Compactly Supported Stationary States of the Degenerate Keller-Segel System in the Diffusion-Dominated Regime

We first show the existence of a unique global minimizer of the free energy for all masses associated with a nonlinear diffusion version of the classical Keller-Segel model when the diffusion dominates over the attractive force of the chemoattractant. The strategy uses an approximation of the variational problem in the whole space by the minimization problem posed on bounded balls with large radii. We show that all stationary states in a wide class coincide up to translations with the unique global minimizer of the free energy, which is compactly supported, radially decreasing, and smooth inside its support. Our results complement and show alternative proofs with respect to [27, 30, 36].