Asymptotic stability of the fourth-order φ⁴ kink for general perturbations in the energy space

The fourth-order φ⁴ model extends the classical φ⁴ model of quantum field theory to the fourth-order case, but sharing the same kink solution. It is also the dispersive counterpart of the well-known parabolic Cahn–Hilliard equation. Mathematically speaking, the kink is characterized by a fourth-order nonnegative linear operator with a simple kernel at the origin but no spectral gap. In this paper, we consider the kink of this theory, and prove orbital and asymptotic stability for any perturbation in the energy space.