Bounds on Growth and Impossibility of Collapse for Point Vortex Systems

We consider 2D point vortex systems and, under certain conditions on the masses of the point vortices, prove that collapse is impossible and provide bounds on the growth of the system. The bounds are typically of the form $O(t^a)$ for some $a<1\mathrm{/}2$, but we obtain various results for various assumptions on the masses.