  In cosmic inflation driven by a scalar gauge singlet field with a tree level
Higgs potential, the scalar to tensor ratio r is estimated to be larger than
0.036, provided the scalar spectral index n_s >= 0.96. We discuss quantum
smearing of these predictions arising from the inflaton couplings to other
particles such as GUT scalars, and show that these corrections can
significantly decrease r. However, for n_s >= 0.96, we obtain r >= 0.02 which
can be tested by the Planck satellite.
