3. Electronic Theses and Dissertations (ETDs) - All submissions
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Item Spectral theory of self-adjoint higher order differential operators with eigenvalue parameter dependent boundary conditions(2012-09-05) Zinsou, BertinWe consider on the interval [0; a], rstly fourth-order di erential operators with eigenvalue parameter dependent boundary conditions and secondly a sixth-order di erential operator with eigenvalue parameter dependent boundary conditions. We associate to each of these problems a quadratic operator pencil with self-adjoint operators. We investigate the spectral proprieties of these problems, the location of the eigenvalues and we explicitly derive the rst four terms of the eigenvalue asymptotics.Item Self-adjoint fourth order differential operators with eigenvalue parameter dependent boundary conditions(2009-09-14T08:40:01Z) Zinsou, BertinThe eigenvalue problem y(4)(¸; x) ¡ (gy0)0(¸; x) = ¸2y(¸; x) with boundary conditions y(¸; 0) = 0; y00(¸; 0) = 0; y(¸; a) = 0; y00(¸; a) + i®¸y0(¸; a) = 0; where g 2 C1[0; a] is a real valued function and ® > 0, has an operator pencil L(¸) = ¸2 ¡ i®¸K ¡ A realization with self-adjoint operators A, M and K. It was shown that the spectrum for the above boundary eigenvalue problem is located in the upper-half plane and on the imaginary axis. This is due to the fact that A, M and K are self-adjoint. We consider the eigenvalue problem y(4)(¸; x) ¡ (gy0)0(¸; x) = ¸2y(¸; x) with more general ¸-dependent separated boundary conditions Bj(¸)y = 0 for j = 1; ¢ ¢ ¢ ; 4 where Bj(¸)y = y[pj ](aj) or Bj(¸)y = y[pj ](aj) + i²j®¸y[qj ](aj), aj = 0 for j = 1; 2 and aj = a for j = 3; 4, ® > 0, ²j = ¡1 or ²j = 1. We assume that at least one of the B1(¸)y = 0, B2(¸)y = 0, B3(¸)y = 0, B4(¸)y = 0 is of the form y[p](0)+i²®¸y[q](0) = 0 or y[p](a)+i²®¸y[q](a) = 0 and we investigate classes of boundary conditions for which the corresponding operator A is self-adjoint.