  Using the seesaw mechanism, we construct a model for the light-neutrino
Majorana mass matrix which yields trimaximal lepton mixing together with
maximal CP violation and maximal atmospheric-neutrino mixing. We demonstrate
that, in our model, the light-neutrino mass matrix retains its form under the
one-loop renormalization-group evolution. With our neutrino mass matrix, the
absolute neutrino mass scale is a function of |U_e3| and of the atmospheric
mass-squared difference. We study the effective mass in neutrinoless double
beta-decay as a function of |U_e3|, showing that it contains a fourfold
ambiguity.
