Gravitational instabilities in helicity-1 waves propagating through matter in equilibrium

TL;DR

This paper investigates how helicity-1 gravitational waves interacting with matter in equilibrium can cause new types of instabilities, including a Jeans-like instability with a critical wavelength related to the speed of light.

Contribution

It introduces a novel instability mechanism caused by helicity-1 gravitational waves interacting with matter, differing from traditional Jeans instability.

Findings

Helicity-1 waves induce shear motion in matter.

Instability occurs above a critical wavelength related to the speed of light.

Different from classical Jeans instability, involving transverse shear motions.

Abstract

It is shown that the interaction of helicity-1 waves of gravity and matter in a thin slab configuration produces new types of instabilities. Indeed, a transverse spin-2 helicity-1 mode interacts strongly with the shear motion of matter. This mode is unstable above a critical wavelength which reminds the Jeans wavelength but with the speed of sound interchanged by the speed of light. The two instabilities are of course different. For the case analyzed, a plane parallel configuration, Jeans instability appears through a density wave perturbation, the material collapsing into a set of plane-parallel slabs. On the other hand, the helicity-1 wave instability induces a transverse motion in the fluid that tends to shear in the material along the node of the perturbation.