Testing the Swampland: H0 tension

The de Sitter Swampland conjecture compels us to consider dark energy models where lambda(phi) = |del phi V|/V is bounded below by a positive constant. Moreover, it has been argued for Quintessence models that the constant lambda scenario is the least constrained. Here we demonstrate that increasing lambda only exacerbates existing tension in the Hubble constant H-0. The identification of dark energy models that both evade observational bounds and alleviate H-0 tension constitutes a robust test for the Swampland program. (C) 2019 The Authors. Published by Elsevier B.V.