Question

Establish energy momentum four vector.

Answer 1

Four-vectors in Relativity. In the literature of relativity, space-time coordinates and theenergy/momentum of a particle are often expressed in four-vector form. They are defined so that the length of afour-vector is invariant under a coordinate transformation. This invariance is associated with physical ideas.

Answer 2

Four-vectors in Relativity. ... The invariance of the space-time four-vector is associated with the fact that the speed of light is a constant. The invariance of the energy-momentum four-vector is associated with the fact that the rest mass of a particle is invariant under coordinate transformations.