Let S be a semitopological
semigroup. Let C be a closed convex subset of a uniformly convex Banach space E
with a Fréchet differentiable norm and S = {T_{a};a in S} be a continuous
representation of S as nonexpansive mappings of C into C such that the common
fixed point set F(S) of S in C is nonempty. We prove in this paper that if S is right
reversible (i.e. S has finite intersection property for closed right ideals), then for each
x in C, the closed convex set W(x) ∩ F(S) consists of at most one point, where
W(x) = ⋂
{K_{s}(x);s in S}, K_{s}(x) is the closed convex hull of {T_{t}x;t ≥ s} and
t ≥ s means t = s or t in Ss. This result is applied to study the problem of
weak convergence of the net{T_{s}x;s in S}, with S directed as above, to a
common fixed point of S. We also prove that if E is uniformly convex with
a uniformly Fréchet differentiable norm, S is reversible and the space of
bounded right uniformly continuous functions on S has a right invariant
mean, then the intersection W(x) ∩ F(S) is nonempty for each x in C if
and only if there exists a nonexpansive retraction P of C onto F(S) such
that PT_{s} = T_{s}P = P for all s in S and P(x) is in the closed convex hull of
{T_{s}(x);s in S}, x in C.
