Rescuing Single Field Inflation from the Swampland
  The difficulty of building metastable vacua in string theory has led some to
conjecture that, in the string theory landscape, potentials satisfy
$\left|\nabla V/V\right|\geq c\sim \mathcal{O}(1)$. This condition, which is
supported by different explicit constructions, suggests that the EFTs which
lead to metastable de-Sitter vacua belong to what is dubbed as swampland. This
condition endangers the paradigm of single field inflation. In this paper, we
show how scalar excited initial states cannot rescue single field inflation
from the swampland, as they produce large local scalar non-gaussianity, which
is in conflict with the Planck upper bound. Instead, we demonstrate that one
can salvage single field inflation using excited initial states for tensor
perturbations, which in this case produce only large flattened non-gaussianity
in the tensor bispectrum. We comment on the possible methods one can prepare
such excited initial conditions for the tensor perturbations.
