# Quasinormal modes in kink excitations and kink-antikink interactions: a toy model

## TL;DR

This paper investigates how quasinormal modes affect kink excitations and collisions in a scalar field theory with a symmetric potential, revealing energy leakage and complex resonance structures.

## Contribution

It introduces a toy model with a tunable square well potential to study the transition from normal to quasinormal modes in kink excitations and their impact on collision dynamics.

## Key findings

- Quasinormal modes cause energy leakage in kink excitations.
- Transition from normal to quasinormal modes alters collision resonance windows.
- Fractal structures in kink-antikink interactions are influenced by mode types.

## Abstract

We study excitations and collisions of kinks in a scalar field theory where the potential has two minima with $Z_2$ symmetry. The field potential is designed to create a square well potential in the stability equation of the kink excitations. The stability equation is analogous to the Schr\"{o}dinger equation, and therefore we use quantum mechanics techniques to study the system. We modify the square well potential continuously, which allows the excitation to tunnel and consequently turns the normal modes of the kink into quasinormal modes. We study the effect of this transition, leading to energy leak, on isolated kink excitations. Finally, we investigate kink-antikink collisions and the resulting scaling and fractal structure of the resonance windows considering both normal and quasinormal modes and compare the results.