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Search Results: 1 - 10 of 208555 matches for " L. Vanzo "
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Some results on dynamical black holes
L. Vanzo
Physics , 2008,
Abstract: We give indications that outer future trapping horizons play a role in the particular semi-classical instability of an evolving black hole that produces the Hawking's radiation. These are obtained with the use of the Hamilton-Jacobi tunneling method. It automatically selects one special expression for the surface gravity of a changing horizon, the one defined a decade ago by Hayward using Kodama's theory of spherically symmetric gravitational fields. The method also applies to point masses embedded in an expanding universe and to general, spherically symmetric black holes.
Black holes with unusual topology
L. Vanzo
Physics , 1997, DOI: 10.1103/PhysRevD.56.6475
Abstract: The Einstein's equations with a negative cosmological constant admit solutions which are asymptotically anti-de Sitter space. Matter fields in anti-de Sitter space can be in stable equilibrium even if the potential energy is unbounded from below, violating the weak energy condition. Hence there is no fundamental reason that black hole's horizons should have spherical topology. In anti-de Sitter space the Einstein's equations admit black hole solutions where the horizon can be a Riemann surface with genus $g$. The case $g=0$ is the asymptotically anti-de Sitter black hole first studied by Hawking-Page, which has spherical topology. The genus one black hole has a new free parameter entering the metric, the conformal class to which the torus belongs. The genus $g>1$ black hole has no other free parameters apart from the mass and the charge. All such black holes exhibits a natural temperature which is identified as the period of the Euclidean continuation and there is a mass formula connecting the mass with the surface gravity and the horizon area of the black hole. The Euclidean action and entropy are computed and used to argue that the mass spectrum of states is positive definite.
Thermal states in Anti-de Sitter space-time and the role of time-like infinity
L. Vanzo,G. Turco
Physics , 1994, DOI: 10.1103/PhysRevD.50.5148
Abstract: The grand-canonical thermodynamic potential for Bose and Fermi fields in anti-de Sitter space-time is introduced and a Mellin complex representation is given. This is used to investigate the high temperature properties of the thermal state at finite charge. The time-like nature of spatial infinity is shown to act as a boundary, and changes the free energy of the field in thermal equilibrium.
Central charges and boundary fields for two dimensional dilatonic black holes
N. Pinamonti,L. Vanzo
Physics , 2003, DOI: 10.1103/PhysRevD.69.084012
Abstract: In this paper we first show that within the Hamiltonian description of general relativity, the central charge of a near horizon asymptotic symmetry group is zero, and therefore that the entropy of the system cannot be estimated using Cardy's formula. This is done by mapping a static black hole to a two dimensional space. We explain how such a charge can only appear to a static observer who chooses to stay permanently outside the black hole. Then an alternative argument is given for the presence of a universal central charge. Finally we suggest an effective quantum theory on the horizon that is compatible with the thermodynamics behaviour of the black hole.
On the sqrt{2} puzzle in AdS_2/CFT_1
G. Catelani,L. Vanzo
Physics , 2000,
Abstract: In this letter we analyze the Hamiltonian formulation of the Jackiw-Teitelboim model of 2D gravity and calculate the central charge associated with the asymptotic symmetries, taking care of boundary terms. For black hole solutions, we show that there is no sqrt{2} discrepancy between the thermodynamical entropy and the statistical one obtained via Cardy's formula.
One-loop Quantum Corrections to the Entropy for an Extremal Reissner-Nordstr?m Black Hole
G. Cognola,L. Vanzo,S. Zerbini
Physics , 1995, DOI: 10.1103/PhysRevD.52.4548
Abstract: The first quantum corrections to the entropy for an eternal 4-dimensional extremal Reissner-Nordstr\"om black hole is investigated at one-loop level, in the large mass limit of the black hole, making use of the conformal techniques related to the optical metric. A leading cubic horizon divergence is found and other divergences appear due to the singular nature of the optical manifold. The area law is shown to be violated.
Tunnelling Methods and Hawking's radiation: achievements and prospects
L. Vanzo,G. Acquaviva,R. Di Criscienzo
Physics , 2011, DOI: 10.1088/0264-9381/28/18/183001
Abstract: The aim of this work is to review the tunnelling method as an alternative description of the quantum radiation from black holes and cosmological horizons. The method is first formulated and discussed for the case of stationary black holes, then a foundation is provided in terms of analytic continuation throughout complex space-time. The two principal implementations of the tunnelling approach, which are the null geodesic method and the Hamilton-Jacobi method, are shown to be equivalent in the stationary case. The Hamilton-Jacobi method is then extended to cover spherically symmetric dynamical black holes, cosmological horizons and naked singularities. Prospects and achievements are discussed in the conclusions.
Quantum Correction to the Entropy of the (2+1)-Dimensional Black Hole
A. A. Bytsenko,L. Vanzo,S. Zerbini
Physics , 1997, DOI: 10.1103/PhysRevD.57.4917
Abstract: The thermodynamic properties of the (2+1)-dimensional non-rotating black hole of Ba\~nados, Teitelboim and Zanelli are discussed. The first quantum correction to the Bekenstein-Hawking entropy is evaluated within the on-shell Euclidean formalism, making use of the related Chern-Simons representation of the 3-dimensional gravity. Horizon and ultraviolet divergences in the quantum correction are dealt with a renormalization of the Newton constant. It is argued that the quantum correction due to the gravitational field shrinks the effective radius of a hole and becomes more and more important as soon as the evaporation process goes on, while the area law is not violated.
Rotating Topological Black Holes
D. Klemm,V. Moretti,L. Vanzo
Physics , 1997, DOI: 10.1103/PhysRevD.60.109902
Abstract: A class of metrics solving Einstein's equations with negative cosmological constant and representing rotating, topological black holes is presented. All such solutions are in the Petrov type-$D$ class, and can be obtained from the most general metric known in this class by acting with suitably chosen discrete groups of isometries. First, by analytical continuation of the Kerr-de Sitter metric, a solution describing uncharged, rotating black holes whose event horizon is a Riemann surface of arbitrary genus $g > 1$, is obtained. Then a solution representing a rotating, uncharged toroidal black hole is also presented. The higher genus black holes appear to be quite exotic objects, they lack global axial symmetry and have an intricate causal structure. The toroidal blackholes appear to be simpler, they have rotational symmetry and the amount of rotation they can have is bounded by some power of the mass.
The extremal limit of D-dimensional black holes
M. Caldarelli,L. Vanzo,S. Zerbini
Physics , 2000,
Abstract: The extreme limit of a class of D-dimensional black holes is revisited. In the static limit, it is shown that well defined extremal limiting procedure exists and it leads to new solutions of the type AdS2 times constant curvature symmetric spaces.
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