Ostriker–Peebles criterion

The Ostriker–Peebles criterion is a criterion in astrophysics used to evaluate the stability of spherical systems of matter under gravitational collapse, particularly in the context of galaxy formation and the large-scale structure of the universe. It is named after the astronomers J. P. Ostriker and P. J. E. Peebles. The criterion assesses whether a system, such as a cloud of gas or a cluster of galaxies, is stable against perturbations.