General Sylvester and Lyapunov operators in real
and complex matrix spaces are studied, which include as a particular case the operators arising in the theory
of linear time-invariant descriptor systems. For linear
matrix operators an index which characterizes the operator
is introduced and determined for general linear matrix
operators. The problem of representing such an
operator as a sum of elementary operators is posed and solved. The dimensions
of the spaces of Lyapunov operators are determined and the concept of symmetrised singular
values of a Lyapunov operator is introduced. The application
of symmetric singular values to the perturbation and error analysis of
Lyapunov equations is discussed.
Keywords :
Linear matrix operators, Sylvester operators, Lyapunov operators, singular values, symmetrised singular values, perturbation analysis and error analysis