Geometric Phases and Monodromy at Singularities
Albers, M. S. and J. E. Marsden
Singular Limits of Dispersive waves, NATO ASI Series C, 320, 273-295
Abstract:
"Phase functions in the quasi-periodic case
have important applications in the theory of evolution equations (where
they appear in connection with the Whitham equations). We investigate
them in the singular (soliton, umbilic soliton and homoclinic) cases. In this
paper we consider the umbilic and homoclinic solutions in this context."