A wide variety of articles, starting with the famous paper [11], is devoted to the uniqueness question for the semilinear elliptic boundary value problem −∆u = λu + u p in Ω, u > 0 in Ω, u = 0 on ∂Ω, where λ ranges between 0 and the first Dirichlet Laplacian eigenvalue. So far, this question was settled in the case of Ω being a ball and, for more general domains, in the case λ = 0. In [16], we proposed a computerassisted approach to this uniqueness question, which indeed provided a proof in the case Ω = (0, 1) 2 , and p = 2. Due to the high numerical complexity, we were not able in [16] to treat higher values of p. Here, by a significant reduction of the complexity, we will prove uniqueness for the case p = 3.
Dedicated to the memory of Wolfgang Walter2010 Mathematics Subject Classification. 35J25, 35J60, 65N15.