- #1
Muh. Fauzi M.
- 17
- 1
Homework Statement
This is just a simple proof of substitution, but after one day struggle, I still can't get where that minus sign appear.
Homework Equations
Here is the equation:
$$ (p_1 - p_3)^2=-(\mathbf p_1 - \mathbf p_3)^2$$
where ##p_1=(E/c,\mathbf p_1)## and ##p_3=(E/c, \mathbf p_3)## is four-momentum of incident and scattered electron respectively, with stationary target.
The Attempt at a Solution
Here is my doodling:
$$
(p_1 - p_3)^2=(E/c+\mathbf p_1-E/c-\mathbf p_3)^2=(\mathbf p_1 - \mathbf p_3)^2.
$$
Which step that I miss?