse in chameleon models
International Nuclear Information System (INIS)
Brax, Ph.; Rosenfeld, R.; Steer, D.A.
2010-01-01
We study the gravitational collapse of an overdensity of nonrelativistic matter under the action of gravity and a chameleon scalar field. We show that the spherical collapse model is modified by the presence of a chameleon field. In particular, we find that even though the chameleon effects can be potentially large at small scales, for a large enough initial size of the inhomogeneity the collapsing region possesses a thin shell that shields the modification of gravity induced by the chameleon field, recovering the standard gravity results. We analyse the behaviour of a collapsing shell in a cosmological setting in the presence of a thin shell and find that, in contrast to the usual case, the critical density for collapse in principle depends on the initial comoving size of the inhomogeneity
The Naimark dilated PT-symmetric brachistochrone
Guenther, Uwe; Samsonov, Boris F.
2008-01-01
The quantum mechanical brachistochrone system with PT-symmetric Hamiltonian is Naimark dilated and reinterpreted as subsystem of a Hermitian system in a higher-dimensional Hilbert space. This opens a way to a direct experimental implementation of the recently hypothesized PT-symmetric ultra-fast brachistochrone regime of [C. M. Bender et al, Phys. Rev. Lett. {\\bf 98}, 040403 (2007)] in an entangled two-spin system.
Naimark-Dilated PT-Symmetric Brachistochrone
Günther, Uwe; Samsonov, Boris F.
2008-12-01
The quantum mechanical brachistochrone system with a PT-symmetric Hamiltonian is Naimark-dilated and reinterpreted as a subsystem of a Hermitian system in a higher-dimensional Hilbert space. This opens a way to a direct experimental implementation of the recently hypothesized PT-symmetric ultrafast brachistochrone regime of Bender et al. [Phys. Rev. Lett. 98, 040403 (2007)PRLTAO0031-900710.1103/PhysRevLett.98.040403] in an entangled two-spin system.
Symmetric states: Their nonlocality and entanglement
Energy Technology Data Exchange (ETDEWEB)
Wang, Zizhu; Markham, Damian [CNRS LTCI, Département Informatique et Réseaux, Telecom ParisTech, 23 avenue d' Italie, CS 51327, 75214 Paris CEDEX 13 (France)
2014-12-04
The nonlocality of permutation symmetric states of qubits is shown via an extension of the Hardy paradox and the extension of the associated inequality. This is achieved by using the Majorana representation, which is also a powerful tool in the study of entanglement properties of symmetric states. Through the Majorana representation, different nonlocal properties can be linked to different entanglement properties of a state, which is useful in determining the usefulness of different states in different quantum information processing tasks.
Supersymmetry of anti-de Sitter black holes
International Nuclear Information System (INIS)
Caldarelli, Marco M.; Klemm, Dietmar
1999-01-01
We examine supersymmetry of four-dimensional asymptotically anti-de Sitter (AdS) dyonic black holes in the context of gauged N = 2 supergravity. Our calculations concentrate on black holes with unusual topology and their rotating generalizations, but we also reconsider the spherical rotating dyonic Ker-Newman-AdS black hole, whose supersymmetry properties have previously been investigated by Kostelecky and Perry within another approach. We find that in the case of spherical, toroidal or cylindrical event horizon topology, the black holes must rotate in order to preserve some supersymmetry; the non-rotating supersymmetric configurations representing naked singularities. However, we show that this is no more true for black holes whose event horizons are Riemann surfaces of genus g > 1, where we find a non-rotating extremal solitonic black hole carrying magnetic charge and permitting one Killing spinor. For the non-rotating supersymmetric configurations of various topologies, all Killing spinors are explicitly constructed
Black hole unitarity and antipodal entanglement
't Hooft, Gerard
Hawking particles emitted by a black hole are usually found to have thermal spectra, if not exactly, then by a very good approximation. Here, we argue differently. It was discovered that spherical partial waves of in-going and out-going matter can be described by unitary evolution operators
Spherical particles formation under biaxial cyclic loading due to mesotunneling effect
Directory of Open Access Journals (Sweden)
A. Shanyavskiy
2015-07-01
Full Text Available Fatigue fracture surfaces of Al-based alloys with fatigue striations pattern and such wear debris pattern as spherical particles were investigated fractographically, on the bases of the OG’e spectroscopic analysis. The sequence of events during fatigue crack edges opening was discovered when the elliptical or spherical shapes of wear debris build up on the fracture surface in crosspieces between mesotunnels under mode III of mode I fatigue crack opening because of volume rotation. The cause of black colour of places with fretting patterns on the fracture surfaces of Al-based alloys is discussed.
Numerical optimization of spherical variable-line-spacing grating X-ray spectrometers
International Nuclear Information System (INIS)
Strocov, V. N.; Schmitt, T.; Flechsig, U.; Patthey, L.; Chiuzbăian, G. S.
