Low-energy brane decoupling in AdS flux vacua

Abstract: We study the decoupling of branes sourcing AdS flux vacua from the asymptotic bulk using scalar-wave absorption probabilities. In a one-modulus truncation, the result depends only on the dimension of the AdS vacuum and on the asymptotic steepness of the scalar potential. We find that for any steepness and for any dimension greater than two the absorption probability vanishes in the low-energy limit, showing that the branes decouple from the bulk. We illustrate the general analysis in several scale-separated AdS vacua. For DGKT we find $P_{\rm abs}\simω<sup>{27/7}$ and an effective transverse dimension $d_{\rm eff}=20/7$. Interestingly, the scalar potential along the brane-induced moduli trajectory agrees with that obtained by compactifying a hypothetical $(4+13/7)$-dimensional gravity theory on a $13/7$-dimensional sphere threaded by flux. We also apply the analysis to scale-separated $\mathrm{AdS}_3$ examples and to the simplest one-modulus KKLT model.