Decay estimates for time-fractional porous medium flow with nonlocal pressure

The main purpose of this paper is to study weak solutions of time-fractional of porous medium equation with nonlocal pressure: $$\partial^\alpha_t u=\operatorname{div}\left( |u|^{m}\nabla (-\Delta)^{-s} u\right) \,\, \text{in } \mathbb{R}^N\times (0,T) \,,$$ with $m\geq 1$, $N\geq 2$, $\frac{1}{2}\leq s<1$, and $\alpha\in(0,1)$. We first prove an existence of weak solutions to the equation with initial data in $L^1(\mathbb{R}^N)\cap L^\infty(\mathbb{R}^N)$ (possibly mixed sign). After that, we establish the $L^q-L^\infty$ decay estimate of weak solutions: $$\|u(t)\|_{L^\infty(\mathbb{R}^N)} \leq C t^{-\frac{\alpha}{q(1-\lambda_0)+ m}} \|u_0\|_{L^{q}(\mathbb{R}^N)}^{\frac{q(1-\lambda_0)}{q(1-\lambda_0) + m}} ,\quad \text{for } t\in(0,\infty),$$ with $\lambda_0=\frac{N-2(1-s)}{N}$.