2011-01-01
Operation of an X-ray spectrometer based on a spherical variable-line-spacing grating is analyzed using dedicated ray-tracing software allowing fast optimization of the grating parameters and spectrometer geometry. Operation of an X-ray spectrometer based on a spherical variable-line-spacing (VLS) grating is analyzed using dedicated ray-tracing software allowing fast optimization of the grating parameters and spectrometer geometry. The analysis is illustrated with optical design of a model spectrometer to deliver a resolving power above 20400 at a photon energy of 930 eV (Cu L-edge). With this energy taken as reference, the VLS coefficients are optimized to cancel the lineshape asymmetry (mostly from the coma aberrations) as well as minimize the symmetric aberration broadening at large grating illuminations, dramatically increasing the aberration-limited vertical acceptance of the spectrometer. For any energy away from the reference, corrections to the entrance arm and light incidence angle on the grating are evaluated to maintain the exactly symmetric lineshape. Furthermore, operational modes when these corrections are coordinated are evaluated to maintain either energy-independent focal curve inclination or maximal aberration-limited spectrometer acceptance. The results are supported by analytical evaluation of the coma term of the optical path function. This analysis thus gives a recipe for designing a high-resolution spherical VLS grating spectrometer operating with negligible aberrations at large acceptance and over an extended energy range
Numerical optimization of spherical variable-line-spacing grating X-ray spectrometers
Energy Technology Data Exchange (ETDEWEB)
Strocov, V. N., E-mail: vladimir.strocov@psi.ch; Schmitt, T.; Flechsig, U.; Patthey, L. [Swiss Light Source, Paul Scherrer Institut, CH-5232 Villigen-PSI (Switzerland); Chiuzbăian, G. S. [UPMC University Paris 06, CNRS UMR 7614, Laboratoire de Chimie Physique - Matière et Rayonnement, 75321 Paris Cedex 05 (France)
2011-03-01
Operation of an X-ray spectrometer based on a spherical variable-line-spacing grating is analyzed using dedicated ray-tracing software allowing fast optimization of the grating parameters and spectrometer geometry. Operation of an X-ray spectrometer based on a spherical variable-line-spacing (VLS) grating is analyzed using dedicated ray-tracing software allowing fast optimization of the grating parameters and spectrometer geometry. The analysis is illustrated with optical design of a model spectrometer to deliver a resolving power above 20400 at a photon energy of 930 eV (Cu L-edge). With this energy taken as reference, the VLS coefficients are optimized to cancel the lineshape asymmetry (mostly from the coma aberrations) as well as minimize the symmetric aberration broadening at large grating illuminations, dramatically increasing the aberration-limited vertical acceptance of the spectrometer. For any energy away from the reference, corrections to the entrance arm and light incidence angle on the grating are evaluated to maintain the exactly symmetric lineshape. Furthermore, operational modes when these corrections are coordinated are evaluated to maintain either energy-independent focal curve inclination or maximal aberration-limited spectrometer acceptance. The results are supported by analytical evaluation of the coma term of the optical path function. This analysis thus gives a recipe for designing a high-resolution spherical VLS grating spectrometer operating with negligible aberrations at large acceptance and over an extended energy range.
Deformation and orientation effects in the binary symmetric decay of 20,21,22Ne*
International Nuclear Information System (INIS)
Singh, BirBikram; Kaur, Manpreet; Gupta, Raj K.
2014-01-01
We have extended the study of binary symmetric decay (BSD) of extremely light mass compound systems 20,21,22 Ne* formed in 10,11 B+ 10,11 B reactions at E lab = 48 MeV, to explore the role of deformations and orientations, using the Dynamical Cluster decay Model (DCM). In the present work, we find that with inclusion of quadruple deformations and 'hot compact' orientations of nuclei σ ff increases in comparison to the case of spherical considerations of nuclei
Stability of the spherical form of nuclei
International Nuclear Information System (INIS)
Sabry, A.A.
1976-08-01
An extension of the mass formula for a spherical nucleus in the drop model to include a largely deformed nucleus of different forms is investigated. It is found that although the spherical form is stable under small deformations from equilibrium, there exists for heavier nuclei another more favourable stable form, which can be approximated by two, or three touching prolate ellipsoids of revolution
Intrinsic cylindrical and spherical waves
International Nuclear Information System (INIS)
Ludlow, I K
2008-01-01
Intrinsic waveforms associated with cylindrical and spherical Bessel functions are obtained by eliminating the factors responsible for the inverse radius and inverse square radius laws of wave power per unit area of wavefront. The resulting expressions are Riccati-Bessel functions for both cases and these can be written in terms of amplitude and phase functions of order v and wave variable z. When z is real, it is shown that a spatial phase angle of the intrinsic wave can be defined and this, together with its amplitude function, is systematically investigated for a range of fixed orders and varying z. The derivatives of Riccati-Bessel functions are also examined. All the component functions exhibit different behaviour in the near field depending on the order being less than, equal to or greater than 1/2. Plots of the phase angle can be used to display the locations of the zeros of the general Riccati-Bessel functions and lead to new relations concerning the ordering of the real zeros of Bessel functions and the occurrence of multiple zeros when the argument of the Bessel function is fixed
Osmotic buckling of spherical capsules.
Knoche, Sebastian; Kierfeld, Jan
2014-11-07
We study the buckling of elastic spherical shells under osmotic pressure with the osmolyte concentration of the exterior solution as a control parameter. We compare our results for the bifurcation behavior with results for buckling under mechanical pressure control, that is, with an empty capsule interior. We find striking differences for the buckling states between osmotic and mechanical buckling. Mechanical pressure control always leads to fully collapsed states with opposite sides in contact, whereas uncollapsed states with a single finite dimple are generic for osmotic pressure control. For sufficiently large interior osmolyte concentrations, osmotic pressure control is qualitatively similar to buckling under volume control with the volume prescribed by the osmolyte concentrations inside and outside the shell. We present a quantitative theory which also captures the influence of shell elasticity on the relationship between osmotic pressure and volume. These findings are relevant for the control of buckled shapes in applications. We show how the osmolyte concentration can be used to control the volume of buckled shells. An accurate analytical formula is derived for the relationship between the osmotic pressure, the elastic moduli and the volume of buckled capsules. This also allows use of elastic capsules as osmotic pressure sensors or deduction of elastic properties and the internal osmolyte concentration from shape changes in response to osmotic pressure changes. We apply our findings to published experimental data on polyelectrolyte capsules.
STU black holes and string triality
International Nuclear Information System (INIS)
Behrndt, K.; Kallosh, R.; Rahmfeld, J.; Shmakova, M.; Wong, W.K.
1996-01-01
We find double-extreme black holes associated with the special geometry of the Calabi-Yau moduli space with the prepotential F=STU. The area formula is STU-moduli independent and has [SL(2,Z)] 3 symmetry in space of charges. The dual version of this theory without a prepotential treats the dilaton S asymmetric vs T,U moduli. We display the dual relation between new (STU) black holes and stringy (S|TU) black holes using a particular Sp(8,Z) transformation. The area formula of one theory equals that of the dual theory when expressed in terms of dual charges. We analyze the relation between (STU) black holes to string triality of black holes: (S|TU), (T|US), (U|ST) solutions. In the democratic STU-symmetric version we find that all three S, T, and U duality symmetries are nonperturbative and mix electric and magnetic charges. copyright 1996 The American Physical Society
STU Black Holes and String Triality
Energy Technology Data Exchange (ETDEWEB)
Shmakova, Marina
2003-05-23
We found double-extreme black holes associated with the special geometry of the Calabi-Yau moduli space with the prepotential F = STU. The area formula is STU-moduli independent and has [SL(2, Z)]{sup 3} symmetry in space of charges. The dual version of this theory without prepotential treats the dilaton S asymmetric versus T,U-moduli. We display the dual relation between new (STU) black holes and stringy (S|TU) black holes using particular Sp(8,Z) transformation. The area formula of one theory equals the area formula of the dual theory when expressed in terms of dual charges. We analyze the relation between (STU) black holes to string triality of black holes: (S|TU), (T|US), (U|ST) solutions. In democratic STU-symmetric version we find that all three S and T and U duality symmetries are non-perturbative and mix electric and magnetic charges.
