1,079 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.
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
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.
Free Fields for Chiral 2D Dilaton Gravity
We give an explicit canonical transformation which transforms a generic
chiral 2D dilaton gravity model into a free field theory.Comment: LaTeX file, 4 pages, to appear in Phys. Rev.
Nonsingular 2-D Black Holes and Classical String Backgrounds
We study a string-inspired classical 2-D effective field theory with {\it
nonsingular} black holes as well as Witten's black hole among its static
solutions. By a dimensional reduction, the static solutions are related to the
coset model, or more precisely its
approximation known as the 3-D charged black
string. The 2-D effective action possesses a propagating degree of freedom, and
the dynamics are highly nontrivial. A collapsing shell is shown to bounce into
another universe without creating a curvature singularity on its path, and the
potential instability of the Cauchy horizon is found to be irrelevent in that
some of the infalling observers never approach the Cauchy horizon. Finally a
nonperturbative coset metric, found and advocated by R.
Dijkgraaf et.al., is shown to be nonsingular and to coincide with one of the
charged spacetimes found above. Implications of all these geometries are
discussed in connection with black hole evaporation.Comment: 30 pages with 2 figures, harvmac, CALT-68-1852 (Discussions on the
gravitational collapse of thin shells in a charged spacetime are clarified.
Two extra references.
Invariance in linear systems
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/32794/1/0000167.pd
Noncommutativity Effects in FRW Scalar Field Cosmology
We study effects of noncommutativity on the phase space generated by a
non-minimal scalar field which is conformally coupled to the background
curvature in an isotropic and homogeneous FRW cosmology. These effects are
considered in two cases, when the potential of scalar field has zero and
nonzero constant values. The investigation is carried out by means of a
comparative detailed analysis of mathematical features of the evolution of
universe and the most probable universe wave functions in classically
commutative and noncommutative frames and quantum counterparts. The influence
of noncommutativity is explored by the two noncommutative parameters of space
and momentum sectors with a relative focus on the role of the noncommutative
parameter of momentum sector. The solutions are presented with some of their
numerical diagrams, in the commutative and noncommutative scenarios, and their
properties are compared. We find that impose of noncommutativity in the
momentum sector causes more ability in tuning time solutions of variables in
classical level, and has more probable states of universe in quantum level. We
also demonstrate that special solutions in classical and allowed wave functions
in quantum models impose bounds on the values of noncommutative parameters.Comment: 13 pages, 5 figure
Dancing the Pluriverse: Indigenous Performance as Ontological Praxis
This article discusses ways that Indigenous dance is an ontological praxis that is embodied and telluric, meaning “of the earth.” It looks at how dancing bodies perform in relationship to ecosystems and entities within them, producing ontological distinctions and hierarchies that are often imbued with power. This makes dance a site of ontological struggle that potentially challenges the delusional ontological universality undergirding imperialism, genocide, and ecocide. The author explores these theoretical propositions through her participation in Oxlaval Q'anil, an emerging Ixil Maya dance project in Guatemala, and Dancing Earth, an itinerant and inter-tribal U.S.-based company founded by Rulan Tangen eleven years ago
Quantum evolution of near-extremal Reissner-Nordstrom black holes
We study the near-horizon AdS_2\timesS^2 geometry of evaporating
near-extremal Reissner-Nordstrom black holes interacting with null matter. The
non-local (boundary) terms t_{\pm}, coming from the effective theory corrected
with the quantum Polyakov-Liouville action, are treated as dynamical variables.
We describe analytically the evaporation process which turns out to be
compatible with the third law of thermodynamics, i.e., an infinite amount of
time is required for the black hole to decay to extremality. Finally we comment
briefly on the implications of our results for the information loss problem.Comment: LaTeX file, 24 pages, 4 ps and 3 eps figures; some typos corrected.
Accepted for publication in Nucl. Phys.
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