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Bibliographic Details
Main Authors: Fischbacher, Christoph, Gesztesy, Fritz, Littlejohn, Lance L.
Format: Preprint
Published: 2025
Subjects:
Online Access:https://arxiv.org/abs/2504.06506
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Table of Contents:
  • This largely pedagogical paper recalls some facts on defect numbers of products of closed operators employing results from the theory of semi-Fredholm operators and then applies these facts to positive integer powers of symmetric operators and subsequently to certain minimal Sturm--Liouville and minimal higher even-order ordinary and partial differential operators. We also point out some unexpected missed opportunities when comparing the work of different groups on this subject.