21 research outputs found
Dilaton black holes in grand canonical ensemble near the extreme state
Dilaton black holes with a pure electric charge are considered in a framework
of a grand canonical ensemble near the extreme state. It is shown that there
exists such a subset of boundary data that the Hawking temperature smoothly
goes to zero to an infinite value of a horizon radius but the horizon area and
entropy are finite and differ from zero. In string theory the existence of a
horizon in the extreme limit is due to the finiteness of a system only.Comment: 8 pages, RevTex 3.0. Presentation improved, discussion on metrics in
string theory simplified. To be published in Phys.Rev.
Action of Singular Instantons of Hawking-Turok Type
Using Kaluza-Klein technique we show that the singularity of Hawking-Turok
type has a fixed point (bolt) contribution to the action in addition to the
usual boundary contribution. Interestingly by adding this contribution we can
obtain a simple expression for the total action which is feasible for both
regular and singular instantons. Our result casts doubt on the constraint
proposed by Turok in the recent calculation in which Vilenkin's instantons are
regarded as a limit of certain constrained instantons.Comment: 14 pages, LaTe
Two-dimensional quantum-corrected black hole in a finite size cavity
We consider the gravitation-dilaton theory (not necessarily exactly
solvable), whose potentials represent a generic linear combination of an
exponential and linear functions of the dilaton. A black hole, arising in such
theories, is supposed to be enclosed in a cavity, where it attains thermal
equilibrium, whereas outside the cavity the field is in the Boulware state. We
calculate quantum corrections to the Hawking temperature , with the
contribution from the boundary taken into account. Vacuum polarization outside
the shell tend to cool the system. We find that, for the shell to be in the
thermal equilibrium, it cannot be placed too close to the horizon. The quantum
corrections to the mass due to vacuum polarization vanish in spite of non-zero
quantum stresses. We discuss also the canonical boundary conditions and show
that accounting for the finiteness of the system plays a crucial role in some
theories (e.g., CGHS), where it enables to define the stable canonical
ensemble, whereas consideration in an infinite space would predict instability.Comment: 21 pages. In v.2 misprints corrected. To appear in Phys. Rev.
On "Non-Geometric" Contribution To The Entropy Of Black Hole Due To Quantum Corrections
The quantum corrections to the entropy of charged black holes are calculated.
The Reissner-Nordstrem and dilaton black holes are considered. The appearance
of logarithmically divergent terms not proportional to the horizon area is
demonstrated. It is shown that the complete entropy which is sum of classical
Bekenstein-Hawking entropy and the quantum correction is proportional to the
area of quantum-corrected horizon.Comment: Latex, 9 page
Classical and Thermodynamic Stability of Black Branes
It is argued that many non-extremal black branes exhibit a classical
Gregory-Laflamme instability if, and only if, they are locally
thermodynamically unstable. For some black branes, the Gregory-Laflamme
instability must therefore disappear near extremality. For the black -branes
of the type II supergravity theories, the Gregory-Laflamme instability
disappears near extremality for but persists all the way down to
extremality for (the black D3-brane is not covered by the analysis of
this paper). This implies that the instability also vanishes for the
near-extremal black M2 and M5-brane solutions.Comment: 21 pages, LaTeX. v2: Various points clarified, typos corrected and
reference adde
Thermal partition function of photons and gravitons in a Rindler wedge
The thermal partition function of photons in any covariant gauge and
gravitons in the harmonic gauge, propagating in a Rindler wedge, are computed
using a local -function regularization approach. The correct Planckian
leading order temperature dependence is obtained in both cases. For the
photons, the existence of a surface term giving a negative contribution to the
entropy is confirmed, as earlier obtained by Kabat, but this term is shown to
be gauge dependent in the four-dimensional case and, therefore is discarded. It
is argued that similar terms could appear dealing with any integer spin in the massless case and in more general manifolds. Our conjecture is
checked in the case of a graviton in the harmonic gauge, where different
surface terms also appear, and physically consistent results arise dropping
these terms. The results are discussed in relation to the quantum corrections
to the black hole entropy.Comment: 29 pages, RevTeX, no figures. Minor errors corrected and a few
comments changed since first submission. To be published on Phys.Rev.
Testing Holographic Principle from Logarithmic and Higher Order Corrections to Black Hole Entropy
The holographic principle is tested by examining the logarithmic and higher
order corrections to the Bekenstein-Hawking entropy of black holes. For the BTZ
black hole, I find some disagreement in the principle for a holography screen
at spatial infinity beyond the leading order, but a holography with the screen
at the horizon does not, with an appropriate choice of a period parameter,
which has been undetermined at the leading order, in Carlip's horizon-CFT
approach for black hole entropy in any dimension. Its higher dimensional
generalization is considered to see a universality of the parameter choice. The
horizon holography from Carlip's is compared with several other realizations of
a horizon holography, including induced Wess-Zumino-Witten model approaches and
quantum geometry approach, but none of the these agrees with Carlip's, after
clarifications of some confusions. Some challenging open questions are listed
finally.Comment: To appear in JHEP. The corrections in Sec.2 with those that follow
are more clearly explained. Careful distingtion between the implications of
my results to AdS/CFT and to the holograhic principl
Two-dimensional Quantum-Corrected Eternal Black Hole
The one-loop quantum corrections to geometry and thermodynamics of black hole
are studied for the two-dimensional RST model. We chose boundary conditions
corresponding to the eternal black hole being in the thermal equilibrium with
the Hawking radiation. The equations of motion are exactly integrated. The one
of the solutions obtained is the constant curvature space-time with dilaton
being a constant function. Such a solution is absent in the classical theory.
On the other hand, we derive the quantum-corrected metric (\ref{solution})
written in the Schwarzschild like form which is a deformation of the classical
black hole solution \cite{5d}. The space-time singularity occurs to be milder
than in classics and the solution admits two asymptotically flat black hole
space-times lying at "different sides" of the singularity. The thermodynamics
of the classical black hole and its quantum counterpart is formulated. The
thermodynamical quantities (energy, temperature, entropy) are calculated and
occur to be the same for both the classical and quantum-corrected black holes.
So, no quantum corrections to thermodynamics are observed. The possible
relevance of the results obtained to the four-dimensional case is discussed.Comment: Latex, 28 pges; minor corrections in text and abstract made and new
references adde
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Large-aperture discharges in E-beam sustained CO/sub 2/ amplifiers
The very large energy fluxes required for the attainment of scientific breakeven in laser-fusion experiments can only be obtained by the construction of multiple-beam, large-aperture lasers. Accordingly, the next generation CO/sub 2/ laser currently being designed at LASL consists of six electron-beam sustained amplifier modules, each module containing 12 large-aperture (approximately 30 x 30 cm) laser discharges sustained by (and surrounding) a single, cylindrical cold-cathode electron gun. The large scale and cylindrical geometry combine to generate substantial electric and magnetic field effects which can affect the uniformity of the electron-beam distribution, causing a number of difficulties including discharge and gain nonuniformities and potential arcing. In an effort to learn the magnitude of the associated difficulties and test various solutions for reducing the effects, a prototype module was constructed. This prototype was constructed full scale in the dimensions which will produce the discharge nonuniformities and measurements were made of the electron beam uniformity, discharge uniformity, and gain uniformity under a wide range of experimental conditions. These results indicate that under worse case conditions and nonuniformities, while severe, are within acceptable limits and can be reduced even further by minor design changes. Perhaps more importantly, calculational models have been developed which agree adequately enough with the data so that they can be used with reasonable confidence as a data base for predicting the performance of the final design of the amplifier modules and the effects of any changes which may be required