V. I. Kozak

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Articles: 2

The inner structure of the block Jacobi type matrix related to the complex moment problem with the measure supported on the second order curve

Mykola Dudkin, Olga Dyuzhenkova, Valentyna Kozak

↓ Abstract   |   Article (.pdf)

MFAT 28 (2022), no. 3, 209-227


We present an exact inner structure of the block Jacobi type matrix related to the complex moment problem with the corresponding measure supported on an arbitrary second order curve in the complex plane. For completeness of the study we also present a solution of the direct and inverse spectral problems for such matrices. In this the way, we give a necessary and sufficient condition under which a matrix in the CMV-form generates a (pre)normal operator, namely, not obligatory a unitary one.

Надано точну внутрішню структуру блочної якоюієвої матриці, яка пов'язана з комплексною проблемою моментів і мірою, що міє носій на довільній кривій другого порядку в комплексній площині. Для повноти дослідження подаємо також розв'язок прямої та оберненої спектральних задачі для таких матриць. Ми також даємо необхідну і достатню умову зв якої CMV-матриця породжує (пре)нормальний оператор, а саме не обов'язково унітарний.

Direct and inverse spectral problems for block Jacobi type bounded symmetric matrices related to the two dimensional real moment problem

Mykola E. Dudkin, Valentyna I. Kozak

↓ Abstract   |   Article (.pdf)

MFAT 20 (2014), no. 3, 219-251


We generalize the connection between the classical power moment problem and the spectral theory of selfadjoint Jacobi matrices. In this article we propose an analog of Jacobi matrices related to some system of orthonormal polynomials with respect to the measure on the real plane. In our case we obtained two matrices that have a block three-diagonal structure and are symmetric operators acting in the space of $l_2$ type. With this connection we prove the one-to-one correspondence between such measures defined on the real plane and two block three-diagonal Jacobi type symmetric matrices. For the simplicity we investigate in this article only bounded symmetric operators. From the point of view of the two dimensional moment problem this restriction means that the measure in the moment representation (or the measure, connected with orthonormal polynomials) has compact support.

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