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941.
H. De Bie 《Journal of Mathematical Analysis and Applications》2008,345(1):147-164
In this paper extensions of the classical Fourier, fractional Fourier and Radon transforms to superspace are studied. Previously, a Fourier transform in superspace was already studied, but with a different kernel. In this work, the fermionic part of the Fourier kernel has a natural symplectic structure, derived using a Clifford analysis approach. Several basic properties of these three transforms are studied. Using suitable generalizations of the Hermite polynomials to superspace (see [H. De Bie, F. Sommen, Hermite and Gegenbauer polynomials in superspace using Clifford analysis, J. Phys. A 40 (2007) 10441-10456]) an eigenfunction basis for the Fourier transform is constructed. 相似文献
942.
We say that A has fractional powers {A
t
}
t≥0 if there exists a nondegenerate C-regularized semigroup {W(t)}
t≥0 such that A=C
−1
W(1); then A
t
≡C
−1
W(t). We show that this generalizes the usual definition of fractional powers for nonnegative operators, and enables many operators
with spectrum containing the entire unit disc to have fractional powers. Our definition gives clear, simple proofs of the
basic properties of fractional powers. We show that, for nonnegative operators, the fractional powers with the property that,
if A is of type θ, then A
t
is of type t
θ, whenever t
θ<π, are unique. More generally, for injective G∈B(X) commuting with A, we show that an operator A of G-regularized type θ has a unique family of fractional powers with the property that A
t
is of G-regularized type t
θ whenever t
θ<π. This leads to a construction of fractional powers of operators with polynomially bounded resolvent outside of an appropriate
sector. We show that an operator is of regularized type if and only if it has exponentially bounded regularized imaginary
powers.
This work was done while the second author was visiting Ohio University, with funding from Universitat de València. He would
like to thank Ohio University and Professor deLaubenfels for their hospitality and support. 相似文献
943.
Lamberton 《Applied Mathematics and Optimization》2008,45(3):283-324
One way to compute the value function of an optimal stopping problem along Brownian paths consists of approximating Brownian
motion by a random walk. We derive error estimates for this type of approximation under various assumptions on the distribution
of the approximating random walk. 相似文献
944.
R. B. Pandey B. L. Farmer 《Journal of polymer science. Part A, Polymer chemistry》2008,46(24):2696-2710
Exfoliation of a stack of sheets (a model for clay platelets) in a dynamic matrix of polymer chains is investigated by a computer simulation model. How the interplay between the thermodynamics (interaction-driven) and conformational (structural constraints) entropy affects the exfoliation of sheets is the subject of this study. A stack of four sheets with a small initial interlayer distance constitutes the layer on a discrete lattice. The layered platelets are immersed in a matrix represented by the mobile polymer chains which occupy a fraction (concentration) of the lattice sites. Both sheets and chains are modeled by the bond-fluctuation mechanism and execute their stochastic motion via Metropolis algorithm. An attractive and a repulsive interaction between the polymer matrix and platelets are considered. Exfoliation of the sheets is examined by varying the molecular weight of the polymer chains forming a dynamic network matrix with various degrees of entanglements. At low-molecular weight of the polymer, exfoliation is achieved with repulsive interaction and the exfoliation is suppressed with attractive matrix as sheets stick together via polymer mediated interaction introduced by intercalated polymer chains. Increasing the molecular weight of the polymer matrix suppresses the exfoliation of sheets primarily due to enhanced entanglement—at high-molecular weight (with the radius of gyration of polymer chains larger than the characteristic linear dimension of the platelets), the stacked (layered) morphology is arrested via entropic trapping and exfoliation ceases to occur. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 2696–2710, 2008 相似文献
945.
E. Ben-Naim F. Vazquez S. Redner 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,49(4):531-538
We model the dynamics of social structure by a simple interacting particle
system. The social standing of an individual agent is represented by an
integer-valued fitness that changes via two offsetting processes. When two
agents interact one advances: the fitter with probability p and the less
fit with probability 1-p. The fitness of an agent may also decline with
rate r. From a scaling analysis of the underlying master equations for
the fitness distribution of the population, we find four distinct social
structures as a function of the governing parameters p and r. These
include: (i) a static lower-class society where all agents have finite
fitness; (ii) an upwardly-mobile middle-class society; (iii) a hierarchical
society where a finite fraction of the population belongs to a middle class
and a complementary fraction to the lower class; (iv) an egalitarian
society where all agents are upwardly mobile and have nearly the same
fitness. We determine the basic features of the fitness distributions in
these four phases. 相似文献
946.
Itai Benjamini 《Journal of Theoretical Probability》1991,4(3):631-637
In this note we construct two quasi-isometric graphs. One admits an infinite dimensional space of nonconstant bounded harmonic functions, while the other admits only constant bounded harmonic functions. Translation of the construction to manifolds answers a problem due to T. Lyons. 相似文献
947.
Robert J. Elliott Brian D.O. Anderson 《Stochastic Processes and their Applications》1985,19(2):327-339
The paper considers a diffusion evolving in n. The stochastic differential equations giving the same process, but with the time parameter evolving in the negative direction, are obtained under a certain integrability hypothesis when the diffusion has a density function on a time varying submanifold of n. 相似文献
948.
Norbert Herrndorf 《Journal of multivariate analysis》1984,15(1):141-146
In this note a functional central limit theorem for ?-mixing sequences of I. A. Ibragimov (Theory Probab. Appl.20 (1975), 135–141) is generalized to nonstationary sequences (Xn)n ∈ , satisfying some assumptions on the variances and the moment condition for some b > 0, ? > 0. 相似文献
949.
有关保险基金投资的研究 总被引:2,自引:0,他引:2
本文我们对保险基金投资的必要性进行了简单说明,然后,利用保费收取与保险赔付之间的时滞,对保险基金进行投资研究,建立了考虑投资人风险偏好的连续时间的保险投资模型,并对最优投资比例进行了研究。 相似文献
950.
Chaos synchronization of two identical Chua systems with the same fractional order is studied by utilizing the Pecora–Carroll (PC) method, the active–passive decomposition (PAD) method, the one-way coupling method and the bidirectional coupling one. The sufficient conditions for achieving synchronization between these two systems are derived via the Laplace transformation theory. Numerical simulations show the effectiveness of the theoretical analyses. 相似文献