Asymptotic curvature divergences and non-gravitational theories

We analyse divergences of the scalar curvature $R$ of the vector multiplet moduli space of type IIA string theory compactified on a Calabi–Yau $X$, along infinite-distance large volume limits. Extending previous results, we classify the origin of the divergence along trajectories which implement decompactifications to F-theory on $X$ and/or emergent heterotic string limits. In all cases, the curvature divergence can be traced back to a 4d rigid field theory that decouples from gravity along the limit. This can be quantified via the asymptotic relation $R\sim ({\mathrm{\Lambda }}_{\mathrm{W}\mathrm{G}\mathrm{C}}\mathrm{/}{\mathrm{\Lambda }}_{\mathrm{s}\mathrm{p}}{)}^{2\nu }$, with ${\mathrm{\Lambda }}_{\mathrm{W}\mathrm{G}\mathrm{C}}\equiv g_{\mathrm{r}\mathrm{i}\mathrm{g}\mathrm{i}\mathrm{d}}{M}_{\mathrm{P}}$ and ${\mathrm{\Lambda }}_{\mathrm{s}\mathrm{p}}$ the species scale. In the UV, the 4d rigid field theory becomes a higher-dimensional, strongly-coupled rigid theory that also decouples from gravity. The nature of this UV theory is encoded in the exponent $\nu$, and it either corresponds to a 5d SCFT, 6d SCFT or a Little String Theory.