  As is well known there are many different inflationary models that can
explain the accelerated expansion occurred in the early Universe. It is
possible that there exists a fundamental property of this period that could
provide the corresponding field theory. Our hypothesis is that the Ricci scalar
should assume a positive constant value during Inflation. Considering a single
scalar field that drives the inflationary phase, we obtain uniquely the scalar
potential and the coupling term between the scalar field and spacetime
geometry. For this potential, that is well known in the inflationary scenario,
the theoretical prediction of the spectral index $n_{s}$ is in perfect
agreement with the experimental data. Interestingly in two dimensions, our
model is equivalent to Liouville gravity.
