Abstract
There is a modification of the SU(2) chiral model, which is integrable in (2+1) dimensions [J. Math. Phys. 29, 386 (1988)]. In addition to localized lumps, it admits extended wave solutions, which move at constant velocity. The interaction of two waves causes each to experience a phase shift. In the interaction between a wave and a lump, the wave suffers no phase shift, but the lump changes shape.