Cauchy-perturbative matching reexamined: Tests in spherical symmetry
International Nuclear Information System (INIS)
Zink, Burkhard; Pazos, Enrique; Diener, Peter; Tiglio, Manuel
2006-01-01
During the last few years progress has been made on several fronts making it possible to revisit Cauchy-perturbative matching (CPM) in numerical relativity in a more robust and accurate way. This paper is the first in a series where we plan to analyze CPM in the light of these new results. One of the new developments is an understanding of how to impose constraint-preserving boundary conditions (CPBC); though most of the related research has been driven by outer boundaries, one can use them for matching interface boundaries as well. Another front is related to numerically stable evolutions using multiple patches, which in the context of CPM allows the matching to be performed on a spherical surface, thus avoiding interpolations between Cartesian and spherical grids. One way of achieving stability for such schemes of arbitrary high order is through the use of penalty techniques and discrete derivatives satisfying summation by parts (SBP). Recently, new, very efficient and high-order accurate derivatives satisfying SBP and associated dissipation operators have been constructed. Here we start by testing all these techniques applied to CPM in a setting that is simple enough to study all the ingredients in great detail: Einstein's equations in spherical symmetry, describing a black hole coupled to a massless scalar field. We show that with the techniques described above, the errors introduced by Cauchy-perturbative matching are very small, and that very long-term and accurate CPM evolutions can be achieved. Our tests include the accretion and ring-down phase of a Schwarzschild black hole with CPM, where we find that the discrete evolution introduces, with a low spatial resolution of Δr=M/10, an error of 0.3% after an evolution time of 1,000,000M. For a black hole of solar mass, this corresponds to approximately 5s, and is therefore at the lower end of timescales discussed e.g. in the collapsar model of gamma-ray burst engines
Near-horizon symmetries of extremal black holes
International Nuclear Information System (INIS)
Kunduri, Hari K; Lucietti, James; Reall, Harvey S
2007-01-01
Recent work has demonstrated an attractor mechanism for extremal rotating black holes subject to the assumption of a near-horizon SO(2, 1) symmetry. We prove the existence of this symmetry for any extremal black hole with the same number of rotational symmetries as known four- and five-dimensional solutions (including black rings). The result is valid for a general two-derivative theory of gravity coupled to Abelian vectors and uncharged scalars, allowing for a non-trivial scalar potential. We prove that it remains valid in the presence of higher-derivative corrections. We show that SO(2, 1)-symmetric near-horizon solutions can be analytically continued to give SU(2)-symmetric black hole solutions. For example, the near-horizon limit of an extremal 5D Myers-Perry black hole is related by analytic continuation to a non-extremal cohomogeneity-1 Myers-Perry solution
Geometric Monte Carlo and black Janus geometries
Energy Technology Data Exchange (ETDEWEB)
Bak, Dongsu, E-mail: dsbak@uos.ac.kr [Physics Department, University of Seoul, Seoul 02504 (Korea, Republic of); B.W. Lee Center for Fields, Gravity & Strings, Institute for Basic Sciences, Daejeon 34047 (Korea, Republic of); Kim, Chanju, E-mail: cjkim@ewha.ac.kr [Department of Physics, Ewha Womans University, Seoul 03760 (Korea, Republic of); Kim, Kyung Kiu, E-mail: kimkyungkiu@gmail.com [Department of Physics, Sejong University, Seoul 05006 (Korea, Republic of); Department of Physics, College of Science, Yonsei University, Seoul 03722 (Korea, Republic of); Min, Hyunsoo, E-mail: hsmin@uos.ac.kr [Physics Department, University of Seoul, Seoul 02504 (Korea, Republic of); Song, Jeong-Pil, E-mail: jeong_pil_song@brown.edu [Department of Chemistry, Brown University, Providence, RI 02912 (United States)
2017-04-10
We describe an application of the Monte Carlo method to the Janus deformation of the black brane background. We present numerical results for three and five dimensional black Janus geometries with planar and spherical interfaces. In particular, we argue that the 5D geometry with a spherical interface has an application in understanding the finite temperature bag-like QCD model via the AdS/CFT correspondence. The accuracy and convergence of the algorithm are evaluated with respect to the grid spacing. The systematic errors of the method are determined using an exact solution of 3D black Janus. This numerical approach for solving linear problems is unaffected initial guess of a trial solution and can handle an arbitrary geometry under various boundary conditions in the presence of source fields.
Ballooning Stability of the Compact Quasiaxially Symmetric Stellarator
International Nuclear Information System (INIS)
Redi, M.H.; Canik, J.; Dewar, R.L.; Johnson, J.L.; Klasky, S.; Cooper, W.A.; Kerbichler, W.
