Neck pinch singularities and Joyce conjectures in Lagrangian mean curvature flow with circle symmetry

Abstract: In this article we consider the Lagrangian mean curvature flow of compact, circle-invariant, almost calibrated Lagrangian surfaces in hyperk\"ahler 4-manifolds with circle symmetry. We show that this Lagrangian mean curvature flow can be continued for all time, through finite time singularities, and converges to a chain of special Lagrangians, thus verifying various aspects of Joyce's conjectures in this setting. We show that the singularities of the flow are neck pinches in the sense conjectured by Joyce. We also give examples where such finite time singularities are guaranteed to occur.