Spin Hall effects in the sky

TL;DR

This paper explores the gravitational spin Hall effect, drawing analogies with optical phenomena, and discusses potential astrophysical observations of this effect in inhomogeneous gravitational fields.

Contribution

It introduces gravitational spin Hall effects, highlighting their similarities with optical spin Hall effects and reviews potential astrophysical experiments to observe them.

Findings

Analogies between optical and gravitational spin Hall effects

Predictions of spin-dependent trajectories in gravitational fields

Potential astrophysical observations of gravitational spin Hall effects

Abstract

In many areas of physics, the propagation of wave packets carrying intrinsic angular momentum is generally influenced by spin-orbit interactions. This is the main mechanism behind spin Hall effects, which result in wave packets following spin-dependent trajectories. Spin Hall effects have been observed in several experiments for electrons in condensed matter systems and for light propagating in inhomogeneous optical media. Similar effects have also been predicted for wave packets propagating in inhomogeneous gravitational fields. We give a brief introduction to gravitational spin Hall effects, emphasizing the analogies with the spin Hall effect of light in optics. Furthermore, we review the most promising astrophysical avenues that could lead to experimental observations of the gravitational spin Hall effect.