Critical mass phenomena in higher dimensional quasilinear Keller-Segel systems with indirect signal production

Abstract: In this paper, we deal with quasilinear Keller--Segel systems with indirect signal production, $$\begin{cases} u_t = \nabla \cdot ((u+1)^{m-1}\nabla u) - \nabla \cdot (u \nabla v), &x \in \Omega,\ t> 0,\ 0 = \Delta v - \mu(t) + w, &x \in \Omega,\ t> 0,\ w_t + w = u, &x \in \Omega,\ t> 0, \end{cases}$$ complemented with homogeneous Neumann boundary conditions and suitable initial conditions, where $\Omega\subset\mathbb R^n$ $(n\ge3)$ is a bounded smooth domain, $m\ge1$ and $$\mu(t) := \frac{1}{|\Omega|} w(\cdot, t) \qquad\mbox{for}\ t>0.$$ We show that in the case $m\ge2-\frac{2}{n}$, there exists $M_c>0$ such that if either $m>2-\frac{2}{n}$ or $\int_\Omega u_0 <M_c$, then the solution exists globally and remains bounded, and that in the case $m\le2-\frac{2}{n}$, if either $m\<2-\frac{2}{n}$ or $M\>2^\frac{n}{2}n^{n-1}\omega_n$, then there exist radially symmetric initial data such that $\int_\Omega u_0 = M$ and the solution blows up in finite or infinite time, where the blow-up time is infinite if $m=2-\frac2n$. In particular, if $m=2-\frac{2}{n}$ there is a critical mass phenomenon in the sense that $\inf\left{M > 0 : \exists u_0 \text{ with } \int_\Omega u_0 = M \text{ such that the corresponding solution blows up in infinite time}\right}$ is a finite positive number.