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4 papers
A Comparison of Two Generalisations of Triplets of Hilbert Spaces
Petru Cojuhari, Aurelian Gheondea
We compare the concept of triplet of closely embedded Hilbert spaces with that of generalised triplet of Hilbert spaces in the sense of Berezanskii by showing when they coincide, w…
Spectral and scattering theory for perturbed block Toeplitz operators
Petru Cojuhari, Jaouad Sahbani
We analyse spectral properties of a class of compact perturbations of block Toeplitz operators associated with analytic symbols. In particular, a limiting absorption principle and…
Triplets of Closely Embedded Hilbert Spaces
Petru Cojuhari, Aurelian Gheondea
We obtain a general concept of triplet of Hilbert spaces with closed (unbounded) embeddings instead of continuous (bounded) ones. The construction starts with a positive selfadjoin…
Lax-Phillips scattering theory for PT-symmetric ρ-perturbed operators
Petru A. Cojuhari, Sergii Kuzhel
The S-matrices corresponding to PT-symmetric ρ-perturbed operators are defined and calculated by means of an approach based on an operator-theoretical interpretation of the Lax-Phi…