The dark dimension and the Swampland

Motivated by principles from the Swampland program, which characterize requirements for a consistent UV completion of quantum gravity, combined with observational data, we are led to a unique corner of the quantum gravity landscape. In particular, using the Distance/Duality conjecture and the smallness of dark energy, we predict the existence of a light tower of states and a unique extra mesoscopic dimension of length l similar to lambda- (1/4) similar to 10(-6) m, with extra massless fermions propagating on it. This automatically 1 leads to a candidate for a tower of sterile neutrinos, and an associated active neutrino mass scale m(nu) similar to(H)(2) lambda-M-1/12 (pl)-2/3 . Moreover, assuming the mechanism for stabilization of this 3 dark dimension leads to similar masses for active and sterile neutrinos we are led to the 1 prediction of a Higgs vev (H) similar to lambda(1/6) M-pl (1/3). Another prediction of the scenario is a species 3 2 scale (M) over cap similar to lambda( 1/12) M-pl(2/3)similar to 10(9)-10(10) GeV, corresponding to the higher-dimensional Planck scale. 3 This energy scale may be related to the resolution of the instability of the Higgs effective potential present at a scale of similar to 10(11) GeV. We also speculate about the interplay between this energy scale and the GZK limit on ultra-high energy cosmic rays.