摘要
本文给出了判定一个给定的复值连续函数属于指定的一致代数的两个充要条件。给出了判定一个复值连续函数和它的复共轭函数同时属于指定的一致代数的一个充要条件。给出了判定指定的一致代数等于C(X)的一个充要条件。
Let X be a compact Itausdorff space. R be an equivalence relation on X,P be the quotient map of X onto the quotient space X/R,A be a uniform algebra on X, f be continuous on X.The union of K and the bounded components of Kc will be denoted by K.This paper proves the following results. (1) f∈A if and only if g∈ C(X/R), if gof*^-1 has a continuous extension h, h is analytic on the interior of S and continuous on S, then goP∈A. (here, S=the convex closure ofR(f), R (f) = {f(x) | x∈X}, (x, y) ER f(x) =f(y). f*(P(x)) =f(x).). (2) f∈A if and only if g∈A, such that f*og*^-1 has a continuous extension h, h is analytic on the interior of S and continuous on S. (here, S= the convex closure of R(g), (x, y)ER g(x) =g(y), f*(P(x)) = f(x), g*(P(x)) =g(x).). (3) f, f-∈A if and only if x, y∈X, f (x) ≠f(y)there is g∈Asuch that g(x) 4:g(y), R (g)is nowhere dense and the complement of R ( g ) is connected. (4) A= C(X)if and only if Vx, y∈X, x≠y there is g∈A such that g ( x ) ≠g ( y ) ,R ( g ) is nowhere dense and the complement of R ( g ) is connected.
基金
福建省教委青年科研基金资助项目.
关键词
一致代数
凸闭包
Uniform algebra, Convex closure