Towards the physical significance of the $(k^2+A)\|u\|$ metric
  We offer an example of the second order Kawaguchi metric function the extremal flow of which generalizes the flat space-time model of the semi-classical spinning particle to the framework of the pseudo-Riemannian space-time. The general shape of the variational Euler-Poisson equation of the fourth order in the (pseudo-)Riemannian space is being developed too. 
Roman Matsyuk
math-ph gr-qc math.DG math.MP