Let G be a locally compact
group that acts continuously by linear transformations on a locally convex space E
and let K be a compact convex subset of E that is invariant under this action. In
order to conclude that K has a nonzero fixed point, it is necessary that both
G and K satisfy certain conditions. With these assumptions on K, it is
shown that the existence of nonzero fixed points is equivalent to polynomial
growth on G, provided G is connected or discrete, finitely generated and
solvable.