Minimal solutions to transfer matrix equations
A. Stephen Morse · IEEE Transactions on Automatic Control · 1976
It is shown that the problem of finding a solutionT(\lambda), of least McMillan degree, to the transfer matrix equationT_{1}(\lambda) = T_{2}(\lambda)T(\lambda)is in essence equivalent to the problem of finding an (A,B)-invariant subspace of least dimension which contains a given subspace.