Inelastic collisions of pulses in coupled Ginzburg-Landau equations

A collision of two solitary pulses (SPs) is considered in a system of two coupled bistable Ginzburg-Landau equations. The bistability means that each seperate equation admits two stable solutions, viz., the trivial one and an SP. The system is considered in a regime where the real parts of its coefficients are small as compared to the imaginary parts, the only coupling terms being non-dissipative cubic ones. It is demonstrated that the collision between the free SPs belonging to the two subsystems results in their fusion into a bound state (bisoliton), or leads to a full annihilation, provided the group velocity difference between the two subsystems is smaller than a certain threshold value. The results obtained lend a natural interpretation to recent experiments with SPs of subcritical traveling-wave convection.