2001-01-01
The magnetohydrodynamic (MHD) ballooning stability of a compact, quasiaxially symmetric stellarator (QAS), expected to achieve good stability and particle confinement is examined with a method that can lead to estimates of global stability. Making use of fully 3D, ideal-MHD stability codes, the QAS beta is predicted to be limited above 4% by ballooning and high-n kink modes. Here MHD stability is analyzed through the calculation and examination of the ballooning mode eigenvalue isosurfaces in the 3-space [s, alpha, theta(subscript ''k'')]; s is the edge normalized toroidal flux, alpha is the field line variable, and theta(subscript ''k'') is the perpendicular wave vector or ballooning parameter. Broken symmetry, i.e., deviations from axisymmetry, in the stellarator magnetic field geometry causes localization of the ballooning mode eigenfunction, with new types of nonsymmetric, eigenvalue isosurfaces in both the stable and unstable spectrum. The isosurfaces around the most unstable points i n parameter space (well above marginal) are topologically spherical. In such cases, attempts to use ray tracing to construct global ballooning modes lead to a k-space runaway. Introduction of a reflecting cutoff in k(perpendicular) to model numerical truncation or finite Larmor radius (FLR) yields chaotic ray paths ergodically filling the allowed phase space, indicating that the global spectrum must be described using the language of quantum chaos theory. However, the isosurface for marginal stability in the cases studied are found to have a more complex topology, making estimation of FLR stabilization more difficult
2017-01-01
We study the G-strand equations that are extensions of the classical chiral model of particle physics in the particular setting of broken symmetries described by symmetric spaces. These equations are simple field theory models whose configuration space is a Lie group, or in this case a symmetric space. In this class of systems, we derive several models that are completely integrable on finite dimensional Lie group G, and we treat in more detail examples with symmetric space SU(2)/S1 and SO(4)/SO(3). The latter model simplifies to an apparently new integrable nine-dimensional system. We also study the G-strands on the infinite dimensional group of diffeomorphisms, which gives, together with the Sobolev norm, systems of 1+2 Camassa–Holm equations. The solutions of these equations on the complementary space related to the Witt algebra decomposition are the odd function solutions. PMID:28413343
Spherical aberration in contact lens wear.
Lindskoog Pettersson, A; Jarkö, C; Alvin, A; Unsbo, P; Brautaset, R
2008-08-01
The aim of the present studies was to investigate the effect on spherical aberration of different non custom-made contact lenses, both with and without aberration control. A wavefront analyser (Zywave, Bausch & Lomb) was used to measure the aberrations in each subject's right eye uncorrected and with the different contact lenses. The first study evaluated residual spherical aberration with a standard lens (Focus Dailies Disposable, Ciba Vision) and with an aberration controlled contact lens (ACCL) (Definition AC, Optical Connection Inc.). The second study evaluated the residual spherical aberrations with a monthly disposable silicone hydrogel lens with aberration reduction (PureVision, Bausch & Lomb). Uncorrected spherical aberration was positive for all pupil sizes in both studies. In the first study, residual spherical aberration was close to zero with the standard lens for all pupil sizes whereas the ACCL over-corrected spherical aberration. The results of the second study showed that the monthly disposable lens also over-corrected the aberration making it negative. The changes in aberration were statistically significant (plenses. Since the amount of aberration varies individually we suggest that aberrations should be measured with lenses on the eye if the aim is to change spherical aberration in a certain direction.
Shiloh, Roy; Remez, Roei; Lu, Peng-Han; Jin, Lei; Lereah, Yossi; Tavabi, Amir H; Dunin-Borkowski, Rafal E; Arie, Ady
2018-03-27
Nearly eighty years ago, Scherzer showed that rotationally symmetric, charge-free, static electron lenses are limited by an unavoidable, positive spherical aberration. Following a long struggle, a major breakthrough in the spatial resolution of electron microscopes was reached two decades ago by abandoning the first of these conditions, with the successful development of multipole aberration correctors. Here, we use a refractive silicon nitride thin film to tackle the second of Scherzer's constraints and demonstrate an alternative method for correcting spherical aberration in a scanning transmission electron microscope. We reveal features in Si and Cu samples that cannot be resolved in an uncorrected microscope. Our thin film corrector can be implemented as an immediate low cost upgrade to existing electron microscopes without re-engineering of the electron column or complicated operation protocols and can be extended to the correction of additional aberrations. Copyright © 2018 The Authors. Published by Elsevier B.V. All rights reserved.
All-optical symmetric ternary logic gate
Chattopadhyay, Tanay
2010-09-01
Symmetric ternary number (radix=3) has three logical states (1¯, 0, 1). It is very much useful in carry free arithmetical operation. Beside this, the logical operation using this type of number system is also effective in high speed computation and communication in multi-valued logic. In this literature all-optical circuits for three basic symmetrical ternary logical operations (inversion, MIN and MAX) are proposed and described. Numerical simulation verifies the theoretical model. In this present scheme the different ternary logical states are represented by different polarized state of light. Terahertz optical asymmetric demultiplexer (TOAD) based interferometric switch has been used categorically in this manuscript.
A Relativistic Symmetrical Interpretation of Quantum Mechanics
Heaney, Michael B.
This poster describes a relativistic symmetrical interpretation (RSI) which postulates: quantum mechanics is intrinsically time-symmetric, with no arrow of time; the fundamental objects of quantum mechanics are transitions; a transition is fully described by a complex transition amplitude density with specified initial and final boundary conditions, and; transition amplitude densities never collapse. This RSI is compared to the Copenhagen Interpretation (CI) for the analysis of Einstein's bubble experiment using both the Dirac and Klein-Gordon equations. The RSI has no zitterbewegung in the particle's rest frame, resolves some inconsistencies of the CI, and gives intuitive explanations of some previously mysterious quantum effects.
Symmetry theorems via the continuous steiner symmetrization
Directory of Open Access Journals (Sweden)
L. Ragoub
2000-06-01
Full Text Available Using a new approach due to F. Brock called the Steiner symmetrization, we show first that if $u$ is a solution of an overdetermined problem in the divergence form satisfying the Neumann and non-constant Dirichlet boundary conditions, then $Omega$ is an N-ball. In addition, we show that we can relax the condition on the value of the Dirichlet boundary condition in the case of superharmonicity. Finally, we give an application to positive solutions of some semilinear elliptic problems in symmetric domains for the divergence case.
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.
Novel Electrically Small Spherical Electric Dipole Antenna
DEFF Research Database (Denmark)
Kim, Oleksiy S.
2010-01-01
This paper introduces a novel electrically small spherical meander antenna. Horizontal sections of the meander are composed of wire loops, radii of which are chosen so that the whole structure is conformal to a sphere of radius a. To form the meander the loops are connected by wires at a meridian...... plane. The antenna operates as an electric dipole, i.e. it radiates the TM10 spherical mode. The antenna is self-resonant and can be matched to a wide range of input feed lines without an external matching network. In this paper, a spherical meander antenna of the size ka = 0.27 and the input impedance...
