Interaction of periodic and stationary bifurcation from multiple eigenvalues (Q1078500)

We give a bifurcation result for stationary or periodic solutions of an evolution equation in Hilbert space when the linearization has critical eigenvalues 0 and \(\pm i\kappa_ 0\). We impose only conditions on the linearization along the trivial equilibria which allow to follow the lines of the classical Hopf bifurcation theorem: reduce it to a one- parameter bifurcation problem by solving for the frequency.