Bifurcation of a reversible Hamiltonian system from a fixed point with fourfold eigenvalue zero

Abstract

Bifurcations are studied from a fixed point with fourfold eigenvalue zero occurring in a two degrees of freedom Hamiltonian system of second-order ordinary differential equations (ODEs) which is additionally reversible with respect to two different linear involutions. Using techniques from Catastrophe Theory we are led to a codimension 2 problem and obtain two different unfoldings of the singularity related to the hyperbolic and elliptic umbilic, respectively. The analysis of the unfolded systems is essentially concerned with the existence and properties of homoclinic and heteroclinic orbits. The studies are motivated by a problem from nonlinear optics concerning the existence of solitons in a χ2-medium.