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Non-self-adjoint Differential Operators
We describe methods which have been used to analyze the spectrum of non-self-adjoint differential operators, emphasizing the differences from the self-adjoint theory. We find that even in cases in which the eigenfunctions can be determined explicitly, they often do not form a basis; this is closely related to a high degree of instability of the eigenvalues under small perturbations of the opera...
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ژورنال
عنوان ژورنال: Transactions of the American Mathematical Society
سال: 1957
ISSN: 0002-9947
DOI: 10.1090/s0002-9947-1957-0088625-6