  We consider cosmological inflation generated by a scalar field slowly rolling
off from a de Sitter maximum of its potential. The models belong to the class
of hilltop models and represent the most general model of this kind in which
the scalar potential can be written as the sum of two exponentials. The
minimally coupled Einstein-scalar gravity theory obtained in this way is the
cosmological version of a two-scale generalization of known holographic models,
allowing for solitonic solutions interpolating between an AdS spacetime in the
infrared and scaling solutions in the ultraviolet. We then investigate
cosmological inflation in the slow-roll approximation. Our model reproduces
correctly, for a wide range of its parameters, the most recent experimental
data for the power spectrum of primordial perturbations. Moreover, it predicts
inflation at energy scales of four to five orders of magnitude below the Planck
scale. At the onset of inflation, the mass of the tachyonic excitation, i.e. of
the inflaton, turns out to be seven to eight orders of magnitude smaller than
the Planck mass.
