on a second critical value for the local existence of solutions in lebesgue spaces

We provide new conditions for the local existence of solutions to the time-weighted parabolic equation $u_t - \Delta u = h(t)f(u) \mbox{ in } \Omega \times (0,T),$ where $\Omega$ is a arbitrary smooth domain, $f\in C(\mathbb{R})$, $h\in C([0,\infty))$ and $u(0)\in L^r(\Omega)$. As consequence of our results, considering a suitable behavior of the non-negative initial data, we obtain a second critical value $\rho^\star = 2r/(p-1),$ when $f(u)=u^p$ and $p> 1 + 2r/N$, which determines the existence (or not) of a local solution $u \in L^\infty((0,T), L^r(\Omega)).$