Spectral gaps of Schrödinger operators with periodic singular potentials

By using quasi-derivatives we develop a Fourier method for studying the spectral gaps of one dimensional Schrodinger operators with periodic singular potentials v. Our results reveal a close relationship between smoothness of potentials and spectral gap asymptotics under a priori assumption v is an element of H-loc(-1)(R). They extend and strengthen similar results proved in the classical case v is an element of L-loc(2)(R).