The effect of a line with nonlocal diffusion on Fisher-KPP propagation

We propose a new model of accelerating fronts, consisting of one equation with non-local diffusion on a line, coupled via the boundary condition with a reaction-diffusion equation in the upper half-plane. The underlying biological question is to understand how transportation networks may enhance biological invasions. We show that the line accelerates the propagation in the direction of the line and enhances the overall propagation in the plane and that the propagation is directed by diffusion on the line, where it is exponentially fast in time. We also describe completely the invasion in the upper half-plane. This work is a nonlocal version of the model introduced in Ref. 15, where the line had a strong but local diffusion described by the classical Laplace operator.