Cosmology with an Action Principle
  The Friedman universe is re-examined in a context that is non-standard only in that the properties of matter are postulated in the form of an action principle. Applications to equilibrium configurations of ideal stars have already been reported. In this paper we apply the same theory to a fresh examination of the Friedman universe. The results agree with standard theory in the case of low densities. A suggestion is made to replace "vacuum energy" by "external force". 
Christian Fronsdal