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81.
Jędrzej Śniatycki 《Journal of Fixed Point Theory and Applications》2008,3(2):307-315
We consider a Hamiltonian action of a connected group G on a symplectic manifold (P, ω) with an equivariant momentum map and its quantization in terms of a K?hler polarization which gives rise to a unitary representation of G on a Hilbert space . If O is a co-adjoint orbit of G quantizable with respect to a K?hler polarization, we describe geometric quantization of algebraic reduction of J
−1(O). We show that the space of normalizable states of quantization of algebraic reduction of J
−1(O) gives rise to a projection operator onto a closed subspace of on which is unitarily equivalent to a multiple of the irreducible unitary representation of G corresponding to O. This is a generalization of the results of Guillemin and Sternberg obtained under the assumptions that G and P are compact and that the action of G on P is free. None of these assumptions are needed here.
Dedicated to Vladimir Igorevich Arnold 相似文献
82.
More efficient estimators for marginal additive hazards model in case-cohort studies with multiple outcomes 下载免费PDF全文
Case-cohort study designs are widely used to reduce the cost of large cohort studies. When several diseases are of interest, we can use the same subcohort. In this paper, we will study the casecohort design of marginal additive hazards model for multiple outcomes by a more efficient version. Instead of analyzing each disease separately, ignoring the additional exposure measurements collected on subjects with other diseases, we propose a new weighted estimating equation approach to improve the efficiency by utilizing as much information collected as possible. The consistency and asymptotic normality of the resulting estimator are established. Simulation studies are conducted to examine the finite sample performance of the proposed estimator, which confirm the efficiency gains. 相似文献
83.
本文研究了来自同一页印刷品的中、英文文字文件,在规则的横、纵切割方式下,碎纸片的拼接复原方法.文中利用碎纸片图片边缘灰度值数据的匹配度和行间距、字高等文字排版数据,建立了一系列拼接复原模型.首先对仅纵切方式下的碎纸片拼接问题,建立了基于碎片边缘匹配的图像拼接复原模型,根据碎片边缘灰度值向量间的距离来衡量两张图片的匹配度.然后对中、英文碎纸片分别提出基于像素点投影和灰度计数的分类方法,将处在同一行的碎片分为一类,使用拼接复原模型完成行内的拼接.最后通过行间距信息完成了行与行之间的匹配,从而完成了整份文件的拼接复原. 相似文献
84.
L. Proville S. Aubry 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,15(3):405-421
We study the effective mass of the bipolarons and essentially the possibility to get both light and strongly bound bipolarons
in the Holstein-Hubbard model and some variations in the vicinity of the adiabatic limit. Several approaches to investigate
the quantum mobility of polarons and bipolarons are proposed for this model. First, the quantum fluctuations are treated as
perturbations of the mean-field (or adiabatic) approximation of the electron-phonon coupling in order to calculate the bipolaron
bands. It is found that the bipolaron mass generally remains very large except in the vicinity of the triple point of the
phase diagram (see [1]), where the bipolarons have several degenerate configurations at the adiabatic limit (single site (S0),
two sites (S1) and quadrisinglet (QS)), while the polarons are much lighter. This degeneracy reduces the bipolaron mass significantly.
Next we improve this result by variational methods (modified Toyozawa Exponential Ansatz or TEA) valid for larger quantum
perturbations away from the adiabatic limit. We first test this new method for the single polaron. We find that the triple
point of the phase diagram is washed out by the lattice quantum fluctuations which thus suppress the light bipolarons. Further
improvements of the method by hybridization of several TEA states do not change this conclusion. Next we show that some model
variations, for example a phonon dispersion may increase the stability of the (QS) bipolaron against the quantum lattice fluctuations.
We show that the triple point of the phase diagram may be stable to quantum lattice fluctuations and a very sharp mass reduction
may occur, leading to bipolaron masses of the order of 100 bare electronic mass for realistic parameters. Thus we argue that
such very light bipolarons could condense as a superconducting state at relatively high temperature when their interactions
are not too large, that is, their density is small enough. This effect might be relevant for understanding the origin of the
high superconductivity of doped cuprates far enough from half filling.
Received 15 September 1999 相似文献
85.
We consider the existence of distributional (or L
2
) solutions of the matrix refinement equation
where P is an r×r matrix with trigonometric polynomial entries.
One of the main results of this paper is that the above matrix refinement equation has a compactly supported distributional
solution if and only if the matrix P
(0) has an eigenvalue of the form 2
n
, . A characterization of the existence of L
2
-solutions of the above matrix refinement equation in terms of the mask is also given.
A concept of L
2
-weak stability of a (finite) sequence of function vectors is introduced. In the case when the function vectors are solutions
of a matrix refinement equation, we characterize this weak stability in terms of the mask.
August 1, 1996. Date revised: July 28, 1997. Date accepted: August 12, 1997. 相似文献
86.
87.
Based on the Husimi operator in pure state form introduced by Fan et al., which is a squeezed coherent state projector, and the technique of integration within an ordered product (IWOP) of operators, as well as the entangled state representations, we obtain the Husimi functions of the excited squeezed vacuum states (ESVS) and two marginal distributions of the Husimi functions of the ESVS. 相似文献
88.
In this paper, two-mode displaced excited squeezed vacuum states (TDESVS) are constructed and their normalization and completeness are investigated. Using the entangled state representation and Weyl ordering form of the Wigner operator, the Wigner functions of TDESVS are obtained and the variations of Wigner functions with the parameters m, n and r are investigated. Besides, two marginal distributions of Wigner functions of TDESVS are obtained, which exhibit some entangled properties of the two-particle's system in TDESVS. 相似文献
89.
We combine Lanczos algorithm with the thought of the refined projection method using QR factorization and propose the refined biothogonalization Lanczos method for computing the desired eigenvalues of large unsymmetric matrix. With low cost of work space and flops the algorithm cures the disease that the Ritz vectors may not converge when the Ritz values converge usingthe Lanczos method. Numerical experiments show our algorithm is considerably more stable and efficient than its counterpart. 相似文献
90.
The utility of Fiedler vectors in interrogating the structure of graphs has generated intense interest and motivated the pursuit of further theoretical results. This paper focuses on how the Fiedler vectors of one graph reveal structure in a second graph that is related to the first. Specifically, we consider a point of articulation r in the graph G whose Laplacian matrix is L and derive a related graph G{r} whose Laplacian is the matrix obtained by taking the Schur complement with respect to r in L. We show how Fiedler vectors of G{r} relate to the structure of G and we provide bounds for the algebraic connectivity of G{r} in terms of the connected components at r in G. In the case where G is a tree with points of articulation rR, we further consider the graph GR derived from G by taking the Schur complement with respect to R in L. We show that Fiedler vectors of GR valuate the pendent vertices of G in a manner consistent with the structure of the tree. 相似文献