Gleason parts and Choquet boundary of a function algebra on a convex compactum

Abstract

Let K be a convex compactum in a complex locally convex space E, P(K) be the uniform algebra of functions on K generated by the restrictions of complex-affine continuous functions on E. For x, yε E, we set H (x,y)={(1−λ)x+λy∶λε ℂ}. It is proved that: (a) the space of maximal ideals of the algebra P(K) coincides with K; (b) distinct points x,y from K belong to the same Gleason part if and only if x and y are relatively interior points of the set H(x,y)∩K (as a subset of H(x,y); (c) the Choquet boundary of the algebra P (K) coincides with the set of complex-extreme points of the compactum K (that is, of points x not belonging to the relative interior of any set of the form H(x,y) ∩ K for y≠x).