matrix exponential function, numerical range
For a given square matrix A, the numerical range for the exponential function e^(At), t in C, is considered. Some geometrical and topological properties of the numerical range are presented.
Chorianopoulos, Christos and Guo, Chun-Hua.
"Numerical Range for the Matrix Exponential Function",
Electronic Journal of Linear Algebra,
Volume 31, pp. 633-645.