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On the spectra of non-selfadjoint differential operators and their adjoints in direct sum spaces. (English) Zbl 1023.34076

Summary: The general ordinary quasidifferential expression \(M_p\) of \(n\)th order, with complex coefficients and its formal adjoint \(M_p^+\) on any finite number of intervals \(I_{p}=(a_p,b_p)\), \(p=1,\dots N\), are considered in the setting of the direct sums of \(L_{w_p}^{2}(a_p,b_p)\)-spaces of functions defined on each of the separate intervals. And a number of results concerning the location of the point spectra and regularity fields of general differential operators generated by such expressions are obtained.

MSC:

34L05 General spectral theory of ordinary differential operators
34L15 Eigenvalues, estimation of eigenvalues, upper and lower bounds of ordinary differential operators
47E05 General theory of ordinary differential operators
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