Existence, uniqueness and blow-up estimates for a reaction-diffusion equation with $p(x,t)$-exponents

Abstract: Let $d \in {3,4,5,\ldots}$ and $\Omega \subset \Ri^d$ be open bounded with Lipschitz boundary. Let $Q = \Omega \times (0,\infty)$ and $p \in C(\overline{Q})$ be such that [ 2 < p^- \le p(\cdot) \le p^+ < 2^* := \frac{2d}{d-2}, ] where $ p^- := \essinf_{(x,t) \in Q} p(x,t) $ and $ p^+ := \esssup_{(x,t) \in Q} p(x,t). $ Consider the reaction-diffusion parabolic problem [ (P) \quad \left{\begin{array}{ll} \displaystyle\frac{u_t}{|x|^2} - \Delta u = k(t) \, |u|^{p(x,t)-2}u & (x,t) \in \Omega \times (0,T), u(x,t) = 0, & (x,t) \in \partial \Omega \times (0,T), \smallskip u(x,0) = u_0(x), & x \in \Omega, \end{array}\right. ] where $T > 0$ and $0 \ne u_0 \in W^{1,2}_0(\Omega)$. We investigate the existence and uniqueness of a weak solution to $(P)$. The upper and lower bounds on the blow-up time of the weak solution are also considered.