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After reviewing a few physical examples in which the sine-Gordon
equation arises as the governing dynamical equation, we discuss
various solutions exhilbiting multisoliton dynamics. Interaction of
solitons and the corresponding velocity-dependent interaction
potentials are derived and discussed. Numerical experiments
are carried out in order to study kink dynamics in an inhomogeneous
medium. Finally, we introduce two kinds of generalized sine-Gordon
equations and discuss their properties.
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