Abstract
The extension problem for closed symmetric operators with a gap is studied. A new kind of parametrization of extensions (the so-called Krein model) is developed. The notion of a singular operator plays the key role in our approach. We give an explicit description of extensions and establish the spectral properties of extended operators.
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Published in Ukrainskii Matematicheskii Zhurnal, Vol. 46, Nos. 1–2, pp. 37–54, January–February, 1994.
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Brasche, J.F., Koshmanenko, V. & Neidhardt, H. New aspects of Krein's extension theory. Ukr Math J 46, 34–53 (1994). https://doi.org/10.1007/BF01056999
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DOI: https://doi.org/10.1007/BF01056999