Luo, Yupeng; Huang, Xiao; Bai, Jian; Du, Juan; Liu, Qun; Luo, Yujie; Luo, Jia
2017-08-01
Large-aperture and long focal-length lens is widely used in high energy laser system. The method based on Talbot interferometry is a reliable method to measure the focal length of such elements. By employing divergent beam and two gratings of different periods, this method could realize full-aperture measurement, higher accuracy and better repeatability. However, it does not take into account the spherical aberration of the measured lens resulting in the moiré fringes bending, which will introduce measurement error. Furthermore, in long-focal measurement with divergent beam, this error is an important factor affecting the measurement accuracy. In this paper, we propose a new spherical aberration compensation method, which could significantly reduce the measurement error. Characterized by central-symmetric scanning window, the proposed method is based on the relationship between spherical aberration and the lens aperture. Angle data of moiré fringes in each scanning window is retrieved by Fourier analysis and statistically fitted to estimate a globally optimum value for spherical-aberration-free focal length calculation. Simulation and experiment have been carried out. Compared to the previous work, the proposed method is able to reduce the relative measurement error by 50%. The effect of scanning window size and shift step length on the results is also discussed.
Calculation of laminar incompressible fluid flow and heat transfer during spherical annulus filling
International Nuclear Information System (INIS)
Tuft, D.B.
1979-04-01
A method of computing laminar incompressible fluid-flow and heat transfer during the filling of a spherical annulus is presented. Transient fluid temperatures and heat flux rates in the spherical annulus are calculated for an insulated outer sphere and a constant temperature inner sphere with heated water filling the annulus from the bottom. To achieve a solution, laminar axially symmetric flow is assumed and the Marker-and-Cell (MAC) free surface computational method is applied to this problem in spherical coordinates. Changes in the standard MAC treatment are incorporated and special methods for handling the free surface are introduced. A variable mesh is used to improve resolution near the inner sphere where temperature and velocity gradients are steep and the governing equations are derived for variable fluid properties to allow an eddy viscosity turbulence model to be applied later. Calculations of velocity, temperature, and inner sphere heat flux in a spherical annulus of 139.7 mm inner radius, and 168.3 mm outer radius within an inlet tube diameter of 38.1 mm are presented
Directory of Open Access Journals (Sweden)
I. V. Makeev
2016-01-01
Full Text Available Stokes flows in cylindrical and spherical geometry are considered. Such flows are rather natural for geophysics. We derive some exact particular solutions of Stokes and continuity equations for particular dependence of viscosity and density on cylindrical coordinates. These solutions correspond to axisymmetric flows for the case when viscosity is a function of radius. We suggest exact particular solutions of Stokes and continuity equations with variable viscosity and density in spherical coordinates for the case of spherically symmetric viscosity and density distributions. We demonstrate how these solutions can be used for creation of test problems suitable for benchmarking numerical algorithms. Examples of such benchmarking are presented. The advantage of this benchmarking approach is the ability to test numerical algorithms for variable viscosity and density gradients. We suggest numerical scheme of multigrid algorithm for solving Stokes and continuity equations with variable viscosity in a spherical coordinate system. Calculations are performed on a sequence of orthogonal staggered grids. The quality of the numerical scheme was verified by comparing the numerical solution with the analytical solution of the test problem.
Reconstructing matter profiles of spherically compensated cosmic regions in ΛCDM cosmology
de Fromont, Paul; Alimi, Jean-Michel
2018-02-01
The absence of a physically motivated model for large-scale profiles of cosmic voids limits our ability to extract valuable cosmological information from their study. In this paper, we address this problem by introducing the spherically compensated cosmic regions, named CoSpheres. Such cosmic regions are identified around local extrema in the density field and admit a unique compensation radius R1 where the internal spherical mass is exactly compensated. Their origin is studied by extending the standard peak model and implementing the compensation condition. Since the compensation radius evolves as the Universe itself, R1(t) ∝ a(t), CoSpheres behave as bubble Universes with fixed comoving volume. Using the spherical collapse model, we reconstruct their profiles with a very high accuracy until z = 0 in N-body simulations. CoSpheres are symmetrically defined and reconstructed for both central maximum (seeding haloes and galaxies) and minimum (identified with cosmic voids). We show that the full non-linear dynamics can be solved analytically around this particular compensation radius, providing useful predictions for cosmology. This formalism highlights original correlations between local extremum and their large-scale cosmic environment. The statistical properties of these spherically compensated cosmic regions and the possibilities to constrain efficiently both cosmology and gravity will be investigated in companion papers.
Born-Infeld and charged black holes with non-linear source in f(T) gravity
Energy Technology Data Exchange (ETDEWEB)
Junior, Ednaldo L.B.; Rodrigues, Manuel E. [Faculdade de Física, PPGF, Universidade Federal do Pará, 66075-110, Belém, Pará (Brazil); Houndjo, Mahouton J.S., E-mail: ednaldobarrosjr@gmail.com, E-mail: esialg@gmail.com, E-mail: sthoundjo@yahoo.fr [Institut de Mathématiques et de Sciences Physiques (IMSP), 01 BP 613, Porto-Novo, Bénin (Benin)
2015-06-01
We investigate f(T) theory coupled with a nonlinear source of electrodynamics, for a spherically symmetric and static spacetime in 4D. We re-obtain the Born-Infeld and Reissner-Nordstrom-AdS solutions. We generalize the no-go theorem for any content that obeys the relationship T{sup 0}{sub 0}=T{sup 1}{sub 1} for the energy-momentum tensor and a given set of tetrads. Our results show new classes of solutions where the metrics are related through b(r)=−Na(r). We do the introductory analysis showing that solutions are that of asymptotically flat black holes, with a singularity at the origin of the radial coordinate, covered by a single event horizon. We also reconstruct the action for this class of solutions and obtain the functional form f(T)=f{sub 0}(−T){sup (N+3)/[2(N+1)]} and L{sub NED}=L{sub 0}(−F){sup (N+3)/[2(N+1)]}. Using the Lagrangian density of Born-Infeld, we obtain a new class of charged black holes where the action reads f(T)=−16β{sub BI}[1−√1+(T/4β{sub BI})].
