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Completely continuous inverses of ordinary differential operators

1969
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Proceedings of the American Mathematical Society
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Many important properties, such as the absence of essential spectrum, follow when an ordinary differential operator comes from a differential expression such that the minimal operator has completely continuous inverse. This always happens in the case of a compact interval. On infinite intervals it happens much less frequently, however. To assure that the minimal operator is 1-1, we analyze the question only on intervals of type I=[a, oo). By an ordinary differential expression r we mean an

doi:10.1090/s0002-9939-1969-0246160-x
fatcat:bfsyo55fxjgwhngtdihjtdvqri