Ricci-flat deformations of asymptotically cylindrical Calabi--Yau manifolds

Abstract

We study a class of asymptotically cylindrical Ricci-flat K\"ahler metrics arising on quasiprojective manifolds. Using the Calabi--Yau geometry and analysis and the Kodaira--Kuranishi--Spencer theory and building up on results of N.Koiso for the case of compact manifolds, we show that under rather general hypotheses any `small' asymptotically cylindrical Ricci-flat deformations of asymptotically cylindrical Ricci-flat K\"ahler metrics are again K\"ahler, possibly with respect to a perturbed complex structure. We also find the dimension of the moduli space for these small deformations. In the class of asymptotically cylindrical Ricci-flat metrics on $2n$-manifolds, the holonomy reduction to SU(n) is an open condition.