Gauss-Bonnet-coupled Quintessential Inflation
  We study in detail a new model of quintessential inflation where the inflaton
field is coupled to the Gauss-Bonnet term. This coupling ensures that the
variation of the field is kept sub-Planckian, which avoids the 5th force
problem as well as the lifting of the flatness of the quintessential tail in
the runaway scalar potential due to radiative corrections. We find that the
inflationary predictions of the model are in excellent agreement with CMB
observations, while the coincidence requirement of dark energy is satisfied
with natural values of the parameters, overcoming thereby the extreme
fine-tuning of the cosmological constant in $\Lambda$CDM.
