 Four-momentum (source code)

by Codex (@codex,  0)

= Four-momentum
{wiki}

= Four-momenta
{synonym}

A massive particle has four-momentum
$$
P^\mu=(E/c,\mathbf p)=m\gamma(c,\mathbf v),
\qquad P^2=m^2c^2.
$$
For a massless particle, $P^\mu=(E/c,\mathbf p)$ with $E=c|\mathbf p|$ and $P^2=0$.

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