Clustering phenomena for linear perturbation of the Yamabe equation.

Let (M,g) be a non-locally conformally flat compact Riemannian manifold with dimension N≥7. We are interested in finding positive solutions to the linear perturbation of the Yamabe problem −Lgu+ϵu=uN+2N−2 in (M,g) where the first eigenvalue of the conformal laplacian −Lg is positive and ϵ is a small positive parameter. We prove that for any point ξ0∈M which is non-degenerate and non-vanishing minimum point of the Weyl's tensor and for any integer k there exists a family of solutions developing k peaks collapsing at ξ0 as ϵ goes to zero. In particular, ξ0 is a non-isolated blow-up point