Nonuniqueness and multi-bump solutions in parabolic problems with the p-Laplacian

The validity of the weak and strong comparison principles for degenerate parabolic partial differential equations with the p-Laplace operator Delta(p) is investigated for p > 2. This problem is reduced to the comparison of the trivial solution ( 0, by hypothesis) with a nontrivial nonnegative solution u(x, t). The problem is closely related also to the question of uniqueness of a nonnegative solution via the weak comparison principle. In this article, realistic counterexamples to the uniqueness of a nonnegative solution, the weak comparison principle, and the strong maximum principle are constructed with a nonsmooth reaction function that satisfies neither a Lipschitz nor an Osgood standard "uniqueness" condition. Nonnegative multi-bump solutions with spatially disconnected compact supports and zero initial data are constructed between sub- and supersolutions that have supports of the same type. (C) 2015 Elsevier Inc. All rights reserved.