1,474 research outputs found
Noncommutative Black Holes and the Singularity Problem
A phase-space noncommutativity in the context of a Kantowski-Sachs
cosmological model is considered to study the interior of a Schwarzschild black
hole. Due to the divergence of the probability of finding the black hole at the
singularity from a canonical noncommutativity, one considers a non-canonical
noncommutativity. It is shown that this more involved type of noncommutativity
removes the problem of the singularity in a Schwarzschild black hole.Comment: Based on a talk by CB at ERE2010, Granada, Spain, 6th-10th September
201
A symplectic extension map and a new Shubin class of pseudo-differential operators
For an arbitrary pseudo-differential operator with Weyl symbol
, we consider the
pseudo-differential operators associated with
the Weyl symbols , where
for all and is a linear symplectomorphism of
. We call the operators symplectic
dimensional extensions of . In this paper we study the relation between
and in detail, in particular their regularity, invertibility
and spectral properties. We obtain an explicit formula allowing to express the
eigenfunctions of in terms of those of . We use this
formalism to construct new classes of pseudo-differential operators, which are
extensions of the Shubin classes of globally
hypoelliptic operators. We show that the operators in the new classes share the
invertibility and spectral properties of the operators in but not the global hypoellipticity property. Finally, we study
a few examples of operators that belong to the new classes and which are
important in mathematical physics.Comment: 28 pages, new version, accepted for publication in JF
A educação ambiental em maricá/rj : uma visão de Darwin e do príncipe wied-neuwied no século XIX e nos dias atuais
O presente trabalho tem por objetivo descrever os relatos dos naturalistas, Príncipe Maximiliano de Wied-Newied (1815) e Charles Darwin (1832), em suas viagens pelo Município de Marica/RJ, as ações do município no que se refere às questões ambientais em Escolas no 1° Segmento do Ensino Fundamental. É uma pesquisa qualitativa de caráter exploratório-descritiva acerca da história do Município de Maricá e da legislação vigente no Município. Dados foram levantados através de questionários e entrevistas com professores de escolas municipais. Deve ser estabelecida uma política, por parte dos órgãos públicos, direcionada à preservação do patrimônio cultural e ambiental do Município e aproximando dos alunos as atividades de Educação Ambiental
Automatic camera pose initialization, using scale, rotation and luminance invariant natural feature tracking
The solution to the camera registration and tracking problem serves Augmented Reality, in order to provide an
enhancement to the user’s cognitive perception of the real world and his/her situational awareness. By analyzing
the five most representative tracking and feature detection techniques, we have concluded that the Camera Pose
Initialization (CPI) problem, a relevant sub-problem in the overall camera tracking problem, is still far from being
solved using straightforward and non-intrusive methods. The assessed techniques often use user inputs (i.e.
mouse clicking) or auxiliary artifacts (i.e. fiducial markers) to solve the CPI problem. This paper presents a novel
approach to real-time scale, rotation and luminance invariant natural feature tracking, in order to solve the CPI
problem using totally automatic procedures. The technique is applicable for the case of planar objects with arbitrary
topologies and natural textures, and can be used in Augmented Reality. We also present a heuristic method
for feature clustering, which has revealed to be efficient and reliable. The presented work uses this novel feature
detection technique as a baseline for a real-time and robust planar texture tracking algorithm, which combines
optical flow, backprojection and template matching techniques. The paper presents also performance and precision
results of the proposed technique
The singularity problem and phase-space noncanonical noncommutativity
The Wheeler-DeWitt equation arising from a Kantowski-Sachs model is
considered for a Schwarzschild black hole under the assumption that the scale
factors and the associated momenta satisfy a noncanonical noncommutative
extension of the Heisenberg-Weyl algebra. An integral of motion is used to
factorize the wave function into an oscillatory part and a function of a
configuration space variable. The latter is shown to be normalizable using
asymptotic arguments. It is then shown that on the hypersufaces of constant
value of the argument of the wave function's oscillatory piece, the probability
vanishes in the vicinity of the black hole singularity.Comment: 4 pages, revtex
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