Truncated moment problems in the class of generalized Nevanlinna functions

• Published in: Mathematische Nachrichten Vol. 285; no. 14-15; pp. 1741 - 1769
• Main Authors: Derkach, Vladimir, Hassi, Seppo, de Snoo, Henk
• Format: Journal Article
• Language: English
• Published: Germany WILEY-VCH Verlag 01-10-2012; WILEY‐VCH Verlag; Wiley Subscription Services, Inc
• Subjects: 46C20; 47A57; asymptotic expansion; factorization; Generalized Nevanlinna function; Hankel matrix; moment problem; MSC Primary: 30E05; Schur-Chebyshev algorithm; Secondary: 15B57; Studies
• ISSN: 0025-584X; 1522-2616
• DOI: 10.1002/mana.201100268

Truncated moment and related interpolation problems in the class of generalized Nevanlinna functions are investigated. General solvability criteria will be established and complete parametrizations of solutions are given. The framework used in the paper allows the treatment of even and odd order problems in a parallel manner. The main new results concern the case where the corresponding Hankel matrix of moments is degenerate. One of the new effects in the indefinite case is that the degenerate moment problem may have infinitely many solutions. However, with a careful application of an indefinite analogue of a step‐by‐step Schur algorithm a complete description of the set of solutions will be obtained.