Analytic feedback control and the algebraic Riccati equation

The central result of this correspondence is Lemma 1.1, which states that the stabilizing solution P*to the algebraic Riccati equation in ( ) depends analytically on ( ). In the remainder of the correspondence, various control- and system-theoretic ramifications of the analyticity lemma are considered. An important consequence of Lemma 1.1 is that any smooth-state feedback control law for a finite-dimensional plant may be implemented using dynamic input-output compensators whose transfer functions depend smoothly on the plant transfer function.