# Evanescent Gravitational Waves

## TL;DR

Evanescent gravitational waves are a new class of solutions to Einstein's equations that decay exponentially in one direction while propagating in another, exhibiting unique properties like transverse spin and potential for distinguishing from modified gravity.

## Contribution

This paper introduces evanescent gravitational waves, revealing their properties and demonstrating their dominance near sub-wavelength sources such as orbiting binaries.

## Key findings

- EGWs carry transverse spin angular momentum.
- Test masses exhibit elliptical trajectories under EGWs.
- EGWs are prevalent near sub-wavelength sources.

## Abstract

We describe the properties of evanescent gravitational waves (EGWs)---wave solutions of Einstein equations which decay exponentially in some direction while propagating in another. Evanescent waves are well-known in acoustics and optics and have recently received much attention due to their extraordinary properties such as their transverse spin and spin-momentum locking. We show that EGWs possess similarly remarkable properties, carrying transverse spin angular momenta and driving freely falling test masses along in elliptical trajectories. Hence, test masses on a plane transverse to the direction of propagation exhibit correlated vector and scalar-like deformation---correlations which can be used to distinguish it from modified gravity. We demonstrate that EGWs are present and dominant in the vicinity of sub-wavelength sources such as orbiting binaries.