de Sitter Swampland, $H_0$ 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 $z \leq 0.1$. We comment
on the implications for the Swampland program.
