Solitons and cavitons in a nonlocal Whitham equation.

Solitons and cavitons (localized solutions with singularities) for the nonlocal Whitham equations are studied. The equation of a fourth order with a parameter in front of fourth derivative for traveling waves is reduced to a reversible Hamiltonian system defined on a two-sheeted four-dimensional space. Solutions of the system which stay on one sheet represent smooth solutions of the equation but those which perform transitions through the branching plane represent solutions with jumps. Using analytic and numerical methods we found many types of homoclinic (and periodic as well) orbits to the equilibria both with a monotone asymptotics and oscillating ones. They correspond to solitons and cavitons of the initial equation. The presence of majority such solutions displays the very complicated dynamics of the system.