Abstract
We consider the spectral problem for the Schrödinger operator with an integral perturbation in the periodic boundary conditions. The unperturbed problem is assumed to have multiple eigenvalues and a system of eigenfunctions forming a Riesz basis in L 2(0, 1). We show that the basis property of systems of root functions of the problem can change under arbitrarily small changes in the kernel of the integral perturbation.
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Original Russian Text © M.A. Sadybekov, N.S. Imanbaev, 2012, published in Differentsial’nye Uravneniya, 2012, Vol. 48, No. 6, pp. 889–893.
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Sadybekov, M.A., Imanbaev, N.S. On the basis property of root functions of a periodic problem with an integral perturbation of the boundary condition. Diff Equat 48, 896–900 (2012). https://doi.org/10.1134/S0012266112060146
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DOI: https://doi.org/10.1134/S0012266112060146