Representation of the dynamic evolution of a system on a diagram connecting kinetic, K, and potential energy, W. Evolution occurs along the straight line K(t)+W(t) = E, approaching on average a virial equilibrium state (VES). The thin lines correspond to fixed values of the virial ratio V given by Eq. (6). The letters C and H denote cold and hot configurations, which are characterized by the values K < |E| and K > |E|, respectively.