Interaction between gravitational waves and domain walls

TL;DR

This paper investigates how gravitational waves interact with thick domain walls, revealing that waves are refracted and their polarization states are altered inside the walls, with specific effects on different polarization modes.

Contribution

It provides a detailed analysis of gravitational wave refraction, reflection, transmission, and polarization changes caused by thick domain walls, including spin content modifications.

Findings

Gravitational waves are refracted by domain walls.

Reflection and transmission coefficients are derived for thin walls.

The '+' polarization mode gains spin 0 and other spin states inside the wall.

Abstract

We study the gravitational perturbations of thick domain walls. The refraction index and spin properties of the solutions interior to the wall are analyzed in detail. It is shown that the gravitational waves suffer a refraction process by domain walls. The reflection and transmission coefficients are derived in the thin wall limit. In relation to the spin content, it is shown that the ``$\times$'' helicity 2 gravitational wave mode maintains in the domain wall the same polarization state as in vacuum. On the contrary, the ``+'' mode, of pure helicity 2 in vacuum, is contaminated inside the wall with a spin 0 state, as well as with spin 2, helicity 0 and 1 states.