de Sitter Swampland, H0 tension & observation

Realising de Sitter vacua in string theory is challenging. For this reason it has been conjectured that de Sitter vacua inhabit the Swampland of inconsistent low-energy effective theories coupled to gravity. Since de Sitter is an attractor for Lambda CDM, the conjecture calls Lambda CDM into question. Reality appears sympathetic to this idea as local measurements of the Hubble constant H-0 are also at odds with Lambda CDM analysis of Planck data. This tension suggests that the de Sitter state is unstable, thereby implying a turning point in the Hubble parameter. We present a model relieving this tension, which predicts a turning at small positive redshift z(*) that is dictated by present-day matter density omega(m). This feature is easily identified by homogeneous surveys covering redshifts z <= 0.1. We comment on the implications for the Swampland program. (C) 2019 The Authors. Published by Elsevier B.V.