10,980 research outputs found
Symmetries and solvable models for evaporating 2D black holes
We study the evaporation process of a 2D black hole in thermal equilibrium
when the ingoing radiation is switched off suddenly. We also introduce global
symmetries of generic 2D dilaton gravity models which generalize the extra
symmetry of the CGHS model.Comment: 4 pages, Latex. Talk given at the Second Conference on Quantum
Gravity and Constrained Dynamics. To appear in Proc. Supp. Nucl. Phys.
Integrable models, degenerate horizons and AdS_2 black holes
The near extremal Reissner-Nordstrom black holes in arbitrary dimensions ca
be modeled by the Jackiw-Teitelboim (JT) theory. The asymptotic Virasoro
symmetry of the corresponding JT model exactly reproduces, via Cardy's formula,
the deviation of the Bekenstein-Hawking entropy of the Reissner-Nordstrom black
holes from extremality. We also comment how can we extend this approach to
investigate the evaporation process.Comment: 4 pages, LaTeX file, uses espcrc2.sty. Talk given at the Third
Conference on Constrained Dynamics and Quantum Gravit
Conformal and Nonconformal Symmetries in 2d Dilaton gravity
We study finite-dimensional extra symmetries of generic 2D dilaton gravity
models. Using a non-linear sigma model formulation we show that the unique
theories admitting an extra (conformal) symmetry are the models with an
exponential potential (), which include the CGHS
model as a particular though limiting () case. These models give rise
to black hole solutions with a mass-dependent temperature. The underlying extra
symmetry can be maintained in a natural way in the one-loop effective action,
thus implying the exact solubility of the semiclassical theory including
back-reaction. Moreover, we also introduce three different classes of
(non-conformal) transformations which are extra symmetries for generic 2D
dilaton gravity models. Special linear combinations of these transformations
turn out to be the (conformal) symmetries of the CGHS and models. We show that one of the non-conformal extra symmetries
can be converted into a conformal one by means of adequate field redefinitions
involving the metric and the derivatives of the dilaton. Finally, by expressing
the Polyakov-Liouville effective action in terms of an invariant metric, we are
able to provide semiclassical models which are also invariant. This generalizes
the solvable semiclassical model of Bose, Parker and Peleg (BPP) for a generic
2D dilaton gravity model.Comment: Latex, no figures. Revised version published i
Black Hole Evaporation by Thermal Bath Removal
We study the evaporation process of 2D black holes in thermal equilibrium
when the incoming radiation is turned off. Our analysis is based on two
different classes of 2D dilaton gravity models which are exactly solvable in
the semiclassical aproximation including back-reaction. We consider a one
parameter family of models interpolating between the Russo-Susskind-Thorlacius
and Bose-Parker-Peleg models. We find that the end-state geometry is the same
as the one coming from an evaporating black hole formed by gravitational
collapse. We also study the quantum evolution of black holes arising in a model
with classical action . The black hole temperature is proportional to the
mass and the exact semiclassical solution indicates that these black holes
never disappear completely.Comment: LaTeX, psfig.sty. 10 pages. 3 figures (included as PS files
Can conformal Transformations change the fate of 2D black holes?
By using a classical Liouville-type model of two dimensional dilaton gravity
we show that the one-loop theory implies that the fate of a black hole depends
on the conformal frame. There is one frame for which the evaporation process
never stops and another one leading to a complete disappearance of the black
hole. This can be seen as a consequence of the fact that thermodynamic
variables are not conformally invariant. In the second case the evaporation
always produces the same static and regular end-point geometry, irrespective of
the initial state.Comment: Some typos corrected. A few comments and two references added.
Accepted for publication in PLB. Latex, 11 pages, no figure
Symmetries in two-dimensional dilaton gravity with matter
The symmetries of generic 2D dilaton models of gravity with (and without)
matter are studied in some detail. It is shown that , one of the
symmetries of the matterless models, can be generalized to the case where
matter fields of any kind are present. The general (classical) solution for
some of these models, in particular those coupled to chiral matter, which
generalizes the Vaidya solution of Einstein Gravity, is also given.Comment: Minor changes have been made; the references have been updated and
some added; 11 pages. To appear in Phys. Rev.
Automatic OSPF Topology map generation using information of the OSPF database
Nowadays, different technologies provide support to different areas of our diverse lifestyles around the world. Highly reputable companies are doing important research on the connectivity of multiple devices to the different types of network. The open Short Path First Protocol (OSPF) is one of the most widespread routing protocols in communications. Through experience, it has been demonstrated that this protocol usually has flaws, either by causes outside the protocol or by configuration, so network administrators should monitor and revise the operation of that protocol. Generally, when you start tracking a network already deployed that uses the OSPF routing protocol, there is very little documented information or even, none of the existing topology, not only because of the dynamism of this connectivity protocol, but also because of the lack of documentation of the installation itself. This project proposes the development of a tool for the generation of a map of the topology of a simple area of the OSPF routing protocol, which will facilitate the establishment of an OSPF area's topology documentation.Keywords: Network logical topology, OSPF, network modelling and mapping
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