Islands in Bianchi type-I Universe

TL;DR

This paper investigates the formation of entanglement islands in an anisotropic Bianchi Type-I universe filled with radiation, identifying conditions and specific times when islands can form, especially near the universe's turnaround point.

Contribution

It extends the study of entanglement islands to anisotropic cosmological models, showing their formation near turnaround points and independence from island shape.

Findings

Islands can form at specific times near the universe's turnaround point.

Existence of islands does not depend on their shape.

Formation of islands aligns with the presence of multiple energy scales.

Abstract

We study the conditions for finding an island in an anisotropic universe - Bianchi Type-I filled with radiation. We verify that the existence of islands does not depend on their shape. We then find that islands may form at certain times, near the turnaround point - where the universe turns from contraction to expansion in one of the directions. This is in line with previous analyses regarding cosmological space-times where islands form if one has two energy scales in the problem, such as the typical temperature of the universe and, on top of that, cosmological constant, curvature, anisotropy, or some mass scale.