Ra. Horn et al., LINEAR-OPERATORS PRESERVING COMPLEX ORTHOGONAL EQUIVALENCE ON MATRICES, SIAM journal on matrix analysis and applications, 15(2), 1994, pp. 519-529
Two complex matrices A and B are said to be (complex) orthogonally equ
ivalent if there exist (complex) orthogonal matrices Q1 and Q2 such th
at A = Q1BQ2. In this note the authors obtain characterization of line
ar operators that preserve complex orthogonal equivalence.