A gain-based lower bound algorithm for real and mixed μμ problems

A new lower bound algorithm for real and mixed μμ problems is presented. The basic idea of this algorithm is to use a related worst-case gain problem to compute the real blocks and, if the block structure is mixed, the standard power iteration to compute the complex blocks. Numerical tests indicate that the algorithm is fast and provides good lower bounds for both real and mixed μμ problems of small to moderate size.