Aspects of compactification on a linear dilaton background

Abstract

We consider the most general Kaluza-Klein (KK) compactification on $S^1/\mathbb{Z}_2$ of a five dimensional ($5D$) graviton-dilaton system, with a non-vanishing dilaton background varying linearly along the fifth dimension. We show that this background produces a Higgs mechanism for the KK vector coming from the $5D$ metric, which becomes massive by absorbing the string frame radion. The $\mathcal{N}=2$ minimal supersymmetric extension of this model, recently built as the holographic dual of Little String Theory, is then re-investigated. An analogous mechanism can be considered for the $4D$ vector coming from the (universal) $5D$ Kalb-Ramond two-form. Packaging the two massive vectors into a spin-$3/2$ massive multiplet, it is shown that the massless spectrum arranges into a $\mathcal{N}=1$, $D=4$ supersymmetric theory. This projection is compatible with an orbifold which preserves half of the original supersymmetries already preserved by the background. The description of the partial breaking $\mathcal{N}=2\rightarrow\mathcal{N}=1$ in this framework, with only vector multiplets and no hypermultiplets, remains an interesting open question which deserves further investigation.