Does the fully parabolic quasilinear 1D Keller-Segel system enjoy long-time asymptotics analogous to its parabolic-elliptic simplification?

TL;DR

This paper investigates the long-term behavior of solutions to the one-dimensional fully parabolic Keller-Segel system with nonlinear diffusion, establishing conditions for global existence and blowup, and comparing it to the parabolic-elliptic case.

Contribution

It extends known blowup results from the parabolic-elliptic Keller-Segel system to the fully parabolic case, analyzing the influence of nonlinear diffusion on solution behavior.

Findings

Global solutions exist for lpha<1 regardless of initial data volume.

For lpha=1, solutions exist for initial masses below a certain threshold.

Finite-time blowup occurs for certain initial data and nonlinear diffusion.

Abstract

We show that the one-dimensional fully parabolic Keller-Segel system with nonlinear diffusion possesses global-in-time solutions, provided the nonlinear diffusion is equal to (1+u)^{-\alpha}, for \alpha < 1, independently on the volume of the initial data. We also show that in the critical case, i.e. for \alpha = 1, the same result holds for initial masses smaller than a prescribed constant. Additionally, we prove existence of initial data for which solution blows up in a finite time for any nonlinear diffusion integrable at infinity. Thus we generalize the known blowup result of parabolic-elliptic case to the fully parabolic one. However, in the parabolic-elliptic case the above mentioned integrability condition on nonlinear diffusion sharply distinguishes between global existence and blowup cases. We are unable to recover the entire global existence counterpart of this result in a fully parabolic case.