A comparison principle for nonlinear parabolic equations with nonlocal source and gradient absorption

This paper investigates the initial-boundary value problem for a nonlinear parabolic equation involving the $p$-Laplacian operator, nonlocal source terms, gradient absorption, and various nonlinearities: $$\frac{\partial u}{\partial t} - \text{div}(|\nabla u|^{p-2} \nabla u ) = \alpha |u|^{k-1}u \int_\Omega |u|^s \, dx - \beta |u|^{l-1}u |\nabla u|^q + \gamma u^m + \mu |\nabla u|^r - \nu |u|^{\sigma-1}u,$$ where $\Omega$ is a bounded domain in $\mathbb{R}^N$, $N \geq 1$, with a smooth boundary $\partial \Omega$. The parameters satisfy $\alpha, l, \sigma > 0$, $\beta, \nu \geq 0$, $k, m, s \geq 1$, $r \geq p - 1 \geq \frac{p}{2}$, and $\gamma, \mu \in \mathbb{R}$. We establish a comparison principle for this problem. Using this principle, we derive blow-up results as well as global-in-time boundedness of solutions. Our results extend and unify previous studies in the literature.