2006/11/18 by Paschalis Karageorgis, Walter A. Strauss, Karageorgis, Paschalis +1
Engineering · Mathematics · #Advanced Mathematical Physics Problems #Analysis of PDEs (math.AP) #FOS: Mathematics #Nonlinear Partial Differential Equations #Stability and Controllability of Differential Equations #math.AP
paper · pdf · doi:10.48550/arxiv.math/0611559
arxiv created 2006/11/18 · openalex publication_date 2006/11/18 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
We consider time-independent solutions of hyperbolic equations such as \dttu -Δu= f(x,u) where f is convex in u. We prove that linear instability with a positive eigenfunction implies nonlinear instability. In some cases the instability occurs as a blow up in finite time. We prove the same result for parabolic equations such as \dt u -Δu= f(x,u). Then we treat several examples under very sharp conditions, including equations with potential terms and equations with supercritical nonlinearities.