Higgs inflation in Einstein-Cartan gravity
  We study inflation driven by the Higgs field in the Einstein-Cartan
formulation of gravity. In this theory, the presence of the Holst and Nieh-Yan
terms with the Higgs field non-minimally coupled to them leads to three
additional coupling constants. For a broad range of parameters, we find that
inflation is both possible and consistent with observations. In most cases, the
spectral index is given by $n_s=1-2/N_\star$ (with $N_\star$ the number of
e-foldings) whereas the tensor-to-scalar ratio $r$ can vary between about
$10^{-10}$ and $1$. Thus, there are scenarios of Higgs inflation in the
Einstein-Cartan framework for which the detection of gravitational waves from
inflation is possible in the near future. In certain limits, the known models
of Higgs inflation in the metric and Palatini formulations of gravity are
reproduced. Finally, we discuss the robustness of inflationary dynamics against
quantum corrections due to the scalar and fermion fields.
