Stem Structures and Novel Localized Wave Molecules of the (2+1)-Dimensional pKP-BKP Equation

In this paper, asymptotic analysis for the (2+1)-dimensional potential Kadomtsev Petviashvili B-type Kadomtsev Petviashvili (pKP-BKP) equation is conducted to establish this limiting. The study examines the stem structures resulting from resonance collisions of the two-soliton solution in the (2+1)-dimensional pKP-BKP equation. The trajectories, amplitudes and velocities of the soliton arms and the lengths of the stem structures are calculated through asymptotic analysis. By combining the characteristic line analysis and the velocity resonance mechanism, novel bound states consisting of transformed wave–soliton molecules and transformed wave molecules are systematically constructed. These results provide explicit insight into the formation and evolution of localized nonlinear waves in the pKP-BKP system, and they offer a concrete theoretical foundation for wave resonance and bound states in higher-dimensional dispersive media.