Combining fast, linear and slow diffusion

Abstract

Although the pioneering studies of G. I. Barenblatt ([8] G. I. Barenblatt, On some unsteady motions of a liquid or a gas in a porous medium, Prikl. Mat. Mekh. 16 (1952), 67–68) and A. G. Aronson and L. A. Peletier ([7] A. G. Aronson and L. A. Peletier, Large time behaviour of solutions of some porous medium equation in bounded domains, J. Differential Equations 39 (1981), 378–412.) did result into a huge industry around the porous media equation, none further study analyzed the effect of combining fast, slow, and linear diffusion simultaneously, in a spatially heterogeneous porous medium. Actually, it might be this is the first work where such a problem has been addressed. Our main findings show how the heterogeneous model possesses two different regimes in the presence of a priori bounds. The minimal steady-state of the model exhibits a genuine fast diffusion behavior, whereas the remaining states are rather reminiscent of the purely slow diffusion model. The mathematical treatment of these heterogeneous problems should deserve a huge interest from the point of view of its applications in fluid dynamics and population evolution.