Identification of a gravitational arrow of time.

  title={Identification of a gravitational arrow of time.},
  author={J. Barbour and T. Koslowski and F. Mercati},
  journal={Physical review letters},
  volume={113 18},
It is widely believed that special initial conditions must be imposed on any time-symmetric law if its solutions are to exhibit behavior of any kind that defines an "arrow of time." We show that this is not so. The simplest nontrivial time-symmetric law that can be used to model a dynamically closed universe is the Newtonian N-body problem with vanishing total energy and angular momentum. Because of special properties of this system (likely to be shared by any law of the Universe), its typical… Expand

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