Higgs inflation, quantum smearing, and the tensor to scalar ratio

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 grand unified theory 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.