SO(18) unification

An SO(18) grand unified theory is presented. All fermions belong to one irreducible 256-dimensional spinor representation. It is shown that (i) in a favorable case there are eight light and eight superheavy families, (ii) masses of neutrinos, superheavy fermions, and horizontal gauge bosons are correlated with each other, (iii) there are new charged-current processes, $B+L$ conserving and $\Delta L=2\mathrm{}$, and (iv) two types of symmetry breaking lead to orthogonal choices of scalars. In one case [SO(18→SU(9)...] scalars may be replaced by fermion composites. Other physical features are also discussed.