This paper defines an equation for causality. This equation is then combined with the postulates of quantum mechanics and mass-energy equivalence to produce a quantum mechanical telegrapher's equation and to reproduce the Schrodinger and Klein-Gordon equations. The incompressible Navier-Stokes equations and dynamic general equilibrium in economics (with an interpretation of a Nash equilibrium) are obtained when the equation of causality refers to itself, i.e. when the cause is its own effect. As it is shown that the Klein-Gordon equation is obtained by Wick rotating the cause vector with de Broglie angular frequency, this paper postulates an equation for Quantum Gravity, which relates the Navier-Stokes equations to the Einstein Field Equations of General Relativity.
A stochastic interpretation of Klein-Gordon equation is proposed. The starting point is the construction of relativistically covariant diffusions satisfying a property similar but not identical to the Markov property. It is then shown that the continuity equation associated with these processes together with the relativistic version of mean Newton equation are equivalent to the Klein-Gordon equation On propose une interpretation stochastique de l'equation de Klein Gordon. Le point de depart est la construction d'une diffusion relativiste covariante qui satisfait une propriete semblable (mais pas identique) a la propriete de Markov. On montre ensuite que l'equation de continuite associee a ce processus plus la version relativiste de l'equation de Newton en moyenne sont equivalentes a l'equation de Klein-Gordon