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991.
We study the class of endomorphisms of the cone of correlation functions generated by probability measures. We consider algebraic properties of the products (·, ?) and the maps K, K ?1 which establish relationships between the properties of functions on the configuration space and the properties of the corresponding operators (matrices with Boolean indices): F(γ) → F?(γ) = {F(α?β)}α,β?γ. For the operators F?(γ) and F?(γ), we prove conditions which ensure that these operators are positive definite; the conditions are given in terms of complete or absolute monotonicity properties of the function F(γ). 相似文献
992.
993.
994.
Ernesto Lpez-Chvez J. M. Martínez Magadn Fray de Landa Castillo-Alvarado 《Journal of magnetism and magnetic materials》2004,280(2-3):293-303
A theory of disordered binary alloys AxB1−x (A=Ni, Co; B=Fe; x0.06) is used to determine the changes in the electronic structure and magnetic properties of body centered cubic (BCC) iron induced by doping with nickel and cobalt impurities. This approximation is an extension of the cluster-Bethe lattice method, in which we incorporate electronic correlations, itinerant and localized nature of electrons 3d, and both long-range and short-range chemical correlations. The magnetism is described by means of a Hubbard Hamiltonian that in conjunction with Green's functions techniques is used to calculate local densities of electronic states. For it we take an atom in the real lattice and it is joined to a Bethe's lattice with like coordination number. The magnetic moments on sites occupied for A and B atoms are obtained self-consistently. Nickel and cobalt impurities in BCC iron can provide crucial information on the modification of the electronic band structure and magnetic moments from pure Fe. The results obtained are compared with those of both pure Fe and binary alloys of Co–Fe and Ni–Fe, which have been obtained by other authors using methods such as: first-principles electronic structure calculations using the layer Korringa–Kohn–Rostoker (KKR), the full-potential linearized augmented plane wave method, the KKR coherent potential approximation combined with the local-density functional method and by the tight-binding linear-muffin-tin orbitals method, obtained good agree. These results and other that recently we have published indicate to us that our methodology can be a new alternative for calculations of the electronic structure and magnetic properties of impurities and alloys of ferromagnetic transition metals. 相似文献
995.
Jean-Marc Belley Michel Virgilio 《Journal of Mathematical Analysis and Applications》2005,306(2):646-662
Conditions are obtained for the Duffing equation with delay and state dependent impulses to admit a periodic solution. 相似文献
996.
Döhler Sebastian Rüschendorf Ludger 《Statistical Inference for Stochastic Processes》2003,6(3):291-307
We prove that the empirical L
2-risk minimizing estimator over some general type of sieve classes is universally, strongly consistent for the regression
function in a class of point process models of Poissonian type (random sampling processes). The universal consistency result
needs weak assumptions on the underlying distributions and regression functions. It applies in particular to neural net classes
and to radial basis function nets. For the estimation of the intensity functions of a Poisson process a similar technique
yields consistency of the sieved maximum likelihood estimator for some general sieve classes.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
997.
998.
Gradimir V. Milovanovi? Aleksandar S. Cvetkovi? 《Journal of Mathematical Analysis and Applications》2005,311(1):191-208
We present some sharp inequalities for symmetric functions and give an application to orthogonal polynomials. 相似文献
999.
C. S. Unnikrishnan 《Pramana》2005,65(3):359-379
I discuss in detail the result that the Bell’s inequalities derived in the context of local hidden variable theories for discrete
quantized observables can be satisfied only if a fundamental conservation law is violated on the average. This result shows
that such theories are physically nonviable, and makes the demarcating criteria of the Bell’s inequalities redundant. I show
that a unique correlation function can be derived from the validity of the conservation law alone and this coincides with
the quantum mechanical correlation function. Thus, any theory with a different correlation function, like any local hidden
variable theory, is incompatible with the fundamental conservation laws and space-time symmetries. The results are discussed
in the context of two-particle singlet and triplet states, GHZ states, and two-particle double slit interferometry. Some observations
on quantum entropy, entanglement, and nonlocality are also discussed. 相似文献
1000.
N. S. Bakhvalov A. V. Knyazev R. R. Parashkevov 《Numerical Linear Algebra with Applications》2002,9(2):115-139
We prove extension theorems in the norms described by Stokes and Lamé operators for the three‐dimensional case with periodic boundary conditions. For the Lamé equations, we show that the extension theorem holds for nearly incompressible media, but may fail in the opposite limit, i.e. for case of absolutely compressible media. We study carefully the latter case and associate it with the Cosserat problem. Extension theorems serve as an important tool in many applications, e.g. in domain decomposition and fictitious domain methods, and in analysis of finite element methods. We consider an application of established extension theorems to an efficient iterative solution technique for the isotropic linear elasticity equations for nearly incompressible media and for the Stokes equations with highly discontinuous coefficients. The iterative method involves a special choice for an initial guess and a preconditioner based on solving a constant coefficient problem. Such preconditioner allows the use of well‐known fast algorithms for preconditioning. Under some natural assumptions on smoothness and topological properties of subdomains with small coefficients, we prove convergence of the simplest Richardson method uniform in the jump of coefficients. For the Lamé equations, the convergence is also uniform in the incompressible limit. Our preliminary numerical results for two‐dimensional diffusion problems show fast convergence uniform in the jump and in the mesh size parameter. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献