On the convergence of biorthogonal series corresponding to nonselfadjoint Sturm-Liouville operator with discontinuous coefficients. (English) Zbl 0613.34021
Extending earlier work of V. A. Il’in [Mat. Zametki 22, 679-698 (1977; Zbl 0364.34011)], the author establishes an expansion theorem for eigenfunctions and associated functions (suitably defined) of the operator L, where \(Lu=(pu')'+qu\) almost everywhere on (a,b), p is a positive step function and q is a locally integrable complex-valued function.
Reviewer: A.L.Andrew
MSC:
34L99 | Ordinary differential operators |
42A20 | Convergence and absolute convergence of Fourier and trigonometric series |