International Nuclear Information System (INIS)
Matausek, M.V.; Milosevic, M.
1986-01-01
In the present paper a generalization is performed of a procedure to solve multigroup spherical harmonics equations, which has originally been proposed and developed for one-dimensional systems in cylindrical or spherical geometry, and later extended for a special case of a two-dimensional system in r-z geometry. The expressions are derived for the axial and the radial dependence of the group values of the neutron flux moments, in the P-3 approximation of the spherical harmonics method, in a cylindrically symmetrical system with an arbitrary number of material regions in both r- and z-directions. In the special case of an axially homogeneous system, these expressions reduce to the relations derived previously. (author)
Otsuki, Soichi
2016-02-01
This paper presents a theory describing totally incoherent multiple scattering of turbid spherical samples. It is proved that if reciprocity and mirror symmetry hold for single scattering by a particle, they also hold for multiple scattering in spherical samples. Monte Carlo simulations generate a reduced effective scattering Mueller matrix, which virtually satisfies reciprocity and mirror symmetry. The scattering matrix was factorized by using the symmetric decomposition in a predefined form, as well as the Lu-Chipman polar decomposition, approximately into a product of a pure depolarizer and vertically oriented linear retarding diattenuators. The parameters of these components were calculated as a function of the polar angle. While the turbid spherical sample is a pure depolarizer at low polar angles, it obtains more functions of the retarding diattenuator with increasing polar angle.
Accuracy of Topcon CM-1000 videokeratoscope on spherical test surfaces.
Pérez-Yern, E; Fimia-Gil, A; Mateos, F; Carretero, L
1997-01-01
Many videokeratoscopes use mathematical formulas to calculate corneal radii; calculations depend on slope, curvature, coordinate position, or focal properties of the surface. Accuracy of each type of videokeratoscope must be evaluated. A controversy exists about whether axial or tangential methods best provide a precise description of corneal shape; therefore results with the Topcon CM-1000 using both methods were evaluated. Measurements were done on black polymethylmethacrylate (PMMA) spherical calibrated surfaces. Lenses were first aligned and measured and then misaligned in different directions and measured. Results for each position were compared with the zero or alignment position. Accuracy of the CM-1000 was high even under extreme misalignment conditions. Tolerance to misalignment was high (about 300 mm). Misalignment-induced variations in the output results were small (usually less than 0.05 mm). However, important variations (more than 1.00 diopter [D]) were found for the lowest measured radius (6 mm). In some cases, small differences between axial and tangential radii for the same point could be found. With the exception of extremely low radii of curvature, the CM-1000 was accurate for measuring spherical surfaces. Further investigation remains to be done on aspheric surfaces and in clinical practice.
Chen, Pei-Tai; Lin, Chorng-Shyan; Yang, Tachung
2002-09-01
Using a coupled BEM/FEM, this work describes a numerical method to compute the response and acoustic radiation for structures partially immersed in fluid. The structures and their responses are assumed to be symmetric about a symmetric plane. A symmetric complex matrix derived from the BEM and a reciprocal principle for surface acoustics is also used to represent the acoustic loading against the structures. In addition, selecting a proper Green's function based on image source method satisfies the boundary conditions of pressure release on the fluid surface and null normal velocity on the symmetric plane. Moreover, a boundary integral equation emerges when the field point approaches the structural surface where the normal derivative of the Green's function over partial, infinitesimal spheres is evaluated. These limiting values depend on locations of the field point on the surface. Owing to the symmetry of the acoustic loading matrix, the matrix for the coupled BEM/FEM is a banded, symmetric one, thereby allowing us to employ a variable banded storage method and invert of the matrix. Doing so markedly increases computational efficiency. Furthermore, an analytical solution of a spherical thin shell with the lower semi-sphere immersed in water is carried out by characteristic function expansions for shell equation and acoustic loading. These analytical solutions compare with the results obtained from the proposed numerical method. A good correlation for low frequencies is obtained and minor discrepancies are observed with an increasing frequency.
Black holes from fluid mechanics
Lahiri, Subhaneil
2009-12-01
We use the AdS/CFT correspondence in a regime where the field theory is well described by fluid mechanics to study large black holes in asymptotically locally anti de Sitter spaces. In particular, we use the fluid description to study the thermodynamics of the black holes and the existence of exotic horizon topologies in higher dimensions. First we test this method by comparing large rotating black holes in global AdSD spaces to stationary solutions of the relativistic Navier-Stokes equations on SD-2. Reading off the equation of state of this fluid from the thermodynamics of non-rotating black holes, we proceed to construct the nonlinear spinning solutions of fluid mechanics that are dual to rotating black holes. In all known examples, the thermodynamics and the local stress tensor of our solutions are in precise agreement with the thermodynamics and boundary stress tensor of the spinning black holes. Our results yield predictions for the thermodynamics of all large black holes in all theories of gravity on AdS spaces, for example, IIB string theory on AdS5 x S 5 and M theory on AdS4 x S7 and AdS7 x S 4. We then construct solutions to the relativistic Navier-Stokes equations that describe the long wavelength collective dynamics of the deconfined plasma phase of N = 4 Yang Mills theory compactified down to d = 3 on a Scherk-Schwarz circle. Our solutions are stationary, axially symmetric spinning balls and rings of plasma. These solutions, which are dual to (yet to be constructed) rotating black holes and black rings in Scherk-Schwarz compactified AdS 5, and have properties that are qualitatively similar to those of black holes and black rings in flat five dimensional gravity. We also study the stability of these solutions to small fluctuations, which provides an indirect method for studying Gregory-Laflamme instabilities. We also extend the construction to higher dimensions, allowing one to study the existence of new black hole topologies and their phase diagram.
3D Printing Electrically Small Spherical Antennas
DEFF Research Database (Denmark)
Kim, Oleksiy S.
2013-01-01
3D printing is applied for rapid prototyping of an electrically small spherical wire antenna. The model is first printed in plastic and subsequently covered with several layers of conductive paint. Measured results are in good agreement with simulations....
