We prove an Alexandrov-type theorem for a quotient space of
. More
precisely, we classify the compact embedded surfaces with constant mean curvature in the
quotient of
by a subgroup of isometries generated by a horizontal translation along horocycles of
and a
vertical translation. We also construct some examples of periodic minimal surfaces in
and
we prove a multivalued Rado theorem for small perturbations of the helicoid in
.
Keywords
constant mean curvature surface, periodic surface,
Alexandrov reflection