Generalized susceptibility of a solitary wave

Abstract

We define a generalized susceptibility for solitary wave solutions of the nonlinear Klein–Gordon equation and obtain its expression in terms of the complete set of functions which arise in the linear stability analysis of the solitary wave. Explicit expressions are presented for the susceptibility of the sine‐Gordon soliton and the φ⁴ kink. Plots are presented for the long‐wave dynamic polarizability of the φ⁴ kink which have application to the response of ferroelectric domain walls to an oscillating external electric field.