On the essential spectrum of a class of singular matrix differential operators. II. Weyl's limit circles for the Hain-Lust operator whenever quasi-regularity conditions are not satisfied
The essential spectrum of the singular matrix differential operator of mixed order determined by the operator matrix [GRAPHICS] is studied. Investigation of the essential spectrum of the corresponding self-adjoint operator is continued but; now without assuming that the quasi-regularity conditions are satisfied. New conditions that guarantee that the operator is semi-bounded from below are derived