In the present Chapter, we consider two prototypical Klein-Gordon models: the integrable sine-Gordon equation and the non-integrable $\phi^4$ model. We focus, in particular, on two of their prototypical solutions, namely the kink-like heteroclinic connections and the time-periodic, exponentially localized in space breather waveforms. Two limits of the discrete variants of these models are contrasted: on the one side, the analytically tractable original continuum limit, and on the opposite end, the highly discrete, so-called anti-continuum limit of vanishing coupling. Numerical computations are used to bridge these two limits, as regards the existence, stability and dynamical properties of the waves. Finally, a recent variant of this theme is presented in the form of $\mathcal{PT}$-symmetric Klein-Gordon field theories and a number of relevant results are touched upon.
CITATION STYLE
Chirilus-Bruckner, M., Chong, C., Cuevas-Maraver, J., & Kevrekidis, P. G. (2014). sine-Gordon Equation: From Discrete to Continuum (pp. 31–57). https://doi.org/10.1007/978-3-319-06722-3_2
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