Domain walls coupled to matter: the symmetron example

TL;DR

This paper investigates the unique properties of domain walls in the symmetron model, highlighting their stability, cosmological implications, and interactions with matter over-densities through analytical and numerical methods.

Contribution

It introduces the effects of non-minimal coupling in symmetron domain walls, including stability criteria and cosmological bounds, which are novel compared to minimally coupled theories.

Findings

Cosmological energy fraction in domain walls is constrained by symmetry breaking redshift.

Spherical symmetron walls can remain stable when pinned on matter halos.

Numerical simulations reveal interaction dynamics between domain walls and matter over-densities.

Abstract

We study properties of domain walls in the symmetron model, in which the scalar gravitational degree of freedom decouples from matter in regions of high density, and exhibits a spontaneously broken $Z_2$ symmetry at low densities. The non-minimal coupling of the scalar to matter leads to a host of interesting properties of the domain walls that are not present in minimally coupled theories. We estimate the cosmological energy fraction in domain walls and find that this leads to an upper bound on the redshift of the symmetry breaking. We also show that a spherical symmetron wall can remain stable if it is "pinned" on matter halos and derive a criterion for the stability. In addition, we present results of numerical simulations of representative interactions between domain walls and matter over-densities.