AdS swampland conjectures and light fermions

Abstract

We consider constraints on D-dimensional theories in MD, dSD and AdSD backgrounds in the light of AdS swampland conjectures as applied to their compactification in a circle. In particular we consider the non-SUSY AdS instability conjecture and the AdS distance conjecture. For MD and dSD vacua the results may be summarized by a light fermion conjecture which states that in theories with ΔD ≥ 0 and a positive first non-vanishing supertrace (−1)k+1StrM2k > 0, a surplus of light fermions with mass mf < Δ1/DD must be present. For dSD this is supported by both AdS swampland conjectures. On the contrary, the cases of MD and AdSD can be made consistent with the mild but not the strong version of the AdS Distance conjecture, since the KK tower in the lower d-dim theory will scale as m < Δαd with α = 1/d. The above constraints also suggest that the Standard Model of particle physics would be inconsistent in Minkowski space but consistent in dS if the lightest neutrino is Dirac and lighter than the cosmological constant scale