30 citations · 56 across the 4 of their papers we have counts for
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A generalization of the Theorem
Vadim Kostrykin, Konstantin A. Makarov, Alexander K. Motovilov
Let be a bounded self-adjoint operator on a separable Hilbert space and a closed invariant subspace of .…
On the existence of solutions to the operator Riccati equation and the tanΘtheorem
Vadim Kostrykin, Konstantin A. Makarov, Alexander K. Motovilov
Let A and C be self-adjoint operators such that the spectrum of A lies in a gap of the spectrum of C and let d>0 be the distance between the spectra of A and C. We prove that under…
Existence and uniqueness of solutions to the operator Riccati equation. A geometric approach
Vadim Kostrykin, Konstantin A. Makarov, Alexander K. Motovilov
We introduce a new concept of unbounded solutions to the operator Riccati equation and give a complete description of its solutions associated…
On a Subspace Perturbation Problem
Vadim Kostrykin, Konstantin A. Makarov, Alexander K. Motovilov
We discuss the problem of perturbation of spectral subspaces for linear self-adjoint operators on a separable Hilbert space. Let and be bounded self-adjoint operators. Assu…
Factorization Theorem for the Transfer Function Associated with an Unbounded Non-Self-Adjoint 2x2 Operator Matrix
V. Hardt, R. Mennicken, A. K. Motovilov
We construct operators which factorize the transfer function associated with a non-self-adjoint 2x2 operator matrix whose diagonal entries can have overlapping spectra and whose of…
Factorization theorem for the transfer function of a 2x2 operator matrix with unbounded couplings
V. Hardt, R. Mennicken, A. K. Motovilov
We consider the analytic continuation of the transfer function associated with a 2x2 operator matrix having unbounded couplings into unphysical sheets of its Riemann surface. We co…