Jeans analysis in modified gravity

MOdified Gravity (MOG) is a covariant modification of Einstein's general relativity. This theory is one of the current alternatives to dark matter models. We describe the dynamics of collisionless self-gravitating systems in the context of MOG. By studying the weak field approximation of this theory, we derive the equations governing the dynamics of the self-gravitating systems. More specifically, we consider the Jeans instability for self-gravitating fluid and stellar systems and derive new Jeans mass limit (M) over tilde (J) and wave-number (k) over tilde (J). Furthermore, considering the gravitational instability in star-forming regions, we show that MOG has not a significant difference with general relativity on this astrophysical scale. However, at larger scales, such as intergalactic space, MOG may lead to different galaxy- and structure-formation processes