Higgs inflation in Gauss-Bonnet braneworld
  The measured masses of the Higgs boson and top quark indicate that the
effective potential of the standard model either develops an unstable
electroweak vacuum or stands stable all the way up to the Planck scale. In the
latter case in which the top quark mass is about $2\sigma$ below its present
central value, the Higgs boson can be the inflaton with the help of a large
nonminimal coupling to curvature in four dimensions. We propose a scenario in
which the Higgs boson can be the inflaton in a five-dimensional Gauss-Bonnet
braneworld model to solve both the unitarity and stability problems which
usually plague Higgs inflation. We find that in order for Higgs inflation to
happen successfully in the Gauss-Bonnet regime, the extra dimension scale must
appear roughly in the range between the TeV scale and the instability scale of
standard model. At the tree level, our model can give rise to a naturally small
nonminimal coupling $\xi\sim\mathcal{O}(1)$ for the Higgs quartic coupling
$\lambda\sim\mathcal{O}(0.1)$ if the extra dimension scale lies at the TeV
scale. At the loop level, the inflationary predictions at the tree level are
preserved. Our model can be confronted with future experiments and observations
from both particle physics and cosmology.
