deletions | additions       diff --git a/special rel.tex b/special rel.tex  index 40fc4df..e42b1ce 100644  --- a/special rel.tex  +++ b/special rel.tex 
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\begin{split}  \mathbf{u} = (\gamma, \gamma v) \\  \mathbf{u} \cdot \mathbf{u} = -1 \\  \mathbf{p_{\rm{photon}} \mathbf{p_{\gamma}}  \cdot \mathbf{p} \mathbf{p_{\gamma}}  = 0 \\ E_{obs} = - p \cdot \mathbf{u}  \end{split}  \end{equation}