Suppose that A is a uniform
algebra on a compact set X and that ϕ : A → C is a nonzero multiplicative linear
functional on A. Let Mϕ be the set of positive representing measures for ϕ. If Mϕ is
finite dimensional, let m be a core measure of Mϕ. The space H1 is the closure of
A in L1(m). The space H∞ is the weak* (i.e. σ(L∞,L1)) closure of A in
L∞(m). The weakly compact sets R in H1 are then those sets such that
for all 𝜖 > 0 there is a bounded set in H∞ which approximates R up to
𝜖.