A class of differential operators with complex coefficients and compact resolvent. (Q1746002)

The authors consider the problem of a second-order singular differential operator with complex coefficients in the discrete spectrum case. The Titchmarsh-Weyl \(m\)-function is constructed without the use of nesting circles, and it is then used to give a representation of the resolvent operator. Under conditions on the growth of the coefficients, the resolvent operator is proved to be Hilbert-Schmidt and the root subspaces are shown to be complete in the associated Hilbert space.