Foliation by area-constrained Willmore spheres near a non-degenerate critical point of the scalar curvature

Let $(M,g)$ be a 3-dimensional Riemannian manifold. The goal of the paper it to show that if $P_0\in M$ is a non-degenerate critical point of the scalar curvature, then a neighborhood of $P_0$ is foliated by area-constrained Willmore spheres. Such a foliation is unique among foliations by area-constrained Willmore spheres having Willmore energy less than $32\pi$, moreover it is regular in the sense that a suitable rescaling smoothly converges to a round sphere in the Euclidean three-dimensional space. We also establish generic multiplicity of foliations and the first multiplicity result for area-constrained Willmore spheres with prescribed (small) area in a closed Riemannian manifold. The topic has strict links with the Hawking mass.