Inverse problems in differential operators and spectral theory constitute a vibrant research area where one seeks to determine unknown parameters within differential equations from observed spectral ...

Pseudo-differential operators have emerged as pivotal tools in modern analysis, generalising classical differential operators to encapsulate non-local behaviour via their symbol calculus. Their ...

Journal of Operator Theory, Vol. 64, No. 2 (Fall 2010), pp. 401-416 (16 pages) We investigate the behaviour of the spectrum of selfadjoint operators in Krein spaces under perturbations with uniformly ...

Our aim is to prove one relation between characteristic determinant and norms of orthogonal eigenvectors of eigenvalue problem for fourth order differential operator equation.That relation as appears ...