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arXiv 1801.06013math.CA
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无穷Hankel矩矩阵的逆

Inverse of Infinite Hankel Moment Matrices

Christian Berg, Ryszard Szwarc

摘要:

令$(s_n)_{n\ge 0}$表示不定Hamburger矩序列,$\mathcal H=\{s_{m+n}\}$表示相应的正定Hankel矩阵.考虑了存在一个无限对称矩阵$\mathcal A=\{a_{j,k}\}$,它是$\mathcal H$的逆,即矩阵乘积$\mathcal A\mathcal H$由绝对收敛级数定义,且$\mathcal A\mathcal H$等于单位矩阵$\mathcal I$,一个性质称为(aci). $\mathcal A$的候选是矩量问题的再生核的系数矩阵,被认为是两个复变量的整函数。我们说矩问题具有性质(aci),如果(aci)对这个矩阵$\mathcal A$成立.我们表明,这是真实的许多经典的不定矩问题,但不是一个三次生灭过程的对称化版本的Valent和合作者研究。本文主要考虑对称不定矩问题,并利用正交多项式的递推系数给出了(aci)成立的若干充分条件。一个充分条件是快速增加的递归系数的意义上说,连续的条款之间的商是一致有界的常数严格小于1。我们还给出一个简单的例子,其中(aci)成立,但$\mathcal H$的逆矩阵是高度非唯一的。

英文摘要:

Let $(s_n)_{n\ge 0}$ denote an indeterminate Hamburger moment sequence and let $\mathcal H=\{s_{m+n}\}$ be the corresponding positive definite Hankel matrix. We consider the question if there exists an infinite symmetric matrix $\mathcal A=\{a_{j,k}\}$, which is an inverse of $\mathcal H$ in the sense that the matrix product $\mathcal A\mathcal H$ is defined by absolutely convergent series and $\mathcal A\mathcal H$ equals the identity matrix $\mathcal I$, a property called (aci). A candidate for $\mathcal A$ is the coefficient matrix of the reproducing kernel of the moment problem, considered as an entire function of two complex variables. We say that the moment problem has property (aci), if (aci) holds for this matrix $\mathcal A$. We show that this is true for many classical indeterminate moment problems but not for the symmetrized version of a cubic birth-and-death process studied by Valent and co-authors. We consider mainly symmetric indeterminate moment problems and give a number of sufficient conditions for (aci) to hold in terms of the recurrence coefficients for the orthonormal polynomials. A sufficient condition is a rapid increase of the recurrence coefficients in the sense that the quotient between consecutive terms is uniformly bounded by a constant strictly smaller than one. We also give a simple example, where (aci) holds, but an inverse matrix of $\mathcal H$ is highly non-unique.

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