Nonequilibrium stationary coupling of solitons

By computer simulation, interaction of two solitons with the same screw sense of the sine-Gordon equation, which retain their shapes and velocities upon collision with other solitons even in the presence of bias and loss terms, are examined. It is confirmed that they can couple when the bias is greater than a critical value. The conditions and mechanism of coupling are examined in detail. They are explained in terms of the energy of interaction between the ripple structures trailed by energy dissipative moving solitons. The distance D between coupled solitons can be expressed as D= (n-1/2-δ) λ (n is an integer), where λ is a wavelength of the ripple structure and δ≪1.