Spreading in Several Space Dimensions

The goal of this last chapter is to provide the beginning of the theory of the spreading speed in multidimensional front propagation in \(\mathbb {R}^N\) . The diffusion kernel will depend on the variable \(x-y\) , but not on the sole variable \(\vert x-y\vert \) ; that is, we do not assume spherical symmetry. This will allow new expressions for the spreading speed.