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

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 spin2 helicity-1 mode interacts strongly with the shear motion of matter. This mode is unstable above a critical wavelength, λc = √ πc2/2Gρ. This should be compared with Jeans wavelength, λJ = √ πcs/Gρ, where cs is the sound speed. 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. PACS numbers: 4.30.-w, 4.30.Nk E-mail: [email protected] E-mail: [email protected]