On collapsing Calabi–Yau fibrations

We develop some techniques to study the adiabatic limiting behaviour of Calabi–Yau metrics on the total space of a fibration, and obtain strong control near the singular fibres by imposing restrictions on the singularity types. We prove a uniform lower bound on the metric up to the singular fibre, under fairly general hypotheses. Assuming a result in pluripotential theory, we prove a uniform fibre diameter bound for a Lefschetz K3 fibred Calabi–Yau 3‑fold, which reduces the study of the collapsing metric to a locally non-collapsed situation, and we identify the Gromov–Hausdorff limit of the rescaled neighbourhood of the singular fibre.