4er-Impuls

$p^{\mu }=m\frac{d{x}^{\mu }}{d\tau }=\gamma m\left(\begin{array}{cccc}c& v^1& v^2& v^3\\ \end{array}\right)=\left(\begin{array}{cc}\frac{E}{c}& p^i\\ \end{array}\right)$ es gilt

$p^{\mu }{p}_{\mu }=m^2{c}^2$