Finite difference method for a general fractional porous medium equation

We formulate a numerical method to solve the porous medium type equation with fractional diffusion $$\frac{\partial u}{\partial t}+(-\Delta)^{\sigma/2} (u^m)=0$$ posed for $x\in \mathbb{R}^N$, $t>0$, with $m\geq 1$, $\sigma \in (0,2)$, and nonnegative initial data $u(x,0)$. We prove existence and uniqueness of the solution of the numerical method and also the convergence to the theoretical solution of the equation with an order depending on $\sigma$. We also propose a two points approximation to a $\sigma$-derivative with order $O(h^{2-\sigma})$.