672 research outputs found
2D Extremal Black Holes as Solitons
We discuss the relationship between two-dimensional (2D) dilaton gravity
models and sine-Gordon-like field theories. We show that there is a one-to-one
correspondence between the solutions of 2D dilaton gravity and the solutions of
a (two fields) generalization of the sine-Gordon model. In particular, we find
a connection between the soliton solutions of the generalized sine-Gordon model
and extremal black hole solutions of 2D dilaton gravity. As a by-product of our
calculations we find a easy way to generate cosmological solutions of 2D
dilaton gravity.Comment: 12 pages, LaTex, no figures, typos correcte
Trace anomaly and Hawking effect in generic 2D dilaton gravity theories
Black hole solutions in the context of a generic matter-coupled
two-dimensional dilaton gravity theory are discussed both at the classical and
semiclassical level. Starting from general assumptions, a criterion for the
existence of black holes is given. The relationship between conformal anomaly
and Hawking radiation is extended to a broad class of two-dimensional dilaton
gravity models. A general and simple formula relating the magnitude of the
Hawking effect to the dilaton potential evaluated on the horizon is derived.Comment: 14 pages, Plain-Tex, 4 figures in a uuencoded-gzipcompressed ps fil
Phase transition and hyperscaling violation for scalar Black Branes
We investigate the thermodynamical behavior and the scaling symmetries of the
scalar dressed black brane (BB) solutions of a recently proposed, exactly
integrable Einstein-scalar gravity model [1], which also arises as
compactification of (p-1)-branes with a smeared charge. The extremal, zero
temperature, solution is a scalar soliton interpolating between a conformal
invariant AdS vacuum in the near-horizon region and a scale covariant metric
(generating hyperscaling violation on the boundary field theory)
asymptotically. We show explicitly that for the boundary field theory this
implies the emergence of an UV length scale (related to the size of the brane),
which decouples in the IR, where conformal invariance is restored. We also show
that at high temperatures the system undergoes a phase transition. Whereas at
small temperature the Schwarzschild-AdS BB is stable, above a critical
temperature the scale covariant, scalar-dressed BB solution, becomes
energetically preferred. We calculate the critical exponent z and the
hyperscaling violation parameter of the scalar-dressed phase. In particular we
show that the hyperscaling violation parameter is always negative. We also show
that the above features are not a peculiarity of the exact integrable model of
Ref.[1], but are a quite generic feature of Einstein-scalar and
Einstein-Maxwell-scalar gravity models for which the squared-mass of the scalar
field is positive and the potential vanishes exponentially as the scalar field
goes to minus infinity.Comment: 20 pages, 4 figures. In the revised version it has been pointed out
that the Einstein-scalar gravity model considered in the paper also arises as
compactification of black p-branes with smeared charge
Dimensional reduction of 4d heterotic string black holes
We perform the spherical symmetric dimensional reduction of
heterotic string theory. We find a class of two-dimensional (2d) dilaton
gravity models that gives a general description of the near-horizon,
near-extremal behavior of four-dimensional (4d) heterotic string black holes.
We show that the duality group of the 4d theory is realized in two dimensions
in terms of Weyl transformations of the metric. We use the 2d dilaton gravity
theory to compute the statistical entropy of the near-extremal 4d,
, black hole.Comment: 12 pages, LaTex fil
Acoustic horizons for axially and spherically symmetric fluid flow
We investigate the formation of acoustic horizons for an inviscid fluid
moving in a pipe in the case of stationary and axi-symmetric flow. We show
that, differently from what is generally believed, the acoustic horizon forms
in correspondence of either a local minimum or maximum of the flux tube
cross-section. Similarly, the external potential is required to have either a
maximum or a minimum at the horizon, so that the external force has to vanish
there. Choosing a power-law equation of state for the fluid, , we solve the equations of the fluid dynamics and show that the two
possibilities are realized respectively for and . These results
are extended also to the case of spherically symmetric flow.Comment: 6 pages, 3 figure
Statistical entropy of the Schwarzschild black hole
We derive the statistical entropy of the Schwarzschild black hole by
considering the asymptotic symmetry algebra near the boundary of
the spacetime at past null infinity. Using a two-dimensional description and
the Weyl invariance of black hole thermodynamics this symmetry algebra can be
mapped into the Virasoro algebra generating asymptotic symmetries of anti-de
Sitter spacetime. Using lagrangian methods we identify the stress-energy tensor
of the boundary conformal field theory and we calculate the central charge of
the Virasoro algebra. The Bekenstein-Hawking result for the black hole entropy
is regained using Cardy's formula. Our result strongly supports a non-local
realization of the holographic principleComment: 3 pages no figure
Quantum gravitational corrections to black hole geometries
We calculate perturbative quantum gravity corrections to eternal
two-dimensional black holes. We estimate the leading corrections to the AdS_2
black hole entropy and determine the quantum modification of N-dimensional
Schwarzschild spacetime.Comment: 15 pages, 6 figures. Revised version: Introduction and conclusion
expanded, section II reshaped, references added. Accepted for publication in
Phys. Rev.
Entropy of 2D black holes from counting microstates
We present a microscopical derivation of the entropy of the black hole
solutions of the Jackiw-Teitelboim theory. We show that the asymptotic symmetry
of two-dimensional (2D) Anti-de Sitter space is generated by a central
extension of the Virasoro algebra. Using a canonical realization of this
symmetry and Cardy's formula we calculate the statistical entropy of 2D black
holes, which turns out to agree, up to a factor , with the
thermodynamical result.Comment: final version, accepted for publication on Phys. Rev.
The 2D analogue of the Reissner-Nordstrom solution
A two-dimensional (2D) dilaton gravity model, whose static solutions have the
same features of the Reissner-Nordstrom solutions, is obtained from the
dimensional reduction of a four-dimensional (4D) string effective action
invariant under S-duality transformations. The black hole solutions of the 2D
model and their relationship with those of the 4D theory are discussed.Comment: 5 pages, Plain-Tex, no figure
Cardy-Verlinde Formula and Achucarro-Ortiz Black Hole
In this paper it is shown that the entropy of the black hole horizon in the
Achucarro-Ortiz spacetime, which is the most general two-dimensional black hole
derived from the three-dimensional rotating BTZ black hole, can be described by
the Cardy-Verlinde formula. The latter is supposed to be an entropy formula of
conformal field theory in any dimension.Comment: 10 pages, LaTeX, v2: minor changes, references added, to appear in
Phys. Rev.
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