The zoo plot meets the swampland: mutual (in)consistency of single-field
  inflation, string conjectures, and cosmological data
  We consider single-field inflation in light of string-motivated "swampland"
conjectures suggesting that effective scalar field theories with a consistent
UV completion must have field excursion $\Delta \phi \lesssim M_{\rm Pl}$, in
combination with a sufficiently steep potential, $M_{\rm Pl} V_\phi/V \gtrsim
{\cal O}(1)$. Here, we show that the swampland conjectures are inconsistent
with existing observational constraints on single-field inflation. Focusing on
the observationally favoured class of concave potentials, we map the allowed
swampland region onto the $n_S$-$r$ "zoo plot" of inflationary models, and find
that consistency with the Planck satellite and BICEP2/Keck Array requires
$M_{\rm Pl} V_\phi/V \lesssim 0.1$ and $-0.02 \lesssim M_{\rm Pl}^2
V_{\phi\phi}/V < 0$, in strong tension with swampland conjectures. Extension to
non-canonical models such as DBI Inflation does not significantly weaken the
bound.
