Blowup for the nonlinear heat equation with small initial data in scale-invariant Besov norms

Lorenzo Brandolese (1) , Fernando Cortez (2)

1 EDPA - Équations aux dérivées partielles, analyse
2 Escuela Politécnica Nacional del Ecuador, Facultad de Ciencias, Departemento de Matemática

We consider the Cauchy problem of the nonlinear heat equation $u_t -\Delta u= u^{b},\ u(0,x)=u_0$, with $b\geq 2$ and $b\in \mathbb{N}$. We prove that initial data $u_0\in \mathcal{S}(\mathbb{R}^{n})$ (the Schwartz class)arbitrarily small in the scale invariant Besov-norm$\dot B^{-2/b}_{n(b-1) b/2,q}(\mathbb{R}^{n})$, can produce solutions that blow up in finite time. The case $b=3$ answers a question raised by Yves Meyer.Our result also proves that the smallness assumption put in an earlier work by C. Miao, B.~Yuan and B. Zhang, for the global-in-time solvability, is essentially optimal.

Mots clés: Besov; Blowup; Nonlinear Heat Equation

Domaines: Equations aux dérivées partielles [math.AP]

Lorenzo Brandolese, Fernando Cortez. Blowup for the nonlinear heat equation with small initial data in scale-invariant Besov norms. Journal of Functional Analysis, 2019, 276, pp.2589-2604. ⟨10.1016/j.jfa.2019.02.004⟩. ⟨hal-02018380⟩