  One way to show that Thompson's group F is non-amenable is to exhibit an
action of F on a locally compact CAT(0) space X containing no F-invariant flats
and having no global fixed points in its boundary-at-infinity. We study the
actions of Thompson's groups F, T, and V on the boundaries-at-infinity of
proper CAT(0) cubical complexes. In particular, we show that Thompson's groups
T and V act without fixing any points in the boundaries of their CAT(0) cubical
complexes. This in particular gives another proof of the well-known fact that
these groups are non-amenable. We obtain a partial description of the fixed set
for F: Thompson's group F fixes an arc in the boundary of its cubical complex.
We leave open the possibility that there are more fixed points, but describe a
region of the boundary which must contain all of the others.