Spherical designs and anticoherent spin states
International Nuclear Information System (INIS)
Crann, Jason; Pereira, Rajesh; Kribs, David W
2010-01-01
Anticoherent spin states are quantum states that exhibit maximally nonclassical behaviour in a certain sense. Any spin state whose Majorana representation is a Platonic solid is called a perfect state. By direct calculation, it has been shown that any perfect state is an anticoherent spin state. We show that any spin state whose Majorana representation is both the orbit of a finite subgroup of O(3) and a spherical t-design must be an anticoherent spin state of order t. Since all Platonic solids are spherical designs, this result gives an explanation of the anticoherence of perfect states and explains their observed order. We also show that any spin state whose Majorana representation lies in any single open hemisphere cannot be anticoherent of any order. This result is then used to give further relations between spherical designs and anticoherent spin states. We also pose some questions relating spherical designs and geometric entanglement.
Transformation of Real Spherical Harmonics under Rotations
Romanowski, Z.; Krukowski, St.; Jalbout, A. F.
2008-08-01
The algorithm rotating the real spherical harmonics is presented. The convenient and ready to use formulae for l = 0, 1, 2, 3 are listed. The rotation in R3 space is determined by the rotation axis and the rotation angle; the Euler angles are not used. The proposed algorithm consists of three steps. (i) Express the real spherical harmonics as the linear combination of canonical polynomials. (ii) Rotate the canonical polynomials. (iii) Express the rotated canonical polynomials as the linear combination of real spherical harmonics. Since the three step procedure can be treated as a superposition of rotations, the searched rotation matrix for real spherical harmonics is a product of three matrices. The explicit formulae of matrix elements are given for l = 0, 1, 2, 3, what corresponds to s, p, d, f atomic orbitals.
Spherical stochastic neighbor embedding of hyperspectral data
CSIR Research Space (South Africa)
Lunga, D
2012-07-01
Full Text Available of spherical coordinates. This allows the use of an Exit probability distribution to discover the nonlinear characteristics that are inherent in hyperspectral data. In addition, the method directly learns the probability distribution over neighboring pixel maps...
Feasibility study for the Spherical Torus Experiment
International Nuclear Information System (INIS)
Lazarus, E.A.; Attenberger, S.E.; Baylor, L.R.
1985-10-01
The design of the Spherical Torus Experiment (STX) is discussed. The physics of the plasma are given in a magnetohydrodynamic model. The structural aspects and instrumentation of the device are described. 19 refs., 103 figs
Spiral CT manifestations of spherical pneumonia
International Nuclear Information System (INIS)
Li Xiaohong; Yang Hongwei; Xu Chunmin; Qin Xiu
2008-01-01
Objective: To explore the Spiral CT manifestations and differential diagnosis of spherical pneumonia. Methods: 18 cases of spherical pneumonia and 20 cases of peripheral pulmonary carcinoma were selected, both of them were confirmed by clinic and/or pathology. The SCT findings of both groups were compared retrospectively. Results: Main spiral CT findings of spherical pneumonia were showed as followings: square or triangular lesions adjacent to pleura; with irregular shape, blurry, slightly lobulated margin, sometimes with halo sign. Small inflammatory patches and intensified vascular markings around the lesions were seen. Lesions became smaller or vanished after short-term anti-inflammatory treatment. Conclusion: Spherical pneumonia showed some characteristics on Spiral CT scan, which are helpful in diagnosis and differential diagnosis of this disease. (authors)
PT -symmetric model of immune response
Bender, Carl M.; Ghatak, Ananya; Gianfreda, Mariagiovanna
2017-01-01
The study of PT -symmetric physical systems began in 1998 as a complex generalization of conventional quantum mechanics, but beginning in 2007 experiments began to be published in which the predicted PT phase transition was clearly observed in classical rather than in quantum-mechanical systems. This paper examines the classical PT phase transition in dynamical-system models that are moderately accurate representations of antigen-antibody systems. A surprising conclusion that can be drawn from these models is that it might be possible treat a serious disease in which the antigen concentration grows out of bounds (and the host dies) by injecting a small dose of a second (different) antigen. In this case a PT -symmetric analysis shows there are two possible favorable outcomes. In the unbroken-PT -symmetric phase the disease becomes chronic and is no longer lethal, while in the appropriate broken-PT -symmetric phase the concentration of lethal antigen goes to zero and the disease is completely cured.
Progressive symmetric exfoliative ichthyosis | Al Aboud | Sudanese ...
African Journals Online (AJOL)
We report an 11–year-old girl with well defined ichthyosiform patches on extremities. There is a history of similar condition in her cousin. We believe that this case represent a new autosomal recessive disorder of cornification that may be better refer to it as ''progressive symmetric exfoliative ichthyosis''. Sudanese Journal of ...
Symmetric intersections of Rauzy fractals | Sellami | Quaestiones ...
African Journals Online (AJOL)
In this article we study symmetric subsets of Rauzy fractals of unimodular irreducible Pisot substitutions. The symmetry considered is re ection through the origin. Given an unimodular irreducible Pisot substitution, we consider the intersection of its Rauzy fractal with the Rauzy fractal of the reverse substitution. This set is ...
A viewpoint on nearly conformally symmetric manifold
International Nuclear Information System (INIS)
Rahman, M.S.
1990-06-01
Some observations, with definition, on Nearly Conformally Symmetric (NCS) manifold are made. A number of theorems concerning conformal change of metric and parallel tensors on NCS manifolds are presented. It is illustrated that a manifold M = R n-1 x R + 1 , endowed with a special metric, is NCS but not of harmonic curvature. (author). 8 refs
Biomechanical benefits of symmetrical strengthening of hip ...
African Journals Online (AJOL)
There is abundant literature encouraging athletes to engage in concurrent strength training. However, little emphasis is placed on the value of biomechanics with regard to symmetrical strengthening of force-couple relationships. A review of literature reveals 565 biomechanical papers versus 2085 physiological papers ...
Bilateral Symmetrical Parietal Extradural Hematoma | Agrawal ...
African Journals Online (AJOL)
is an uncommon consequence of craniocerebral trauma, and acute symmetrical bilateral epidural hematomas are extremely rare. We discuss the technique ... A 55-year-old patient presented with history of fall of branch of tree on her head. She had loss of ... Initially, left parietal trephine craniotomy was performed and ...
