 Jeans instability

Jeans instability is the gravitational growth of density perturbations whose self-gravity overcomes pressure support. For physical sound speed $c_s$, the comoving threshold isModes with $k\ll k_J$ grow gravitationally, whereas modes with $k\gg k_J$ undergo pressure-supported acoustic oscillations.

Jeans instability is a concept in astrophysics and cosmology that describes the conditions under which a cloud of gas can collapse under its own gravity, leading to the formation of stars or other structures in the universe. The instability is named after the British physicist Sir James Jeans, who formulated the conditions for this collapse in 1902.