2 citations · 6 across the 8 of their papers we have counts for
8 papers
Invertible completions of FLI and FRI upper triangular operator matrices
Nikola Sarajlija
If and are given operators, denote by an operator matrix of the form $$M_C=\begin{pmatrix} A & C\\ 0 & B \end{pm…
Completion problem of upper triangular operator matrices on arbitrary Banach spaces
Nikola Sarajlija, Dragan S. Djordjević
We solve the completion problem of upper triangular operator matrix acting on a direct sum of Banach spaces and hence generalize the famous result of Han, Lee, Lee (Proc…
Invertibility properties of operator matrices on Hilbert spaces
Nikola Sarajlija
Denote by an upper triangular operator matrix of dimension whose diagonal entries are given and the others are unknown. In this article we provide necessary and suff…
Upper triangular operator matrices and stability of their various spectra
Nikola Sarajlija
Denote by an upper triangular operator matrix of dimension whose diagonal entries are known, where is an unknown tuple of operat…
Intersections of various spectra of operator matrices
Nikola Sarajlija
This paper is concerned with general upper triangular operator matrices with given diagonal entries. We characterize perturbations of the left (right) essential spectru…
Fredholmness and Weylness of block operator matrices
Nikola Sarajlija
This paper has aim to characterize Fredholmness and Weylness of upper triangular operator matrices having arbitrary dimension n. We present various characterization results in the…
Algebraic properties of the group inverse
Nikola Sarajlija
We investigate properties of the group inverse in rings with unit related to products and differences of idempotents, and thus we extend some results from \cite{DENG} to more gener…
Perturbing the spectrum of operator
Nikola Sarajlija
Let denote a partial upper triangular operator matrix whose diagonal entries are given and the others unknown. In this article we have aim to find characterizations of (…