content_image/295378.jpg content_image/295377.jpg content_image/295376.jpg content_image/295375.jpg
where µ is the mass of the photon. 

Consider the variation of the new, massive photon part of the Lagrangian: 

<img src='content_image/295378.jpg'>

Therefore 

<img src='content_image/295377.jpg'>

And 

<img src='content_image/295376.jpg'>

This agrees with Jackson problem 12.16 (a) [235]. Note that we recover T µν EM for µ → 0. 

## F.1.3 Classical Bremsstrahlung Radiation 

E&M 

The E&M Lagrangian coupled to a classical source is 

<img src='content_image/295375.jpg'>

