Extremality of mass in the bimetric theory of gravitation

In the bimetric theory of gravitation, the static spherically symmetric case involving matter characterized by density and pressure is considered. It is found that the condition that the mass be stationary under small variations of the field variables (including the density) for a fixed number of baryons leads to the field equations and to the equilibrium condition. If one considers only solutions of the field equations, then the mass for a fixed baryon number is stationary (one can expect it to be extremal in most cases) if the equilibrium condition holds.Dedicated to Achille Papapetrou on the occasion of his retirement.