Variable gravity: A suitable framework for quintessential inflation
  In this paper, we investigate a scenario of variable gravity and apply it to
the unified description of inflation and late time cosmic acceleration dubbed
quintessential inflation. The scalar field called "cosmon" which in this model
unifies both the concepts reduces to inflaton at early epochs. We calculate the
slow-roll parameters, the Hubble parameter at the end of inflation, the
reheating temperature,the tensor-to-scalar ration and demonstrate the agreement
of the model with observations and the Planck data.As for the post inflationary
dynamics, cosmon tracks the background before it exits the scaling regime at
late times. The scenario gives rise to correct epoch sequence of standard
cosmology, namely, radiative regime, matter phase and dark-energy. We show that
the long kinetic regime after inflation gives rise to enhancement of relic
gravity wave amplitude resulting into violation of nucleosynthesis constraint
at the commencement of radiative regime in case of an inefficient reheating
mechanism such as gravitational particle production. Instant preheating is
implemented to successfully circumvent the problem. As a generic feature, the
scenario gives rise to a blue spectrum for gravity waves on scales smaller than
the comoving horizon scale at the commencement of the radiative regime.
