Solution
= Solution
A positive-frequency on-shell <Dirac spinor> obeys
$$
\boxed{(\not p-m)u(s,p)=0,
\qquad p^0=+\sqrt{\mathbf p^2+m^2}.}
$$
= Solution
A positive-frequency on-shell <Dirac spinor> obeys
$$
\boxed{(\not p-m)u(s,p)=0,
\qquad p^0=+\sqrt{\mathbf p^2+m^2}.}
$$