We show that nonnegative solutions of $$ \begin{aligned} & u_{t}-u_{xx}+f(u)=0,\quad x\in \Bbb R,\quad t>0, \\ & u=\alpha \bar u,\quad x\in \Bbb R,\quad t=0, \quad \operatorname{supp}\bar u \hbox{ compact } \end{aligned} $$ either converge to zero, blow up in $\operatorname{L}^{2}$-norm, or converge to the ground state when $t\to\infty$, where the latter case is a threshold phenomenon when $\alpha>0$ varies. The proof is based on the fact that any bounded trajectory converges to a stationary solution. The function $f$ is typically nonlinear but has a sublinear growth at infinity. We also show that for superlinear $f$ it can happen that solutions converge to zero for any $\alpha>0$, provided $\operatorname{supp}\bar u$ is sufficiently small.
@article{119030, author = {Eva Fa\v sangov\'a}, title = {Asymptotic analysis for a nonlinear parabolic equation on $\Bbb R$}, journal = {Commentationes Mathematicae Universitatis Carolinae}, volume = {39}, year = {1998}, pages = {525-544}, zbl = {0963.35080}, mrnumber = {1666798}, language = {en}, url = {http://dml.mathdoc.fr/item/119030} }
Fašangová, Eva. Asymptotic analysis for a nonlinear parabolic equation on $\Bbb R$. Commentationes Mathematicae Universitatis Carolinae, Tome 39 (1998) pp. 525-544. http://gdmltest.u-ga.fr/item/119030/
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