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.


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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