Electromagnetic stress–energy tensor

Summary

The electromagnetic stress–energy tensor is a symmetric $4 \times 4$ tensor field on spacetime. It collects the energy density, the energy flux, the momentum density and the momentum flux of the electromagnetic field. Its components are the field energy density, the Poynting vector and the Maxwell stress tensor. Its conservation law contains both Poynting's theorem and the balance of momentum. In general relativity it is the source term of the Einstein field equations for an electromagnetic field.