Phenomenological consequences of the refined swampland conjecture

Abstract

We discuss phenomenological consequences of the recently introduced refinements of the de Sitter swampland conjecture, which constrains the first and the second derivative of the scalar potential in terms of two $O(1)$ constants $c$ and ${c}^{\ensuremath{'}}$. Contrary to the original de Sitter swampland conjecture, the refinement has no constraints on spontaneous breaking scenarios, such as the Higgs, the chiral symmetry breaking, and the QCD axion. However, the refinement still strongly constrains inflation models. While we can achieve sufficient number of e-foldings, single-field inflationary models have trouble reproducing the observed valued of density perturbations, when $c$ and ${c}^{\ensuremath{'}}$ are $O(1)$. We point out that this constraint can be evaded for example by curvaton scenarios, which typically leads to detectable non-Gaussianities. Our work can also be regarded as bottom-up constraints on the values of $c$ and ${c}^{\ensuremath{'}}$.