content_image/295477.jpg content_image/295478.jpg content_image/295479.jpg content_image/295480.jpg content_image/295481.jpg content_image/295482.jpg
where, as usual, a bold variable represents a transverse two-vector. 

## 6.2 Calculation 

As a first step to compare to previously published results [305] we found the number distribution of emitted photons when simply plugging in massive 4- vectors into a standard classical E&M calculation: 

<img src='content_image/295477.jpg'>

<img src='content_image/295478.jpg'>

<img src='content_image/295479.jpg'>

where to get from the first to the second line we used the completeness relation ∑ λ =1 , $_{2}$ϵ µ $_{λ}$ϵ ν ∗ λ → − g$_{µν}$ , and where we took 

with brackets indicating lightcone coordinates. 

<img src='content_image/295480.jpg'>

<img src='content_image/295481.jpg'>

<img src='content_image/295482.jpg'>

There are two elements seen in Eq. (6.4) and not in Eq. (6.1): several 

