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271.
In this paper, we are interested in the derivation of macroscopic equations from kinetic ones using a moment method in a relativistic framework. More precisely, we establish the general form of moments that are compatible with the Lorentz invariance and derive a hierarchy of relativistic moment systems from a Boltzmann kinetic equation. The proof is based on the representation theory of Lie algebras. We then extend this derivation to the classical case and general families of moments that obey the Galilean invariance are also constructed. It is remarkable that the set of formal classical limits of the so-obtained relativistic moment systems is not identical to the set of classical moments quoted in Ref. 21 and one could use a new physically relevant criterion to derive suitable moment systems in the classical case. Finally, the ultra-relativistic limit is considered. 相似文献
273.
We compare two estimates of the cumulant generating function of a stationary linear process. The first estimate is based on
the empirical moment generating function. The second estimate uses the linear representation of the process and the empirical
moment generating function of the innovations. Asymptotic expressions for the mean square errors are derived under short-
and long-range dependence. For long-memory processes, the estimate based on the linear representation turns out to have a
better rate of convergence. Thus, exploiting the linear structure of the process leads to an infinite gain in asymptotic efficiency. 相似文献
274.
275.
276.
利用渐近方法和对角化技巧研究了伴有边界摄动的高维非线性系统边值问题的奇摄动,在适当的假设下,证得摄动问题解的存在并导出其解关于ε的高阶近似. 相似文献
277.
Zenon J. Jablonski 《Proceedings of the American Mathematical Society》2007,135(9):2811-2819
An operator multivariate moment problem with contractive solutions having regular unitary dilation is characterized in terms of the initial data. This extends a recent result of Sebestyén and Popovici, but the ideas of our proof differ from those used by them. The connection between the operator multivariate moment problem and harmonizable multivariate discrete processes is mentioned.
278.
本文提出了半赋权向量概念 ,讨论了高阶加权均方矩的平均值性质 ,运用半赋权向量的性质推出了高阶加权平均值的一些性质 .本文还介绍了半赋权向量与高阶加权平均值在宏观经济分析中的应用 ,讨论了其应用前景 . 相似文献
279.
The effects of cubic crystal fields on the saturation magnetic moment of Sm3+ ion in ferromagnetic compounds have been investigated. In samarium compounds with magnetic elements, the exchange fieldH
ex acting on Sm3+ ion is taken to be proportional to the sublattice magnetization of the magnetic element, while in compounds with nonmagnetic
elementsH
ex is taken to be proportional to the spin average of the Sm3+ ion and is determined self-consistently. In both types of compoundsH
ex is assumed to be along [001] direction. The saturation magnetic moment is calculated by taking into account the admixture
of excited (J=7/2 andJ=9/2) levels into the ground (J=5/2) level of Sm3+ ion by crystal fields and exchange fields. It is shown that depending upon the strength, the crystal fields quench or enhance
the magnetic moment from the free ion value, and in some cases force Sm3+ ion to behave effectively like an (L+S) ion rather than an (L−S)ion. The crystal fields may have important bearing on the performance of samarium compounds as permanent magnet materials. 相似文献
280.
Based on an idea of Rosenblatt, the methods of interpolation theory are used to establish moment inequalities and equivalence relations for measures of dependence between two or more families of random variables. A couple of “interpolation” theorems proved here appear to be new. 相似文献