Invariance of the strict Hurwitz property for bivariate polynomials under coefficient perturbations

A result is given that enables one to determine the interval within which the coefficients of a real bivariate polynomial might be allowed to vary, centered around their respective nominal values, so that the strict Hurwitz property remains invariant. These results are suitable for generalization to multivariate polynomials with complex coefficients. Applications can be found in branches of network and control theory concerned with robust stability analysis. Such analysis should be of interest because of the established role of multivariate realizability theory in systems research and also because of the increasing importance that is being attached to the design of multidimensional feedback control systems.<>