8,819 research outputs found

    Evolution of a Self-interacting Scalar Field in the spacetime of a Higher Dimensional Black Hole

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    In the spacetime of n-dimensional static charged black hole we examine the mechanism by which the self-interacting scalar hair decay. It is turned out that the intermediate asymptotic behaviour of the self-interacting scalar field is determined by an oscilatory inverse power law. We confirm our results by numerical calculations.Comment: RevTex, 6 pages, 8 figures, to be published in Phys.Rev.D1

    Dyonic dilaton black holes

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    The properties of static spherically symmetric black holes, which are both electrically and magnetically charged, and which are coupled to the dilaton in the presence of a cosmological constant, Lambda, are considered. It is shown that apart from the Reissner-Nordstrom-de Sitter solution with constant dilaton, such solutions do not exist if Lambda > 0 (in arbitrary spacetime dimension >=4 ). However, asymptotically anti-de Sitter dyonic black hole solutions with a non-trivial dilaton do exist if Lambda < 0. Both these solutions and the asymptotically flat (Lambda = 0) solutions are studied numerically for arbitrary values of the dilaton coupling parameter, g_0, in four dimensions. The asymptotically flat solutions are found to exhibit two horizons if g_0 = 0, 1, \sqrt{3}, \sqrt{6}, ..., \sqrt{n(n+1)/2},..., and one horizon otherwise. For asymptotically anti-de Sitter solutions the result is similar, but the corresponding values of g_0 are altered in a non-linear fashion which depends on Lambda and the mass and charges of the black holes. All dyonic solutions with Lambda <= 0 are found to have zero Hawking temperature in the extreme limit, however, regardless of the value of g_0.Comment: 24 pages, phyzzx, epsf, 7 in-text figures. Small addition to introduction, and a few extra reference

    Resonance NLS Solitons as Black Holes in Madelung Fluid

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    A new resonance version of NLS equation is found and embedded to the reaction-diffusion system, equivalent to the anti-de Sitter valued Heisenberg model, realizing a particular gauge fixing condition of the Jackiw-Teitelboim gravity. The space-time points where dispersion change the sign correspond to the event horizon, and the soliton solutions to the AdS black holes. The soliton with velocity bounded above describes evolution on the hyperboloid with nontrivial winding number and create under collisions the resonance states with a specific life time.Comment: Plain Tex, 12 pages, 6 figure

    Charged Dilaton Black Holes with a Cosmological Constant

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    The properties of static spherically symmetric black holes, which are either electrically or magnetically charged, and which are coupled to the dilaton in the presence of a cosmological constant, are considered. It is shown that such solutions do not exist if the cosmological constant is positive (in arbitrary spacetime dimension >= 4). However, asymptotically anti-de Sitter black hole solutions with a single horizon do exist if the cosmological constant is negative. These solutions are studied numerically in four dimensions and the thermodynamic properties of the solutions are derived. The extreme solutions are found to have zero entropy and infinite temperature for all non-zero values of the dilaton coupling constant.Comment: 12 pages, epsf, phyzzx, 4 in-text figures incl. (minor typos fixed, 1 reference added

    Estimación de abundancia de tunina overa en el sector oriental del Estrecho de Magallanes, Chile = Abundance estimation of Commerson’s dolphin in the eastern area of the Strait of Magallan-Chile

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    Abundance of Commerson‘s dolphin, Cephalorhynchus commersonii (LacĂ©pĂšde 1804), in the eastern portion of the Strait of Magellan was estimated by means of aerial transects in autumn (June 1996). Using a helicopter at 100 m altitude and 129 km h-1, 58 sightings representing 98 animals (average group size Es = 1.7, SD = 0.13) along 818.6 km of linear transects were recorded. Data analysis with "Distance" software gave a density estimation of 0.34 ind km-2 (CV = 0.27) and a population size of 1,206 (95% CI 711-2,049 individuals). Commerson’s dolphin showed a habitat preference for the narrows, compared to open waters in the study area

    Direct CP violation in neutral kaon decays

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    The final result is presented of the NA48 Experiment performed at CERN SPS neutral kaon beams on the direct CP violation parameter Re(epsilon'/epsilon), as maesured from the decay rates of neutral kaons into two pions. The data collected in years 1997-2001 yield the evidence for direct CP violation with Re(epsilon'/epsilon)=(14.7+-2.2)10^-4. Description of expermental method and systematics, comparison with world data and some discussion of implications for theory are given.Comment: 5 pp., 3 figs, presented on behalf of NA48 Collaboration at PASCOS 2003 Conference, Mumbai, India, 2-8 Jan 2003, to appear in Praman

    A Comparison of Quintessence and Nonlinear Born-Infeld Scalar Field Using Gold Supernova data

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    We study the Non-Linear Born-Infeld(NLBI) scalar field model and quintessence model with two different potentials(V(ϕ)=−sϕV(\phi)=-s\phi and 1/2m2ϕ2{1/2}m^2\phi^2). We investigate the differences between those two models. We explore the equation of state parameter w and the evolution of scale factor a(t)a(t) in both NLBI scalar field and quintessence model. The present age of universe and the transition redshift are also obtained. We use the Gold dataset of 157 SN-Ia to constrain the parameters of the two models. All the results show that NLBI model is slightly superior to quintessence model.Comment: 17 pages, 10 figures, some references adde

    More about Birkhoff's Invariant and Thorne's Hoop Conjecture for Horizons

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    A recent precise formulation of the hoop conjecture in four spacetime dimensions is that the Birkhoff invariant ÎČ\beta (the least maximal length of any sweepout or foliation by circles) of an apparent horizon of energy EE and area AA should satisfy ÎČ≀4πE\beta \le 4 \pi E. This conjecture together with the Cosmic Censorship or Isoperimetric inequality implies that the length ℓ\ell of the shortest non-trivial closed geodesic satisfies ℓ2≀πA\ell^2 \le \pi A. We have tested these conjectures on the horizons of all four-charged rotating black hole solutions of ungauged supergravity theories and find that they always hold. They continue to hold in the the presence of a negative cosmological constant, and for multi-charged rotating solutions in gauged supergravity. Surprisingly, they also hold for the Ernst-Wild static black holes immersed in a magnetic field, which are asymptotic to the Melvin solution. In five spacetime dimensions we define ÎČ\beta as the least maximal area of all sweepouts of the horizon by two-dimensional tori, and find in all cases examined that ÎČ(g)≀16π3E \beta(g) \le \frac{16 \pi}{3} E, which we conjecture holds quiet generally for apparent horizons. In even spacetime dimensions D=2N+2D=2N+2, we find that for sweepouts by the product S1×SD−4S^1 \times S^{D-4}, ÎČ\beta is bounded from above by a certain dimension-dependent multiple of the energy EE. We also find that ℓD−2\ell^{D-2} is bounded from above by a certain dimension-dependent multiple of the horizon area AA. Finally, we show that ℓD−3\ell^{D-3} is bounded from above by a certain dimension-dependent multiple of the energy, for all Kerr-AdS black holes.Comment: 25 page

    Uniqueness and non-uniqueness of static vacuum black holes in higher dimensions

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    We prove the uniqueness theorem for asymptotically flat static vacuum black hole solutions in higher dimensional space-times. We also construct infinitely many non-asymptotically flat regular static black holes on the same spacetime manifold with the same spherical topology.Comment: to appear in Progress of Theoretical Physics Supplement No. 14
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