Eigenvector-Free Solutions to the Matrix EquationAXBH=Ewith Two Special Constraints
The matrix equationAXBH=EwithSX=XRorPX=sXQconstraint is considered, whereS, Rare Hermitian idempotent,P, Qare Hermitian involutory, ands=±1. By the eigenvalue decompositions ofS, R, the equationAXBH=EwithSX=XRconstraint is equivalently transformed to an unconstrained problem whose coefficient matrices contain the corresponding eigenvectors, with which the constrained solutions are constructed. The involved eigenvectors are released by Moore-Penrose generalized inverses, and the eigenvector-free formulas of the general solutions are presented. By choosing suitable matricesS, R, we also present the eigenvector-free formulas of the general solutions to the matrix equationAXBH=EwithPX=sXQconstraint.