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arXiv 1302.4093math.APmath.DG
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双曲空间上的径向快速扩散

Radial Fast Diffusion on the Hyperbolic Space

Gabriele Grillo, Matteo Muratori

摘要:

考虑双曲空间$\mathbb{H}^{N}$上快扩散方程$u_t=Δu^m$的径向解,其中$N \ge 2$,$m\in(m_s,1)$,$m_s=\frac{N-2}{N+2}$ .通过径向,我们的意思是仅取决于距给定点$o \in \mathbb{H}^N$的测地距离$r$的解。我们调查他们的罚款渐近灭绝时间$T$附近的形式${\mathcal V}(r,t)=(1-t/T)^{1/(1-m)}V^{1/m}(r)$,其中$V$是唯一的正能量的解决方案,径向w.r. t的可分离的解决方案。$o$,到$-ΔV=c\,V^{1/m}$,对于合适的$c>0$,在\cite{MS08},\cite{BGGV}中深入研究的半线性椭圆问题。我们发现,$u$收敛到${\mathcal V}$的相对误差,在这个意义上,$\|{u^m(\cdot,t)}/{{\mathcal V}^m(\cdot,t)}-1\|_\infty\to0$作为$t\to T^-$。特别地,该解在接近消光时间$T$处由$(1-t/T)^{1/(1-m)}e^{-(N-1)r/m}$的倍数上下界定。

英文摘要:

We consider radial solutions to the fast diffusion equation $u_t=Δu^m$ on the hyperbolic space $\mathbb{H}^{N}$ for $N \ge 2$, $m\in(m_s,1)$, $m_s=\frac{N-2}{N+2}$. By radial we mean solutions depending only on the geodesic distance $r$ from a given point $o \in \mathbb{H}^N$. We investigate their fine asymptotics near the extinction time $T$ in terms of a separable solution of the form ${\mathcal V}(r,t)=(1-t/T)^{1/(1-m)}V^{1/m}(r)$, where $V$ is the unique positive energy solution, radial w.r.t. $o$, to $-ΔV=c\,V^{1/m}$ for a suitable $c>0$, a semilinear elliptic problem thoroughly studied in \cite{MS08}, \cite{BGGV}. We show that $u$ converges to ${\mathcal V}$ in relative error, in the sense that $\|{u^m(\cdot,t)}/{{\mathcal V}^m(\cdot,t)}-1\|_\infty\to0$ as $t\to T^-$. In particular the solution is bounded above and below, near the extinction time $T$, by multiples of $(1-t/T)^{1/(1-m)}e^{-(N-1)r/m}$.

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