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Model Spaces for Compositions of Q ‐ Functions
Author(s) -
Kaltenbäck Michael
Publication year - 1998
Publication title -
mathematische nachrichten
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.913
H-Index - 50
eISSN - 1522-2616
pISSN - 0025-584X
DOI - 10.1002/mana.19981950109
Subject(s) - mathematics , extension (predicate logic) , pure mathematics , function (biology) , connection (principal bundle) , composition (language) , tensor (intrinsic definition) , relation (database) , hilbert space , mathematical analysis , geometry , linguistics , philosophy , database , evolutionary biology , computer science , biology , programming language
Given two Q ‐ functions f and g , a symmetric relation and a selfadjoint extension is constructed whose Q ‐ function is the composition f o g. To obtain this result we use the concept of tensor products of Hilbert spaces. Furthermore for a symmetric relation S and a selfadjoint extension A the Q ‐ function of S and A is related to the Q ‐ function of S −1 and A −1 . This connection is used to characterize some properties of S and A by means of their Q ‐ function.