  We study, using both theory and simulations, a system of self-gravitating
sheets. A new statistical mechanics theory - free of any adjustable parameters
- is derived to quantitatively predict the final stationary state achieved by
this system after the process of collisionless relaxation is completed. The
theory shows a very good agreement with the numerical simulations. The model
sheds new light on the general mechanism of relaxation of self-gravitating
systems and may help us to understand cold matter distribution in the Universe.