Efficient and convenient synthesis of symmetrical carboxylic ...
African Journals Online (AJOL)
An efficient and convenient procedure for the synthesis of symmetrical carboxylic anhydrides from carboxylic acids with sulfated zirconia by PEG-1000 phase transfer catalysis has been developed. The reactions proceeded under mild and solvent-free conditions to provide the carboxylic anhydrides in good to excellent ...
Unary self-verifying symmetric difference automata
CSIR Research Space (South Africa)
Marais, Laurette
2016-07-01
Full Text Available We investigate self-verifying nondeterministic finite automata, in the case of unary symmetric difference nondeterministic finite automata (SV-XNFA). We show that there is a family of languages Ln=2 which can always be represented non...
Prevalence and incidence of symmetrical symptomatic peripheral ...
African Journals Online (AJOL)
Background. Symptomatic symmetrical peripheral neuropathy (SSPN) is common in patients with HIV infection. It is also a common adverse event associated with both tuberculosis (TB) treatment and antiretroviral therapy (ART), particularly stavudine. While tenofovir is the one of recommended first-line nucleotide reverse ...
Symmetric corticobasal degeneration (S-CBD).
Hassan, Anhar; Whitwell, Jennifer L; Boeve, Bradley F; Jack, Clifford R; Parisi, Joseph E; Dickson, Dennis W; Josephs, Keith A
2010-03-01
Corticobasal degeneration (CBD) is a neurodegenerative disease characterized pathologically by neuronal loss, gliosis and tau deposition in neocortex, basal ganglia and brainstem. Typical clinical presentation is known as corticobasal syndrome (CBS) and involves the core features of progressive asymmetric rigidity and apraxia, accompanied by other signs of cortical and extrapyramidal dysfunction. Asymmetry is also emphasized on neuroimaging. To describe a series of cases of CBD with symmetric clinical features and to compare clinical and imaging features of these symmetric CBD cases (S-CBD) to typical cases of CBS with CBD pathology. All cases of pathologically confirmed CBD from the Mayo Clinic Rochester database were identified. Clinical records were reviewed and quantitative volumetric analysis of symmetric atrophy on head MRI using atlas based parcellation was performed. Subjects were classified as S-CBD if no differences had been observed between right- and left-sided cortical or extrapyramidal signs or symptoms. S-CBD cases were compared to 10 randomly selected typical CBS cases. Five cases (2 female) met criteria for S-CBD. None had limb dystonia, myoclonus, apraxia or alien limb phenomena. S-CBD cases had significantly less asymmetric atrophy when compared with CBS cases (p=0.009); they were also younger at onset (median 61 versus 66 years, pCBD cases. CBD can have a symmetric presentation, clinically and radiologically, in which typical features of CBS, such as limb apraxia, myoclonus, dystonia and alien limb phenomenon, may be absent. Copyright (c) 2009 Elsevier Ltd. All rights reserved.
efficient and convenient synthesis of symmetrical carboxylic
African Journals Online (AJOL)
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strong acidity and high activity in light alkane conversions at relatively mild temperatures [36,. 37]. In this paper, we wish to report an efficient and convenient method for the preparation of symmetrical carboxylic anhydrides from the corresponding carboxylic acids with sulfated zirconia by phase transfer catalysis without any ...
Picosecond optical nonlinearities in symmetrical and unsymmetrical ...
Indian Academy of Sciences (India)
We present our experimental results on the picosecond nonlinear optical. (NLO) studies of symmetrical and unsymmetrical phthalocyanines, examined using the. Z-scan technique. Both the open-aperture ... Z-scan measurements were performed using the amplified Ti:sapphire laser system. (LEGEND, Coherent) delivering ...
Spectrum generating algebra of the symmetric top
Energy Technology Data Exchange (ETDEWEB)
Bijker, R. [Universidad Nacional Autonoma de Mexico, Mexico City (Mexico). Inst. de Ciencias Nucleares; Leviatan, A. [Racah Institute of Physics, The Hebrew University, Jerusalem 91904 (Israel)
1998-03-02
We consider an algebraic treatment of a three-body system. We develop the formalism for a system of three identical objects and show that it provides a simultaneous description of the vibrational and rotational excitations of an oblate symmetric top. (orig.) 8 refs.
Spectrum generating algebra of the symmetric top
International Nuclear Information System (INIS)
Bijker, R.
1998-01-01
We consider an algebraic treatment of a three-body system. We develop the formalism for a system of three identical objects and show that it provides a simultaneous description of the vibrational and rotational excitations of an oblate symmetric top. (orig.)
The symmetric Mellin transform in quantum calculus
Directory of Open Access Journals (Sweden)
Brahim Kamel Brahim
2015-12-01
Full Text Available In this paper, we define the q-analogue of Mellin Transform symmetric under interchange of q and 1/q, and present some of its main properties and explore the possibility of using the integral transform to solve a class of differential equations q-differences.
Fourier transforms on a semisimple symmetric space
Ban, E.P. van den; Schlichtkrull, H.
1994-01-01
Let G=H be a semisimple symmetric space, that is, G is a connected semisimple real Lie group with an involution ?, and H is an open subgroup of the group of xed points for ? in G. The main purpose of this paper is to study an explicit Fourier transform on G=H. In terms of general representation
Fourier transforms on a semisimple symmetric space
Ban, E.P. van den; Carmona, J.; Delorme, P.
1997-01-01
Let G=H be a semisimple symmetric space, that is, G is a connected semisimple real Lie group with an involution ?, and H is an open subgroup of the group of xed points for ? in G. The main purpose of this paper is to study an explicit Fourier transform on G=H. In terms of general representation
3D Printing Electrically Small Spherical Antennas
DEFF Research Database (Denmark)
Kim, Oleksiy S.
2013-01-01
3D printing is applied for rapid prototyping of an electrically small spherical wire antenna. The model is first printed in plastic and subsequently covered with several layers of conductive paint. Measured results are in good agreement with simulations.......3D printing is applied for rapid prototyping of an electrically small spherical wire antenna. The model is first printed in plastic and subsequently covered with several layers of conductive paint. Measured results are in good agreement with simulations....