Virialization
= Virialization
<virialization> is relaxation toward a gravitationally supported bulk state satisfying an appropriate virial balance. For an isolated approximately stationary Newtonian system with negligible boundary terms, $2K+W\simeq0$. It does not require every collisionless constituent to reach collisional <thermal equilibrium>, and ongoing infall, tides or pressure at a boundary modify the balance.