Slow-roll inflation in f(R,T) gravity and a modified Starobinsky-like
  inflationary model
  In this work, we studied the slow-roll approximation of cosmic inflation
within the context of $f(R,T)$ gravity, where $R$ is the scalar curvature, and
$T$ is the trace of the energy-momentum tensor. By choosing a minimal coupling
between matter and gravity, we obtained the modified slow-roll parameters, the
scalar spectral index ($n_s$), the tensor spectral index ($n_{\textrm{T}}$),
and the tensor-to-scalar ratio ($r$). We computed these quantities for a
general power-law potential, Natural & Quartic Hilltop inflation, and the
Starobinsky model, plotting the trajectories on the $(n_s,r)$ plane. We found
that one of the parameters of Natural/Hilltop models is non-trivially modified.
Besides, if the coupling is in the interval $-0.5 < \alpha < 5.54$, we
concluded that the Starobinsky-like model predictions are in good agreement
with the last Planck measurement, but with the advantage of allowing a wide
range of admissible values for $r$ and $n_{\textrm{T}}$.
