Dark matter as the signal of grand unification

We argue that the existence of dark matter (DM) is a possible consequence of grand unification (GUT) symmetry breaking. In GUTs like SO(10), discrete Z(2) matter parity (-1)(3(B-L)) survives despite broken B - L, and group theory uniquely determines that the only possible Z(2)-odd matter multiplets belong to representation 16. We construct the minimal nonsupersymmetric SO(10) model containing one scalar 16 for DM and study its predictions below M-G. We find that electroweak symmetry breaking occurs radiatively due to DM couplings to the standard model Higgs boson. For thermal relic DM the mass range M-DM similar to O(0.1-1) TeV is predicted by model perturbativity up to M-G. For M-DM similar to O(1) TeV to explain the observed cosmic ray anomalies with DM decays, there exists a lower bound on the spin-independent direct detection cross section within the reach of planned experiments.