Kharitonov region

A Kharitonov region is a concept in mathematics. It arises in the study of the stability of polynomials.
Let formula_1 be a simply-connected set in the complex plane and let formula_2 be the polynomial family.
formula_1 is said to be a Kharitonov region if
is a subset of formula_5 Here, formula_6 denotes the set of all vertex polynomials of complex interval polynomials formula_7 and formula_8 denotes the set of all vertex polynomials of real interval polynomials formula_9