The collision of two-kinks defects

TL;DR

This study numerically investigates the head-on collision of two-kink and two-antikink pairs in a generalized $^4$ model, revealing annihilation, oscillon formation, and transient lump-like structures depending on impact velocity.

Contribution

It introduces a new spectral algorithm for simulating kink collisions and uncovers novel quasi-stationary lump-like structures formed during the process.

Findings

Two-kink pairs are mostly annihilated with radiation emission.

Oscillons can form and persist after collisions.

Transient lump-like solutions appear depending on impact velocity.

Abstract

We have investigated the head-on collision of a two-kink and a two-antikink pair that arises as a generalization of the $\phi^4$ model. We have evolved numerically the Klein-Gordon equation with a new spectral algorithm whose accuracy and convergence were attested by the numerical tests. As a general result, the two-kink pair is annihilated radiating away most of the scalar field. It is possible the production of oscillons-like configurations after the collision that bounce and coalesce to form a small amplitude oscillon at the origin. The new feature is the formation of a sequence of quasi-stationary structures that we have identified as lump-like solutions of non-topological nature. The amount of time these structures survives depends on the fine-tuning of the impact velocity.