On the maximal ideal space of extended polynomial and rational uniform algebras

Let K and X be compact plane sets such that K X. Let P(K)be the uniform closure of polynomials on K. Let R(K) be the closure of rationalfunctions K with poles o K. Dene P(X;K) and R(X;K) to be the uniformalgebras of functions in C(X) whose restriction to K belongs to P(K) and R(K),respectively. Let CZ(X;K) be the Banach algebra of functions f in C(X) suchthat fjK = 0. In this paper, we show that every nonzero complex homomorphism' on CZ(X;K) is an evaluation homomorphism ez for some z in XnK. By con-sidering this fact, we characterize the maximal ideal space of the uniform algebraP(X;K). Moreover, we show that the uniform algebra R(X;K) is natural.