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Gleiser M 《Physical review D: Particles and fields》1990,42(10):3350-3361
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In this paper we show that if Vaidya's radiation metric is considered from the point of view of kinetic theory in general relativity, the corresponding phase space distribution function can be generalized in a particular way. The new family of spherically symmetric radiation metrics obtained contains Vaidya's as a limiting situation. The Einstein field equations are solved in a comoving coordinate system. Two arbitrary functions of a single variable are introduced in the process of solving these equations. Particular examples considered are a stationary solution, a nonvacuum solution depending on a single parameter, and several limiting situations. 相似文献
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Carlos O. Nicasio Reinaldo Gleiser Jorge Pullin 《General Relativity and Gravitation》2000,32(10):2021-2042
We consider perturbations of a Schwarzschild black hole that can be of both even and odd parity, keeping terms up to second order in perturbation theory, for the l = 2 axisymmetric case. We develop explicit formulae for the evolution equations and radiated energies and waveforms using the Regge–Wheeler–Zerilli approach. This formulation is useful, for instance, for the treatment in the "close limit approximation" of the collision of counterrotating black holes. 相似文献
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P. M. Gleiser D. H. Zanette 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,53(2):233-238
We analyze the interplay of synchronization and structure
evolution in an evolving network of phase oscillators. An initially
random network is adaptively rewired according to the dynamical
coherence of the oscillators, in order to enhance their mutual
synchronization. We show that the evolving network reaches a
small-world structure. Its clustering coefficient attains a maximum
for an intermediate intensity of the coupling between oscillators,
where a rich diversity of synchronized oscillator groups is
observed. In the stationary state, these synchronized groups are
directly associated with network clusters. 相似文献
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Einstein equations are derived for D-dimensional space-time that spontaneously compactify to the product M4 × Πi = 1α Mdi in which the metric is taken to be of the generalized Robertson-Walker form. Cosmological solutions for these equations are studied with power law, oscillatory and exponential behaviour for the D-dimensional Einstein-Maxwell, N = 2, D = 10 and N = 1, D = 11 supergravity models. In the Einstein-Maxwell case the presence of a cosmological constant forces the extra dimensions to be static. Nevertheless, it is possible to find solutions with vanishing effective 4 dimensional cosmological constant with an expanding 4-dimensional space-time. In the supergravity models the requirement of having compact extra dimensions restricts the solutions to have expansion only in the 4-dimensional space-time. Matter contribution is added to the energy-momentum tensor in an attempt to find new solutions. 相似文献
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We show that a newly proposed Shannon-like entropic measure of shape complexity applicable to spatially-localized or periodic mathematical functions known as configurational entropy (CE) can be used as a predictor of spontaneous decay rates for one-electron atoms. The CE is constructed from the Fourier transform of the atomic probability density. For the hydrogen atom with degenerate states labeled with the principal quantum number n, we obtain a scaling law relating the n-averaged decay rates to the respective CE. The scaling law allows us to predict the n-averaged decay rate without relying on the traditional computation of dipole matrix elements. We tested the predictive power of our approach up to n =?20, obtaining an accuracy better than 3.7% within our numerical precision, as compared to spontaneous decay tables listed in the literature. 相似文献