Composite-kink solutions of coupled nonlinear wave equations

We obtain exact traveling-wave solutions of the coupled nonlinear partial differential equations that describe the dynamics of two classical scalar fields in 1+1 dimensions. The solutions are kinks interpolating between neighboring vacua. We compute the classical kink mass and show that it saturates a Bogomol’nyi-type bound. We also present exact traveling-wave solutions of a more general class of models. Examples include coupled ${\varphi }^4$ and sine-Gordon models.