Abstract and Applied Analysis
Volume 2010 (2010), Article ID 902638, 18 pages
Research Article

Green's Function and Convergence of Fourier Series for Elliptic Differential Operators with Potential from Kato Space

Department of Mathematical Sciences, University of Oulu, P. O. Box 3000, 90014 Oulu, Finland

Received 29 August 2009; Accepted 4 February 2010

Academic Editor: Martin D. Schechter

Copyright © 2010 Valery Serov. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


We consider the Friedrichs self-adjoint extension for a differential operator A of the form A=A0+q(x), which is defined on a bounded domain Ωn, n1 (for n=1 we assume that Ω=(a,b) is a finite interval). Here A0=A0(x,D) is a formally self-adjoint and a uniformly elliptic differential operator of order 2m with bounded smooth coefficients and a potential q(x) is a real-valued integrable function satisfying the generalized Kato condition. Under these assumptions for the coefficients of A and for positive λ large enough we obtain the existence of Green's function for the operator A+λI and its estimates up to the boundary of Ω. These estimates allow us to prove the absolute and uniform convergence up to the boundary of Ω of Fourier series in eigenfunctions of this operator. In particular, these results can be applied for the basis of the Fourier method which is usually used in practice for solving some equations of mathematical physics.