We study the behaviour of nonnegative global solutions to the quasilinear heat equation with a reaction localized in a ball ut=Δum+a(x)up,\documentclass[12pt]{minimal}
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\begin{document}$$\begin{aligned} u_t={\varDelta } u^m+a(x)u^p, \end{aligned}$$\end{document}for m>0\documentclass[12pt]{minimal}
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\begin{document}$$m>0$$\end{document}, 0<p≤max{1,m}\documentclass[12pt]{minimal}
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\begin{document}$$0<p\le \max \{1,m\}$$\end{document}, a(x)=1BL(x)\documentclass[12pt]{minimal}
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\begin{document}$$a(x)=\mathbb {1}_{B_L}(x)$$\end{document}, 0<L<∞\documentclass[12pt]{minimal}
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\begin{document}$$0<L<\infty $$\end{document} and N≥2\documentclass[12pt]{minimal}
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\begin{document}$$N\ge 2$$\end{document}. We study when the solutions are bounded or unbounded. In particular we show that the precise value of the length L plays a crucial role in the critical case p=m\documentclass[12pt]{minimal}
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\begin{document}$$p=m$$\end{document} for N≥3\documentclass[12pt]{minimal}
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\begin{document}$$N\ge 3$$\end{document}. We also obtain the asymptotic behaviour of unbounded solutions and prove that the grow-up rate is different in most of the cases to the one obtained when L=∞\documentclass[12pt]{minimal}
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\begin{document}$$L=\infty $$\end{document}.