Maximal Ball Packings of Symplectic-Toric Manifolds

Let (M, σ, ψ) be a symplectic-toric manifold of dimension at least four. This article investigates the symplectic ball packing problem in the toral equivariant setting. We show that the set of toric symplectic ball packings of M admits the structure of a convex polytope. Previous work of the first author shows that up to equivalence, only (ℂℙ1)2 and ℂℙ2 admit density one packings when n = 2 and only ℂℙn admits density one packings when n > 2. In contrast, we show that for a fixed n ≥ 2 and each δ ∈ (0, 1), there are uncountably many genuinely inequivalent 2n-dimensional symplectic-toric manifolds with a maximal toric packing of density δ. This result follows from a general analysis of how the densities of maximal packings change while varying a given symplectic-toric manifold through a family of symplectic-toric manifolds that are equivariantly diffeomorphic but not equivariantly symplectomorphic.