Solutions with many mixed positive and negative interior spikes for a semilinear Neumann problem

We study the existence of sign-changing multiple interior spike solutions for the following Neumann problem ε^2∆v−v+f(v)=0inΩ, ∂v =0 on ∂Ω, where Ω is a smooth bounded domain of R^N , ε is a small positive parameter, f is a superlinear, subcritical and odd nonlinearity. No symmetry on Ω is assumed. To our knowledge, only positive interior peak solutions have been obtained for this problem and it remains a question whether or not multiple interior peak solutions with mixed positive and negative peaks exist. In this paper we assume that Ω is a two-dimensional strictly convex domain and, provided that k is sufficiently large, we construct a (k + 1)-peak solutions with k positive interior peaks aligned on a closed curve near ∂Ω and 1 negative interior peak located in a more centered part of Ω.