5,316 research outputs found
News vs Information
We consider the relative entropy between the vacuum state and a coherent
state in linearized quantum gravity around a stationary black hole spacetime.
Combining recent results by Casini et al. and Longo with the Raychaudhuri
equation, the following result is obtained: Let be the algebra of
observables assoiciated with a region that is the causal future of some compact
set in the interior of the spacetime. Let be the relative entropy with
respect to this algebra, the area of the horizon cross section defined by
the region, computed to second order in the gravitational perturbation. If the
region is time-translated by the Killing parameter , then , with the flux of the gravitational/matter radiation
(integrated squared news tensor) emitted towards the future of the region.Comment: 11 pages, 1 figure. arXiv admin note: text overlap with
arXiv:1903.07508, v2: some details added on function spaces and decay of
solutions, refs. adde
Coating of plasma polymerized film
Plasma polymerized thin film coating and the use of other coatings is suggested for passivation film, thin film used for conducting light, and solid body lubrication film of dielectrics of ultra insulators for electrical conduction, electron accessories, etc. The special features of flow discharge development and the polymerized film growth mechanism are discussed
Comparison between various notions of conserved charges in asymptotically AdS-spacetimes
We derive hamiltionian generators of asymptotic symmetries for general
relativity with asymptotic AdS boundary conditions using the ``covariant phase
space'' method of Wald et al. We then compare our results with other
definitions that have been proposed in the literature. We find that our
definition agrees with that proposed by Ashtekar et al, with the spinor
definition, and with the background dependent definition of Henneaux and
Teitelboim. Our definition disagrees with the one obtained from the
``counterterm subtraction method,'' but the difference is found to consist only
of a ``constant offset'' that is determined entirely in terms of the boundary
metric. We finally discuss and justify our boundary conditions by a linear
perturbation analysis, and we comment on generalizations of our boundary
conditions, as well as inclusion of matter fields.Comment: 64p, Latex, no figures, v2: references added, typos corrected, v3:
some equations correcte
The initial value problem for linearized gravitational perturbations of the Schwarzschild naked singularity
The coupled equations for the scalar modes of the linearized Einstein
equations around Schwarzschild's spacetime were reduced by Zerilli to a 1+1
wave equation with a potential , on a field . For smooth metric
perturbations is singular at , the
mode harmonic number, and has a second order pole at . This is
irrelevant to the black hole exterior stability problem, where , and
, but it introduces a non trivial problem in the naked singular case
where , and the singularity appears in the relevant range of
. We solve this problem by developing a new approach to the evolution of the
even mode, based on a {\em new gauge invariant function}, -related
to by an intertwiner operator- that is a regular function of the
metric perturbation {\em for any value of }. This allows to address the
issue of evolution of gravitational perturbations in this non globally
hyperbolic background, and to complete the proof of the linear instability of
the Schwarzschild naked singularity, by showing that a previously found
unstable mode is excitable by generic initial data. This is further illustrated
by numerically solving the linearized equations for suitably chosen initial
data.Comment: typos corrected, references adde
On the stability of naked singularities
We study the linearised stability of the nakedly singular negative mass
Schwarzschild solution against gravitational perturbations. There is a one
parameter family of possible boundary conditions at the singularity. We give a
precise criterion for stability depending on the boundary condition. We show
that one particular boundary condition is physically preferred and show that
the spacetime is stable with this boundary condition.Comment: 20 pages. 5 figure
Probing the effect of point defects on the leakage blocking capability of Al0.1Ga0.9N/Si structures using a monoenergetic positron beam
Vacancy-type defects in Al0.1Ga0.9N were probed using a monoenergetic positron beam. Al0.1Ga0.9N layers with different carbon doping concentrations ([C] = 5 x 10(17) -8 x 10(19) cm(-3)) were grown on Si substrates by metalorganic vapor phase epitaxy. The major defect species in Al0.1Ga0.9N was determined to be a cation vacancy (or cation vacancies) coupled with nitrogen vacancies and/or with carbon atoms at nitrogen sites (C(N)s). The charge state of the vacancies was positive because of the electron transfer from the defects to C-N-related acceptors. The defect charge state was changed from positive to neutral when the sample was illuminated with photon energy above 1.8 eV, and this energy range agreed with the yellow and blue luminescence. For the sample with high [C], the charge transition of the vacancies under illumination was found to be suppressed, which was attributed to the trapping of emitted electrons by C-N-related acceptors. With increasing [C], the breakdown voltage under the reverse bias condition increased. This was explained by the trapping of the injected electrons by the positively charged vacancies and C-N-related acceptors
RECENT FOOD CONSUMPTION PATTERN OF JAPANESE HOUSEHOLDS: DRIVING FORCES BEHIND WESTERNIZATION
A complete demand system for 11 aggregated food categories with 24 demographic variables, is specified following QUAIDS and is estimated using Japanese household level data. The estimation results suggest that westernization is due to the income effect and the tendency is further enhanced by the demographic factors.Food Consumption/Nutrition/Food Safety,
Introducing Dynamical Triangulations to the Type IIB Superstrings
In order to consider non-perturbative effects of superstrings, we try to
apply dynamical triangulations to the type IIB superstrings. The discretized
action is constructed from the type IIB matrix model proposed as a constructive
definition of superstring theory. The action has the local N=2 supersymmetry
explicitly, and has no extra fermionic degrees of freedom. We evaluate the
partition function for some simple configurations and discuss constraints
required from the finiteness of partition functions.Comment: LATTICE99, 3 pages, LaTeX with 2 figures, espcrc2.st
Naked Singularity and Thunderbolt
We consider quantum theoretical effects of the sudden change of the boundary
conditions which mimics the occurrence of naked singularities. For a simple
demonstration, we study a massless scalar field in -dimensional
Minkowski spacetime with finite spatial interval. We calculate the vacuum
expectation value of the energy-momentum tensor and explicitly show that
singular wave or {\em thunderbolt} appears along the Cauchy horizon. The
thunderbolt possibly destroys the Cauchy horizon if its backreaction on the
geometry is taken into account, leading to quantum restoration of the global
hyperbolicity. The result of the present work may also apply to the situation
that a closed string freely oscillating is traveling to a brane and changes
itself to an open string pinned-down by the ends satisfying the Dirichlet
boundary conditions on the brane.Comment: 12 pages, 1 figure, references added, to appear in Phys. Rev.
Importance of electronic correlations for structural and magnetic properties of the iron pnictide superconductor LaFeAsO
We present calculations of structural and magnetic properties of the
iron-pnictide superconductor LaFeAsO including electron-electron correlations.
For this purpose we apply a fully charge self-consistent combination of
Density-Functional Theory with the Dynamical Mean-Field theory, allowing for
the calculation of total energies. We find that the inclusion of correlation
effects gives a good agreement of the Arsenic z position with experimental data
even in the paramagnetic (high-temperature) phase. Going to low temperatures,
we study the formation of the ordered moment in the striped spin-density-wave
phase, yielding an ordered moment of about 0.60, again in good agreement with
experiments. This shows that the inclusion of correlation effects improves both
structural and magnetic properties of LaFeAsO at the same time.Comment: 7 pages, 5 figures, published versio
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