16,689 research outputs found
Algebraically special perturbations of the Schwarzschild solution in higher dimensions
We study algebraically special perturbations of a generalized Schwarzschild
solution in any number of dimensions. There are two motivations. First, to
learn whether there exist interesting higher-dimensional algebraically special
solutions beyond the known ones. Second, algebraically special perturbations
present an obstruction to the unique reconstruction of general metric
perturbations from gauge-invariant variables analogous to the Teukolsky scalars
and it is desirable to know the extent of this non-uniqueness. In four
dimensions, our results generalize those of Couch and Newman, who found
infinite families of time-dependent algebraically special perturbations. In
higher dimensions, we find that the only regular algebraically special
perturbations are those corresponding to deformations within the Myers-Perry
family. Our results are relevant for several inequivalent definitions of
"algebraically special".Comment: 23 pages, no figures. v2: references added; discussion improved;
matches published versio
Euclidean analysis of the entropy functional formalism
The attractor mechanism implies that the supersymmetric black hole near
horizon solution is defined only in terms of the conserved charges and is
therefore independent of asymptotic moduli. Starting only with the near horizon
geometry, Sen's entropy functional formalism computes the entropy of an extreme
black hole by means of a Legendre transformation where the electric fields are
defined as conjugated variables to the electric charges. However, traditional
Euclidean methods require the knowledge of the full geometry to compute the
black hole thermodynamic quantities. We establish the connection between the
entropy functional formalism and the standard Euclidean formalism taken at zero
temperature. We find that Sen's entropy function 'f' (on-shell) matches the
zero temperature limit of the Euclidean action. Moreover, Sen's near horizon
angular and electric fields agree with the chemical potentials that are defined
from the zero-temperature limit of the Euclidean formalism.Comment: 37 pages. v3: Footnote and Reference added. Published versio
False vacuum decay: effective one-loop action for pair creation of domain walls
An effective one-loop action built from the soliton field itself for the
two-dimensional (2D) problem of soliton pair creation is proposed. The action
consists of the usual mass term and a kinetic term in which the simple
derivative of the soliton field is replaced by a covariant derivative. In this
effective action the soliton charge is treated no longer as a topological
charge but as a Noether charge. Using this effective one-loop action, the
soliton-antisoliton pair production rate is calculated and one recovers Stone's
exponential factor and the prefactor of Kiselev, Selivanov and Voloshin. The
results are also valid straightforwardly to the problem of pair creation rate
of domain walls in dimensions greater than 2.Comment: 12 pages, Late
The NESSUS finite element code
The objective of this development is to provide a new analysis tool which integrates the structural modeling versatility of a modern finite element code with the latest advances in the area of probabilistic modeling and structural reliability. Version 2.0 of the NESSUS finite element code was released last February, and is currently being exercised on a set of problems which are representative of typical Space Shuttle Main Engine (SSME) applications. NESSUS 2.0 allows linear elastostatic and eigenvalue analysis of structures with uncertain geometry, material properties and boundary conditions, which are subjected to a random mechanical and thermal loading environment. The NESSUS finite element code is a key component in a broader software system consisting of five major modules. NESSUS/EXPERT is an expert system under development at Southwest Research Institute, with the objective of centralizing all component-specific knowledge useful for conducting probabilistic analysis of typical Space Shuttle Main Engine (SSME) components. NESSUS/FEM contains the finite element code used for the structural analysis and parameter sensitivity evaluation of these components. The task of parametrizing a finite element mesh in terms of the random variables present is facilitated with the use of the probabilistic data preprocessor in NESSUS/PRE. An external database file is used for managing the bulk of the data generated by NESSUS/FEM
Quasinormal modes of asymptotically flat rotating black holes
We study the main properties of general linear perturbations of rotating
black holes in asymptotically flat higher-dimensional spacetimes. In
particular, we determine the quasinormal mode (QNM) spectrum of singly spinning
and equal angular momenta Myers-Perry black holes (MP BHs). Emphasis is also
given to the timescale of the ultraspinning and bar-mode instabilities in these
two families of MP BHs. For the bar-mode instabilities in the singly spinning
MP BH, we find excellent agreement with our linear analysis and the non-linear
time evolution of Shibata and Yoshino for d=6,7 spacetime dimensions. We find
that d=5 singly spinning BHs are linearly stable. In the context of studying
general relativity in the large dimension limit, we obtain the QNM spectrum of
Schwarzschild BHs and rotating MP BHs for large dimensions. We identify two
classes of modes. For large dimensions, we find that in the limit of zero
rotation, unstable modes of the MP BHs connect to a class of Schwarzschild QNMs
that saturate to finite values.Comment: 52 pages. 25 figure
Renormalisation scheme for vector fields on T2 with a diophantine frequency
We construct a rigorous renormalisation scheme for analytic vector fields on
the 2-torus of Poincare type. We show that iterating this procedure there is
convergence to a limit set with a ``Gauss map'' dynamics on it, related to the
continued fraction expansion of the slope of the frequencies. This is valid for
diophantine frequency vectors.Comment: final versio
A certificação das embalagens de madeira: importante avanço na importação e exportação de produtos e na segurança biológica.
bitstream/CENARGEN/30150/1/cultivar050207.pdfPublicado em 05/02/2007. Disponível em: Cultivar, cultivar050207; Abrafit, abrafitnr9807; Agrosoft, agrosoft050207; Pets, pets050207; ClicNews, clicnews050207; Ruralnet, ruralnet050207; Hotel Virtual, hvirtual050207; Boletim Pecuário, bpecuario050207; Zoonews, zoonews050207; D.O. Municípios Ceará, domceara050207
Plantas do futuro no presente [2].
bitstream/CENARGEN/30151/1/odisseu310507.pdfPublicado em 30/01/2007. Disponível em: Boletim Pecuário, boletimpecuario300107; ClicNews, clicnews300107; Hotel Virtual, hotelvirtual300107; Cultivar, cultivar280107; Página Rural, pgrural300107; Portal Agronegócio, pagronegocio310107; Criar e Plantar, criareplantar300107; Zoonews, zoonews020207; Pets, pets300107; Agrosoft, agrosoft300107; Ruralnet, ruralnet300107; Gazeta do Oeste, gazetadooeste020207
- …