Quadratically normal and congruence-normal matrices
A matrix A ∈ C n×n is unitarily quasidiagonalizable if A can be brought by a unitary similarity transformation to a block diagonal form with 1 × 1 and 2 × 2 diagonal blocks. In particular, the square roots of normal matrices, i.e., the so-called quadratically normal matrices are unitarily quasidiagonalizable. A matrix A ∈ C n×n is congruence-normal if \( B = A\overline A \) is a conventional normal matrix. We show that every congruence-normal matrix A can be brought by a unitary congruence transformation to a block diagonal form with 1 × 1 and 2 × 2 diagonal blocks. Our proof emphasizes andexploitsalikenessbetween theequations X 2 = B and \( X\overline X = B \) for a normal matrix B. Bibliography: 13 titles.
KeywordsRussia Similarity Transformation Normal Matrix Diagonal Block Diagonal Form
Unable to display preview. Download preview PDF.