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Crashworthiness of the AT-400A shipping container
Shipping containers used for transporting radioactive material must be certified using federal regulations. These regulations require the container be tested or evaluated in severe mechanical and thermal environments which represent hypothetical accident scenarios. The containers are certified if the inner container remains leaktight. This paper presents results from finite element simulations of the accidents which include subjecting the AT-400A (for Pu from dismantled nuclear weapons) to a 30-foot (9 m) drop onto an unyielding target and crushing the container with an 1100 lb (500 kg) steel plate dropped from 30 feet. The nonlinear PRONTO3D finite element results were validated using test results. The simulations of the various impacts and crushes identified trends and worst-case orientations. They also showed that there is a significant margin of safety based on the failure of the containment vessel
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.
Event horizon - Magnifying glass for Planck length physics
An attempt is made to describe the `thermodynamics' of semiclassical
spacetime without specifying the detailed `molecular structure' of the quantum
spacetime, using the known properties of blackholes. I give detailed arguments,
essentially based on the behaviour of quantum systems near the event horizon,
which suggest that event horizon acts as a magnifying glass to probe Planck
length physics even in those contexts in which the spacetime curvature is
arbitrarily low. The quantum state describing a blackhole, in any microscopic
description of spacetime, has to possess certain universal form of density of
states which can be ascertained from general considerations. Since a blackhole
can be formed from the collapse of any physical system with a low energy
Hamiltonian H, it is suggested that when such a system collapses to form a
blackhole, it should be described by a modified Hamiltonian of the form
where .I also show
that it is possible to construct several physical systems which have the
blackhole density of states and hence will be indistinguishable from a
blackhole as far as thermodynamic interactions are concerned. In particular,
blackholes can be thought of as one-particle excitations of a class of {\it
nonlocal} field theories with the thermodynamics of blackholes arising
essentially from the asymptotic form of the dispersion relation satisfied by
these excitations. These field theoretic models have correlation functions with
a universal short distance behaviour, which translates into the generic
behaviour of semiclassical blackholes. Several implications of this paradigm
are discussed
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
Black Hole Evaporation in the Presence of a Short Distance Cutoff
A derivation of the Hawking effect is given which avoids reference to field
modes above some cutoff frequency in the free-fall frame
of the black hole. To avoid reference to arbitrarily high frequencies, it is
necessary to impose a boundary condition on the quantum field in a timelike
region near the horizon, rather than on a (spacelike) Cauchy surface either
outside the horizon or at early times before the horizon forms. Due to the
nature of the horizon as an infinite redshift surface, the correct boundary
condition at late times outside the horizon cannot be deduced, within the
confines of a theory that applies only below the cutoff, from initial
conditions prior to the formation of the hole. A boundary condition is
formulated which leads to the Hawking effect in a cutoff theory. It is argued
that it is possible the boundary condition is {\it not} satisfied, so that the
spectrum of black hole radiation may be significantly different from that
predicted by Hawking, even without the back-reaction near the horizon becoming
of order unity relative to the curvature.Comment: 35 pages, plain LaTeX, UMDGR93-32, NSF-ITP-93-2
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.
A Study of Phase Transition in Black Hole Thermodynamics
This paper deals with five-dimensional black hole solutions in (a)
Einstein-Maxwell-Gauss-Bonnet theory with a cosmological constant and
(b)Einstein-Yang-Mills-Gauss-Bonnet theory for spherically symmetric space
time. In both the cases the possibility of phase transition is examined and it
is analyzed whether the phase transition is a Hawking-Page type phase
transition or not.Comment: 16 figure
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
Thermodynamics of Reissner-Nordstrom-anti-de Sitter black holes in the grand canonical ensemble
The thermodynamical properties of the Reissner-Nordstr\"om-anti-de Sitter
black hole in the grand canonical ensemble are investigated using York's
formalism. The black hole is enclosed in a cavity with finite radius where the
temperature and electrostatic potential are fixed. The boundary conditions
allow us to compute the relevant thermodynamical quantities, e.g. thermal
energy, entropy and charge. The stability conditions imply that there are
thermodynamically stable black hole solutions, under certain conditions.
Instantons with negative heat capacity are also found.Comment: 15 pages, 9 figures, Revtex. Published version. Changes: figures
added to tex
Black Hole Entropy without Brick Walls
We present evidence which confirms a suggestion by Susskind and Uglum
regarding black hole entropy. Using a Pauli-Villars regulator, we find that 't
Hooft's approach to evaluating black hole entropy through a
statistical-mechanical counting of states for a scalar field propagating
outside the event horizon yields precisely the one-loop renormalization of the
standard Bekenstein-Hawking formula, S=\A/(4G). Our calculation also yields a
constant contribution to the black hole entropy, a contribution associated with
the one-loop renormalization of higher curvature terms in the gravitational
action.Comment: 15 pages, plain LaTex minor additions including some references;
version accepted for publicatio
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