S. Micciche et Jb. Griffiths, Soliton solutions with real poles in the Alekseev formulation of the inverse-scattering method, CLASS QUANT, 17(1), 2000, pp. 1-9
A new approach to the inverse-scattering technique of Alekseev is presented
which permits real-pole soliton solutions of the Ernst equations to be con
sidered. This is achieved by adopting distinct real poles in the scattering
matrix and its inverse. For the case in which the electromagnetic field va
nishes, some explicit solutions are given using a Minkowski seed metric. Th
e relation with the corresponding soliton solutions that can be constructed
using the Belinskii-Zakharov inverse-scattering technique is determined.