# Entanglement in anisotropic expanding spacetime

## TL;DR

This paper investigates how space anisotropy in an expanding universe influences quantum entanglement in scalar and Dirac fields, revealing unique entanglement behaviors including revivals, distortions, and anisotropy-induced entanglement.

## Contribution

It demonstrates the impact of anisotropic expansion on entanglement patterns in different quantum fields, highlighting phenomena absent in isotropic models.

## Key findings

- Massive scalar fields show entanglement revivals at specific momenta.
- Massive Dirac fields exhibit distorted entanglement profiles with maxima at non-zero momenta.
- Massless fields of both types can only become entangled due to anisotropy, with maximum entanglement at non-zero momenta.

## Abstract

We study the effect of space anisotropy in the entanglement generated by expanding universe on spin 0 and 1/2 fields. For massive scalar field we find revivals of entanglement entropy vs momentum after decreasing from the maximum at k = 0. In massive Dirac field the effect is a slight distortion of the non-monotonic profile giving rise to the maximum of entanglement entropy at k > 0. More interestingly, massless field of both type can only get entangled through anisotropy, with a maximum of entanglement entropy occurring at k > 0.