It is proved that, for the following classes of groups, Gamma, the reduced
group C*-algebra C-lambda*(Gamma) has stable rank 1:
(i) hyperbolic groups which are either torsion-free and non-elementary or w
hich are cocompact lattices in a real, noncompact, simple, connected Lie gr
oup of real rank 1 having trivial center;
(ii) amalgamated free products of groups, Gamma = G(1 *H) G(2), where H is
finite and there is gamma is an element of Gamma such that gamma(-1) H gamm
a boolean AND H = {1}.
The proofs involve some analysis of the free semigroup property, which is o
ne way of saying that a group r has an abundance of free sub-semigroups, an
d of the l(2)-spectral radius property, which says that spectral radius of
appropriate elements in C-lambda*(Gamma) may be computed with the 2-norm. (
C) Elsevier, Paris.