A massive gravitational field in flat spacetime. II. Conservation laws and gravitational variability of the inertial mass

For a linear massive spinless field adapted as a gauge-invariant model of gravity in the framework of the special theory of relativity, a canonical energy-momentum tensor is constructed and the laws of conservation of energy and momentum are formulated. It is shown that the general requirement of a positive definiteness of the energy density of any physical reality in the case of an attractive field determines its scalar nature and far-reaching gravitational variability of the inertial mass of matter particles.