425 research outputs found
Gravitational waves from quasi-spherical black holes
A quasi-spherical approximation scheme, intended to apply to coalescing black
holes, allows the waveforms of gravitational radiation to be computed by
integrating ordinary differential equations.Comment: 4 revtex pages, 2 eps figure
Gravitational Waves from a Fissioning White Hole
We present a fully nonlinear calculation of the waveform of the gravitational
radiation emitted in the fission of a vacuum white hole. At early times, the
waveforms agree with close-approximation perturbative calculations but they
reveal dramatic time and angular dependence in the nonlinear regime. The
results pave the way for a subsequent computation of the radiation emitted
after a binary black hole merger.Comment: 11 pages, 6 figures, RevTeX
Complete null data for a black hole collision
We present an algorithm for calculating the complete data on an event horizon
which constitute the necessary input for characteristic evolution of the
exterior spacetime. We apply this algorithm to study the intrinsic and
extrinsic geometry of a binary black hole event horizon, constructing a
sequence of binary black hole event horizons which approaches a single
Schwarzschild black hole horizon as a limiting case. The linear perturbation of
the Schwarzschild horizon provides global insight into the close limit for
binary black holes, in which the individual holes have joined in the infinite
past. In general there is a division of the horizon into interior and exterior
regions, analogous to the division of the Schwarzschild horizon by the r=2M
bifurcation sphere. In passing from the perturbative to the strongly nonlinear
regime there is a transition in which the individual black holes persist in the
exterior portion of the horizon. The algorithm is intended to provide the data
sets for production of a catalog of nonlinear post-merger wave forms using the
PITT null code.Comment: Revised version, to appear in Phys. Rev. D. July 15 (2001), 41 pages,
11 figures, RevTeX/epsf/psfi
Mode coupling in the nonlinear response of black holes
We study the properties of the outgoing gravitational wave produced when a
non-spinning black hole is excited by an ingoing gravitational wave.
Simulations using a numerical code for solving Einstein's equations allow the
study to be extended from the linearized approximation, where the system is
treated as a perturbed Schwarzschild black hole, to the fully nonlinear regime.
Several nonlinear features are found which bear importance to the data analysis
of gravitational waves. When compared to the results obtained in the linearized
approximation, we observe large phase shifts, a stronger than linear generation
of gravitational wave output and considerable generation of radiation in
polarization states which are not found in the linearized approximation. In
terms of a spherical harmonic decomposition, the nonlinear properties of the
harmonic amplitudes have simple scaling properties which offer an economical
way to catalog the details of the waves produced in such black hole processes.Comment: 17 pages, 20 figures, abstract and introduction re-writte
The formation of planetary disks and winds: an ultraviolet view
Planetary systems are angular momentum reservoirs generated during star
formation. This accretion process produces very powerful engines able to drive
the optical jets and the molecular outflows. A fraction of the engine energy is
released into heating thus the temperature of the engine ranges from the 3000K
of the inner disk material to the 10MK in the areas where magnetic reconnection
occurs. There are important unsolved problems concerning the nature of the
engine, its evolution and the impact of the engine in the chemical evolution of
the inner disk. Of special relevance is the understanding of the shear layer
between the stellar photosphere and the disk; this layer controls a significant
fraction of the magnetic field building up and the subsequent dissipative
processes ougth to be studied in the UV.
This contribution focus on describing the connections between 1 Myr old suns
and the Sun and the requirements for new UV instrumentation to address their
evolution during this period. Two types of observations are shown to be needed:
monitoring programmes and high resolution imaging down to, at least,
milliarsecond scales.Comment: Accepted for publication in Astrophysics and Space Science 9 figure
Cómo se viven los derechos reproductivos en Ecuador: escenarios, contextos y circunstancias
La Comisión de Transición hacia el Consejo de las Mujeres y la Igualdad de Género es el mecanismo especializado del Estado, cuyo mandato es la definición de la institucionalidad pública que garantice la igualdad entre hombres y mujeres. Para su cumplimiento el Directorio de la Comisión una vez instalado, definió como objetivos estratégicos que guiaron la gestión institucional, los siguientes: 1. Impulsar un Sistema de Igualdad entre mujeres y hombres, que fortalezca al Estado
democrático para el Buen Vivir.
