The structured distance to nearly normal matrices
The author studies the class of complex tridiagonal \(n \times n\) matrices \(T\) such that \(T^*T-T T^*=\Delta\), where \(\Delta\) is a fixed real diagonal matrix. Some results concerning the characterization of these matrices, with respect to the diagonal matrix \(\Delta\), together with various distance-type formulas based on the Frobenius norm are also derived.
scientific article; zbMATH DE number 5692979