  In this paper we study space-times which evolve out of Cauchy data
$(\Sigma,{}^3g,K)$ invariant under the action of a two-dimensional commutative
Lie group. Moreover $(\Sigma,{}^3g,K)$ are assumed to satisfy certain
completeness and asymptotic flatness conditions in spacelike directions. We
show that asymptotic flatness and energy conditions exclude all topologies and
group actions except for a cylindrically symmetric $R^3$, or a periodic
identification thereof along the $z$-axis. We prove that asymptotic flatness,
energy conditions and cylindrical symmetry exclude the existence of compact
trapped surfaces. Finally we show that the recent results of Christodoulou and
Tahvildar-Zadeh concerning global existence of a class of wave-maps imply that
strong cosmic censorship holds in the class of asymptotically flat
cylindrically symmetric electro-vacuum space-times.
