The origin of the GUT scale from the top down perspective is explored. The
GUT gauge symmetry is broken by the renormalization group effects, which is an
extension of the radiative electroweak symmetry breaking scenario to the GUT
models. That is, in the same way as the origin of the electroweak scale, the
GUT scale is generated from the Planck scale through the radiative corrections
to the soft SUSY breaking mass parameters. This mechanism is applied to a
perturbative SO(10) GUT model, recently proposed by us. In the SO(10) model,
the relation between the GUT scale and the Planck scale can naturally be
realized by using order one coupling constants.Comment: 5 pages, no figure, final version to be published in Eur. Phys. J.