http://arxiv.org/abs/1808.06424
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, $V_\phi/V \gtrsim M_{\rm Pl}$. Here, we show that the swampland conjectures are inconsistent with existing observational constraints on single-field inflation. 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 $V_\phi/V \lesssim 0.1 M_{\rm Pl}$, in strong tension with swampland conjectures. Extension to non-canonical models such as DBI Inflation does not significantly weaken the bound.
W. Kinney, S. Vagnozzi and L. Visinelli
Tue, 21 Aug 18
31/71
Comments: 5 pages, 1 figure. The busy reader should skip directly to Fig. 1, where the swampland-allowed region is mapped onto the $n_S$-$r$ plane
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