On soliton clusters and collision blow up for the $L^2$-critical Hartree equation

We consider the $L^2$-critical nonlinear Hartree equation in ${\mathbb{R}}^{1+4}$ and multisoliton solutions for which the trajectories are approximated to leading order by an $m$-body law. We obtain soliton clusters asymptotically following hyperbolic-parabolic trajectories of the corresponding $m$-body problem. By pseudo-conformal invariance, we then conclude finite-time collision blow-up with any number of clusters, each consisting of an arbitrary number of solitons, colliding simultaneously at distinct prescribed points.