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.

Classical and Quantum Gravity 36, 11 (2019)
Click the Cite button above to demo the feature to enable visitors to import publication metadata into their reference management software.
Click the Slides button above to demo Academic’s Markdown slides feature.

Supplementary notes can be added here, including code and math.

Luca Visinelli
Luca Visinelli
Tenure-track Associate Professor, Shanghai Jiao Tong University; Fellow, Tsung-Dao Lee Institute

PhD in Physics, working on Particle Astrophysics and Dark Matter modeling.