Limitations of the concept of free fields in Einstein's theory of gravitation

It is shown explicitly that the linearized theory does not constitute any approximation to the exact solutions in the case of free fields. The only regular solution satisfying, as boundary condition, the requirement of a sufficiently rapid decrease at infinity is a flat space. The problem of conservation laws is discussed anew. The continuity equation satisfied by Einstein's pseudotensor does not guarantee the existence of global conservation laws. Solutions violating the energy conservation are interpretable as representing gravitational radiation absorbed or emitted by sources at infinity.