2 problems

Let $A=B+iC\in\mathcal A_n$, where $B$ and $C$ are the real and imaginary parts of an accretive-dissipative matrix, and suppose that … Here $\kappa$ denotes the condition number an…

Let $A\in \mathbb{M}_{n}(\bold C)$ be an accretive-dissipative matrix, partitioned as … where $A_{11}$ is an $m\times m$ principal block and $A_{22}$ is the complementary block. Sh…