CRITICAL MASS ON THE KELLER-SEGEL SYSTEM WITH SIGNAL-DEPENDENT MOTILITY

This paper is concerned with the global boundedness and blow-up of solutions to the Keller-Segel system with density-dependent motility in a two-dimensional bounded smooth domain with Neumman boundary conditions. We show that if the motility function decays exponentially, then a critical mass phenomenon similar to the minimal Keller-Segel model will arise. That is, there is a number m(*) > 0, such that the solution will globally exist with uniform-in-time bound if the initial cell mass (i.e., L-1-norm of the initial value of cell density) is less than m(*), while the solution may blow up if the initial cell mass is greater than m(*).