ศัพท์ทางคณิตศาสตร์
Let us clarify how the diagonal blocks of order two appear in the block diagonal form of a normal solu
tion X. Each of these blocks is again a solution to Eq. (1) (for n = 2) and is also a normal matrix. We denote
such a block by the same symbol X (omitting the indices) and consider representation (2) as the algebraic
form of this block.
The following two situations may occur:
1. At least one of the matrices A and B has a real spectrum.
2. For both A and B, some of the eigenvalues are nonreal.
We perform separate analyses for these two cases.