On the robust stability of 2D Schur polynomials

In this note, the problem of the robust stability for a two-dimensional (tw o-variable) Schur polynomial which is the characteristic polynomial of a di screte-time linear time-invariant system is investigated. A new approach ba sed on the Rouche theorem is adopted. The extension to the robust stability for multidimensional (multivariable) polynomials is also provided. Interes ting sufficient conditions for such robust stability are derived. A two-dim ensional example is included to support the theoretical result.