SPECTRAL EXPANSION SERIES WITH PARENTHESIS FOR THE NONSELF-ADJOINT PERIODIC DIFFERENTIAL OPERATORS

摘要

In this paper we construct the spectral expansion for the differential operator generated in L-2 (-infinity, infinity) by ordinary differential expression of arbitrary order with periodic complex-valued coefficients by introducing new concepts as essential spectral singularities and singular quasimomenta and using the series with parenthesis. Moreover, we find a criteria for which the spectral expansion coincides with the Gelfand expansion for the self-adjoint case.