  Without supersymmetry, the gauge couplings in the standard model with five
Higgs doublets unify around 10^14 GeV. In this case, the trinified model,
SU(3)_C x SU(3)_L x SU(3)_R x Z_3, with the minimal Higgs sector required for
symmetry breaking, is the ideal grand-unified candidate. Small neutrino masses
are generated via a radiative seesaw mechanism, without the need for
intermediate scales, additional Higgs fields, or higher-dimensional operators.
The proton lifetime is above the experimental limits, with the decay modes p ->
\bar\nu K^+ and p -> mu^+ K^0 potentially observable. The split-SUSY version of
the model, with one light Higgs doublet, is equally attractive.

High Energy Physics - Phenomenology