Constraints on Single-Field Inflation
  Many alternatives to canonical slow-roll inflation have been proposed over
the years, one of the main motivations being to have a model, capable of
generating observable values of non-Gaussianity. In this work, we (re-)explore
the physical implications of a great majority of such models within a single,
effective field theory framework (including novel models with large
non-Gaussianity discussed for the first time below.) The constraints we
apply---both theoretical and experimental---are found to be rather robust,
determined to a great extent by just three parameters: the coefficients of the
quadratic EFT operators $(\delta N)^2$ and $\delta N \delta E$, and the
slow-roll parameter $\varepsilon$. This allows to significantly limit the
majority of single-field alternatives to canonical slow-roll inflation. While
the existing data still leaves some room for most of the considered models, the
situation would change dramatically if the current upper limit on the
tensor-to-scalar ratio decreased down to $r < 10^{-2}$. Apart from inflationary
models driven by plateau-like potentials, the single-field model that would
have a chance of surviving this bound is the recently proposed slow-roll
inflation with weakly-broken galileon symmetry. In contrast to
\textit{canonical} slow-roll inflation, the latter model can support $r <
10^{-2}$ even if driven by a convex potential, as well as generate observable
values for the amplitude of non-Gaussianity.
