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排序方式: 共有4485条查询结果,搜索用时 15 毫秒
41.
Alain Joye 《Journal of statistical physics》1994,75(5-6):929-952
The spectrum of the Floquet operator associated with time-periodic perturbations of discrete Hamiltonians is considered. If the gap between successive eigenvalues
j
of the unperturbed Hamiltonian grows as
j
-
j-1
j
and the multiplicity of
j
grows asj
with >0 asj tends to infinity, then the corresponding Floquet operator possesses no absolutely continuous spectrum provided the perturbation is smooth enough. 相似文献
42.
We present an algorithm for numerically computing an absolutely continuous invariant measure associated with a piecewiseC
2 expanding mappingS: on a bounded region R
N. The method is based on the Galerkin projection principle for solving an operator equation in a Banach space. With the help of the modern notion of functions of bounded variation in multidimension, we prove the convergence of the algorithm. 相似文献
43.
Andrea Posilicano 《Potential Analysis》1996,5(3):241-271
We prove a convergence theorem for sequences of Diffusion Processes corresponding to Dirichlet Forms of the kind
.We obtain convergence in total variation norm of the corresponding probability measures on the path space C(+;d) under hypotheses which, for example, are satisfied in the case of H
loc
1
(
d
)-convergence of the 's, but we can allow more singular situations as regards the approximating sequences. We use then these results to give a criterion of convergence for generalized Schrödinger operators in which the potential function should not necessarily exists as a measurable function. We obtain convergence not only in strong resolvent sense, but we also obtain convergence in the uniform operator topology up to sets of arbitrarily small Lebesgue measure. Applications to the problem of the approximation of ordinary Schrödinger operators by generalized ones corresponding to zero-range interactions are given. 相似文献
44.
Michael Renardy 《Proceedings of the American Mathematical Society》1996,124(8):2451-2453
Let be the infinitesimal generator of a -semigroup of operators in a Hilbert space. We consider the class of operators , where is bounded. It is proved that the spectrum of determines the growth of the associated semigroup for ``most" operators (in the sense of Baire category).
45.
Friedbert Prü fer Franco Tricerri Lieven Vanhecke 《Transactions of the American Mathematical Society》1996,348(11):4643-4652
We first prove that a Riemannian manifold with globally constant additive Weyl invariants is locally homogeneous. Then we use this result to show that a manifold whose Laplacian commutes with all invariant differential operators is a locally homogeneous space.
46.
47.
André Julg 《Theoretical chemistry accounts》1988,74(4):323-330
The complete symmetrization with respect to x, p
x,... of the operators associated with dynamical properties can sometimes lead to results different from those obtained by the conventional quantum formalism based on the rule op (A
2)=(op A)2. For example, angular momentum operators M
z
2
and M
2 are modified by the additive constants
2/2 and 3
2/2 respectively (M
20 for electron in the ground state of H atom, rotator never at rest, but spectra unchanged); the average quadratic dispersion of energy is different from zero. These results can be interpreted by assuming that the system is never strictly isolated but communicates with the other systems of the universe by means of electromagnetic interactions. Quantum mechanics would give only average values over a sufficiently long time and would exhibit a quasi-ergodic character. Examples supporting this possibility are given, in particular that of arsines for which quantum forecasts correspond to average values over one year.Dedicated to Professor J. Koutecký on the occasion of his 65th birthday 相似文献
48.
Let X
1, X
2, ..., X
n be independent observations from an (unknown) absolutely continuous univariate distribution with density f and let % MathType!MTEF!2!1!+-% feaafeart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXafv3ySLgzGmvETj2BSbqefm0B1jxALjhiov2D% aebbfv3ySLgzGueE0jxyaibaiiYdd9qrFfea0dXdf9vqai-hEir8Ve% ea0de9qq-hbrpepeea0db9q8as0-LqLs-Jirpepeea0-as0Fb9pgea% 0lrP0xe9Fve9Fve9qapdbaqaaeGacaGaaiaabeqaamaabaabcaGcba% GabmOzayaajaGaaiikaiaadIhacaGGPaGaeyypa0Jaaiikaiaad6ga% caWGObGaaiykamaaCaaaleqabaGaeyOeI0IaaGymaaaakmaaqadaba% Gaam4saiaacUfadaWcgaqaaiaacIcacaWG4bGaeyOeI0Iaamiwamaa% BaaaleaacaWGPbaabeaakiaacMcaaeaacaWGObGaaiyxaaaaaSqaai% aadMgacqGH9aqpcaaIXaaabaGaamOBaaqdcqGHris5aaaa!5356!\[\hat f(x) = (nh)^{ - 1} \sum\nolimits_{i = 1}^n {K[{{(x - X_i )} \mathord{\left/ {\vphantom {{(x - X_i )} {h]}}} \right. \kern-\nulldelimiterspace} {h]}}} \] be a kernel estimator of f(x) at the point x, \s-<x<, with h=h
n
(h
n
O and nh
n
, as n) the bandwidth and K a kernel function of order r. Optimal rates of convergence to zero for the bias and mean square error of such estimators have been studied and established by several authors under varying conditions on K and f. These conditions, however, have invariably included the assumption of existence of the r-th order derivative for f at the point x. It is shown in this paper that these rates of convergence remain valid without any differentiability assumptions on f at x. Instead some simple regularity conditions are imposed on the density f at the point of interest. Our methods are based on certain results in the theory of semi-groups of linear operators and the notions and relations of calculus of finite differences.This research was supported in part by grants from the Natural Sciences and Engineering Research Council of Canada and the University of Alberta Central Research Fund. 相似文献
49.
C-半群的Lumer-Phillips定理与C-Hermitian算子 总被引:1,自引:0,他引:1
本文给出了稠定闭算子A(或A的扩张)生成压缩C-半群的充分条件,且在C是等距算子时,证明了该条件是必要的,推广了Lumer-Phillips定理.并用结果刻划了等距C-群的生成元. 相似文献
50.
In this paper, the authors study the integral operator
Sφf(z) = Z
C
φ(z, w)f(w)dλα(w)
induced by a kernel function φ(z, ·) ∈ F
∞α between Fock spaces. For 1 ≤ p ≤ ∞, they
prove that Sφ : F
1
α → F
p
α is bounded if and only if
sup
a∈C
kSφkakp,α < ∞, (?)
where ka is the normalized reproducing kernel of F
2
α; and, Sφ : F
1
α → F
p
α is compact if and
only if
lim
|a|→∞
kSφkakp,α = 0.
When 1 < q ≤ ∞, it is also proved that the condition (?) is not sufficient for boundedness
of Sφ : F
q
α → F
p
α .
In the particular case φ(z, w) = eαzw?(z ? w) with ? ∈ F
2
α, for 1 ≤ q < p < ∞, they
show that Sφ : F
p
α → F
q
α is bounded if and only if ? = 0; for 1 < p ≤ q < ∞, they give
sufficient conditions for the boundedness or compactness of the operator Sφ : F
p
α → F
q
α. 相似文献