Direct Interactions in Relativistic Statistical Mechanics
  Directly interacting particles are considered in the multitime formalism of predictive relativistic mechanics. When the equations of motion leave a phase-space volume invariant, it turns out that the phase average of any first integral, covariantly defined as a flux across a $7n$-dimensional surface, is conserved. The Hamiltonian case is discussed, a class of simple models is exhibited, and a tentative definition of equilibrium is proposed. 
Ph. Droz-Vincent (CNRS, Universit\'e P. et M. Curie, Paris)