The holographic correspondence between non-gravitational field theories
and gravitational theories in one higher dimension can be used to study
time dependent phenomena in gravity and in field theories. One such
phenomenon is that of quantum quench, where a coupling of the field
theory is time dependent and typically asymptotes to constants at early
and late times. In the gravity dual this can describe, under suitable
circumstances, either black hole formation, or passage through a
spacelike region of high curvature similar to a cosmological
singularity. On one hand this has taught us about the meaning of
cosmological singularities, while on the other hand this has thrown
light on the process of thermalization in strongly coupled field
theories. In particular in recent work holography has been used to study
situations where quantum quench happens across a critical point, and has
revealed interesting scaling properties.