TITLE:
On the Spectra of General Ordinary Quasi-Differential Operators and Their L2w-Solutions
AUTHORS:
Sobhy El-Sayed Ibrahim
KEYWORDS:
General Ordinary Quasi-Differential Expressions, Regular and Singular End-Points, Singular Differential Operators, Essential Spectra, Point Spectra and Regularity Fields
JOURNAL NAME:
Advances in Pure Mathematics,
Vol.12 No.3,
March
21,
2022
ABSTRACT: In this paper, we consider the general ordinary quasi-differential expression τ of order n with complex coefficients and its formal adjoint τ+ on the interval [a,b). We shall show in the case of one singular end-point and under suitable conditions that all solutions of a general ordinary quasi-differential equation are in the weighted Hilbert space provided that all solutions of the equations and its adjoint are in . Also, a number of results concerning the location of the point spectra and regularity fields of the operators generated by such expressions may be obtained. Some of these results are extensions or generalizations of those in the symmetric case, while the others are new.