Spectral flow and variational bifurcation
J. Pejsachowicz
Abstract
We show that the principle "nonvanishing of spectral flow of the linearization along the trivial branch entails bifurcation of nontrivial solutions ", proved in \cite{FPR} for critical points of one parameter families of $C^2$ functionals with Fredholm Hessian, holds true for variational perturbations of paths of unbounded self-adjoint Fredholm operators with a fixed domain.