2. Incidir en los Sistemas de Participación Pública y Política para lograr la autonomía política y
toma de decisiones de las mujeres.
3. Incidir en la construcción de un Sistema de Justicia y de Protección de derechos que permita
la Autonomía de las mujeres.
4. Incidir en la construcción de un Sistema económico social y solidario que garantice la
autonomía económica de las mujeres.
Uno de los temas enfatizados para la consecución del Objetivo 3 fue la contratación de varios
estudios sobre la problemática de la salud sexual y reproductiva de las mujeres. En este marco
presenta la recopilación de tres estudios sobre la problemática del aborto abordada desde diferentes entradas que se consideran insumos estratégicos para la construcción de política pública.
La actual coyuntura política del país, en la que se debaten leyes que podrían ampliar el ejercicio
de los derechos reproductivos de las mujeres o restringirlos más todavía, constituye el escenario
propicio para la presentación de esta publicación que se confía, servirá para reafirmar derechos o
desechar información incorrecta y prejuicios que sobre la temática existen en el imaginario social
ecuatoriano.
Se espera que este aporte guíe hacia un cambio legislativo que garantice a las mujeres su derecho a decidir y optar legalmente por continuar o interrumpir sus maternidades, en concordancia con sus deseos y circunstancias personales.
Comisión de Transición hacia el Consejo de las Mujeres y la Igualdad de Género.COMISIÓN DE TRANSICIÓN HACIA EL CONSEJO DE LAS MUJERES Y LA IGUALDAD DE GÉNER
Bondian frames to couple matter with radiation
A study is presented for the non linear evolution of a self gravitating
distribution of matter coupled to a massless scalar field. The characteristic
formulation for numerical relativity is used to follow the evolution by a
sequence of light cones open to the future. Bondian frames are used to endow
physical meaning to the matter variables and to the massless scalar field.
Asymptotic approaches to the origin and to infinity are achieved; at the
boundary surface interior and exterior solutions are matched guaranteeing the
Darmois--Lichnerowicz conditions. To show how the scheme works some numerical
models are discussed. We exemplify evolving scalar waves on the following fixed
backgrounds: A) an atmosphere between the boundary surface of an incompressible
mixtured fluid and infinity; B) a polytropic distribution matched to a
Schwarzschild exterior; C) a Schwarzschild- Schwarzschild spacetime. The
conservation of energy, the Newman--Penrose constant preservation and other
expected features are observed.Comment: 20 pages, 6 figures; to appear in General Relativity and Gravitatio
Design of a continuous production energy machine from marine trochoidal waves
This paper describes the development of a continuous production energy
machine from marine trochoidal waves. Studying the characteristics of trochoidal
waves in a geographical area near Cartagena, we have developed a device, which
taking advantage of the marine surface oscillation in order to produce the movement
of a mechanical device, is able to transforming the mechanical energy into
electrical energy.Peer Reviewe
Modelization of a hybrid system with renewable energy for electric propulsion in boats. Application to a robotic floating platform
A model of a hybrid system with renewable energy for electric propulsion
in boats in which energy generated by photovoltaic panels and hydrogenerator is
stored in the main battery which exerts its function as central element of a renewable
cycle is presented. Additionally, hydrogen plays a role being generated by an
electrolyzer for later to be stored in cylinders aboard in order to generate electric
power by a fuel cell. Both, batteries and cylinders can be used to feed the different elements
of the system, more specially the thruster while the excess of power is stored
in another battery which is auxiliary and it is able to feed the first when it is necessary.Peer Reviewe
Amplification of evanescent waves in a lossy left-handed material slab
We carry out finite-difference time-domain (FDTD) simulations, with a
specially-designed boundary condition, on pure evanescent waves interacting
with a lossy left-handed material (LHM) slab. Our results provide the first
full-wave numerical evidence for the amplification of evanescent waves inside a
LHM slab of finite absorption. The amplification is due to the interactions
between the evanescent waves and the coupled surface polaritons at the two
surfaces of the LHM slab and the physical process can be described by a simple
model.Comment: 4 pages, 2 figure
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