Optimal criteria for blowup of radial and $N$-symmetric solutions of   chemotaxis systems
  A simple proof of concentration of mass equal to $8\pi$ for blowing up $N$-symmetric solutions of the Keller--Segel model of chemotaxis in two dimensions with large $N$ is given. Moreover, a criterion for blowup of solutions in terms of the radial initial concentrations, related to suitable Morrey spaces norms, is derived for radial solutions of chemotaxis in several dimensions. This condition is, in a sense, complementary to the one guaranteeing the global-in-time existence of solutions. 
Piotr Biler, Grzegorz Karch, Jacek Zienkiewicz
math.AP