Screw-symmetric gravitational waves: a double copy of the vortex

TL;DR

This paper explores screw-symmetric gravitational waves, revealing they are the classical double copy of electromagnetic vortices, and clarifies how additional symmetries influence particle dynamics in these wave backgrounds.

Contribution

It demonstrates that screw-symmetric gravitational waves are the classical double copy of electromagnetic vortices, clarifying the role of sixth isometries in particle dynamics.

Findings

Screw symmetry in gravitational waves corresponds to electromagnetic vortices.

The sixth isometry does not independently affect particle dynamics.

Screw-symmetric gravitational waves are the double copy of electromagnetic vortices.

Abstract

Plane gravitational waves can admit a sixth `screw' isometry beyond the usual five. The same is true of plane electromagnetic waves. From the point of view of integrable systems, a sixth isometry would appear to over-constrain particle dynamics in such waves; we show here, though, that no effect of the sixth isometry is independent of those from the usual five. Many properties of particle dynamics in a screw-symmetric gravitational wave are also seen in a (non-plane-wave) electromagnetic vortex; we make this connection explicit, showing that the screw-symmetric gravitational wave is the classical double copy of the vortex.