Assisted Fibre Inflation in Perturbative LVS

Abstract: We propose a multi-field fiber inflation scenario in type IIB perturbative large volume compactifications, showing that the multi-field dynamics suppresses trans-Planckian displacements of the canonical inflaton. Considering a concrete K3-fibred Calabi-Yau (CY) threefold with $h^{1,1}({\rm CY})=3$ and having certain underlying symmetries, we show that the presence of multi-fibre moduli creates an assisted inflation scenario where multiple moduli collectively help in producing the cosmological observables consistent with the experimental observations. We further argue that individual field range excursions $(\Delta\phi_n)$ corresponding to each of the inflaton fields can be estimated as $\Delta\phi_n = \Delta\phi/\sqrt{n}$, where $\Delta\phi$ denotes to the effective single-field inflaton range needed to generate the desired cosmological observables, and $n$ is the number of moduli assisting the multi-fibre inflation. We also present various numerical benchmark models consistently producing cosmological observables in the lights of the recent ACT experiments.