BoundaryCondition

If an electron, travelling in a straight line, emits a photon perpendicular to its direction of motion (as seen from the inertial lab frame), will the frequency of the photon be the same in the inertial lab frame as that in the rest frame of the electron?

I've just begun learning about 4-vectors from Griffith's. By free indices you mean the rank of the tensor?

Is the following contraction of the Electromagnetism (or Faraday) Tensor a Lorentz scalar? i.imgur.com/GZXeWJ2.png