arXiv subjects

Takasi Senba

Publications and source records attributed to Takasi Senba.

4 recordsLinked to original sources

arXiv2026

Infinite time blow-up of solutions to the classical Keller-Segel model of chemotaxis in higher dimensions

We study the simplest parabolic-elliptic model of chemotaxis in ${\bf R^N}$, and show the optimal criteria for the existence of infinite time blow-up of solutions with the initial data below the Chandrasekhar singular solution when $N \geq 10$. In particular, we exhibit the differences of the criteria between the cases $N \geq 11$ and $N = 10$. Our argument is based on the study of the Cauchy problem for the transformed equation involving the averaged mass of the solution and the asymptotic expansions of solutions to the Liouville equation.

math.AP↗

arXiv2021

Global boundedness of solutions to a parabolic-parabolic chemotaxis system with local sensing in higher dimensions

This paper deals with classical solutions to the parabolic-parabolic system \begin{align*} \begin{cases} u_t=Δ(γ(v) u ) &\mathrm{in}\ Ω\times(0,\infty), \\[1mm] v_t=Δv - v + u &\mathrm{in}\ Ω\times(0,\infty), \\[1mm] \displaystyle \frac{\partial u}{\partial ν} = \frac{\partial v}{\partial ν} = 0 &\mathrm{on}\ \partialΩ\times (0,\infty), \\[1mm] u(\cdot,0)=u_0, \ v(\cdot,0)=v_0 &\mathrm{in}\ Ω, \end{cases} \end{align*} where $Ω$ is a smooth bounded domain in $\mathbf{R}^n$($n \geq 3$), $γ(v)=v^{-k}$ ($k>0$) and the initial data $(u_0,v_0)$ is positive and regular. This system has striking features similar to those of the logarithmic Keller--Segel system. It is established that classical solutions of the system exist globally in time and remain uniformly bounded in time if $k \in (0,n/(n-2))$, independently the magnitude of mass. This constant $n/(n-2)$ is conjectured as the optimal range guaranteeing global existence and boundedness in the corresponding logarithmic Keller--Segel system. We will derive sufficient estimates for solutions through some single evolution equation that some auxiliary function satisfies. The cornerstone of the analysis is the refined comparison estimate for solutions, which enables us to control the nonlinearity of the auxiliary equation.

math.AP↗

arXiv2021

Global existence and infinite time blow-up of classical solutions to chemotaxis systems of local sensing in higher dimensions

This paper deals with the fully parabolic chemotaxis system of local sensing in higher dimensions. Despite the striking similarity between this system and the Keller--Segel system, we prove the absence of finite-time blow-up phenomenon in this system even in the supercritical case. It means that for any regular initial data, independently of the magnitude of mass, the classical solution exists globally in time in the higher dimensional setting. Moreover, for the exponential decaying motility case, it is established that solutions may blow up at infinite time for any magnitude of mass. In order to prove our theorem, we deal with some auxiliary identity as an evolution equation with a time dependent operator. In view of this new perspective, the direct consequence of the abstract theory is rich enough to establish global existence of the system.

math.AP↗

arXiv2018

Boundedness of solutions to the critical fully parabolic quasilinear one-dimensional Keller-Segel system

In this paper we consider a one-dimensional fully parabolic quasilinear Keller-Segel system with critical nonlinear diffusion. We show uniform-in-time boundedness of solutions, which means, that unlike in higher dimensions, there is no critical mass phenomenon in the case of critical diffusion. To this end we utilize estimates from a well-known Lyapunov functional and a recently introduced new Lyapunov-like functional in [3].

math.AP↗