On the Decay of Soliton Excitations
  In field theory the scattering about spatially extended objects, such as solitons, is commonly described by small amplitude fluctuations. Since soliton configurations often break internal symmetries, excitations exist that arise from quantizing the modes that are introduced to restore these symmetries. These modes represent collective distortions and cannot be treated as small amplitude fluctuations. Here we present a method to embrace their contribution to the scattering matrix. In essence this allows us to compute the decay widths of such collective excitations. As an example we consider the Skyrme model for baryons and explain that the method helps to solve the long--standing Yukawa problem in chiral soliton models. 
H. Weigel